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EDUCATION EXHIBIT |
Department of Radiologic Pathology, Armed Forces Institute of Pathology, Washington, DC, Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md
PTCLs represent a diverse group of neoplasms that are derived from mature T cells. Although some of the diseases in this group may have a protracted clinical course, the majority are among the most aggressive hematopoietic and lymphoid neoplasms. In general, they have a poorer response to therapy and shorter survival times than B-cell lymphomas and Hodgkin lymphoma. Fortunately, PTCLs are relatively uncommon, representing 12% of all non-Hodgkin lymphomas (1).
Cytologic features and immunophenotypic markers have not been useful in the accurate pathologic diagnosis of PTCLs (2). Unlike with B-cell lymphomas, immunophenotypic variation exists within specific disease entities and many antigens are shared by different diseases. In addition, specific genetic abnormalities have not been identified for many of the PTCLs. Therefore, the diagnostic and classification system for PTCLs proposed by the World Health Organization emphasizes integrating clinical manifestations with morphologic, genetic, and immunologic features (3). The clinical syndrome and disease location (nodal vs extranodal) are important not only in diagnosis but also in staging and prognosis.
In this issue of RadioGraphics, Lee et al (4) superbly illustrate the imaging and pathologic spectrum of PTCLs. The diseases that make up PTCL have complex clinical and pathologic features despite their nonspecific imaging appearances. We believe that three of the entities described by Lee et al (4) are worthy of further comment: nasal NK/T-cell lymphoma, enteropathy-type T-cell lymphoma, and mycosis fungoides/Sézary syndrome.
Nasal NK/T-cell lymphoma manifests as an impressive lesion in the nasal cavity, often with bone destruction and extension into the nasopharynx or palate. The CT and MR imaging findings are nonspecific, and it usually cannot be differentiated from other neoplasms such as squamous cell carcinoma, minor salivary gland tumors, or rhabdomyosarcoma and aggressive nonneoplastic conditions such as Wegener granulomatosis, sarcoidosis, cocaine abuse, leprosy, or syphilis. It deserves mention that T2-weighted MR images may occasionally show slight decreased signal intensity of the tumor mass. This finding should raise suspicion for the diagnosis of lymphoma.
Nasal NK/T-cell lymphoma may also occur in the gastrointestinal tract and should be considered in the differential diagnosis for enteropathy-type T-cell lymphoma of the gastrointestinal tract (5,6). Enteropathy-type T-cell lymphoma of the gastrointestinal tract is rare, accounting for less than 1% of non-Hodgkin lymphomas (1). Unlike the more common B-cell lymphomas of the gastrointestinal tract, which may manifest as bulky annular masses or polypoid lesions in the distal small intestine, enteropathy-type T-cell lymphoma typically forms circumferential ulcers with short strictures in the proximal small intestine. Thick, nodular small bowel folds have also been reported as a manifestation of enteropathy-type T-cell lymphoma (7). Mesenteric adenopathy is typically identified at CT (8).
The relationship between celiac disease and enteropathy-type T-cell lymphoma is unclear, and the present consensus is that not all cases occur in the setting of celiac disease (9). Most patients have adult- or childhood-onset celiac disease. There are clearly cases, however, in which there is no history of celiac disease or biopsy evidence of gluten sensitivity. Some have suggested that these patients may have latent celiac disease in which the jejunal mucosa is normal histologically. However, this has not been firmly established.
Ulcerative jejunoileitis is a rare complication of celiac disease that is associated with thickened folds, multiple ulcers, strictures, and obstruction. Not only is its clinical and radiologic appearance identical to that of enteropathy-type T-cell lymphoma, but ulcerative jejunoileitis may coexist with lymphoma (10). Therefore, careful histopathologic examination and immunologic staining of tissue removed in patients with ulcerative jejunoileitis is recommended to identify occult lymphoma (9).
Mycosis fungoides and Sézary syndrome are the most common forms of cutaneous T-cell lymphoma. Mycosis fungoides typically has a long natural history. Those with limited disease have similar survival rates as the normal population. In contrast, Sézary syndrome has an aggressive course with a 5-year survival rate of 10%–20% (11). CT for staging and follow-up of lymphadenopathy and visceral organ involvement is clearly indicated in patients with advanced disease (mycosis fungoides stage > I), Sézary syndrome, and atypical variants of cutaneous T-cell lymphoma. However, the literature is not clear on the use of CT during the initial staging of patients with clinical stage I mycosis fungoides. Although some studies report no benefit from the routine use of CT in patients with early-stage disease (12,13), others report clear benefit in staging, management, and prognosis (14–16). Bass et al (16) emphasize the detection of benign reactive adenopathy (dermatopathic adenopathy) as an important prognostic factor and the use of chest, abdominal, and pelvic CT for detection of clinically occult adenopathy.
In conclusion, PTCL represents a diverse group of neoplasms that may involve many organs within the body. The imaging features are often nonspecific. The diagnosis is based on clinical and pathologic features. However, knowledge of the disease spectrum is important for radiologists since imaging plays a crucial role in staging and management.
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