Extranodal follicular dendritic cell sarcoma of the pharyngeal region: a potential diagnostic pitfall, with literature review.

Extranodal follicular dendritic cell sarcoma (FDCS) of the pharyngeal region is a rare malignant tumor recognized in recent years, with approximately 37 cases so far reported in the literature. It is often not considered at the initial evaluation and may be misdiagnosed in a small biopsy specimen. We report 4 cases of extranodal FDCS, 2 cases in the nasopharynx that were diagnosed as undifferentiated carcinomas because they were characterized by syncytial epithelial cells with sheet or nest-like distribution and 2 cases in the tonsil and soft palate that were characterized by vaguely concentric whorls consisting of spindle to ovoid cells. The latter case was diagnosed as ectopic meningioma. The analysis of all cases from the literature and ours shows that 58% (21/36) of the cases are misdiagnosed initially, often as undifferentiated carcinoma or meningioma, which the differential diagnoses should be mostly focused on. With a median follow-up of 27 months, the recurrence, metastasis, and mortality rates are 23%, 21%, and 3%, respectively, suggesting that extranodal FDCS of the pharyngeal region remains a low-grade sarcoma. Radical surgery is recommended, whereas there is no evidence to support adjuvant therapy.