(Radiographics. 1999;19:569-581.)
© RSNA, 1999
Imaging Features of Uncommon Adrenal Masses with Histopathologic Correlation1
Philippe Otal, MD,
Ghislaine Escourrou, MD,
Catherine Mazerolles, MD,
Bertrand Janne D'Othee, MD,
Sana Mezghani, MD,
Sandrine Musso, MD,
Daniel Colombier, MD,
Hervé Rousseau, MD and
Francis Joffre, MD
1 From the Departments of Radiology (P.O., B.J.D., S. Mezghani, S. Musso, D.C., H.R., F.J.) and Pathology (G.E., C.M.), University Hospital Rangueil, 1 Avenue Jean-Poulhès, 31403 Toulouse 4, France. Presented as a scientific exhibit at the 1997 RSNA scientific assembly. Received April 21, 1998; revision requested May 7; final revision received October 8; accepted November 6. Address reprint requests to P.O.
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Abstract
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Uncommon adrenal masses include cystic lesions (hydatid cyst, endothelial cyst), solid lesions (hemangioma, ganglioneuroma, angiosarcoma, primary malignant melanoma), and solid fatty lesions (myelolipoma, collision tumor). Most of these lesions do not have specific imaging features. The liquid content of adrenal cysts is clearly demonstrated on ultrasonographic scans, computed tomographic scans, and magnetic resonance images. Nevertheless, the histologic type cannot be predicted except at some stages of hydatid disease in which pathognomonic features are present. The most typical imaging features of hemangioma are phleboliths and enhancement of peripheral vascular lakes. Ganglioneuroma has nonspecific radiologic features, but this diagnosis should be considered in cases with early enhancement of fine septa and progressive filling. The radiologic features of angiosarcoma and primary malignant melanoma are nonspecific. A macroscopic lipid content within an adrenal mass is theoretically characteristic of myelolipoma. This diagnosis should be made with caution, especially when the lipid content is not predominant, because of the possible association with an adenoma.
Index Terms: Adrenal gland, cysts, 86.311 • Adrenal gland, neoplasms, 86.30
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INTRODUCTION
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The most common tumors of the adrenal gland are adenoma, pheochromocytoma, adrenocortical carcinoma, and metastases. Although the imaging features of these tumors are established, the imaging characteristics of uncommon adrenal masses are less well known.
This article presents our experience with uncommon adrenal masses, which include cystic lesions (hydatid cyst, endothelial cyst), solid lesions (hemangioma, ganglioneuroma, angiosarcoma, primary malignant melanoma), and solid fatty lesions (myelolipoma, collision tumor). The most characteristic features at ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging are demonstrated. When possible, the imaging features are correlated with the findings at gross and microscopic analysis.
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CYSTIC LESIONS
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Hydatid Cyst
Hydatid cyst of the adrenal gland is rare; this entity represents only 7% of all adrenal cysts (1). It occurs in cases of disseminated infection by Echinococcus granulosus beyond the hepatic and pulmonary filters. Out of every 200 such cases, the adrenal gland is affected in only one case.
The content of the lesion is initially purely liquid and is limited by two layers. The inner, germinal layer is composed of the parasite, which is one cell thick, whereas the outer layer allows the passage of nutrients. The inner layer produces the laminar membrane and scoleces and secretes the cystic fluid.
The infection is usually asymptomatic. When symptoms are present, most are related to local visceral compression. Eosinophilia occurs in one-fourth of cases; the sensitivity of serologic tests is 90%.
The imaging features depend on the stage of evolution of the disease. Early lesions appear purely cystic; after modifications of the germinal layer and reduction of intraluminal pressure, the capsule becomes fibrotic and sometimes calcified, while the daughter cysts discharge from the wall and float in the lumen.
The most common classification is that of Gharbi et al (2), which is based on US features and includes five types. Type 1 is a well-defined, anechoic lesion. Type 2 demonstrates separation of the membrane; the "water lily" sign is formed by the undulating membrane. Type 3 is characterized by septa and intraluminal daughter cysts (Fig 1). Type 4 is a nonspecific solid mass. Type 5 is a solid mass with a calcified capsule.
