Progressive Non-scarring Alopecia Caused by Diffuse Melanocytic Neuroma in a Patient Without NF

Summary: A 29-year-old female presented to the clinic with a 16-year history of a soft subcutaneous mass on the crown. A soft non-mobile 6.2 x 6.5 cm subcutaneous, soft, spongy, nodule with overlying alopecia was present on exam. Ultrasound of the mass read as thickened soft tissue without evidence of fluid. Joint decision was to perform an incisional biopsy. Grossly the tissue had glassy pale amorphous soft tissue replacing dermis. On histologic examination there was a diffuse SOX10 and Melan-A positive spindle cells spanning the dermis and subcutis. After expert consultation, it was classified as diffuse melanocytic neurofibroma. Melanocytic neurofibroma’s are rare variants of benign nerve sheath tumors, accounting for less than 1% of all neurofibromas.1 Based on tumor characteristics, excision may be recommended to exclude rare simultaneous occurrence of malignant melanoma or progression to a malignant peripheral nerve sheath tumor (MPNST). While MPNST is associated with plexiform neurofibromas and neurofibromatosis, malignant transformation of sporadic diffuse neurofibromas are reported.2,3 Postoperative hematomas can occur and bleeding precautions should be taken due to the vascular nature of these tumors.4 Although uncommon, recurrent diffuse neurofibromas can present with malignancy. In this case, decision was made to perform staged incisional removals of the tissue mass.