Rare malignant adnexal tumour of the skin involving distal phalanx of right thumb with co-existing primary lung cancer in a 72-year-old patient: A case report

INTRODUCTION AND IMPORTANCE: Malignant adnexal tumours of the skin are a group of rare malignancies. These tumours can further differentiate into eccrine, apocrine, sebaceous, sweat duct, or ceruminous glands within the skin or follicular cells. Sebaceous carcinoma, a malignant adnexal tumour of the skin, is a rare and malignant tumour of the sebaceous glands. They can occur anywhere in the body where sebaceous glands are present, the most common being the head and neck region. CASE REPORT: Here we report a case of a 72-year-old man who presented with a bleeding ulcer on the distal right thumb, which was progressively increasing in size. Biopsy and histology confirmed the diagnosis of MATS with sebaceous differentiation. He had been diagnosed with metastatic non-small cell lung carcinoma six months back. CLINICAL DISCUSSION AND CONCLUSION: SC is a rare and unusual tumour amounting to less than 1% of all cutaneous malignancies. Phalanges are an infrequent extra-ocular site of involvement, and initial presentation can be mistaken for a benign occurrence. Any patient presenting with extra-ocular SC is advised to undergo genetic and immunohistochemistry testing to rule out complex genetic syndromes like Muir Torre syndrome and Cowden syndrome.