Endothelial Cyst
Adrenal endothelial cysts are rare. In the series of adrenal cysts reported by Asbeshouse et al (1), 41% were lymphangiomatous and 13% were hemangiomatous. These lesions must be distinguished from pseudocysts (39% of cases) (which do not have an epithelial lining but are limited by a fibrotic capsule, which is generally due to intraglandular hemorrhage) and infectious cysts (7% of cases), which are generally of hydatid origin.
Adrenal endothelial cysts are usually an incidental finding; symptoms (flank pain, nausea, vomiting) result from local compression. Exceptional cases of arterial hypertension due to an adrenal endothelial cyst have been reported; these cases were cured after surgical treatment, and there was no evidence of hormonal dysfunction (3). Acute complications such as hemorrhage, rupture, and infection are possible.
Plain radiographs show mural calcifications in 15% of cases (4). Usually, an adrenal cyst demonstrates a homogeneously liquid content at imaging; the cyst wall is thin and regular. Large cysts must be distinguished from renal, hepatic, splenic, and pancreatic cysts. Multiplanar images are helpful in localizing the origin of the cyst.
Sometimes, the cyst does not appear as a purely liquid mass; the content may be slightly echoic or hyperechoic. Sedimentation is present in the hemorrhagic form. Hemorrhagic content appears hyperintense on T1-weighted MR images. Hemorrhage may have a pseudonodular appearance; for a nodule to be diagnosed, absence of a Doppler signal or of contrast material uptake has to be shown (5). Internal septa, which are observed in lymph-angiomatous cysts and pseudocysts, are better demonstrated with US than with CT (Fig 2). Hemangiomatous cysts are commonly uniloculated (Fig 3).
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Figure 2a. Lymphangiomatous cyst. (a) US scan shows a septated cystic mass of the right adrenal gland (arrows). (b) Contrast material–enhanced CT scan shows a lobulated cystic mass with calcified septa. (c) Spin-echo T2-weighted MR image (2,000/90 [repetition time msec/echo time msec]) shows the septa clearly due to the high signal intensity of the cystic fluid. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows dilated vascular structures (*) with an inflammatory and fibrotic wall.
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Figure 2b. Lymphangiomatous cyst. (a) US scan shows a septated cystic mass of the right adrenal gland (arrows). (b) Contrast material–enhanced CT scan shows a lobulated cystic mass with calcified septa. (c) Spin-echo T2-weighted MR image (2,000/90 [repetition time msec/echo time msec]) shows the septa clearly due to the high signal intensity of the cystic fluid. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows dilated vascular structures (*) with an inflammatory and fibrotic wall.
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Figure 2c. Lymphangiomatous cyst. (a) US scan shows a septated cystic mass of the right adrenal gland (arrows). (b) Contrast material–enhanced CT scan shows a lobulated cystic mass with calcified septa. (c) Spin-echo T2-weighted MR image (2,000/90 [repetition time msec/echo time msec]) shows the septa clearly due to the high signal intensity of the cystic fluid. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows dilated vascular structures (*) with an inflammatory and fibrotic wall.
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Figure 2d. Lymphangiomatous cyst. (a) US scan shows a septated cystic mass of the right adrenal gland (arrows). (b) Contrast material–enhanced CT scan shows a lobulated cystic mass with calcified septa. (c) Spin-echo T2-weighted MR image (2,000/90 [repetition time msec/echo time msec]) shows the septa clearly due to the high signal intensity of the cystic fluid. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows dilated vascular structures (*) with an inflammatory and fibrotic wall.
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Figure 3a. Hemangiomatous cyst. (a–c) MR images show a lobulated mass of the right adrenal gland that extends to the inferior aspect of the liver. (a) Coronal spin-echo T2-weighted MR image (2,500/138) shows a markedly hyperintense mass limited by a regular wall. (b) Sagittal fast low-angle shot (FLASH) two-dimensional gradient-echo T1-weighted MR image (122/5, 75° flip angle) shows that the mass has heterogeneous signal intensity with peripheral high signal intensity, which is consistent with hematoma. (c) Corresponding MR image obtained after intravenous injection of gadolinium contrast material shows that the mass has weak contrast enhancement, which is limited to a thin, peripheral rim. (d) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a vascular structure with a fibrotic wall and rare residual adrenal cells (arrow).
