Retrospective analysis of CD56 and SMA immunreactivity in basal cell carcinoma

Basal cell carcinoma (BCC) is the most common malignancy in humans, accounting for 70% of all skin tumors. BCCs may show keratotic, eccrine, apocrine, matrixial, sebaceous, follicular differentiations as well as myoepithelial, neuronal, and neuroendocrine differentiation that can be detected immunohistochemically. The possible pluripotent stem cell origin of BCCs, whose origins are controversial today, is thought to be the main reason for the histopathologically different morphologies of these tumors. The aim of this study is to evaluate the neuroendocrine and smooth muscle differentiation profiles in BCCs and to investigate whether there is a relationship between the results obtained and the histopathological subtypes and the risk of recurrence. 128 cases diagnosed with BCC and basosquamous carcinoma between 2013-2020, in Bursa Uludag University Faculty of Medicine, Department of Surgical Pathology were included in the study. Immunohistochemical studies of CD56, synaptophysin, chromogranin-A, smooth muscle actin (SMA), desmin, caldesmon, bcl-2 and ki67 were applied. 77.3% of the cases expressed CD56, 13.3% expressed chromogranin-A in and 0.8% expressed synaptophysin. 78.1% of the cases showed SMA positivity while no tumor showed desmin and caldesmon immunoreactivity. A statistically significant correlation between histopathological recurrence risk groups and CD56 expression was found (p<0.05). No significant correlation was found between recurrence, histopathological recurrence risk groups and SMA expression. In conclusion, while SMA expression is observed in most BCCs, the absence of staining with other smooth muscle markers does not support smooth muscle differentiation in these tumors. While CD56 expression is detected in most BCCs, the low rate of staining with other neuroendocrine markers indicates that CD56 alone cannot be a predictor of neuroendocrine differentiation. Although the expression of at least one of the other neuroendocrine markers together with CD56 may support neuroendocrine differentiation in BCCs, it has no prognostic significance. CD56 can be used for prognostic purposes in the detection of high recurrence risk BCCs. After the investigation of the expression rates of these two antigens in different cutaneous tumors, it may be appropriate to use them for diagnostic purposes in BCCs.