Expression of Androgen Receptor by Fibroepithelioma of Pinkus: Evidence Supporting Classification as a Basal Cell Carcinoma Variant?

Abstract

The classification of fibroepithelioma of Pinkus as basal cell carcinoma or trichoblastoma remains controversial. Immunohistochemical stains for androgen receptor may be useful in differentiating basal cell carcinoma from trichoepithelioma or trichoblastoma. We studied androgen receptor expression in 13 fibroepitheliomas of Pinkus, 11 basal cell carcinomas, 12 trichoepitheliomas, and 3 trichoblastomas. Androgen receptor expression was present in 77% (10/13) of fibroepitheliomas of Pinkus, 73% (8/11) of basal cell carcinomas, 17% (2/12) of trichoepitheliomas, and 0% (0/3) of trichoblastomas. Androgen receptor expression was significantly higher in fibroepitheliomas of Pinkus compared with trichoepitheliomas and trichoblastomas (P = .0007), but not basal cell carcinoma (P = 1.00). Tumor-associated Merkel cells, a feature of benign follicular tumors, was identified by cytokeratin 20 stains. Merkel cells were identified in 85% (11/13) of fibroepitheliomas of Pinkus, 27% (3/11) of basal cell carcinoma cases, and 73% (11/15) of benign follicular tumors. Cytokeratin 20 expression was significantly higher in fibroepithelioma of Pinkus and benign follicular tumors compared with basal cell carcinomas (P = 0.0111 and P = 0.025, respectively). No significant difference was found between fibroepitheliomas of Pinkus and trichoepitheliomas and trichoblastomas (P = 1.00). Similar to basal cell carcinomas, fibroepitheliomas of Pinkus express androgen receptors, potentially supporting classification as a basal cell carcinoma. Conversely, fibroepithelioma of Pinkus demonstrates retention of Merkel cells, a feature of benign follicular tumors. Immunophenotypic evidence for the classification of fibroepithelioma of Pinkus remains inconclusive. In small, partial biopsy specimens, coexpression of androgen receptor and cytokeratin 20 may aid in the diagnosis of fibroepithelioma of Pinkus.

Fibroepithelioma of Pinkus (FeP) Located in the Left Lower Quadrant of the Abdomen - Case Report and Review of the Literature

“…In basal cell carcinomas and trichofolliculomas, however, MC was found near proliferating tumour cells. Androgen receptors are expressed in BCCs, but only exceptionally in trichoepitheliomas [ 7 ]. Katona et al (2007) observed that 10 out of 13 FeP, as well as 8 out of 11 BCCs, stained positively for androgen receptors [ 7 ]; only 2 out of 15 trichoepitheliomas expressed androgen receptors [ 7 ].…”

“…Recent research has highlighted the fact that BCC and trichoepithelioma have the same origin; that is, the epithelial stem cells of the hair follicle [ 5 , 6 ]. Such a concept has led to the proposal that FeP might be a trichoblastic tumour intermediate between trichoepithelioma and BCC [ 7 ]. The clinical presentation of FeP is that of a flesh-coloured, well-demarcated, sessile, dome-shaped papule or pedunculated tumour frequently often located in the lumbosacral area.…”

“…The pathogenesis of FeP is still a matter of debate. As is the case with conventional BCC, theories include mutations in the tumour suppressor gene P53 and the PATCHED gene, inducing inhibitory signals in the Hedgehog pathway [ 7 ]. There are several reports on the dermatoscopic, reflectance confocal microscopic, and histopathologic features of FeP.…”

“…The treatment of choice is complete surgical excision. Other surgical techniques, such as cryosurgery, electrodesiccation and Mohs micrographic surgery have also been performed successfully [ 7 ].…”

Vulvar Merkel Carcinoma: A Case Report

“…The immunohistochemistry is positive for cytokeratins, epithelial membrane antigen, neurofilaments, neuron-specific enolase, and chromogranin A. Electron microscopy could reveal intermediate filaments in a typical globular paranuclear arrangement [16]. Merkel cells are usually identified by cytokeratin 20 stains [17]. Staging evaluation includes C/T and recently PET scan [18].…”