Case 1: Lobules of sebaceous cells with vacuolated cytoplasm with basaloid germinal cells comprise this benign tumor. The lobules are well-circumscribed.
Sebaceous adenomas are usually solitary discrete tumors. In some instances, they may arise in the context of Muir-Torre syndrome (sebaceous neoplasms and GI or GU malignancy). This syndrome is associated with mutations in various DNA mismatch repair genes.
Histologically, lobules of mature sebaceous cells with vacuolated cytoplasm and scalloped nuclei are admixed with basaloid germinal cells. Usually, sebocytes predominate but in some cases the basaloid cells may be increased, creating a more solid-appearing lobule. Cystic change is not uncommon. Unlike sebaceous carcinoma, there is no atypia or infiltration into the surrounding stroma (Fletcher, Busam).
Clinically, they appear as a small (<1 cm) yellow nodule on the face of middle-age adults. Often they are thought of as a basal cell carcinoma until removed.
→May be seen in association with Muir-Torre syndrome, an autosomally inherited disorder of mismatch repair genes leading to visceral malignancies (colon, breast, GU tract) and skin lesions such as sebaceous tumors and keratoacanthomas.
Basam KJ. Dermatopathology: Foundations in Diagnostic Pathology 1st Ed. Philadelphia, PA: Elsevier; 2010: 431.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1451.