Unusual presentation of metastatic sebaceous carcinoma and its response to chemotherapy: is genotyping a right answer for guiding chemotherapy in rare tumours?

Sebaceous carcinoma is a rare malignant tumour of skin. It commonly occurs in the head and neck region. The standard of care for localized disease is wide local excision followed by radiotherapy. Occasionally, sebaceous carcinoma can be associated with Muir-Torre syndrome, which is characterized by sebaceous lesions and carcinomas in the visceral organs. Metastatic sebaceous carcinoma is even rarer, with very little evidence about the role of chemotherapy in the treatment of metastatic disease. Here, we report a case of recurrent sebaceous carcinoma metastatic to the rectum (initially mimicking rectal cancer and Muir-Torre syndrome) in which the disease responded to multiple lines of chemotherapy. We also review the available literature on chemotherapy in this disease and discuss the role of tumour profiling and genotype-guided selection of chemotherapeutics in such rare tumours.