Wagner‑Meissner neurilemmoma of the lip occurring in a patient with neurofibromatosis type 1: A case report

Wagner‑Meissner corpuscles are specialized mechanoreceptors located in the dermal papillae. Wagner‑Meissner corpuscle‑like structures are occasionally a component of certain types of tumors, such as melanocytic nevus and neurofibroma. Benign tumorous lesion entirely composed of Wagner‑Meissner corpuscles are described as Wagner‑Meissner neurilemmoma, and only four such cases have been reported. Here, we report the first case of Wagner‑Meissner neurilemmoma in a patient with neurofibromatosis type 1. A 16‑year‑old Japanese male with neurofibromatosis type 1 presented with a tumorous lesion on the upper lip. Resection of the tumor was performed under a clinical diagnosis of neurofibroma. Histopathological examination revealed an unencapsulated, poorly‑circumscribed tumor, comprised of abundant Wagner‑Meissner corpuscle‑like structures, which were composed of 5‑15 lamellated Schwann cells containing eosinophilic cytoplasm and peripherally located nuclei. No spindle‑shaped neoplastic cell proliferation, as seen in conventional neurofibroma, was observed. Accordingly, a diagnosis of Wagner‑Meissner neurilemmoma was made. The pathogenesis of Wagner‑Meissner neurilemmoma remains unclear. The hamartomatous or reactive proliferative nature has been proposed. In addition, this lesion may represent an extreme form of diffuse neurofibroma with abundant Wagner‑Meissner corpuscles associated with neurofibromatosis type 1, even though the previously reported four patients did not have neurofibromatosis. Therefore, further studies are needed to clarify the pathogenesis of this extremely rare tumor, including its association with neurofibromatosis.