Malignant sebaceous tumours

Sebaceous carcinoma

Definition

Sebaceous carcinoma is a malignant tumour composed of sebaceous cells of varying maturity that are arranged in sheets and/or nests with different degrees of pleomorphism, nuclear atypia and invasiveness.

ICD-O code 8410/3

Epidemiology

There is a bimodal age distribution with a peak incidence in the third decade and the 7th and 8th decades of life (range 17- 93 years) {669,896,901}. The male and female incidence is almost equal. Unlike sebaceous neoplasms of the skin {1132, 2214}, there is no increased risk of developing a visceral carcinoma in patients with a salivary gland sebaceous tumour.

Localization

 Approximately 90% arise in the parotid area, with occasional tumours in the oral cavity, vallecula, sublingual gland, submandibular gland and epiglottis {107, 602,669,693,896}.

Clinical features

 Patients typically present with a painful mass with varying degrees of facial nerve paralysis and occasional fixation to the skin.

Macroscopy

 Tumours have ranged from 0.6-8.5 cm in greatest dimension and vary from yellow, tan-white, greyish-white, white, to pale pink {896}. They are well circumscribed or partially encapsulated, with pushing or locally infiltrating margins.

Histopathology

Tumours are composed of multiple large foci and nests or sheets of cells with hyperchromatic nuclei and abundant clear to eosinophilic cytoplasm. Cellular pleomorphism and cytologic atypia are present to varying degrees and are much more prevalent than in sebaceous adenomas. Squamous differentiation is common. There may be areas of basaloid differentiation, particularly at the periphery of cellular nests. Areas of necrosis and fibrosis are common. Perineural invasion is seen in greater than 20% of tumours; vascular invasion is infrequent. Rare oncocytes and foreign body giant cells with histiocytes may be observed, but lymphoid tissue with follicles or subcapsular sinuses is not seen.

 Prognosis and predictive factors

The treatment of choice is wide surgical excision for low stage carcinomas. Adjunctive radiation therapy is recommended for higher-stage and grade tumours. The overall 5-year survival rate is 62% {669,896}. , slightly less than the survival for similar tumours arising in the skin and orbit (84.5%) {234}.

Sebaceous lymphadenocarcinoma

Definition

 Sebaceous lymphadenocarcinoma is the malignant counterpart of sebaceous lymphadenoma. It is a carcinoma arising in a sebaceous lymphadenoma.

ICD-O code 8410/3

Synonym

Carcinoma ex sebaceous lymphadenoma.

Epidemiology

 It is the rarest salivary gland sebaceous tumour. To date, only three have been reported {901,1525}. All three patients were in their seventh decade; two patients were male and one female.

Localization

The tumours arose within the parotid gland or in periparotid lymph nodes.

Clinical features

 Patients had histories of a mass, two of which were present for more than 20 years.

Macroscopy

Tumour colour varies from yellow-tan to grey.

 Histopathology

These carcinomas are partially encapsulated and locally invasive with foci of sebaceous lymphadenoma intermixed with or adjacent to regions of pleomorphic carcinoma cells exhibiting varying degrees of invasiveness. The malignant portion has ranged from sebaceous carcinoma to sheets of poorly differentiated carcinoma, with areas of ductal differentiation, adenoid cystic carcinoma-like areas or foci of epithelial-myoepithelial carcinoma. Perineural invasion, collections of histiocytes and a foreign body giant cell reaction may occur. Cellular atypia is not observed in the sebaceous lymphadenoma portion of the tumour.