Track: Case Reports

Abstract:

Intraepidermal sebaceous carcinoma (ISC), also known as sebaceous carcinoma in situ, is an exceedingly rare variant of sebaceous carcinoma. Histologically, ISC presents as a well-circumscribed lesion confined to the epidermis involving sebaceous glands, ducts, or follicular epithelium, with smooth borders, nuclear atypia and mitotic figures. An 80-year-old female presented for Mohs Micrographic Surgery (MMS) of an ISC on the right tragus. The original biopsy demonstrated prominent atypical clear cell change, multifocal and pagetoid architecture, overlying parakeratosis, and an accentuated epidermal granular cell layer. Lesional cells were positive for epithelial membrane antigen (EMA), variably positive for adipophilin and negative for androgen receptor. MMS was performed and the first stage was positive for ISC at the lateral and deep margins. Despite completing five stages of MMS, complete tumor clearance could not be achieved due to extension into the external auditory canal. The patient was referred to otolaryngology who performed a right partial auriculectomy with reconstruction. All re-excision specimens were negative for residual ISC. EMA staining was negative and there was patchy epidermal clear cell change and variable keratinocytic atypia at multiple margins. These findings were felt to be insufficient residual ISC and a diagnosis of severely atypical actinic keratosis versus borderline early evolving squamous cell carcinoma in situ was favored. A majority of reported cases of ISC are found in association with actinic keratoses as with the patient in the present case and this suggests a shared carcinogenic pathway. This case highlights the rare presentation of ISC and its distinctive histologic features.

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Krystina Khalil