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 with central umbilication on the skin of the face or scalp over a period of several months.
Some middle-aged and older individuals may have multiple papules (as described above) or nondescript papules on their faces or other parts of their skin surface.
Physical
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 image below).
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.
At times, these tumors have a polypoid appearance or central umbilication. Sebaceous adenomas sometimes present as tan or pink-to-red papules.
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.
The clinical impression prior to the time of biopsy is usually that of basal cell carcinoma or a nondescript papule without definitive clinical diagnosis. See the image below.
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.
Causes
Sebaceous adenomas form part of the spectrum of the Muir-Torre syndrome. A genetic predisposition exists in some cases of the Muir-Torre syndrome, and this syndrome has been found in association with the so-called cancer family syndrome.
The identification of a truncating germline mutation in the mismatch repair (MMR) gene, hMLH1 or hMSH2, by DNA molecular genetic study in some patients having cystic sebaceous tumors with Muir-Torre syndrome highlights the value of recognizing cutaneous markers of internal malignancy. [10]
In 1999, Rütten et al [11] studied 19 patients with Muir-Torre syndrome using DNA molecular genetic analysis and reported that 8 (42%) of these patients presented with a cystic variant of sebaceous tumors (including sebaceous adenomas). They concluded that the cystic sebaceous neoplasm is a marker for the MMR-deficient subtype of Muir-Torre syndrome and is associated with a high risk for developing internal malignancies later in life.
The genetic disorder in Muir-Torre syndrome is an autosomal dominant inherited germline mutation in one of the DNA mismatch repair genes, most commonly hMSH2. [12] It is inherited with a high degree of penetrance and variable expression, with a male-to-female ratio of 3:2. Children of an individual with Muir-Torre syndrome, therefore, may have a 50% risk of inheriting the cancer predisposition. In families in which the germline mutation can be identified, those individuals who have inherited the mutation should undergo regular screening examinations, particularly of the gastrointestinal tract, colorectum, genitourinary tract, and female genital tract.
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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.
