Diagnosis of extraskeletal small cell osteosarcoma in cytology specimen. Report of a case of rare tumor and review of the literature

Extraskeletal small cell osteosarcoma (ESCOS) is a rare tumor which may present a challenging primary diagnosis on cytologic assessment. The cytomorphology of this tumor is similar to other small round blue cell tumors (SRBT), and in potential absence of osteoid material in cytology specimens, diagnostic error may not be avoided. The diagnostic challenge is even greater with extraskeletal location. The most important reason to be able to differentiate ESCOS from other SRBT is the effect of this diagnosis on guiding appropriate therapy. We present a case of a 62 year old male with the diagnosis of ESCOS based solely on cytologic specimen evaluation.