“Medusa‐Head” cells, “Starfish” cells, and interconnecting long cytoplasmic processes as diagnostic cytologic clues for follicular dendritic cell sarcoma in fine needle aspiration samples

A 19-year-old woman with no significant medical history presented with a large mobile, nontender left neck mass posterior to the angle of the mandible that had not responded to a 3-week course of antibiotic treatment. The patient was otherwise asymptomatic and all her laboratory test results were within normal limits. A fine needle aspiration (FNA) of the neck mass performed at another hospital was diagnosed as showing “atypical cells”; upon review it was diagnosed as follicular dendritic cell sarcoma (FDCS). The most striking cytomorphologic feature seen in this highly cellular aspirate was the presence of long, slender, cytoplasmic processes surrounding the tumor cells circumferentially, and interconnecting them into a meshwork (Fig. 1A–D). These cytoplasmic processed were better seen in Diff-QuikVR preparations and were longer and more abundant in multinucleated cells. They appeared as long sweeping hair bundles, or like the serpents surrounding the head of the mythical monster Medusa (Fig. 2A– D). Shorter, less abundant or agglutinated cell processes were seen in Papanicolaou-stained smears and conferred the cells a starfish-like appearance (Fig. 3A–C). The tumor cells were frequently multinucleated or multilobated, and had pale granular or fibrillary cytoplasm. Their ovoid to spindle shaped nuclei had a thin chromatinic rim and irregular contours, showing grooves, clefts, notches and rare pseudoinclusions, finely granular, pale chromatin and visible to prominent nucleoli and even macronucleoli (Fig. 3D). The polygonal or spindle-shaped tumor cells were present singly, in syncytial sheets and loose cell aggregates of interconnected cells in a background of polymorphous lymphoid cells (Fig. 4A–C). The loose spindle or epithelioid cell aggregates interspersed with lymphocytes resembled either lymphohistiocytic aggregates of reactive lymph nodes of, due to the haphazard “fish-in-a-net” orientation or their nuclei, to granulomas (Fig. 4D). Cell block sections demonstrated atypical pleomorphic spindle cells with irregular nuclear contours, vesicular chromatin and prominent, sometimes multiple, nucleoli admixed with a small mature lymphocytes (Fig. 5A–C). The tumor cells stained for TTF-1, CD21, and CD23 (Fig. 5D), while D2-40, S-100, and CD68 were negative. Additional immunohistochemical stains performed at the outside institution were negative, including cytokeratins AE1/AE3, OSCAR, CK5, CK7, CK 8/18, and CK20, p16, S100, Melan A, CA-125, ER, thyroglobulin, PAX5, CD10, CD20, CD30, CD68, CD79a, ALK-1, cyclin D1, and MUM1. The small lymphocytes present in the background stained with CD45, CD3 and CD5. Department of Pathology, Loyola University Medical Center, Maywood, Illinois *Correspondence to: Stefan E. Pambuccian, MD, Department of Pathology, Loyola University Medical Center, 2160 S 1st Ave Suite 110 2242, Maywood, IL 60153. E-mail: spambuccian@lumc.edu Received 22 November 2016; Revised 22 December 2016; Accepted 3 January 2017 DOI: 10.1002/dc.23664 Published online 3 February 2017 in Wiley Online Library (wileyonlinelibrary.com).