[2][6] Due to the rarity of this tumor and variability in clinical and histological presentation, SGc is often misdiagnosed as an inflammatory condition or a more common neoplasm.
[6] SGc is commonly treated with wide local excision or Mohs micrographic surgery, and the relative survival rates at 5 and 10 years are 92.72 and 86.98%, respectively.
The periocular region, which includes the meibomian, Zeis, and sebaceous glands of the caruncle and eyelid, is the most common site accounting for up to 75% of SGc.
[7] Periocular SGc most commonly presents as a yellow, hard, painless, subcutaneous nodule or papule, which may rapidly enlarge, and may be confused with chalazion, blepharitis, conjunctivitis, or other inflammatory conditions of the eye.
[14] Reports have also shown the onset of SGc within the field of irradiation for patients undergoing radiotherapy for retinoblastoma, eczema, or cosmetic epilation.
[5] MTS is an autosomal dominant cancer syndrome characterized by multiple sebaceous and visceral neoplasms, the most common being colorectal adenocarcinoma.
[5][14] MTS results from defects in DNA mismatch repair genes, MLH1, MSH2, and MSH6, leading to a buildup of unstable microsatellite sequences and replication errors predisposing to various malignancies.
[10] Besides mutations in mismatch repair genes, Wnt/beta-catenin signaling is known to be altered and play a significant role in the development of sebaceous tumors.
[11] Altered expression of beta-catenin, p21, sonic hedgehog signaling (Shh), and E-cadherin have been associated with invasion, metastasis, and poor clinical outcomes.
[17] Given the aggressive growth and pagetoid spread of SGc, full thickness biopsy with microscopic examination is required for definitive diagnosis of sebaceous carcinomas.
[18] A full thickness biopsy of the eyelid (in suspected periocular SGc) includes the skin, tarsus, and palpebral conjunctiva.
[15] Map biopsies, taken from distinct areas of the conjunctiva are recommended in cases exhibiting pagetoid spread in order to determine the extent of disease.
[17] Periocular sebaceous gland carcinoma exhibits pagetoid (intraepithelial) spread, an upward growth of abnormal cells invading the epidermis, it is most often seen in the lid margin and/or conjunctiva.
[22] Periorbital SGc also presents with multicentric origins, in the upper and lower eyelids, increasing the risk of local recurrence.
[2] SGc tumor cells stain positive with epithelial membrane antigen (EMA), cytokeratin -7 (CK-7), Ber-EP4, adipophilin, perilipin, and androgen receptor (AR).
[17][6] Immunohistochemistry may also be used to differentiate SGc from benign growths and certain markers may predict an increased chance of recurrence or metastasis including Ki-67, ALDH1, and AR.
[6] The absence of staining for DNA mismatch repair MSH2, MSH6, and MLH1 may suggest a diagnosis of MTS and identify patients for further genetic testing.
[6][23] Patients with extraocular SGc and a Mayo MTS risk score greater than or equal to 2 (2 or more sebaceous tumors, age under 60 at presentation of sebaceous carcinoma, family history of any Lynch-related cancers, personal history of any Lynch-related cancers) should undergo genetic testing for MTS.
[2] Treatment for nodal metastasis confirmed via SLNB involves advanced imaging studies (CT with or without PET scan), followed by removal of the primary tumor and regional lymph nodes, with adjuvant radiotherapy.
[6][14] Unlike wide local excision, MMS allows for precise and accurate removal of the tumor and complete assessment of margins.
[6] Postsurgical adjuvant radiation therapy has been used in locally advanced primary tumors and those with positive margins or perineural invasion.
[9] Periocular SGc most commonly metastasizes to regional lymph nodes and rarely the lungs, liver, brain, or bone.