History
Patients with sebaceous adenomas typically experience a gradual onset of small, usually less than 0.5 cm in diameter (2-4 mm), smooth, yellow, sometimes speckled papules that may feature crusting or central umbilication. Typically, they grow on the skin of the face or scalp over the course of a few months and are asymptomatic.
Identification of sebaceous adenomas is crucial because of their association with Muir-Torre syndrome. In Muir-Torre syndrome, germline mutations in mismatch repair genes result in regions of DNA microsatellite instability and subsequent increased risk of developing internal malignancies, commonly colorectal and genitourinary carcinomas.
Physical Examination
Sebaceous adenoma is defined as a benign epithelial neoplasm composed of sebaceous gland–like structures or tumors with well-recognized sebaceous differentiation by microscopic examination.
Sebaceous adenomas range from less than 1 cm (usually 2-4 mm) to greater than 5 cm in maximum dimension. Tumors most frequently appear as a yellow, speckled, smooth-surfaced, circumscribed papule or nodule (see the image below). They can be tan or pink-to-red, and they may feature a polypoid appearance, crusting, and/or central umbilication.
A biopsy-proven sebaceous adenoma on the forehead of a 64-year-old man. The tumor appeared as a dome-shaped, elevated nodule with a circumscribed margin. It measured 8 mm in diameter, with a smooth, shiny, yellow, and speckled appearance. The tumor had a history of slow growth, and the patient had noticed it for more than a year. Note the pearly appearance and the presence of a few capillaries traversing the tumor surface, a feature closely mimicking the clinical appearance of that of a basal cell carcinoma. The total surgical removal of this tumor was uneventful. The patient has not experienced a recurrence.
Tumors are commonly located on the face, the scalp, and the neck. Occasionally, tumors may be seen at other sites, including the trunk and the legs. Sebaceous adenomas have been described on the caruncle of the eye, [19] eyelid, [20] bulbar conjunctiva, [21] and buccal mucosa. [22]
The clinical impression prior to the time of biopsy is usually that of basal cell carcinoma or a nondescript papule without definitive clinical diagnosis.
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A biopsy-proven sebaceous adenoma on the forehead of a 64-year-old man. The tumor appeared as a dome-shaped, elevated nodule with a circumscribed margin. It measured 8 mm in diameter, with a smooth, shiny, yellow, and speckled appearance. The tumor had a history of slow growth, and the patient had noticed it for more than a year. Note the pearly appearance and the presence of a few capillaries traversing the tumor surface, a feature closely mimicking the clinical appearance of that of a basal cell carcinoma. The total surgical removal of this tumor was uneventful. The patient has not experienced a recurrence.
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Low-power view of a photomicrograph of sebaceous adenoma. Note the dome-shaped elevation of the epidermal surface, the sharp circumscription from the adjacent dermal tissue, and the slight central cystic appearance with eosinophilic secretory material. Patients with sebaceous tumors showing more prominent cystic change have been found to have DNA abnormalities that are linked to a higher risk of the development of internal malignancies at a later date.
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A medium-power view of the well-differentiated SA on the forehead of a 64-year-old man, showing proliferation of well-differentiated sebaceous lobules with central, larger, mature sebocytes and peripheral, smaller, less-differentiated, basaloid, germinative cells. Note that the sebaceous lobules are connected to the overlying epidermis and are slightly off-center in this field; a collection of eosinophilic, pink-colored, keratinous material is present in a dilated follicular ostium within the tumor (hematoxylin and eosin, original magnification X75). In contrast to a sebaceous hyperplasia, a sebaceous adenoma such as seen in this microscopic field contains sebaceous lobules with a 2-cell type and not a single-cell type of sebocytes as seen in the former. The neoplasm was completely removed, with no known recurrences to date.
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Higher-power view of a photomicrograph of a sebaceous adenoma. Note the intermingled 2 cell types, ie, well-differentiated pale-staining sebocytes containing vacuolated (bubbly) cytoplasm and smaller, darkly stained, basaloid, less-differentiated matrix cells. An occasional mitotic figure (arrow) was present. The tumor was completely excised, and no recurrence was noted in this patient after 5 years of follow-up (hematoxylin and eosin, original magnification X200).
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A close-up, higher-power view of the same sebaceous adenoma. The cytologic details are evident. Notice the predominant, larger sebocytes (arrow) containing pale-staining, bubbly cytoplasm (intracytoplasmic compartmentalization) and a few smaller, basaloid, germinative cells of pilosebaceous structures. The nuclei are vesicular without overt pleomorphism or mitotic activity (hematoxylin and eosin, original magnification X300).
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Multiple sebaceous neoplasms on the skin of the chest and the trunk of a 62-year-old man. The tumors were biopsy-proven sebaceous tumors with varying degrees of sebaceous differentiation. The patient was found to have a well-differentiated adenocarcinoma of the colon by subsequent colonoscopy, CT scan, and MRI examination.
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Sebaceous adenoma. Multilobulated and similar in organization to a normal sebaceous gland. Characterized by multiple layers of basaloid germinative cells located peripherally with mature sebocytes comprising the lobule center.
