Rippled-pattern sebaceous trichoblastoma

There is a large spectrum trichoblastoma; of which, several histologic variants have been described including a rippled-pattern variant. Three cases of rippled-pattern trichoblastoma are described which also exhibited definitive foci of sebaceous differentiation.

Three cases were retrieved from the archives of the Dermatopathology Laboratory at the University of California Irvine (Orange, CA, USA). All specimens were stained with hematoxylin and eosin (H&E). In addition, sections were submitted for immunohistochemical studies with epithelial membrane antigen (EMA).

All three biopsies were composed of well-circumscribed multiple variously sized tumor lobules present in the upper to deep dermis comprised of with rounded or slightly elongated basaloid cells with scant eosinophilic cytoplasm. The lobules were separated by a slightly hyalinized stroma. The unique finding present in all three specimens was a peculiar arrangement of the basaloid cells in linear rows parallel to one another. This gave the tumors a rippled pattern similar to the palisading of nuclei of Verocay bodies seen in schwannomas. In addition all three biopsies showed definite sebaceous differentiation.

Three additional cases of rippled-pattern trichoblastoma are presented. All three were located on the scalp and showed additional features of foci of sebaceous differentiation. No associations with Muir-Torre Syndrome were found in these patients. Because this appears to be a distinct variant within the large spectrum of trichoblastoma, the term rippled-pattern sebaceous trichoblastoma is suggested.