Guidelines for the diagnosis of sebaceous epithelioma vary according to different authors. Some use the '50% rule' and designate those tumors with sebaceous differentiation that are composed of more than 50% basaloid cells as sebaceous epithelioma. Unfortunately, this simple definition would also include tumors that probably have limited aggressive potential and which would be better designated as sebaceomas. Therfore it would be preferable to reserve the term sebaceous epithelioma for those tumors that have infiltrating characteristics or which could be comfortably called basal cell carcinoma based on other criteria.  Actually, it might be better to abandon the term sebaceous epithelioma entirely..

This particular example has an in situ epidermal component.
 

	Scan power view. Tumor lobules have invaded into the reticular dermis in the lower right corner of this picture.
	Low power view of one of the nests of tumor in the lower right hand corner of the picture above. There is focal retraction from the surrounding stroma, and there is sebaceous differentiation within the central part of this tumor nest.
	High power view of above. Peripheral palisading of nuclei is present, and the cells in the left side of the nest would be acceptable for a basal cell carcinoma.Vacuoles of varying size occasionally distort the outlines of nuclei, and this is sebaceous differentiation when seen in this setting.
	Low power view of the surface part of the tumor. There is an in situ component demonstrated in this biopsy.
	Medium power view of above.

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