Interdigitating dendritic reticulum cell tumor of lymph nodes: case report with differential diagnostic considerations.

A 66-yr-old man with a history of interdigitating reticulum cell tumor (IDRCT) presented with an enlarging right cervical lymph node suspicious of recurrent disease. He reported no fevers or night sweats and was otherwise asymptomatic at the time of the fine-needle aspiration (FNA). FNA of the lymph node showed a spindle cell lesion with plump, at times deeply convoluted, large nuclei, coarsely granular chromatin, with one or two distinct nucleoli, intimately associated with mature-appearing lymphocytes. A cell block was made and immunohistochemistry was carried out. Immunopositivity for vimentin, S-100, and CD68 and immunonegativity for CD21 and AE1/AE3 were noted. This case report is the first to illustrate the FNA cytomorphology of IDRCT and to discuss the cytologic differential diagnosis of this rare tumor type in lymph nodes.