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(Radiographics. 1999;19:807-811.)
© RSNA, 1999

SPECIAL EXHIBITS

Residents' Teaching Files1

Mucinous Cystic Neoplasm of the Pancreas

Jose E. de Lima, Jr, MD, Marcia C. Javitt, MD and Sharad C. Mathur, MD

1 From the Departments of Radiology (J.E.d.L., M.C.J.) and Pathology (S.C.M.), The George Washington University Medical Center, 901 23rd St NW, Washington, DC 20037. Received November 20, 1998; revision requested January 4, 1999, and received February 3; accepted February 4. Address reprint requests to J.E.d.L.

Index Terms: Pancreas, cysts, 770.31222 • Pancreas, neoplasms, 770.31222


   INTRODUCTION
Top
 INTRODUCTION
CASE PRESENTATION
 DISCUSSION
 CONCLUSIONS
 References
 
Most cystic lesions of the pancreas are pseudocysts; only rare cases are related to proliferative disease because true cysts of the pancreas are rather uncommon. Benign cystic neoplasms are of two types: microcystic, also known as serous cystadenoma, and macrocystic, also known as mucinous cystic neoplasm. These unusual proliferative pancreatic cysts have a slow growth rate and are frequently large when they are symptomatic. The less common malignant form, cystadenocarcinoma, has clinical features similar to those of the benign variants. The diagnosis requires histopathologic confirmation.

Most patients present with a long-standing history of intermittent abdominal or lower back pain, nausea and vomiting, and occasionally diarrhea and early satiety. At physical examination, a left upper quadrant mass can often be palpated, especially on deep inspiration. Laboratory investigations are not helpful in the diagnosis.

Differentiation between pseudocysts and cystic neoplasms is of utmost importance because the treatment options are completely different. Even though an accurate distinction can be made in most cases, there are many published reports of various cystic neoplasms masquerading as pseudocysts. Ultrasonography (US) can be a useful screening tool, but enhanced computed tomography (CT) better demonstrates the lesion in most cases.

We describe a representative case of mucinous cystic neoplasm of the pancreas in which the diagnosis was accurately verified with CT.


   CASE PRESENTATION
Top
 INTRODUCTION
 CASE PRESENTATION
DISCUSSION
 CONCLUSIONS
 References
 
A 43-year-old woman with no significant medical history presented for evaluation of left upper quadrant and epigastric pain that radiated to the back. She denied alcohol consumption, trauma, and previous pancreatitis. She also denied significant nausea, vomiting, dyspepsia, diarrhea, and weight loss. Initial laboratory values, which included a complete blood cell count, electrolyte levels, results of liver function tests, and pancreatic enzyme levels, were normal. Physical examination revealed a large, firm, palpable mass in the left upper quadrant.

A scout radiograph of the abdomen demonstrated a large mass of soft-tissue opacity in the left upper quadrant that displaced bowel loops. CT of the abdomen and pelvis demonstrated an 18 x 18 x 15-cm, well-circumscribed, lobulated, multiseptated, calcified, cystic pancreatic mass. It extended to the abdominal wall anteriorly with displacement of the large and small intestine, to the spleen laterally, and to the left kidney posteriorly with slight compression of the kidney but no hydronephrosis. The head of the pancreas and part of the body were normal. The distal pancreatic body and the pancreatic tail were replaced by the mass. There were no signs of tumor invasion of adjacent organs (Figs 1, 2). Metastases, ascites, and lymphadenopathy were not present. CT scans of the pelvis were normal.



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  		Figure 1. Figures 1, 2. (1) CT scan shows a large cystic mass with evident septation in the left upper quadrant that displaces bowel loops. The mass is well circumscribed, and no signs of adjacent organ invasion can be seen. (2) CT scan of an upper portion of the mass shows its relationship to the remainder of the pancreas. Gross calcifications are noted within the cyst wall. Again, the cystic nature of the mass and the septations are clearly seen.

 


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  		Figure 2. Figures 1, 2. (1) CT scan shows a large cystic mass with evident septation in the left upper quadrant that displaces bowel loops. The mass is well circumscribed, and no signs of adjacent organ invasion can be seen. (2) CT scan of an upper portion of the mass shows its relationship to the remainder of the pancreas. Gross calcifications are noted within the cyst wall. Again, the cystic nature of the mass and the septations are clearly seen.