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Figure 3b. Hemangiomatous cyst. (a–c) MR images show a lobulated mass of the right adrenal gland that extends to the inferior aspect of the liver. (a) Coronal spin-echo T2-weighted MR image (2,500/138) shows a markedly hyperintense mass limited by a regular wall. (b) Sagittal fast low-angle shot (FLASH) two-dimensional gradient-echo T1-weighted MR image (122/5, 75° flip angle) shows that the mass has heterogeneous signal intensity with peripheral high signal intensity, which is consistent with hematoma. (c) Corresponding MR image obtained after intravenous injection of gadolinium contrast material shows that the mass has weak contrast enhancement, which is limited to a thin, peripheral rim. (d) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a vascular structure with a fibrotic wall and rare residual adrenal cells (arrow).
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Figure 3c. Hemangiomatous cyst. (a–c) MR images show a lobulated mass of the right adrenal gland that extends to the inferior aspect of the liver. (a) Coronal spin-echo T2-weighted MR image (2,500/138) shows a markedly hyperintense mass limited by a regular wall. (b) Sagittal fast low-angle shot (FLASH) two-dimensional gradient-echo T1-weighted MR image (122/5, 75° flip angle) shows that the mass has heterogeneous signal intensity with peripheral high signal intensity, which is consistent with hematoma. (c) Corresponding MR image obtained after intravenous injection of gadolinium contrast material shows that the mass has weak contrast enhancement, which is limited to a thin, peripheral rim. (d) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a vascular structure with a fibrotic wall and rare residual adrenal cells (arrow).
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Figure 3d. Hemangiomatous cyst. (a–c) MR images show a lobulated mass of the right adrenal gland that extends to the inferior aspect of the liver. (a) Coronal spin-echo T2-weighted MR image (2,500/138) shows a markedly hyperintense mass limited by a regular wall. (b) Sagittal fast low-angle shot (FLASH) two-dimensional gradient-echo T1-weighted MR image (122/5, 75° flip angle) shows that the mass has heterogeneous signal intensity with peripheral high signal intensity, which is consistent with hematoma. (c) Corresponding MR image obtained after intravenous injection of gadolinium contrast material shows that the mass has weak contrast enhancement, which is limited to a thin, peripheral rim. (d) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a vascular structure with a fibrotic wall and rare residual adrenal cells (arrow).
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If an incidentally discovered adrenal lesion meets all of the radiologic criteria for a solitary cyst, a conservative approach is recommended. Sometimes, modifications of the cystic wall and lumen may result in diagnostic difficulty if they simulate a soft-tissue lesion with a predominant necrotic component, such as adrenocortical carcinoma, metastasis, or pheochromocytoma (6). MR imaging is not always useful in distinguishing a hemorrhagic cyst from hemorrhagic adrenocortical carcinoma. Tung et al (7) recommend percutaneous aspiration because it allows biologic and cytologic analysis of the cystic fluid. Biopsy of a thickened wall or a surgical approach can also be recommended.
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SOLID LESIONS
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Hemangioma
Hemangioma of the adrenal gland is extremely uncommon, with fewer than 15 cases reported in the literature in 1991 (8). It affects people between the ages of 50 and 70 years; women are affected twice as often as men. Bilateral involvement has been reported twice (9).
Adrenal hemangiomas are generally asymptomatic. If symptoms are present, they are related to the volume of the tumor, which does not produce hormones.
Hemangioma usually involves the adrenal cortex; the tumor is well delimited and encapsulated. Multiple cavities are seen at the periphery, whereas complex central modifications involve necrosis, calcification, fibrosis, thrombosis, and hemorrhage. At microscopic analysis, hemangiomas are usually cavernous and rarely capillary (10).
Plain radiographs demonstrate calcifications in 64% of cases; these calcifications are similar to phleboliths. The US appearance is nonspecific: The tumor may be hypoechoic, hyperechoic, or of mixed echogenicity. At CT, phleboliths are more conspicuous (11). Nonenhanced scans show a hypoattenuating mass with necrotic areas (Fig 4); after intravenous administration of contrast material, peripheral enhancement reveals contrast material–filled lakes. Centripetal enhancement is less frequent than in hepatic hemangiomas because the frequencies of inner necrosis and fibrosis are higher in adrenal hemangiomas. Nonenhanced T1-weighted MR images show heterogeneous low signal intensity (12); nonenhanced T2-weighted MR images show marked high signal intensity except in the central fibrotic areas. The enhancement pattern is the same as that seen at CT.
