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

Abstract

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. K E Y W O R D S alveolar rhabdomyosarcoma, fine-needle aspiration cytology, glandular schwannoma, pseudoglandular schwannoma

Malignant granular cell tumors: Combining cytological and pathological findings for a definitive diagnosis

“…Although few reports have described the FNA cytology findings of MGCTs, previous reports documented FNA cytology findings such as nuclear pleomorphism, spindle‐shaped cells, increased N:C ratio, vesicular nuclei with enlarged nucleoli, granular chromatin, and hyperchromasia indicative of a malignant nature in addition to characteristic findings of GCT 6–9 . However, other malignancies such as malignant melanoma, 6,11 rhabdomyosarcoma, 6,12 alveolar soft part sarcoma, 6,8 and apocrine carcinoma 6,13 showing granular cytoplasm, nuclear pleomorphism, and, occasionally, spindle‐shaped or epithelioid cells should be considered for differential diagnoses of MGCT. The main cytomorphological and IHC findings for differential diagnoses are shown in Table 1.…”