Sebaceous carcinoma of the vulva: critical approach to grading and review of the literature

Background. Sebaceous glands are abundant on the vulva, but vulvar sebaceous carcinoma (SC) is an uncommon neoplasm. Methods. We report a case of SC of the vulva in a 51 year-old woman. Results. The patient presented a 6-month history of an asymptomatic 2.5 x 1.5 cm exophytic tumour localized on the left labium majora. Tumorectomy was performed. Histologically, the lesion had an irregular lobular growth pattern composed of lobules or sheets of malignant cells separated by fibrovascular stroma. There was a mixture of sebaceous-type differentiation, small ducts and areas showing basaloid or squamous features. Centrally-located tumour cells showed moderate EMA immunoreactivity, especially enhancing cytoplasmic "bubbliness". Tumour cells were immunoreactive for CAM 5.2. The immunoreactivity for intranuclear p53 staining was > 10%. Southern blot hybridization and PCR studies did not detect HPV DNA. Hemivulvectomy was performed. After 18 months of follow-up, the patient has no evidence of recurrence, metastases or other malignant tumours. Conclusions. The grading of cutaneous SC proposed by Rutten et al. (World Health Organization Classification of Skin Tumours) and Patterson & Wick (Nonmelanocytic Tumours of the Skin. Armed Forces Institute of Pathology) is based on patterns of tumour growth rather than cytological features. Such grading of skin SC, including vulvar SC, should not be used since its prognostic value has not been sufficiently documented. As the number of reported vulvar SCs is very limited, their natural history is unknown and the optimal treatment has not been established. The follow-up of 7 reported cases supports the general opinion that the tumour may be aggressive. SC groin node metastases carry a devastating prognosis, and unrecognized disease in the inguino-femoral lymph nodes is nearly always fatal. The use of sentinel lymph nodes (SLN) has evolved as an effective surgical technique for identifying early subclinical regional nodal involvement for many solid tumours throughout the body for staging disease; this is because extra-ocular SCs cause widespread metastatic disease. In our opinion, SLN should be used in conjunction with wide local excision of the primary tumour to investigate regional subclinical metastases. In the presence of a positive sentinel node, early lymphadenectomy with or without radiotherapy could be used to reduce tumour-related morbidity and mortality. The histopathologic differential diagnosis of SC is wide-ranging, including virtually all other malignant clear cell tumours of the skin. The proliferative pattern, immunostaining and cytologic features permit exclusion of neoplasms that mimic SC, but a diagnosis of SC should be rendered only if the overall attributes of the lesion are appropriate for such a interpretation.