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Figure 4a. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4b. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4c. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4d. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4e. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4f. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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Figure 4g. Hemangioma. (a) US scan shows a heterogeneous, hypoechoic mass. (b, c) CT scans obtained before (b) and after (c) injection of contrast material show a well-circumscribed soft-tissue mass with a punctate calcification (arrow in b) and peripheral nodular enhancement (arrow in c). (d) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after intravenous injection of gadolinium contrast material shows enhancement similar to that in the CT scan (c). (e) Corresponding MR image obtained 7 minutes later shows centripetal incomplete filling of the lesion. (f) Photograph of the gross specimen shows peripheral vascular lakes (arrows) and central fibrosis (*). (g) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows hemangiomatous proliferation dissected by a hematoma (*) and surrounded by a thick fibrotic wall (arrow). Arrowhead = residual peripheral adrenal elements.
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The most typical characteristics are the presence of phleboliths and enhancement of the peripheral vascular lakes. This pattern has also been reported in two cases of malignant hemangioblastoma (13). If the lesion has a necrotic center, other benign and malignant adrenal neoplasms have to be considered. If a radiologic diagnosis of hemangioma is suggested, a surgical approach is recommended.
Ganglioneuroma
Ganglioneuroma is a rare benign neoplasm that originates from sympathetic ganglia. It belongs to the group of neurogenic tumors, which also include ganglioneuroblastoma and neuroblastoma. The retroperitoneum is the first or second most common location of ganglioneuroma (32%–52% of cases). Most cases of adrenal ganglioneuroma occur in people older than 40 years (14).
Ganglioneuromas are often asymptomatic even if they reach a large size. Otherwise, abdominal pain or the palpation of an abdominal mass are the most frequent clinical features. Hormonally active forms have been reported; the secretion of catecholamines, vasoactive intestinal polypeptide, or androgenic hormones explains such symptoms as hypertension, diarrhea, and virilization (15,16).
Retroperitoneal ganglioneuromas appear as well-defined masses that are oval, crescentic, or lobulated. They tend to surround major blood vessels; the result is absent or mild compromise of the lumen (15,17,18). The US appearance is nonspecific with the mass demonstrating a heterogeneous solid structure. CT clearly demonstrates the tumor; the relationship to the vessels is best shown with helical acquisition. CT is the most sensitive method of detecting calcifications, which are present in 2.4%–40% of cases (16,19), although none was observed in our case (Fig 5). Areas of low attenuation that do not enhance are common. Enhancement is usually poor. Early enhancement of linear septa has not been reported.
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Figure 5a. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5b. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5c. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5d. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5e. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5f. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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Figure 5g. Ganglioneuroma. (a) Spin-echo T2-weighted MR image (2,000/90) shows a moderately hyperintense mass. (b) T1-weighted MR image (690/12) shows a homogeneously hypointense mass. The lesion is close to the inferior vena cava (*) and pancreatic head (arrow). (c) FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained immediately after injection of gadolinium contrast material shows enhancement of only fine septa. (d, e) Corresponding MR images obtained 2 minutes (d) and 4 minutes (e) after contrast material injection show delayed incomplete filling of the mass. (f) Photograph of the gross specimen shows a densely fibrous, well-limited tumor. Scale is in centimeters. (g) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows bundles of ganglion cells (*) encompassing the adrenal gland (arrow).
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An interesting pattern consists of delayed heterogeneous uptake of contrast material; the result is incomplete filling of the tumor without a centripetal tendency. This pattern was reported by Ichikawa et al (17,18), who attributed such enhancement to the presence of abundant myxoid matrices, which explains the progressive accumulation of contrast material in the extracellular space. According to Ichikawa et al (17,18), this pathologic characteristic may also explain the MR imaging appearance of ganglioneuroma, which is hypointense on T1-weighted images and heterogeneously but markedly hyperintense on T2-weighted images. However, in our experience, the tumor was only slightly hyperintense on T2-weighted images and the histologic study did not reveal abundant myxoid matrices.
