A Rare Case of Poorly Differentiated Synovial Sarcoma of the Superficial Neck: Diagnostic Approach in a Fine‐Needle Aspiration Specimen

ABSTRACT

Synovial sarcoma (SS) is a rare and aggressive soft tissue malignancy that is more common in the extremities and has an unusual occurrence in the head and neck region. SS has two main subtypes: biphasic and monophasic. Some rare subtypes include poorly differentiated (round cell), monophasic epithelial, calcifying/ossifying, and myxoid types. Here, we present a rare case of a 61‐year‐old male with two left‐sided neck masses abutting the supraclavicular fossa. One of the masses was present for over a year and gradually increased in size. The second mass was noticed a week before he presented to our institution. The fine‐needle aspiration (FNA) specimen consists of tight clusters of monotonous epithelioid cells with scant amphophilic cytoplasm, hyperchromatic ovoid nuclei, increased mitotic activity (up to 6 per 10 HPF), and scattered apoptotic bodies. The tumor cells showed patchy expression for cytokeratins and claudin‐4 and demonstrated strong and diffuse expression for TLE and SS18‐SSX, consistent with a diagnosis of synovial sarcoma. Deep morphological analysis and targeted immunohistochemical workup can aid in the diagnosis of this rare entity in the head and neck area.