Immunohistochemistry Panel for Differential Diagnosis of Basal Cell Carcinoma and Trichoblastoma

INTRODUCTION: Basal cell carcinoma (BCC) is the most common malignant neoplasm in the skin and is considered to have a low degree of malignancy. BCC is invasive but rarely metastatic and originates in hair follicle-derived cells or interfollicular zones of the epidermis. Trichoblastoma (TB) is an infrequent benign skin neoplasm that differentiates toward follicular germinative cells. Both of these cutaneous lesions comprise nests of basaloid cells, and because the differential diagnosis is hard to obtain between them histologically due to their similarity, the correct diagnosis must be established. MATERIALS AND METHODS: The sample size of this descriptive study consisted of 20 cases: 10 paraffin-embedded tissues that were diagnosed with carcinoma of solid basal cells with follicular differentiation and 10 TB tissues. The diagnosis of all samples was confirmed morphologically with hematoxylin and eosin. One-micron-thick sections were cut from each sample and analyzed semiquantitatively by immunohistochemistry (IHC). Differences in staining between BCC and TB were analyzed by Chi-square test. RESULTS: Two of 10 TB cases were positive for Ki-67 versus 10 of 10 BCC samples. Cytokeratins 6 was expressed in 1 of 10 TB samples and in all BCC tissues. Staining with clone 34BE12 generated signals in all lesions at various intensities. CONCLUSION: The diagnosis between TBs and BCCs must be made histologically, because the treatment of BCC is radical and can compromise aesthetics and function, even for experienced pathologists. Because their morphological diagnosis is difficult, the histopathology results must be supported by an IHC panel.