Angiosarcoma
Malignant mesenchymal tumors of the adrenal gland are extremely uncommon. The few reported cases of soft-tissue sarcoma have included tumors of vascular and smooth muscle origin (20). Leiomyosarcomas probably arise from the smooth muscle wall of the adrenal veins (21). Two cases of angiosarcoma of the adrenal gland have been reported (22,23); one case occurred in association with an adrenal hemangioma. The main diagnostic difficulty is distinguishing the adrenal tumor from a metastatic lesion or from direct extension of a retroperitoneal tumor.
The case that we report appeared as a mass with punctate calcifications, intense peripheral enhancement, and a necrotic center. The lesion was associated with an intrahepatic hematoma due to local hemorrhage from the tumor (Fig 6).
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Figure 6a. Angiosarcoma. (a) Contrast-enhanced CT scan shows a mass with soft-tissue attenuation and punctate calcifications. Enhancement is intense peripherally, and the center of the lesion appears necrotic. There is an associated intrahepatic hematoma (*) due to local hemorrhage from the tumor. (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained after injection of contrast material shows intense peripheral enhancement, which reveals the necrotic center. The adjacent hematoma appears as a cystic lesion. (c) Photograph of the gross specimen shows a bulky, irregular mass with internal vascular lakes. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows vascular clefts (*) lined with one or more layers of tumor cells.
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Figure 6b. Angiosarcoma. (a) Contrast-enhanced CT scan shows a mass with soft-tissue attenuation and punctate calcifications. Enhancement is intense peripherally, and the center of the lesion appears necrotic. There is an associated intrahepatic hematoma (*) due to local hemorrhage from the tumor. (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained after injection of contrast material shows intense peripheral enhancement, which reveals the necrotic center. The adjacent hematoma appears as a cystic lesion. (c) Photograph of the gross specimen shows a bulky, irregular mass with internal vascular lakes. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows vascular clefts (*) lined with one or more layers of tumor cells.
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Figure 6c. Angiosarcoma. (a) Contrast-enhanced CT scan shows a mass with soft-tissue attenuation and punctate calcifications. Enhancement is intense peripherally, and the center of the lesion appears necrotic. There is an associated intrahepatic hematoma (*) due to local hemorrhage from the tumor. (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained after injection of contrast material shows intense peripheral enhancement, which reveals the necrotic center. The adjacent hematoma appears as a cystic lesion. (c) Photograph of the gross specimen shows a bulky, irregular mass with internal vascular lakes. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows vascular clefts (*) lined with one or more layers of tumor cells.
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Figure 6d. Angiosarcoma. (a) Contrast-enhanced CT scan shows a mass with soft-tissue attenuation and punctate calcifications. Enhancement is intense peripherally, and the center of the lesion appears necrotic. There is an associated intrahepatic hematoma (*) due to local hemorrhage from the tumor. (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) obtained after injection of contrast material shows intense peripheral enhancement, which reveals the necrotic center. The adjacent hematoma appears as a cystic lesion. (c) Photograph of the gross specimen shows a bulky, irregular mass with internal vascular lakes. (d) Photomicrograph (original magnification, x10; hematoxylin-eosin stain) shows vascular clefts (*) lined with one or more layers of tumor cells.
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Primary Malignant Melanoma
Primary malignant melanoma of the adrenal gland is very rare. The main diagnostic difficulty is distinguishing primary melanoma in the adrenal gland from a metastatic lesion arising from a melanoma in the skin or another location (24). The existence of primary melanoma of the adrenal gland is explained by the neuroectodermal origin of the medulla. Chromaffin cells and melanocytes have a common embryogenesis; histologic similarities also exist with pheochromocytoma.
Diagnostic criteria for primary adrenal melanoma are unilateral involvement, the presence of melanin in the tumor, absence of prior or current melanoma (of cutaneous, squamous mucosal, or ocular origin), and absence of an extraadrenal lesion at autopsy (25).
The tumor is usually voluminous, black, hemorrhagic, and necrotic. Radiologic features are not specific (26). Calcifications are not common. However, the case that we report appeared as a bulky right adrenal mass that was necrotic and calcified with associated hepatic metastases (Fig 7).
