Malignant Transformation of a Giant Solitary Trichoepithelioma With Extensive Craniofacial Invasion: An Unusual Case Report and Review of Literature

Trichoepithelioma is a rare benign follicular adnexal neoplasm with hair follicle differentiation, most commonly occurring on the face. Malignant transformation is exceptionally uncommon, with fewer than 10 cases reported in the literature, all arising in patients with multiple familial trichoepitheliomas. To the best of our knowledge, this is the first reported case of malignant transformation of a giant solitary trichoepithelioma with extensive craniofacial invasion. We report the case of a 52-year-old man who presented with a rapidly progressive ulcerative lesion over the right side of the face, associated with restricted ocular movements and diminished vision. He had undergone excision of a similar lesion at the same site two years earlier, which was histopathologically diagnosed as trichoepithelioma. Radiological imaging demonstrated a locally aggressive soft-tissue mass with extension into the orbit, adjacent musculature, and underlying facial bones. Histopathological examination revealed infiltrative nests and cords of basaloid tumour cells within a desmoplastic stroma, with perineural, muscle, and bone invasion, consistent with malignant transformation of trichoepithelioma. The patient underwent radical craniofacial resection with histologically negative margins followed by reconstruction. He remains disease-free at 30 months, with serial clinical examinations every three months and contrast-enhanced computed tomography every six months. This case highlights the importance of considering malignant transformation in recurrent or rapidly enlarging trichoepitheliomas and signifies the role of complete surgical excision and long-term surveillance.