Multiple Cutaneous Solitary Circumscribed Neuroma in a Patient with Neurofibromatosis Type 2: An "Incidentaloma" or New Association?

Solitary circumscribed neuroma formerly known as palisaded encapsulated neuroma is a rare, benign neural tumor that usually presents as a painless firm nodule or papule on the face and within oral cavity, although they can occur elsewhere on the body. No association with neurofibromatosis has been reported in the literature. Herein, we report, a previously unreported unique association of neurofibromatosis type 2 (NF-2) with multiple cutaneous solitary circumscribed neuromas in a 24-year-old female. A 24-year-old female with history of NF-2 presented with two slow-growing soft-to-firm papules on the chin and forehead that had been gradually increasing in size over a period of 5 years. The papule on the chin was increasingly tender to palpation. Histologic sections demonstrated a dermal based almost encapsulated, smoothly contoured tumefactive mass composed of spindle cell proliferation with neuroid structures and foci of palisaded growth (resembling schwannoma) and intralesional cleft like spaces. By immunohistochemistry, the lesional cells were strongly and diffusely positive for S-100 and SOX10 with multifocal neurofilament expression while the "capsule" was diffusely reactive for epithelial membrane antigen. The overall features were considered prototypic for solitary circumscribed neuroma. The patient is 18-months post-surgical resection with no evidence of recurrence. In summary, we report for the first time a case of multiple solitary circumscribed neuromas in a patient with known NF2. We highlight pertinent diagnostic clues relevant to surgical pathologist to facilitate recognition (as this tumor is often mistaken for schwannoma or neurofibroma). The clinical behavior is excellent and surgical resection is considered curative.