Polypoid Dermal Hemangiopericytoma? An Alternative Point of View

To the Editor: With great interest, we read the recent article “Polypoid dermal hemangiopericytoma” by Pollock and Sweeney (1) describing “an exceptionally rare, if not unique, case of intradermal hemangiopericytoma.” As the authors correctly state, “definition of hemangiopericytoma causes considerable problems” and has led “some pathologists (as well as dermatopathologists) to claim that it does not exist as an entity”(2). We are among them. Our interpretation of this case is that of an epithelioid cell histiocytoma with prominent hemangiopericytoma-like vasculatur. Epithelioid cell histiocytoma was first described in 1989 in the British Journal of Dermatology by Wilson Jones et al. (3), who also stressed its frequent misinterpretation as a Spitz nevus. Epithelioid cell histiocytoma characteristically occurs as a pink polypoid lesion on the extremities of young women. Histologically, it exhibits prominent epidermal hyperplasia with lateral collarette and a sheet-like infiltrate of epithelioid cells with scalloped cytoplasmic cell extensions. Histochemically, these lesions show a fine network of reticulin fibers around individual cells. Immunohistochemically, they are consistently positive with KiM1p, variably for factor XIIIa, with E9, an anti-metallothionein marker, and NK1C3 (CD57). Ultrastructurally, epithelioid cell histiocytomas are indistinct, but frequently reveal large amounts of rough endoplasmic reticulum. All these characteristics (apart from some immunohistochemical stainings that were not performed) nicely fit the lesion in question. The originality of this case results from its prominent antler-to staghorn-like vascularity, which convinced the authors that it was a dermal hemangiopericytoma. Yet, such features are unspecific and may occur in a wide variety of lesions, such as solitary fibrous tumor, myofibroma or myofibromatosis, glomangiopericytoma, myopericytoma, malignant glomus tumor, monophasic synovial sarcoma, mesenchymal condrosarcoma, and so on (2), including, last but not least, hemangiopericytoma-like fibrous histiocytoma(4). From our point of view, this case combines two unusual features that may occur in dermatofibromas: epithelioid cells in a polypoid lesion with prominent collarette and hemangiopericytoma-like vascularity. Analogous to combined nevi we have termed dermatofibromas with a complex combination of two or more architectural or cellular/stromal peculiarities within one lesion combined dermatofibromas(5). Similar examples in the literature have been published under various bizarre terminologies. Thus, in our opinion, for example, primitive polypoid granular cell tumor (6) is an epithelioid cell histiocytoma with prominent granular cell features; giant cell collagenoma (7) a combination of sclerotic dermatofibroma with monster cells; some myxomas (8), mostly myxoid dermatofibromas besides remnants of ordinary dermatofibromas. We hope Drs. Pollock and Sweeney and the colleagues from the other papers (6–8) are unoffended by our alternative points of view and comments. Moreover, we do not want the readership of the American Journal of Dermatopathology to believe us, but instead hope that we can animate them to think about a problem or concept with an open mind. “Mens candida ” is a frequent exhortation of this. Bettina G. Zelger M.D. Bernhard Zelger M.D.