 
At surgery, an approximately 19 x 17 x 15-cm cystic tumor was removed by means of partial distal pancreatectomy (Fig 3). Splenectomy was performed because of adhesions to the spleen. Drainage of the multiple cysts produced 3 L of thick, dark brown fluid. At dissection, the cysts had a wall thickness of 1.5–3.5 cm. The walls were composed of homogeneous grayish white and glistening tan tissue. Thick, brown, bloody fluid and an inner lining of old clotted blood and regions of smooth, glistening epithelial lining were noted on opening the cysts. No papillary or solid areas were present.



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  		Figure 3.  Photograph of the mass during surgical resection shows its large size and smooth, well-defined margins.

 
Histologic examination of the cyst wall showed mucin-producing columnar epithelium overlying dense stroma and fibrous tissue (Fig 4a). Extensive sampling revealed a few areas of micropapillary epithelial pattern with mild cytologic atypia and some degree of nuclear crowding and stratification (Fig 4b). Rare mitotic figures were observed. There was no evidence of stromal invasion or frankly malignant epithelium. Pancreatic acini or islets were not present in the cyst wall. The histopathologic diagnosis was mucinous cystic neoplasm of the pancreas with low malignant potential.



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  		Figure 4a.  (a) Photomicrograph (original magnification, x25; hematoxylin-eosin stain) of the cyst wall shows mucinous epithelium overlying dense stroma and fibrous tissue. (b) Photomicrograph (original magnification, x50; hematoxylin-eosin stain) shows a micropapillary epithelial pattern with mild atypia and nuclear crowding.

 


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  		Figure 4b.  (a) Photomicrograph (original magnification, x25; hematoxylin-eosin stain) of the cyst wall shows mucinous epithelium overlying dense stroma and fibrous tissue. (b) Photomicrograph (original magnification, x50; hematoxylin-eosin stain) shows a micropapillary epithelial pattern with mild atypia and nuclear crowding.

 

   DISCUSSION
Top
 INTRODUCTION
 CASE PRESENTATION
 DISCUSSION
CONCLUSIONS
 References
 
Pancreatic cysts were recognized as early as 1816. The first known report was by Becourt in 1824, who noted a tumor "the size of a child's head and composed of very strong fibrous walls." In 1978, Compagno and Oertel (1) definitively established the link between histologic appearance and natural history. They demonstrated that the microcystic form is benign. However, they also demonstrated that the macrocystic form has a wide spectrum of malignant potential and should be considered premalignant or malignant. The reason is because 80% of mucinous cystic neoplasms harbor epithelium that is atypical or frankly malignant (2,3). This fact suggests that histologically benign-appearing neoplasms may behave in a malignant fashion. However, this observation also could be explained by transformation of a cystadenoma into a cystadenocarcinoma or by failure to detect a small focus of invasion due to inadequate histologic sampling.

True pancreatic cysts are uncommon, and it is difficult to determine their prevalence (2–4). Mucinous cystic neoplasms are proliferative cysts arising from the epithelium of the pancreatic ducts. They represent approximately 10% of pancreatic cysts and 1% of pancreatic neoplasms (5). Mucinous cystic neoplasms occur predominantly in middle-aged women (>95% of cases) (5) with a peak frequency between the 5th and 6th decades of life (3,4). These cysts usually arise from the pancreatic tail or sometimes the pancreatic body (>90% of cases) (2–6).

Mucinous cystic neoplasms can manifest as abdominal pain (which sometimes radiates to the back), a palpable mass, dyspepsia, anorexia with weight loss, or nausea and vomiting. They may also be found incidentally during the evaluation of unrelated symptoms or diseases. The symptoms of these tumors are commonly insidious and of long duration (2,7,8). Symptoms usually result from compression or displacement of neighboring organs when the tumor becomes large. In rare cases, the tumor may be locally invasive or metastasize to the liver. When located in the pancreatic head, the tumor can cause early jaundice; this symptom is noted most commonly in frankly malignant mucinous cystic tumors. There are rare reports of systemic manifestations caused by production of gastrin and vasoactive intestinal polypeptide by the tumor.

