Dermatopathology Studies on the cellular origin of neurothekeoma: Clinical, light microscopic, immunohistochemical, and ultrastructural observations Raymond L. Barnhill, MD,a G. Richard Dickersin, MD,a Volker Nickeleit, MD,a Atul K. Bhan, MD,a Jan E. Muhlbauer, MD,b Mildred E. Phillips, MD,c and Martin C. Mihm, Jr., MD a Boston, Massachusetts The clinical, histopathologic, and immunohistochemical features of 11 cases of neurothek- eoma are reported. One case was examined by electron microscopy. The mean age of the pa- tients was 27.1 years; the study comprised eight female and three male patients. Most lesions were nondescript papules and located on the upper part of the body, seven cases of neurothekeoma on the head. Eight cases were classified as cellular neurothekeoma on the ba- sis of a striking fascicular pattern and three cases as myxomatous neurothekeoma because of prominent myxoid stromal change. All cellular neurothekeomas failed to express S-l00 protein, whereas the three myxomatous types were strongly positive for this marker. Other than vimentin, there was no significant immunoreactivity with other immunohistochemical markers. Ultrastructural study of onecase of cellular neurothekeoma was inconclusivefor cell type although a perineurial origin could not be excluded. On the basis of these results, we conclude that cellular neurothekeoma differs from myxomatous neurothekeoma not only by clinical and histologic findings but also by immunoreactivity with S-l00 protein. These find- ings also suggest the existence of two distinct subtypes of neurothekeoma and possible origin of the two variants of neurothekeoma from different cell types or at least variation in phe- notypicexpression of a common cell type. On the other hand, it cannot be excluded that these two variants are different stages in the natural history of neurothekeoma. (J AM ACAD DER- MATOL 1991;25:80-8.) Table 1. Antibodies used in immunohistochemical studies "'Dakopatts, Glostrup, Denmark. tEnzo Biochem Inc" New York City. :\:Becton Dickinson Co., Mountain View, Calif. §Lab Systems, Chicago. 1:100 1:20 1:400 1:30 1:30 1:30 1:30 1:800 1:10 1:100 Prediluted DAKO* DAKOKit (K536) DAKOKit (K531) Enzot Becton Dickinson* Lab Systems§ DAKO DAKO DAKO DAKO DAKO DAKO Becton Dickinson HMB-45 Leu-? (HNK-1) GFAP Keratin al-Antichymotrypsin Lysozyme aI-Antitrypsin Desmin Vimentin Neurofilament S-100 protein Epithelial membrane antigen Myelin basic protein ___ A_nti_'b_od_ Y So_ur_ce 1 Dilution 1:100 Prediluted Neurothekeoma (NT, nerve-sheath myxoma) is an uncommon proliferation of peripheral nerve sheath origin that affects the skin and oral mucosa and has received little attention until recently,!-l3 NT has characteristic lightmicroscopicfindings and can be subclassified into cellular and myxomatous variants. 13 Although still unsettled, the light micro- scopic and some ultrastructural and immunohis- tochemical evidence has suggested that NT is de- rivedfrom either Schwann cells,5 perineurium,4, 8,10 or fibroblasts. 3 To provide additional information about the histogenesis of NT, we report 11 cases with particular attention to immunohistochemical and ultrastructural findings. From the Dermatopathology Division and Department of Pathology, Massachusetts General Hospital and Harvard Medical School"; Muhlbauer Dermatopathology Laboratory, Pittsford, N.y.b; and the Departments of Dermatology and Pathology, SUNY·Stony Brook. c Reprints not available. 16/1/27988 80