Bcl‐2, CD34 and CD10 expression in basaloid follicular hamartoma, vellus hair hamartoma and neurofollicular hamartoma demonstrate full follicular differentiation

Abstract

Generalized basaloid follicular hamartoma syndrome (GBFHS) is a rare, recently-described, autosomal-dominantly inherited disorder that presents with disseminated milia, palmoplantar pitting, hypotrichosis and basaloid follicular hamartomas (BFH). BFH is a benign adnexal tumor that resembles basal cell carcinoma (BCC). In this study, we report two cases of GBFHS and stain BFH, a vellus hair hamartoma (VHH) and a neurofollicular hamartoma (NH) with CD34, bcl-2 and CD10 to characterize and compare the staining patterns of these follicular tumors. Standard immunohistochemistry labeling with CD34, bcl-2 and CD10 was performed on paraffin-embedded, formalin-fixed tissue sections of five BFH (four for CD10), one VHH and one NH. CD34 stromal staining was observed in all specimens. Bcl-2 stained the outermost cell layers of the basaloid nests in all specimens. CD10 stained the peritumoral stroma of all specimens. The BFH, NFH and the VHH showed CD10 staining of matrical cells. CD34 and CD10 stain peritumoral stroma of BFH, VHH and NH. Bcl-2 stains the outermost cell layer of these tumors. CD10 was also observed to stain matrical cells. These results show the similarities in differentiation between these benign follicular neoplasms and trichoepithelioma.

Congenital localized basaloid follicular hamartoma: a case report and review of the literature

“…These findings are consistent with the histopathologic features of BFH. Moreover, immunohistochemical study indicated CD34 and CD10 positive fibroblasts and CD10 negative basal cells in the matrix, which also supports the diagnosis of BFH 8,9 . In the patient, there were localized plaque and nodules on the right face, and the lesions did not distribute along Blaschko’s lines.…”

Histologic Mimics of Basal Cell Carcinoma

“…54,63,[65][66][67] A similar pattern of tumor expression in BCC and stromal expression in TE/TB has been proposed for CD34, but some reports have not found this stain diagnostically useful. 61,64,68,69 Although p75NTR is more likely to show diffuse expression in DTE than in mBCC, 70 a later study 71 demonstrated limited specificity, with diffuse expression in 36% of mBCC and 44% of microcystic adnexal carcinomas. In recent studies, strong and diffuse expression of PHLDA1 (TDAG51), a follicular stem-cell marker, has been shown to be highly specific for TE/TB, 53,55,72 although expression in micronodular BCC has been reported.…”

Basaloid Follicular Hamartoma of the Eyelid

“…The former is overwhelmingly BER-EP4 negative while the latter is diffusely positive. The stroma of BCC (including the fibroepithelioma of Pinkus variant) is CD34 negative but positive in BFH, 16 which feature it shares with other benign follicular tumors. Basal cell carcinoma expresses androgen receptors whereas BFH does not.…”

“…17 BCL-2 positivity is scattered throughout the lobules and cords of BCC but is restricted to the peripheral cells of the trabeculae constituting BFH. 16 Ki-67…”