Case Presentation - Winter, 2006

Follicular Dendritic Cell Sarcoma

ThinPrep® Non-gyn Cytology

NOTE: The diagnosis and analysis for this case study were provided by an independent physician. All conclusions and opinions are those of the physician and not Hologic, Inc.

History: 50 year old female

Specimen type: FNA of the left neck

Case provided by: Mount Auburn Hospital, Cambridge, Massachusetts

ThinPrep® Cytology Slide Description:

Cytologic diagnosis: Metastatic cancer involving the lymph node

Biopsy diagnosis: Follicular dendritic cell sarcoma

IPX Positive: Vimentin, CD23, Fascin (focal), EMA, CD68 (rare tumor cell)

IPX Negative: AE1/AE3, CK7, CK903, CAM5.2, HMB45, MART1, S-100, LCA, CD20, CD30, CD3, Desmin, SMA, Thyroglobulin

Follicular dendritic cell sarcomas are extremely rare neoplasms that originate from the follicular dendritic cells, located in primary and secondary lymphoid follicles. The role of follicular dendritic cells is to present antigen to B-cells, creating a primary immune response. These cells are most commonly present in lymph nodes, but can also be found in non-lymphoid organs, on epithelial surfaces and in the gastrointestinal tract.

Follicular dendritic cell sarcoma affects males and females equally, usually between the ages of 30-50 years. About 10-20% of these cases are associated with Castlemen's disease, a rare disorder that causes benign tumors, typically in lymphoid tissue throughout the body. Tumor sites include the lymph nodes, especially those in the cervical, mediastinal, axillary, retro-peritoneal or intestinal areas. Other sites include skin, tonsils, oral cavity, spleen, intestine, soft tissue and liver. A common presentation of follicular dendritic cell sarcoma is lymph node enlargement.

This tumor cannot be definitively diagnosed based on its cytomorphology. Follicular dendritic cell sarcomas can vary in their shape, size and color. Tumor cells can be polygonal, ovoid, or spindle shaped. The cells usually have indistinct cell borders with a moderate amount of cytoplasm that stains a light eosinophilic color. The nuclei are often oval to round with smooth contours, have fine chromatin, distinct nucleoli, and occasional nuclear pseudoinclusions. Nucleoplasm is either clear or granular. The cells often form syncytia.

In histologic sections, tumor cells can exhibit storiform, whorled, diffuse, fascicular, trabecular or follicle-like patterns, and usually present in more than one pattern. Mitotic counts vary by case and can range from 1-20 per high-power field. Scattered small lymphocytes are a common finding with these tumors. Networks of small blood vessels and coagulative necrosis have also been noted in some cases of follicular dendritic cell sarcomas. It has been noted that moderate nuclear pleomorphism, mitotic counts of greater than 5 per high-power field, and the presence of coagulative necrosis lead to greater morbidity and mortality.

The differential diagnoses of follicular dendritic cell sarcomas include the common tumors of the head and neck region, mediastinal masses arising with lymphoid milieu, ectopic meningioma, ectopic thymoma, malignant fibrous histiocytoma, amelanotic malignant melanoma, and undifferentiated carcinoma.

Treatment and Prognosis
An optimal treatment for follicular dendritic cell sarcoma has yet to be identified. Treatment can be tailored to the individual patient according to the location, or the predictors of aggressive behavior of the lesion, such as high mitotic count and presence of significant necrosis and cellular atypia. Excision of the lesion with or without the combination of either radiation or chemotherapy is common.

The recurrence rate for follicular dendritic cell sarcoma is 43%, the mortality rate is 17%, the metastasis rate is 24% and the median recurrence time is 12 months. Mortality and morbidity seem to increase as tumors grow larger than 6cm, if they are located intra-abdominally, and if there is a lack of postoperative adjuvant therapy.

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