bromochloroacetic-acid and Dendritic-Cell-Sarcoma--Follicular

Extranodal follicular dendritic cell sarcomas are infrequent diagnostically challenging tumors. Because of their rarity, heterogeneous histomorphologic features and variable histologic grades a significant number of extranodal lesions are prone to be misdiagnosed. Even though they have a characteristic immunoprofile, expression of a range of nonspecific markers is well documented. Even though they are typically negative for keratins, few authors have reported lesions expressing keratin. Keratin expressing tumors are more likely to be misinterpreted by pathologists further deterring their inclusion in the differential diagnosis. We report an intraabdominal mesenteric follicular dendritic cell sarcoma in a 44-year-old male that immunophenotypically expressed keratin antigens. The lesion showed a high-grade pleomorphic epithelioid appearance and the initial differential diagnosis included lymphoma, sarcomas, melanoma, and carcinomas. Follicular dendritic cell sarcoma was not considered. Expression of epithelial membrane antigen and keratin further deterred the diagnosis which was reached only after extensive use of immunomarkers. The tumor cells expressed CD21, CD23, and D2-40. Morphologically, the tumor showed some thymoma-like features with occasional TDT-expressing background T-lymphocytes. These features were hints to reconsider our differential diagnosis to include follicular dendritic cell tumors. Awareness of this aberrant staining of epithelial immunomarkers and attention to certain clues should encourage pathologists to consider this entity. Speculative assumptions may explain this unusual keratin expression in some lesions. The histomorphologic and immunohistochemical heterogeneity may suggest different variants and grades of follicular dendritic cell sarcomas. The prevalence, importance, and histogenesis of keratin expression in follicular dendritic cell sarcomas warrant further studies.

Topics: Adult; Biomarkers, Tumor; Carcinoma; Dendritic Cell Sarcoma, Follicular; Dendritic Cells, Follicular; Diagnosis, Differential; Humans; Keratins; Male; Sarcoma

Two cases of primary follicular dendritic cell sarcoma (FDCS) of the pleura are presented. The patients are a woman 76-years-old and a man 64-years-old who presented with nonspecific symptoms including chest pain, dyspnea, and cough. Clinical history did not disclose any pertinent history of previous malignancy. Diagnostic imaging showed the presence of a pleural-based mass in both patients and a thoracotomy with resection of the pleural mass was performed. Both tumors were described as solid, light tan, and with ill-defined borders. Histologically, both tumors showed similar histological features, namely the presence of a spindle cellular proliferation composed of elongated cells with fibrillary cytoplasm, oval nuclei, and conspicuous nucleoli. Mild to moderate cellular atypia was present, while mitotic figures ranged from 3 to 4 per 10 high power fields. Mature lymphocytes and plasma cells were also present dispersed throughout the tumor. Immunohistochemical stains in both cases show positive staining for CD21 and CD35 while focal staining was present for D2-40 and clusterin, while negative for other markers including keratin, desmin, S-100 protein, calretinin, and STAT-6. Clinical follow up shows that both patients have remained alive 12 and 14 months after initial diagnosis. The cases herein described represent an unusual occurrence of FDCS arising in the pleural surface and one that must be kept in mind when dealing with spindle cell tumors of the pleura.

Topics: Aged; Biomarkers, Tumor; Dendritic Cell Sarcoma, Follicular; Female; Humans; Keratins; Male; Middle Aged; Pleura; S100 Proteins