Factor VIII-related antigen staining by immunoperoxidase technic in smaller laboratories: a potential problem.

A case of metastatic squamous cell carcinoma to bone was studied using immunoperoxidase methods for Factor VIII-related antigen, producing positive staining in the tumor cells. Electron microscopy proved the squamous nature of the tumor, and, subsequently, a pulmonary primary tumor was found. Testing of additional tumor types revealed positive staining for Factor VIII in squamous cell carcinomas, tumors with squamous differentiation, and in renal cell carcinoma. Problems of antibody purity and specificity always must be considered, but in the smaller laboratory where personnel and expertise for such quality control do not exist, there is a hazard of nonspecific reaction and misdiagnosis.