Relationship of ectopic ACTH production to tumor differentiation: a morphologic and immunohistochemical study of prostatic carcinoma with Cushing's syndrome.

A case of Cushing's syndrome in a patient with an ACTH-producing prostatic carcinoma is presented. Initial transurethral biopsy showed a moderately well-differentiated adenocarcinoma. The development of Cushing's syndrome was associated with a change in the morphology of the tumor; repeat transurethral prostatic biopsy and autopsy showed an admixture of moderately well-differentiated adenocarcinoma and anaplastic carcinoma. Immunoperoxidase studies revealed ACTH only within the anaplastic component of the tumor, which also showed strong argyrophilia. Electron microscopic studies revealed abundant dense-core granules within the anaplastic portion of the tumor with only very scanty granules in the differentiated portion. This case strongly supports the contention that cells with APUD characteristics can differentiate within epithelial tissues of multiple embryologic origins, and that the possession of APUD features does not necessarily imply origin from any specific neuroendocrine progenitor cell.