Extraocular sebaceous carcinoma is an uncommon neoplasm, known to be locally aggressive but rarely metastasizes[1]. Among 4000 cutaneous malignancies reported in a study conducted in the US, sebaceous carcinoma represented only 0.7% of skin cancers [2]. They occur in Areas with a particularly high density of sebaceous glands, most commonly in the ocular region. Extraocular sites account for only about 25% of the cases and usually include the skin of the head and neck region[3]. Most studies report an average age of onset in the 60s [4].
The pathogenesis of sebaceous carcinoma is poorly understood, and its cause is still unknown[5]. Clinical features can be diverse, going from skin-colored to erythematous papules or nodules clinically similar to other forms of skin cancer. Histology is ultimately required to settle diagnosis.
Kyllo et al. described the classic histologic appearance of sebaceous carcinoma to be unencapsulated, lobular, dermally based collections of sebaceous and undifferentiated cells[6]. Four histologic patterns are commonly seen: lobular, comedocarcinoma, papillary and mixed[4], [5], [7]. Differentiation of sebaceous carcinoma from other malignant neoplasms may require immunohistochemistry (IHC), as sebaceous carcinomas show an overexpression of p53 and Ki-67 much more frequently than sebaceous adenomas[8].
An epidemiologic study that included 1836 cases of sebaceous carcinoma found nodal metastasis in only 2.4%, with an incidence from extraocular head and neck skin sites significantly lower than from eyelid tumors. It concluded that sentinel lymph node biopsy is necessary in eyelid sebaceous carcinomas, however in extraocular head and neck lesions, clinicians may reasonably consider observation of regional lymphatics[7]. Distant metastases can also occur, thus a regular long-term follow-up should be advised.
The association of sebaceous carcinoma to Muir Torre Syndrome (MTS) was described and according to Cohen et al. 30% of patients with MTS can have sebaceous carcinoma [9]. The risk for metastasis in these patients appears to be lower than in non-associated sebaceous carcinomas [10]. Our patient had no known family history of neoplasms or malignancies. Consequently, the diagnosis of MTS was excluded.
The available literature on treatment recommends wide surgical excision with tumor-free margins with removal of regional lymph nodes, followed sometimes by adjuvant radiotherapy [3]. The use of radiation therapy for sebaceous carcinoma should be narrowed to recurrent and metastatic lesions or palliative treatment in patients who are not candidates for surgical excision [6].
Chemotherapy is not acknowledged as a traditional treatment in sebaceous carcinoma, only few case reports are available on therapies that involved chemotherapy as induction treatment before surgery, sometimes with objective responses [11], [12]. An article summarizing these reports suggested that association of 5-fluorouracil with platinum-based agents such as cisplatin, is particularly effective[13]. More studies should be conducted to define treatment protocols for metastatic sebaceous carcinoma.
Unlike our case, extraocular sebaceous carcinomas were classically believed to be a less aggressive neoplasm than their ocular equivalent. Epidemiologic data shows that extraorbital sebaceous carcinoma has a reduced tendency for regional metastasis (1.4% for extraorbital vs 4.4% for periorbital) supports this theory[7].