MIC2 analysis of small cell carcinoma.

Small cell carcinomas (SCCs) and peripheral neuroectodermal tumors (PNETs) are two distinct neoplasms that show considerable histologic, immunohistochemical, and clinical overlap, but differ in their therapies and prognoses. In an attempt to further diagnostically distinguish the two, 33 SSCs were analyzed from both pulmonary and extrapulmonary sites for the MIC2 gene product, a cell surface antigen strongly and reliably expressed in PNETs and Ewing's sarcoma (ES). Two of the 33 SCCs stained positively, but the staining was less intense than that seen with PNET and ES. The remaining 31 tumors did not stain. These data indicate that, in combination with a panel of immunohistochemical stains, analysis of neuroendocrine tumors for MIC2 expression may be useful in distinguishing between small cell carcinomas of both pulmonary and extrapulmonary origins and soft tissue PNETs.