Pseudoglandular schwannoma mimicking alveolar rhabdomyosarcoma: A diagnostic challenge on fine-needle cytology

Pseudoglandular schwannoma (PGS) is a rare morphological variant of benign schwannoma. PGS is quite distinct from the somewhat better characterized glandular schwannoma variant. PGS is characterized by the presence of gland-like structures lined with pseudocolumnar or cuboidal-like neoplastic Schwann cells lining variably sized cystic space cells. Herein, we describe a rare case of PGS in a 17-year-old adolescent boy with a neck mass 8.5 cm in diameter present for 2 years with a recent increase in size. Fine-needle aspiration (FNA) demonstrated abundant rhabdoid-like cuboidal cells, plasmacytoid cells, binucleation, clusters of round to oval cells with scant cytoplasm, and a lack of stromal cells with spindle or oval nuclei. These findings were challenging and were reminiscent of alveolar rhabdomyosarcoma on FNA. Magnetic resonance imaging was also suggestive of malignancy. However, the histologic picture and the immunohistochemical analysis of the resected mass were consisted with PGS. The numerous rhabdoid-like cuboidal neoplastic Schwann cells with a plasmacytoid appearance, paving cystic spaces, and the lack of blunt-ended proliferating stromal cells on smears mimicked alveolar rhabdomyosarcoma on FNA. To our knowledge, cytological features of PGS have not been previously reported. This is the first published report of an unusual PGS case located in the neck region causing a diagnostic dilemma on cytology.