INTRODUCTION Cutaneous adnexal neoplasms showing sebaceous differentiation are difficult to classify. Because of the intimate relationship of sebaceous glands with other adnexal structures associated with the pilosebaceous unit these lesions often display complex histologic features combining sebaceous, hair follicle, and sweat gland tissues. Sebaceous neoplasms run the gamut from benign to malignant lesions. These include sebaceous gland proliferation (sebaceous hyperplasia), congenital sebaceous hamartomas (nevus sebaceum), sebaceous adenoma, and sebaceous carcinoma. Sebaceous adenoma is an uncommon, often solitary lesion usually seen in patients over 40 years of age, with a predilection for the eyelid and brow, occurring in elderly patients.
CLINICAL PRESENTATION These present as a slowly enlarging well-demarcated firm dome-shaped lesion, generally less than 0.5 cm in diameter. They are smooth, yellow speckled papules, and sometimes may be pink to red. Fine telangiectatic vessels may be present within the lesion. Lesions are usually single, but in elderly patients may be multiple. Occasionally they may be polypoid or have a central umbilication. Occasionally they may ulcerate and bleed. Lesions may occur in combination with keratoacanthoma as part of the Muir-Torre syndrome (skin lesions occurring in association with an internal malignancy, typically adenocarcinoma of the colon), but here the sebaceous lesions tend to be cystic.
HISTOPATHOLOGY Sebaceous adenomas are composed of multiple sharply circumscribed sebaceous lobules.
The tumor is usually located in the mid dermis, but it may connect to the epidermis. The
sebaceous lobules comprising the tumor have a peripheral germinative layer of small basophilic cells, then a zone of transitional cells, and finally mature sebaceous cells in the center of the lobule. Mature sebaceous cells outnumber the germinative cells.
DIFFERENTIAL DIAGNOSIS The differential diagnosis includes benign lesions such as seborrheic keratosis, apocrine hidradenoma, nevus sebaceous, sebaceous hyperplasia, and dermoid cyst, as well as malignant tumors such as sebaceous cell carcinoma, and basal cell carcinoma.
TREATMENT Surgical removal is indicated for diagnosis or if there is a sudden increase in size. Complete excision with clear margins is necessary as incompletely excised lesions commonly recur. Alternative treatments include electrodessication and radiotherapy.
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