SUPERFICIAL EPITHELIOMA WITH SEBACEOUS DIFFERENTIATION or
 
RETICULATED ACANTHOMA WITH SEBACEOUS DIFFERENTIATION
Plaques that are composed of interconnecting rete ridges that contain clusters of cells having sebaceous differentiation have been described under both of the terms shown above. I suppose one could make up additional terms such as intraepidermal sebomatricoma or intraepidermal sebaceoma if one were so inclined. The term epithelioma has behavioral connotations that are ambiguous, but the behavior of these lesions appears to be benign. Lesions described as reticulated acanthomas may have foci of differentiation representative of one or several of the components of the pilosebaceous unit, including the apocrine gland. The relationship, if any, to the Muir-Torre syndrome is problematical since there have been so few cases reported.

From a thigh of an elderly female:
 
Scan power view. Multiple aggregates of cells staining more darkly than their neighbors are found within the epidermis. Interconnecting rete ridges are prominent.
A medium power view of part of one of the intraepidermal cell nests (right side of picture) plus a small nest in the bottom of the epidermis. Notice how the cells within these nests stand out in sharp contrast with the neighboring keratinocytes. Note the interconnecting bands of keratinocytes.
A high power view of the small nest shown above.
A high power view from another section on the same slide. Two sebaceous ducts are seen in the left side of the picture, and there is a focus of minimal sebaceous differentiation in the right side of the picture.
A medium power view from another area that shows sebaceous differentiation in within a cluster of germinative cells.

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