Squamous cell carcinoma arising in an epidermoid cyst

A 48-year-old Caucasian male presented with an inflamed, discharging left buttock mass. An asymptomatic mass, present for 28 years, had increased in size following blunt trauma to the buttock 3 months earlier. On examination a 5×5×3 cm tender fluctuant mass was found in the left gluteal region with an enlarged left inguinal lymph node. An infected epidermoid cyst was diagnosed and incision and drainage performed. Biopsies revealed proliferating squamous epithelium of the cyst wall with areas of cytonuclear atypia, in keeping with invasive well-differentiated squamous cell carcinoma (Figure 1). The patient was reviewed at 3 weeks, when an ulcerating lesion with overriding skin edges and enlarged left inguinal nodes were discovered (Figure 2). A wide local excision of the carcinoma and the left inguinal lymph node was performed. Histological examination showed the tumour infiltrating the subcutaneous tissue although the deep and lateral resection margins were clear. The lymph node had been replaced by necrotizing squamous cell carcinoma with prominent extra-nodal spread. A computed tomography scan revealed no distant metastases but an irregularity in the left groin was consistent with an enlarged left inguinal lymph node. The patient was referred for radiotherapy but, despite an initial response, the wound continued to discharge pus. Antibiotics were commenced. A followup examination 4.5 months later revealed tumour deposits in the left groin and ill-defined opacities on chest X-ray, suggestive of pulmonary metastases. He was admitted to hospital 10 days later in an acute confusional state, suffering from hypercalcaemia and pneumonia and died 5 days later, only 5 months after his initial presentation.