Microcystic adnexal carcinoma (MAC) is a rare skin neoplasm that has not been characterized on a molecular basis.
We aimed to assess expression profiles of hedgehog (HH) signaling molecules in MAC and control tumours.
Immunohistochemistry was performed for Sonic HH (SHH), Indian HH (IHH), Patched 1 (PTCH1), and Smoothened (SMO) on patients’ MAC (n=26) tissue and control tumour tissue, including syringoma (SyG; n=11), trichoepithelioma (TE; n=11), and basal cell carcinoma (BCC; n=12).
PTCH1 and SMO immunoreactivity was significantly higher in BCC than in SyG, TE, and MAC (P = 0.000002 and P = 0.029, respectively). The highest IHH expression was observed in BCC and TE when compared to SyG and MAC (P = 0.038). Notably, the highest SHH protein expression was observed in SyG as compared to MAC, TE, and even BCC (P = 0.00075). In MAC patients, SMO immunoreactivity significantly (r = 0.51; P = 0.0086) correlated with PTCH1 expression. Further correlation studies did not show significant associations between the HH expression markers assessed (P > 0.05).
Our results indicate that alterations of the HH signaling are unlikely to play a major role in the pathogenesis of MAC, which is in contrast to the morphologically similar BCC and TE. Our observation provides additional information to the limited molecular pathology knowledge on this rare tumour.

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