Clinicopathologic and Molecular Characterization of a Series of Sporadic Trichoblastic Neoplasms

This study examined 16 sporadic trichoblastic neoplasms in 9 males and 7 females, with a median age of 64 years. The tumors were located in various body regions and had a median size of 1.6 cm. Histologically, they showed a dermal multinodular growth of basaloid epithelial cells with fibrotic stroma. Malignant transformation was noted in one case, and another case showed features of trichogerminoma. RNA sequencing of six tumors revealed a high tumor mutational burden without a UV-related signature, aiding in distinguishing these tumors from others. A FOXK1::GRHL1 fusion was identified in the trichogerminoma case. Clinical follow-up of 15 patients over a median of 65 months showed no residual or metastatic disease.