Radiography may demonstrate discontinuous peripheral calcifications, which occur in approximately 16% of cases. Calcifications (as in this case) or osseous metaplasia can be seen in the wall or septa of a mucinous cystic neoplasm. Mass effect with displacement of organs—especially bowel loops—can be seen.

At US, mucinous cystic neoplasms have a cystic appearance, showing multilocular characteristics with good through-transmission and posterior wall enhancement. The presence of six or fewer cysts greater than 2 cm in diameter is highly indicative of a mucinous cystic neoplasm (93% of cases) (5). This characteristic permits differentiation between these lesions and microcystic cystadenomas. Calcifications in the walls or septa of the cysts may produce echogenic foci with posterior shadowing. Cystic lesions within the liver can suggest the presence of metastatic disease.

CT of the abdomen is often the initial choice in the radiologic work-up of patients with vague abdominal symptoms. The CT findings are usually sufficient for a confident diagnosis, as in this case. CT demonstrates a well-encapsulated, lobulated, cystic mass. Because the cyst contents can vary in attenuation according to the degree of hemorrhage or protein in the mucoid cysts, different levels of attenuation may be seen within the cyst cavities. Cyst wall and septal calcifications are exquisitely demonstrated with CT. When local invasion is present, disruption of adjacent organ margins and obliteration of fat planes will be evident. Metastatic lesions appear as solitary or multiple cysts in the liver (5).

Magnetic resonance imaging does not demonstrate calcifications as well as does CT but can demonstrate the cystic nature of the lesion and its extent (5).

Fine-needle aspiration contributes little useful information, and the results can be misleading (2). However, an elevated level of amylase in the cystic fluid is suggestive of a pseudocyst, whereas an elevated level of carcinoembryonic antigen can be present in mucinous cystic neoplasm (6,9,10).

The main differential diagnosis is pancreatic pseudocyst, although numerous other lesions can simulate mucinous cystic neoplasms. Pseudocysts represent 85% of pancreatic cysts (6). Pancreatic pseudocysts usually complicate an episode of clinically apparent acute or chronic pancreatitis. A history of pancreatitis, trauma, or alcoholism; the temporal evolution of the lesion; and an elevated serum amylase level (noted in 65% of cases) are key to the diagnosis. Although pancreatic neoplasms rarely arise in the setting of pancreatitis, clinically and histopathologically evident pancreatitis has been reported in conjunction with pancreatic cystic neoplasms (6). The differential diagnosis can be especially difficult when a rare unilocular mucinous cystic neoplasm is encountered. Imaging results favor the diagnosis of a pseudocyst when peripancreatic fat stranding or calcifications associated with chronic pancreatitis are seen.

Serous cystadenoma has symptoms similar to those of mucinous cystic neoplasm but can be differentiated by evaluation of the size of the lesions and the number of septa. As stated previously, mucinous cystic neoplasms have six or fewer cysts greater than 2 cm in diameter; they will be correctly diagnosed by means of this criterion in 93% of cases with US and in 95% of cases with CT (5). The presence of adjacent organ invasion or hepatic metastatic disease virtually excludes serous cystadenoma.

Ductal adenocarcinoma and other types of pancreatic adenocarcinoma can manifest as partially cystic masses or cystic degeneration but are more aggressive, often demonstrating adenopathy, metastasis, and involvement of adjacent organs. Cystic metastases to the pancreas are not uncommon. Sources can be renal cell carcinoma, lung tumors, ovarian carcinoma, hepatocellular cancer, or melanoma. Metastases from ovarian carcinoma are the most likely to have a predominantly cystic appearance. Cystic metastases cannot be differentiated from mucinous cystic neoplasms radiographically. These neoplastic cysts have a rather characteristic appearance at gross analysis: round, smooth, grayish tan masses with relatively few loculi. The cyst wall is dense and fibrous, and focal calcifications may be present. The cut surface reveals a honeycomb of cysts of varying sizes, which are filled with a thick mucoid and viscous fluid. The fluid is often cloudy brown or hemorrhagic and may contain clotted blood and necrotic material.

Complete surgical resection of a mucinous cystic neoplasm is diagnostic and therapeutic. When the tumor is located in the pancreatic body or tail, a distal pancreatectomy is indicated. When the pancreatic head is the site of involvement, the Whipple operation may be required. If there are adhesions to the spleen or splenomegaly is present secondary to splenic vein thrombosis, splenectomy may be necessary (3,4,11,12).

