The terminology associated with tumors having moderately prominent sebaceous differentiation can be confusing. Consider the following:

• Sebaceous epithelioma: This term has been used inclusively for tumors within which 50% or less of the cells show sebaceous differentiation. This definition makes no distinction between sebaceous tumors that are locally aggressive and those that are not. Those that have infiltrating patterns would be better classified as basal cell carcinoma having sebaceous differentiation. If the term sebaceous epithelioma is to be used for tumors having benign profiles, a modifying adjective such as benign should be added to the term.
• Sebaceoma: This term, if restricted to tumors having a moderate degree of sebaceous differentiation and benign growth patterns, would be a better alternative to the sebaceous epithelioma term.  These could also be thought of as sebaceous adenomas that are only moderately differentiated. It should be noted that some of these are associated with the Muir-Torre syndrome.
• Sebaceous trichoblastoma: This term was suggested to me, referrring to the case shown below,  in an e-mail communication from Richard J. Reed, M.D..  This would be a modification of trichoblastoma as defined by Headington¹: "Trichoblastomas are rare tumors of hair germ that are purely epithelial and therefore lack a potentially inductive stroma. They tend to present as discrete, circumscribed subcutaneous  nodules in non-sun-exposed areas."

 

 

I wish someone would come up with a Working Classification of Adnexal Tumors similar to that created by the hematopathologists for lymphomas. Such a classification would incorporate a prognostic estimate into the term. A tumor such as this might be classified as adnexal tumor having moderate sebaceous differentiation, benign. Tumors having a similar mixture of cellular elements but other growth patterns could be qualified as having minimal potential for infiltration or marked potential for infiltration as the case may be. This is just a thought.

---

	Very low power view (direct scan of glass slide) showing an encapsulated mass in the subcutis and lower dermis. The tumor is devoid of recognizable specialized stroma. This pattern of growth is characteristic of a benign adnexal tumor. The lack of cytologic evidence of malignancy confirms the benign nature of this tumor. The clear areas within the tumor are the result of sebaceous differentiation.
	Medium power view of an area within which there is prominent sebaceous differentiation.
	High power view of above.
	Medium power view of an area within which most of the cells are much less differentiated.
	High power view of above. Although most of the cells are devoid of a recognizable line of differentiation, they lack the malignant cytologic features of a sebaceous carcinoma.

Ref: 1. Headington JT. Tumors of hair follicle differentiation. In: Farmer ER,
       Hood AF, eds. Pathology of the Skin 2nd Edition, East Norwalk, Conn: Appleton & Lange; 2000:1015 & 1016.

Click on your browser's 'Back' button to return to the previous page.