Cellular neurothekeoma with a plexiform morphology: a case report with a discussion of the plexiform lesions of the skin

Abstract

Neurothekeoma is a rare benign dermal lesion that is commonly seen in children and teenagers. Despite its name, the true nature of this lesion is uncertain and controversial, particularly after the emergence of the cellular (spindle/epithelioid) variant. We describe the histological and immunohistochemical findings of a right thigh skin lesion in an 11-year-old girl. It consists of a dermal ill-defined plexiform mass composed of nests and fascicles of spindle cells with pale eosinophilic cytoplasm that lie within a sclerotic stroma. The immunohistochemistry shows diffuse reactivity to CD68, matrix metalloproteinase-II, CD10 and PGP9.5 with focal reactivity to CD57 and CD34. The lesion is negative for S100, factor XIIIa, smooth muscle markers and melanocytic markers. The features are compatible with a cellular variant of neurothekeoma with plexiform pattern that also exhibits an unusual pattern of fibrohistiocytic phenotype. Although such a lesion is benign, it has a wide but important differential diagnoses that are reviewed briefly together with a brief discussion about the origin of this rare entity.

A Benign Cutaneous Plexiform Hybrid Tumor of Perineurioma and Cellular Neurothekeoma

“…47 The nests of neoplastic cells often exhibit a concentric or whorling arrangement, and a plexiform pattern may be sometimes seen, at least focally. 48,49 Some of the cells may show large hyperchromatic nuclei, and a few mitoses and multinucleate cells are not rare. The immunophenotype of neoplastic cells in cellular neurothekeoma is different from that found in nerve sheath myxoma, as they do not express S100 protein, CD57, and GFAP but do stain with S100A6 protein, 49-52 NKI/C3, 46,49,53,54 PGP9.5, 46,49 NSE, 46,49 and, in some cases, SMA.…”

CD34‐reactive tumors of the skin. An updated review of an ever‐growing list of lesions

“…CD34 expression has also been reported in sporadic cases of angiomatoid fibrous histiocytoma 168 and in one case of cellular neurothekeoma, 169 two neoplasms commonly considered CD34‐negative 170,171 …”

Ossifying Plexiform Tumor: Report of Two New Cases

“…17 As an architectural pattern, this can be seen in a variety of cutaneous neoplasms, including atypical fibroxanthoma, tufted angioma, melanoma, melanocytic nevi, neurofibroma, schwannoma, giant cell tumor, perineuroma, dermatofibroma, and plexiform fibrohistiocytic tumor. 18 Ossifying plexiform tumor, as its name implies, has both prominent ossification and a plexiform architecture. This newly identified neoplasm has only been described in a single case report by Rooney et al in 1994 which highlighted a 30-year-old woman with a recurrent 1.6-cm superficial raised nodule of the left thumb.…”

“…The most pertinent among these is cellular neurothekeoma. 3,[18][19][20][21] Clinical similarities between the two include a female predominance and a relatively small tumor size (cellular neurothekeomas are typically ,2.0 cm). Under the microscope, a resemblance is noted in that both tumors are dermally located and have a lobular architecture.…”