Steroidogenic acute regulatory (StAR) protein is a useful marker for sex-cord-stroma tumors and normal/neoplastic adrenocortical tissue

Abstract

Abstract Introduction/Objective Steroidogenic acute regulatory (StAR) protein is a mitochondrial transport protein with a critical regulatory role for steroid hormone production. As its expression is limited to few normal tissues, the immunohistochemical analysis of StAR was proposed to be diagnostically useful. Methods/Case Report To comprehensively evaluate the diagnostic utility of immunohistochemical StAR expression analysis, a tissue microarray containing 19,202 samples from 152 different tumor types and subtypes and 608 samples of 76 different normal tissue types was analyzed by immunohistochemistry (IHC). Melan-A “cross-reactive” data were available from a previous study for comparison. Results (if a Case Study enter NA) StAR immunostaining occurred in 198 (1.2%) of the 17,135 analyzable tumors. StAR expression was observed in 27 of 152 tumor categories, 9 of which included at least one strongly positive case. The highest rate of StAR positivity occurred in Leydig cell tumors of the testis and the ovary (100%), steroid cell tumors of the ovary (100%), adrenocortical carcinomas (93%) and adenomas (87%), Sertoli-Leydig cell tumors (67%) and granulosa cell tumors of the ovary (56%) as well as in seminomas (7%). As compared to Melan A, StAR was more often positive in adrenocortical neoplasms and in Leydig cell tumors while StAR (but not Melan-A) was negative in Sertoli cell tumors. Conclusion Our data provide a complete overview on the patterns of StAR immunostaining in human tumors and suggest a diagnostic utility of StAR immunohistochemistry for supporting a diagnosis of Leydig cell tumors or of normal or neoplastic adrenocortical tissue. In contrast to Melan A, StAR appears to be more sensitive for these tumors while StAR is always negative in malignant melanoma, a frequent source of adrenal metastasis.