Presence of eosinophilic intracytoplasmic inclusions diagnosed by fine needle aspiration cytology in perivascular epithelioid cell tumor (PEComa) arising from the cecum

Abstract

Perivascular epithelioid cell tumor, also known as PEComa or PEC tumor is a relatively rare mesenchymal neoplasm arising from the endothelial cells in the various body sites. The most common locations in the gastrointestinal sites are the colon followed by the small intestine, the rectum, and the stomach. However, PEComa arising from the cecum is an exceedingly rare entity. Our case is the fourth in the literature. Recently, we came across an interesting case of PEComa arising from the cecum having eosinophilic intracytoplasmic inclusions (EIIs) diagnosed by the fine needle aspiration cytology (FNAC). The presence of EIIs fin cytological material from a cecal PEComa has not previously been documented to the best of our knowledge. A 69-year-old man come to our hospital for an annual health check and both CT and endoscopic examination revealed a large obstructive tumor measuring 4.1 × 4.0 × 3.2 cm in the cecal submucosa. Laboratory tests showed no abnormalities of the tumor markers. Laparoscopic surgery was performed and subsequently, FNAC was performed on the surgical sample by using a 22G needle. Smears from FNAC were fixed with 95% ethanol alcohol and stained with Papanicolaou stain. Immunocytochemistry (ICC) was performed on spare fixed slides by using the Envision system HRP (DAKO; Denmark A/S). Antibodies to SMA (DAKO), HMB45 (DAKO), Melan A (DAKO), CD34 (DAKO), c-kit (DAKO), DOG1 (Nichirei, Japan), desmin (DAKO), S-100 (DAKO), AE1/AE3 (DAKO), ER (DAKO), Pg (DAKO), synaptophysin (DAKO), and (MIB-1) (DAKO) were employed by using the respective recommended dilution and demasking procedures by the producers. The FNAC sample revealed that most of the tumor cells either shed singly or formed small to large cohesive clusters. The neoplastic cells had high nuclear cytoplasmic (N/C) ratio with elongated slightly cyanophilic and granular cytoplasm and spindle-shaped nuclei. These latter had spindled shape with blunted ends, showed moderate pleomorphism with fine to coarsely granular chromatin and evident nucleoli. In addition, EIIs were noted in the cytoplasm of the tumor cells (Figure 1). Histopathology showed that the tumor cells with spindle-shaped and epithelioid features were originating from small vessels. Granular cytoplasms showed polygonal to fiber-like shape with EIIs as observed in smears. The nuclei showed granular chromatin and nuclear irregularity with large round nucleolus. The ICC of the tumor cells showed diffuse and granular positivity for HMB45, Melan A, SMA, CD34, and chromogranin A (Figure 2). c-kit, DOG1, desmin, S-100, AE1/AE3, ER, PgR, and synaptophysin stains were negative. MIB-1 was 2% for each high power magnification field (40×). On electron microscopy, melanosomes and myogenic filaments could be demonstrated in the cytoplasm of the tumor cells. Gene mutational analysis for KIT and PDGFα on frozen tissue did not show any significant results. TFE3 ICC staining in this case gave negative result. It is well known that PEComa lesions constitute a relatively rare nonepithelial group of neoplasms arising from various body sites. However, their pathogenesis, prognostic factors, cytological diagnostic criteria, and optimal treatment guidelines are not well established due to their relative rarity. In the present case, the FNAC sample from the cecal PEComa showed the following cytological features: small and large cohesive clusters of epithelioid and spindle-shaped cells, oval or elongated hyperchromatic nuclei with irregular margins, large and round nucleoli having intracytoplasmic EIIs and delicate vessels. Although, benign PEComa or clear cell “sugar” tumor from the lung has been reported on FNAC, EIIs were not described in the tumor cells. When evaluating cellular material from intra-abdominal visceral tumors of submucosa such as lymphoma, carcinoid tumor, and GIST, it