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Figure 7. Primary malignant melanoma. Contrast-enhanced CT scan shows a necrotic and calcified adrenal mass (*) with associated hepatic metastases (arrow). (Courtesy of J. L. Puech, MD, Clinique Saint-Jean Languedoc, Toulouse, France.)
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SOLID FATTY LESIONS
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Myelolipoma
Adrenal myelolipoma is a rare benign tumor composed of mature fat tissue associated with proliferating hematopoietic cells. The prevalence at autopsy has been estimated to be 0.08%–0.4% (27,28).
Although adrenal myelolipoma is asymptomatic in most cases, it may cause discomfort or flank pain due to compression or hemorrhage. An association with endocrine dysfunction (Cushing syndrome, Conn syndrome, adrenogenital syndrome) has been reported, but this association is probably related to coexistence with adenoma (29–31).
US findings may suggest the diagnosis when a hyperechoic adrenal lesion is demonstrated (Fig 8). CT features are characteristic if a lipid content is demonstrated (32,33). Use of thin sections is recommended if the fatty tissue is not predominant. CT values are higher than those of retroperitoneal fat because of the presence of hematopoietic tissue in myelolipoma. Calcifications are rarely present and are usually punctate. Sometimes, this classic pattern may be modified by intratumoral hemorrhage. Fat has high signal intensity on T1-weighted and T2-weighted MR images, but the contrast enhancement is weak. Fat saturation is useful in cases with a poor lipid content. MR imaging usually provides little information about tissue characteristics but does help determine the origin of the tumor.
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Figure 8a. Myelolipoma. (a) US scan shows a hyperechoic, well-limited mass of the right adrenal gland. (b) CT scan obtained after injection of contrast material shows a well-defined mass with hypoattenuating areas, which indicate a fat content. (c) Spin-echo T1-weighted MR image (690/12) shows high signal intensity in some areas of the tumor (arrows). This high signal intensity is comparable with that of fat. (d) Photograph of the gross specimen shows an association of soft-tissue (*) and fatty (arrows) components.
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Figure 8b. Myelolipoma. (a) US scan shows a hyperechoic, well-limited mass of the right adrenal gland. (b) CT scan obtained after injection of contrast material shows a well-defined mass with hypoattenuating areas, which indicate a fat content. (c) Spin-echo T1-weighted MR image (690/12) shows high signal intensity in some areas of the tumor (arrows). This high signal intensity is comparable with that of fat. (d) Photograph of the gross specimen shows an association of soft-tissue (*) and fatty (arrows) components.
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Figure 8c. Myelolipoma. (a) US scan shows a hyperechoic, well-limited mass of the right adrenal gland. (b) CT scan obtained after injection of contrast material shows a well-defined mass with hypoattenuating areas, which indicate a fat content. (c) Spin-echo T1-weighted MR image (690/12) shows high signal intensity in some areas of the tumor (arrows). This high signal intensity is comparable with that of fat. (d) Photograph of the gross specimen shows an association of soft-tissue (*) and fatty (arrows) components.
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Figure 8d. Myelolipoma. (a) US scan shows a hyperechoic, well-limited mass of the right adrenal gland. (b) CT scan obtained after injection of contrast material shows a well-defined mass with hypoattenuating areas, which indicate a fat content. (c) Spin-echo T1-weighted MR image (690/12) shows high signal intensity in some areas of the tumor (arrows). This high signal intensity is comparable with that of fat. (d) Photograph of the gross specimen shows an association of soft-tissue (*) and fatty (arrows) components.
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As for differential diagnosis, lipoma and liposarcoma must be considered in the case of a mass with a significant lipid content, but an adrenal location of these tumors is very rare. Hemorrhagic adrenal adenoma, adrenocortical carcinoma, and adenocarcinoma metastatic to the adrenal gland may also simulate myelolipoma (34–36). Angiomyolipoma of the upper renal pole is sometimes difficult to distinguish from adrenal myelolipoma, but multiplanar CT reconstruction images and MR imaging allow assessment of renal integrity.
Collision Tumor
The presence of a macroscopic fat content within an adrenal mass may stem from the association of a solid soft-tissue lesion with a myelolipoma. Such an association, which we have encountered in two cases (Figs 9, 10), has been reported more frequently for adenomas (37–39) than for pheochromocytomas (40) or metastases (41). The term collision tumor refers to independently coexisting neoplasms without significant tissue admixture. The term composite tumor refers to coexisting neoplasms with considerable admixture of the two different cell types. Our two cases can be considered collision tumors in view of the sharp demarcation between myelolipomatous and adenomatous components.
