Sebaceous carcinoma by silhouette
The subject of sebaceous neoplasms in the skin has been addressed previously in this section of the journal (Dermatopathology: Practical and Conceptual 1997;3:11). Since then, we have reconsidered the matter of sebaceous carcinoma and have formulated what we conceive to be compelling arguments to the effect that so-called sebaceous “adenoma” is simply a superficial, well-differentiated expression of sebaceous carcinoma.* Moreover, silhouettes of different manifestations of sebaceous carcinoma, identifiable easily at a glance at scanning power, are remarkably repeatable.
The malignant neoplasm termed heretofore “sebaceous adenoma” is, as a rule, oriented horizontally and characterized by pyriform lobules with smooth borders. The lobules are in contiguity with the surface of the skin (Fig. 1A). The lesion often is eroded or ulcerated, may be slightly or markedly asymmetrical, and lobules of neoplastic cells may have peculiar geometric shapes with a tendency to become confluent. Immature sebocytes at the periphery of the lobules have large, pleomorphic nuclei that are crowded and display prominent nucleoli. Mitotic figures are identifiable readily. Rarely, a relatively mature sebocyte near the center of a lobule also may be observed in mitosis.
Lobules in contiguity with the surface of the skin.
Another distinctive silhouette of sebaceous carcinoma belongs to the condition previously called “cystic sebaceous adenoma” (Fig. 1B). This neoplasm is asymmetrical and its center houses sebaceous secretion surrounded by lobules of neoplastic cells that have bizarre shapes and tend to confluence. The cytologic features of the neoplastic sebocytes and their distribution in the lobules are just like those already described in the superficial sebaceous carcinoma, named incorrectly “sebaceous adenoma,” pictured in Figure 1A.
Another distinctive silhouette of sebaceous carcinoma.
Yet another pattern of sebaceous carcinoma is that seen in Figure 1C. The neoplasm is strikingly asymmetrical and is composed of aggregations of neoplastic cells that vary markedly in size and shape, and that form nodules and sometimes sheets. Immature sebocytes tend to predominate in this type of sebaceous carcinoma and, like the neoplastic cells at the periphery of lobules described previously for the sebaceous carcinomas in Figs. 1A and 1B, their large pleomorphic nuclei are crowded. Many of them are in mitosis. A variation on this particular type of sebaceous carcinoma is characterized by prominent zones of necrosis en masse of neoplastic cells.
Another pattern of sebaceous carcinoma.
Sebaceoma (which also has been discussed previously in this journal) is benign, an authentic “adenoma,” and wholly unrelated to sebaceous carcinoma.
*Nussen S, Ackerman AB. Sebaceous “adenoma” is sebaceous carcinoma. Dermatopathol: Pract and Conc 1998;4(1):5-14.
From the Institute. Reviewed by Kenneth S. Resnik, M.D.