Poorly Differentiated Extraocular Sebaceous Carcinoma Masquerading as an Abscess.

Extraocular sebaceous carcinoma (SC) is an uncommon but potentially aggressive tumor. Typical presentation is a red-yellow nodule, often ulcerated, on the head and neck of an older individual. Factors increasing the risk of SC include genetic mutations, ultraviolet light exposure, prior radiation, and immunosuppression. A 63-year-old Caucasian man presented with an enlarging, painful subcutaneous mass on his left arm, which was ultimately diagnosed as a poorly differentiated extraocular SC. Given the aggressive tumor subtype and large size of the lesion, he was definitively treated with wide local excision and sentinel lymph node biopsy. While his past medical history and family history were significant for colon cancer, he declined further genetic workup and testing. Risk factors for metastasis of SC include a tumor diameter greater than 2 cm, rapid growth, high histologic grade, or poor differentiation. As poorly differentiated extraocular SC is associated with a higher rate of nodal involvement, management with complete surgical resection and evaluation (sentinel lymph node biopsy or imaging) to determine whether metastatic spread has occurred may be of benefit to establish if further procedures, radiation, or therapeutics are indicated.