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Figure 9a. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 9b. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 9c. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 9d. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 9e. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 9f. Collision tumor with associated myelolipoma and adenoma. (a) Contrast-enhanced CT scan shows a regular, ovoid mass of the right adrenal gland with a fatty component (-84 HU). (b) Coronal FLASH two-dimensional gradient-echo T1-weighted MR image (690/12) shows a heterogeneous mass with some well-limited hyperintense areas (arrow). (c) T2-weighted MR image (2,000/90) shows that these areas (arrow) have the same high signal intensity as retroperitoneal fat. (d) T1-weighted MR image (690/12) obtained with fat suppression shows heterogeneous enhancement and the lipidic nature of the corresponding areas (arrow). (e) Photograph of the gross specimen shows the lipidic areas as yellow nodules (arrowheads). (f) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows the association of adenomatous tissue (white *), fatty tissue (solid arrow), fibrotic tissue (open arrow), and hemorrhagic vascular structures (black *).
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Figure 10a. Collision tumor with associated myelolipoma and adenoma. (a, b) Nonenhanced (a) and contrast-enhanced (b) CT scans show a heterogeneous mass of the left adrenal gland. The mass represents the association of a soft-tissue mass, calcification, and a fatty component. (c) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a sharp demarcation between myelolipomatous (left side of image) and adenomatous (right side of image) elements.
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Figure 10b. Collision tumor with associated myelolipoma and adenoma. (a, b) Nonenhanced (a) and contrast-enhanced (b) CT scans show a heterogeneous mass of the left adrenal gland. The mass represents the association of a soft-tissue mass, calcification, and a fatty component. (c) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a sharp demarcation between myelolipomatous (left side of image) and adenomatous (right side of image) elements.
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Figure 10c. Collision tumor with associated myelolipoma and adenoma. (a, b) Nonenhanced (a) and contrast-enhanced (b) CT scans show a heterogeneous mass of the left adrenal gland. The mass represents the association of a soft-tissue mass, calcification, and a fatty component. (c) Photomicrograph (original magnification, x4; hematoxylin-eosin stain) shows a sharp demarcation between myelolipomatous (left side of image) and adenomatous (right side of image) elements.
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Myelolipomatous foci are commonly seen in the adrenal gland in Cushing disease (39), but the increasing frequency of reports of the myelolipoma-adenoma association is probably related to the increasing incidental detection of adrenal tumors. The cause of this association is debated; some authors suggest that the microenvironment may play a role in the development of the myelolipomatous foci (40). Myelolipomas also develop in the course of regressive or necrotic degeneration of cortical cells by hormonal disorders, stress, circulatory disturbance, or other unknown factors (28). Whatever the mechanism, this association reminds us that the presence of fat within a large soft-tissue mass is not specific for myelolipoma.
When the lipidic component is predominant, the lesion can be managed as a myelolipoma. The decision to perform surgery is based on the importance of the symptoms; in the case of a large tumor, this decision is based on the risk of hemorrhage. If the nonfatty component predominates, the approach should be more delicate and the lesion should be managed like other non–fat-containing tumors.
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CONCLUSIONS
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Most of the adrenal masses discussed in this article do not have specific imaging features. The liquid content of adrenal cysts is clearly demonstrated on US scans, CT scans, and MR images. Nevertheless, the histologic type cannot be predicted except at some stages of hydatid disease in which pathognomonic features are present. The most typical imaging features of hemangioma are phleboliths and enhancement of peripheral vascular lakes. Ganglioneuroma has nonspecific radiologic features, but this diagnosis should be considered in cases with early enhancement of fine septa and progressive filling. The radiologic features of angiosarcoma and primary malignant melanoma are nonspecific. A macroscopic lipid content within an adrenal mass is theoretically characteristic of myelolipoma. However, this diagnosis should be made cautiously, especially when the lipid content is not predominant, because of the possible association with an adenoma.
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Footnotes
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Abbreviation: FLASH = fast low-angle shot
CME FEATURE This
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Abstract
INTRODUCTION
