Meningioma-like Tumor of the Skin Revisited

Abstract

The term meningioma-like tumor of the skin (MLTS) was coined in 1993 to designate a particular whorled spindle cell superficial cutaneous tumor. No additional confirmed cases of this entity have been reported to date. Some authors have speculated that these cases might be cellular neurothekeomas. In order to delineate the histologic spectrum and the immunophenotype of this unusual tumor, we studied 5 cases, 2 previously unreported and the 3 original cases. The immunohistochemical findings of case 5, however, were limited to those from the original study. Clinically, the tumor presented as a reddish papule, plaque, or nodule, located in the extremities or trunk. The patient often referred to a recent growth of a longstanding lesion. Histologically, the characteristic whorled spindle and stellate dendritic cell population, commonly in a perivascular arrangement, and variable myxoid component, were consistently found in all cases. A prominent microvasculature was also a constant finding. The presence of large deciduoid cells was conspicuous in one case. A reticular pattern of multivacuolated cells giving a chordoma-like appearance was evident in another case. Tumor cells were diffusely positive for CD34 in all 4 cases studied, and negative for S-100, EMA, NKI-C3, CD68, and smooth muscle markers. No complete loss of retinoblastoma protein was found. No brachyury immunostaining was found in the case with chordoid features. No EWSR1 or NAB2-STAT6 gene fusions were found. From these findings, we demonstrate that MLTS is a distinct CD34+ spindle cell benign dermal tumor, unrelated to cellular neurothekeoma, and exhibiting myxoid, deciduoid, or chordoma-like features.