With complete surgical excision, the prognosis for mucinous cystic neoplasm is very favorable. There are numerous documented cases in which the tumor was present for years before surgery, and long-term survivors after resection are common. The 5-year survival rate was 70% in one study (3) and 74.5% in a recent study of 50 patients (5). The prognosis for cystadenocarcinoma is considerably worse but is considered more hopeful than that for adenocarcinoma because some patients with metastases have had prolonged survival (3,4).


   CONCLUSIONS
Top
 INTRODUCTION
 CASE PRESENTATION
 DISCUSSION
 CONCLUSIONS
References
 
Mucinous cystic neoplasms of the pancreas typically arise within the pancreatic tail and manifest as large, multiloculated, cystic masses in middle-aged women. Although these neoplasms should be considered premalignant lesions, they are low-grade tumors that infrequently metastasize or invade surrounding structures. US and especially enhanced CT are the mainstays of radiologic evaluation. Differentiation from other cystic lesions of the pancreas can pose a problem especially when trying to distinguish a unilocular mucinous cystic neoplasm and a pseudocyst. Because the treatment for pseudocysts is essentially medical, as opposed to surgical resection in the case of mucinous cystic neoplasms, such differentiation is important and often depends on clinical correlation. Histopathologic confirmation is ultimately required. If complete resection is achieved, long-term survival can be expected.


   References
Top
 INTRODUCTION
 CASE PRESENTATION
 DISCUSSION
 CONCLUSIONS
 References
 

  1. Compagno J, Oertel JE. Mucinous cystic neoplasms of the pancreas with overt and latent malignancy (cystadenocarcinoma and cystadenoma): a clinicopathologic study of 41 cases. Am J Clin Pathol 1978; 69:573-580.[Medline]
  2. Hoover E, Natesha R, Dao A, Adams CZ, Jr, Barnwell S. Proliferative pancreatic cysts: pathogenesis and treatment options. Am J Surg 1991; 162:274-277.[Medline]
  3. Yang EY, Joehl RJ, Talamonti MS. Cystic neoplasms of the pancreas. J Am Coll Surg 1994; 179:747-757.[Medline]
  4. Barbee CL, DeMello FB, Grage TB. Cystadenoma and cystadenocarcinoma of the pancreas. J Surg Oncol 1976; 8:1-10.[Medline]
  5. Buetow PC, Rao P, Thompson LDR. Mucinous cystic neoplasms of the pancreas: radiologic-pathologic correlation. RadioGraphics 1998; 18:433-449.[Abstract]
  6. Sachs JR, Deren JJ, Sohn M, Nusbaum M. Mucinous cystadenoma: pitfalls of differential diagnosis. Am J Gastroenterol 1989; 84:811-816.[Medline]
  7. Lewandrowski K, Warshaw A, Compton C. Macrocystic serous cystadenoma of the pancreas: a morphologic variant differing from microcystic adenoma. Hum Pathol 1992; 23:871-875.[Medline]
  8. Doberstein C, Kirchner R, Gordon L, Silberman AW, Morgenstern L, Shapiro S. Cystic neoplasms of the pancreas. Mt Sinai J Med 1990; 57:102-105.[Medline]
  9. Young NA, Villani MA, Khoury P, Naryshkin S. Differential diagnosis of cystic neoplasms of the pancreas by fine-needle aspiration. Arch Pathol Lab Med 1991; 115:571-577.[Medline]
  10. Lewandrowski KB, Southern JF, Pins MR, Compton CC, Warshaw AL. Cyst fluid analysis in the differential diagnosis of pancreatic cysts: a comparison of pseudocysts, serous cystadenomas, mucinous cystic neoplasms, and mucinous cystadenocarcinoma. Ann Surg 1993; 217:41-47.[Medline]
  11. Delcore R, Thomas JH, Foster J, Hermreck AS. Characteristics of cystic neoplasms of the pancreas and results of aggressive surgical treatment. Am J Surg 1992; 164:441-442.
  12. Bergmann LS, Russel JC, Gladstone A, Devers T. Cystadenomas of the pancreas. Am Surg 1992; 58:65-71.[Medline]



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