[Why is it important to differentiate trichoblastic carcinomas (CT) from basal cell carcinomas (CBC). About 21 cases].

Trichoblastic carcinoma is a rare epithelial malignant epithelial tumor, its diagnosis is difficult and the therapeutic management is non-consensual. This retrospective study, carried out between 2009 and 2015, covered 21 cases and analyzed the diagnostic and therapeutic characteristics of trichoblastic carcinomas. Sex ratio is 2. Trichoblastic carcinoma predominated in the face (65% of cases), particularly in perinasal (30% of cases). Its clinical presentation is in 95% of cases as basal cell carcinoma, which is the first clinical diagnosis evoked. The average size of the tumors was 2.3cm in diameter (from 0.7cm to 15cm). The treatment of these tumors is surgical: the margins retained were on average 0.7cm (0.5cm to 1cm). The first excision was mostly performed under local anesthesia, healthy borders were found in less than 40% of cases, requiring another intervention under general anesthesia with reconstruction by flap or skin graft in nearly 80% of cases. The lymph node metastasis rate was 5%. Three cases of recurrence (17%) occurred between 18 months and 6 years follow-up, despite complete resection. One case recurred three times. These results highlight the difficulty of diagnosing trichoblastic carcinomas, often confused with basal cell carcinomas. Though larger, poorly limited and infiltrating, trichoblastic carcinomas are not really distinguished from basal cell carcinomas. Only the anatomopathological examination of the excision piece make it possible to conclude, the biopsy being most often insufficient. Their local aggressiveness requires a greater margin of excision. The micrographic analysis of Mohs, for the periorificial lesions of the face, would reduce margins, increase their reliability and limit the number of surgical revisions. Finally, the literature reports a high rate of ganglion and visceral metastases (between 9.5 and 11%). Initial search for distal lymph node or metastatic involvement is essential, as well as regular clinical follow-up.