Perineal metatypical basal cell carcinoma: Case report of atypical location and challenges of diagnosis and treatment

Introduction: Metatypical carcinoma is a rare morphological variant of basal cell carcinoma (BCC) exhibiting histopathological features of both basal and squamous cell carcinomas. BCC's histologic subtypes are distinguished by a higher risk of local recurrence and a more aggressive clinical course. Its occurrence in sun-protected areas, such as the perianal and perineal regions, is uncommon and poses significant diagnostic and therapeutic challenges. Clinicians must know these atypical presentations to ensure timely and effective treatment, leading to better patient outcomes. Presentation of case: We present a case of a 74-year-old male who sought medical attention for an ulcerated lesion in the anterior perineal area, near the anal sphincter and base of the right scrotum. Histopathological examination of an incisional biopsy revealed a pigmented, nodular form of metatypical basal cell carcinoma, a rare presentation in an atypical location. Although basal cell carcinoma is a common skin malignancy, the lesion's location and histological subtype are unusual. The patient underwent surgical excision and a V-Y advancement flap closure, preserving both function and aesthetic appearance. Discussion: Metatypical BCC, arising in less visible or protected body areas, often escapes early detection, increasing the risk of local tissue invasion and recurrence. Early diagnosis through dermoscopy or imaging techniques such as MRI and high-resolution ultrasound is crucial for assessing disease extent. Treatment options may include conventional excision or Mohs micrographic surgery. Conclusion: We reported an uncommon case of metatypical BCC, for which surgical resection and skin flap reconstruction resulted in a favorable outcome.