Abstract

A 25-year-old man visited our clinic with complaint of a rapidly enlarging tumor on the right lower back. The tumor was tender, firm, and measured 15×10×4cm. Histological examination of the biopsy specimen revealed a subcutaneous tumor composed of compact nests of atypical clear cells. Rosette was not detected. Immunohistochemically, the tumor cells expressed NSF, S-100 protein and vimentin. Clear cell sarcoma was suspected from these histological findings. Following 9 cycles of chemotherapy, he underwent radical excision of the tumor. The tumor of the excised specimen proved to be composed of small round cells that formed Homer-Wright rosettes. Ultrastructurally, interdigitating cytoplasmic processes containing dense core granules were observed, which established the diagnosis of PNET. In spite of additional chemotherapy and radiotherapy, he died with multiple metastases to the lung 5 months after excision.
PNET is a highly aggressive neurogenic tumor that affects the central and sympathetic nervous system and soft tissues. Although PNETs are usually small round cell tumors, present case demonstrated that they may show histological features of clear cell tumor.