Myxoid Cellular Neurothekeoma: A New Entity of S100-Negative, CD68-Positive Myxoid Neurothekeoma.

Neurothekeoma is a rare cutaneous neoplasm, occurring as a cutaneous papule or nodule on the face, shoulders, and upper extremities. Neurothekeoma has been subclassified as either the myxoid, cellular, or mixed type, depending on the amount of myxoid matrix and on immunohistochemical analysis. We observed a clinical case with conflicting histopathological and immunohistochemical findings. In this case, microscopic examination showed the typical presentation of myxoid neurothekeoma; however, immunohistochemical staining was negative for S100 protein and positive for CD68, which is the characteristic pattern of cellular neurothekeoma. We report a very rare form of myxoid cellular neurothekeoma of the face in a young woman.