Solitary Fibrous Tumor of the Adrenal Gland with Unusual Immunophenotype: A Potential Diagnostic Problem and a Brief Review of Endocrine Organ Solitary Fibrous Tumor

Solitary fibrous tumor was initially thought to be a pleura-based tumor. However, over the last two decades, its involvement in a variety of extrapleural sites gained recognition. Nonetheless, a primary involvement of the endocrine organs is rare, and in this report, we detail an instance where the tumor affected the adrenal gland of a 71-year-old Arab man. On histology, besides the typical morphologic features seen in solitary fibrous tumor, the neoplasm also exhibited unusual features on immunohistochemistry such as positive staining for cytokeratin AE1/3 and calponin in conjunction with diffuse expression for S-100. The genetic tests for t(X:18) as seen in synovial sarcoma were negative, and the overall histological appearance favored a diagnosis of solitary fibrous tumor. To the best of our knowledge, this report represents the fifth case of a solitary fibrous tumor primarily occurring in the adrenal gland. The differential diagnoses of this neoplasm in our case and a brief summary of solitary fibrous tumor primarily involving the various endocrine organs are presented.