Cellular ‘neurothekeoma’: an epithelioid variant of pilar eiomyoma? Morphological and immunohistochemical analysis of a series

Abstract

Cellular neurothekeoma is a recently recognized benign cutaneous neoplasm, which is currently regarded as being of nerve sheath origin and is thought to represent a variant of conventional neurothekeoma (dermal nerve sheath myxoma). Nine new cases presenting predominantly in adolescents or young adults are described. Morphologically they were characterized by short fascicles or small nests of palely eosinophilic epithelioid or spindle-shaped cells which ramified in an ill-defined manner between dermal collagen bundles. Myxoid matrix was absent or sparse. Scattered normal mitoses and multinucleate giant cells were often present. Immunohistochemically all nine cases were strongly NK1/C3 positive, seven were weakly NSE positive and three were smooth muscle actin positive. Staining for S-100 protein, PGP 9.5, epithelial membrane antigen and desmin was negative in all cases. In view of its distinctive architecture and immunophenotype, both of which are totally different from conventional neurothekeoma, it is proposed that cellular 'neurothekeoma' is a separate discrete entity which may represent an epithelioid variant of pilar leiomyoma.

Microphthalmia transcription factor and NKI/C3 expression in cellular neurothekeoma

“…5,[9][10][11] It has, however, been noted to stain with some neural markers, including PGP 9.5, and, more interestingly, melanocyte markers, including NKI/C3. 11,12 Other studies have shown it to be smooth muscle actin positive (see Table 5). The goal of this study was to characterize the combination of Mitf and NKI/C3 expression in cellular neurothekeomas.…”

“…Other studies have also shown that cellular neurothekeoma does not actually represent a variant of neurothekeoma and is in fact a tumor of another cell type. 21 Calonje et al, 12 suggested with their immunohistochemical and light microscopic study that cellular neurothekeoma was in fact an epithelioid variant of a pilar leiomyoma. In addition, Mitf positivity has been shown in PEComas.…”

“…This observation should help prevent diagnostic error in classification of cellular neurothekeoma and may be evidence that cellular neurothekeoma is a type of myomelanocytic tumor in the family of perivascular epithelioid cell tumors. 24 11 Colllagen type IV, SMA, calponin S-100, GFAP, CD57, CD34, EMA, NF, p75ngfr, Factor XIIIa Chang et al, 1999 25 1 NKI/C3,SMA, NSE, synaptophysin, chromogranin S-100, CD34, Factor XIIIa, CD68, HMB-45, CK, EMA Zelger et al, 1998 21 15 NKI/C3, KiM1p, PCNA, NSE, Factor XIIIa, SMA, vimentin S-100, CD68, MBp, GFAP, NSE, NF, CD34, CD31, Factor VIII, ulex, desmin, myoglobin, KL1, EMA, E9 Tomasini et al, 1996 26 2 Vimentin, SMA, S-100, HMB-45, NSE, EMA, CK, desmin, CD68 Argenyi et al, 1995 19 11 Collagen type IV, SMA, NSE, vimentin S-100, CD57, GFAP, MBp, NSE, DP keratin, HMB-45, CD34, Factor XIIIa Husain et al, 1994 23 14+ MBP, EMA A-1-ACT, MAC-387, KP-1, SMA Argenyi et al, 1993 20 4 NSE,SMA, CD57 S-100, Collagen IV, GFAP, NF, EMA, MBp, DP keratin, HMB-45, chromogranin, A1-ACT, desmin Calonje et al, 1992 12 9 NKI/C3, NSE, SMA S-100, desmin, EMA, PGP 9.5, HMB-45 Barnhill et al, 1991 9 8 Vimentin S-100, MBP, EMA, GFAP Barnhill and Mihm 1990 16 5 S-100, MBP, EMA, keratin, A1-ACT, lysozyme, A1-AT, Rosati et al, 1986 7 3 S-100, lysozyme, A1-AT, MBP, Factor VIII, keratin, desmin …”

Cellular neurothekeoma: analysis of 37 cases emphasizing atypical histologic features

“…There have been many theories regarding the histogenesis of these lesions with authors regarding them as variants of dermatofibromas, leiomyomas, or nerve sheath tumors. [19][20][21][22] It has been noted that cellular neurothekeoma can resemble a melanocytic tumor by virtue of its growth pattern, but lack of expression of S100 protein was against a melanocytic origin. 12,22 It is reasonable to classify cellular neurothekeoma as fibrohistiocytic tumors, as suggested by Fetsch et al, 3 although this category is itself somewhat of a wastebasket term.…”

Nerve Sheath Myxoma (Neurothekeoma) of the Gingiva, A Case Report and Review of the Literature

“…Fetsch et al postulated a tendency of NSM to recruit histiocytic cells and to differentiate into myofibroblasts [13]. SMA positivity suggests some similarity to the epithelioid variant of leiomyoma or myofibroblastic proliferations [14]. GFAP positivity is rare in NSM; however, its positivity further supports a peripheral nerve sheath origin as occasional peripheral nerve sheath tumors may co-express GFAP and S100 [15].…”