Background: Histopathologic differentiation between benign and malignant tissue is of utmost importance for the Mohs surgeon. Folliculocentric basaloid proliferation (FBP) shares many histologic features with basal cell carcinoma (BCC). It is most commonly associated with tumors of areas with abundant hair follicles such as nasal and perinasal skin. Residual BCC incorrectly identified as a horizontally sectioned hair follicle undoubtedly increases the risk of tumor recurrence. Excision of additional layers of normal tissue to remove "funny looking follicles" may have profound impacts on tissue conservation, preservation of function, and cosmesis. Electron microscope studies of BCC revealed a significant reduction of desmosomes compared with normal basal cells and hair follicle keratinocytes.
Objective: This study has assessed the potential of rapid staining with monoclonal antidesmoglein antibody (33-3D) to discriminate between BCC, horizontally sectioned hair follicles, and FBP.
Methods: A rapid immunoperoxidase technique with 33-3D antidesmoglein antibody was performed on Mohs frozen sections. We selected 18 patients with BCC of nasal and perinasal locations where histologic discrimination between residual tumor and tumor-free margins with FBP or horizontally sectioned hair follicle was equivocal.
Results: Fourteen sections disclosed the preservation of desmoglein marker delineating the cell membranes ("perimembranous" pattern) consistent with normal hair follicles. The sections were identified as tumor-free and no additional stages were performed. The remaining four sections revealed absent perimembranous pattern but presence of diffuse cytoplasmic staining. These were diagnosed as positive for residual BCC requiring the excision of another layer of tissue to obtain tumor-free margins. A follow-up period ranging from 6 to 24 months revealed no instance of recurrent disease.
Conclusion: Rapid detection of desmoglein with 33-3D antibody is a promising tool for discrimination between residual BCC and FBP or horizontally sectioned hair follicles. It may enhance the sensitivity of Mohs surgery by disclosing the hidden foci of BCC, thus preventing tumor recurrence and unnecessary excision of normal tissue.