Cytologic findings of myxoid neurothekeoma: Case report based on fine-needle aspiration cytology, immunohistochemistry, and correlating histopathology

Myxoid neurothekeomas (nerve sheath myxomas) are rare benign cutaneous neoplasms that may morphologically mimic other myxoid neoplasms of skin and soft tissue. The cytologic and histopathologic features of this lesion may resemble various myxoid sarcomas, chordoma, myxoid neurofibroma, dermal cutaneous mucinosis, and cutaneous myxoma as well as other myxoid or chondroid neoplasms. In this study, a myxoid neurothekeoma was analyzed using multiple techniques. We found that myxoid neurothekeomas reveal a nonspecific pattern by fine-needle aspiration, including stellate cells embedded within an abundant metachromatic myxoid stromal matrix. These are cytologic features shared by various other subcutaneous neoplasms and thus may not be helpful in forming a definitive diagnosis. Histopathologically, the tumor is composed of nodules of myxoid stroma containing interspersed bland spindled and stellate cells. Immunohistochemical studies show tumor cell positivity for S-100 protein and vimentin, a profile shared by other neoplasms with similar cytologic features and therefore of little diagnostic value. The histologic and cytologic differential of subcutaneous and soft tissue myxomatous lesions is broad and, therefore, is of unique value to the cytopathologist to consider myxoid neurothekeomas among the differential of other myxomatous neoplasms.