Epidermal basaloid proliferation in cutaneous myxomas

Background:  Basaloid epidermal proliferations, which histologically resemble basal cell carcinoma, have been described overlying dermatofibromas. Several etiologies have been proposed. Cutaneous myxomas are also benign mesynchymal tumors. Purpose:  Basaloid proliferations have been noted overlying cutaneous myxomas. We have undertaken a study to attempt to differentiate whether these are basal cell carcinomas or benign basaloid proliferations. Methods:  Thirty cases of cutaneous myxomas were included in this study. The lesions were stained with hematoxylin–eosin and alcian blue. Immunohistochemical staining for both epidermal growth factor receptor (EGF‐r) and p53 protein was performed on the cutaneous myxomas with epidermal basaloid proliferation. Results:  Of the 30 cases of cutaneous myxomas, nine were found to have an associated overlying basaloid proliferation. The basaloid proliferations were limited to the epidermis overlying the myxoid changes within the dermis. Mitotic figures were rare. Staining for p53 protein showed scattered positive staining in the basal cells in both the basaloid proliferations and adjacent epidermis. EGF‐r showed positive staining of the overlying epidermis and basaloid proliferation in five cases. Conclusions:  We report basaloid proliferations overlying cutaneous myxomas and propose that these represent benign adnexal proliferations rather than superficial basal cell carcinoma and are analogous to the basaloid proliferations overlying dermatofibromas.