Fine-Needle Aspiration Cytology of Follicular Dendritic Cell Sarcoma of Cervical Lymph Node: A Challenging Diagnosis.

Follicular dendritic cell sarcoma (FDCS) is a rare malignant tumor that could arise in both nodal and extranodal sites, with only nine previously reported cases demonstrating cytologic features. In this report, we describe a case of FDCS in a 60-year-old female who presented with neck mass. Fine-needle aspiration cytology and subsequent core biopsy were suggestive of metastatic carcinoma. The cytologic features were epithelioid-to-spindle cell morphology, vesicular nuclei, prominent nucleoli, intranuclear inclusions, and occasional binucleated and multinucleated forms. However, absence of cytokeratin expression was against the diagnosis of metastatic carcinoma. The definitive diagnosis was reached by the demonstration of CD21 and CD23 expression. The pathologist should be aware of this rare malignant tumor, especially its cytologic features in aspirated material. The differential diagnosis in the above case was metastatic carcinoma, melanoma, and malignant granular cell tumor. The demonstration of expression of one or more dendritic cell marker is the clue for the diagnosis, which could be applied on cytological preparations with sufficient material.