Expression of androgen receptor by fibroepithelioma of Pinkus: evidence supporting classification as a basal cell carcinoma variant?

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.

Langerhans cell histiocytosis associated with myelodysplastic syndrome in adults.

BACKGROUND: Myelodysplastic syndrome (MDS) is a group of bone marrow disorders associated with dyplasia of myeloid elements that may have cutaneous manifestations including infections, vasculitis, Sweet's syndrome, pyoderma gangrenosum, erythema elevatum diutinum, and leukemia cutis. These cutaneous manifestations are attributed to the underlying bone marrow defect. Langerhans cell histiocytosis (LCH) is primarily a pediatric disease, and rarely LCH has been described in association with pediatric MDS. We are aware of only a single case report of LCH associated with MDS in an adult. METHODS: We report two new cases of LCH in elderly patients with underlying MDS. The specimens were examined by routine microscopy as well as immunohistochemical stains for S100 protein and CD1a. RESULTS: Both patients were elderly men with established diagnoses of MDS. One presented with a solitary pruritic papule while the other had a 2-year history of erythematous papules involving the trunk and extremities. Histologic examination revealed intraepidermal and dermal collections of mononuclear cells with reniform nuclei. The cells were strongly positive for S100 and CD1a, confirming their identity as Langerhans cells. CONCLUSION: Cutaneous LCH may be associated with underlying MDS in adults and should be considered in the differential diagnosis of cutaneous eruptions in patients with MDS.

Amphiregulin overexpression results in rapidly growing keratinocytic tumors: an in vivo xenograft model of keratoacanthoma.

Keratoacanthoma (KA) is a variant of cutaneous squamous cell carcinoma (SCC) known for rapid growth and potential for involution. Little is known about the basis for the rapid growth because of the dearth of model systems. We hypothesized that amphiregulin (AR), a keratinocyte autocrine growth factor, had a significant role. Using immunohistochemistry, we compared 21 KA, 6 conventional SCC, and 6 basal cell carcinomas (BCC) for AR expression. All KA were positive for AR, the majority with strong immunoreactivity. The SCC were positive (5 of 6), with generally weak staining; no BCC were positive. We developed laboratory model systems to study AR overexpression in keratinocytes and its role in the pathogenesis of KA. A retroviral transduction strategy was used to overexpress AR in the HaCaT keratinocyte-like cell line. The AR overexpressing cells (HaCaT-AR) displayed autonomous proliferation in serum-free media when compared with controls (HaCaT-NIE). To develop an in vivo model, xenografts of HaCaT-AR and HaCaT-NIE were grown on SCID mice. The HaCaT-NIE cells formed thin tumors resembling conventional SCC. The HaCaT-AR cells formed rapidly growing tumors with AR expression similar to KA. HaCaT-AR cells may represent a new system for the further evaluation of KA.