Cutaneous Congenital Plexiform Cellular Schwannoma: A Simulant of Malignant Peripheral Nerve Sheath Tumor of Childhood – A Case Report and Literature Review

Abstract

Cutaneous plexiform schwannoma is a rare multilobulated variant of benign schwannoma. When presenting as the cellular subtype with significantly increased proliferative rate, diagnostic consideration of a malignant peripheral nerve sheath tumor is prompted. However, follow up demonstrates a benign natural history with propensity for local recurrence and typical lack of association with neurocutaneous syndromes. These lesions most commonly occur as cutaneous and subcutaneous masses of the extremities in the first four decades. Only 9 cases of congenital tumors are reported. A case of congenital plexiform cellular schwannoma, presenting as a cutaneous mass measuring 3.5 × 2.5 × 2.0 cm, excised from the left upper arm of a 16 month old female is discussed. Regions of increased cellularity and proliferation co‐localized and were unassociated with nuclear anaplasia. Mitotic figures numbered 7 per 10 400x fields. The tumor cells were strongly immunoreactive for S‐100 protein. The MIB‐1index was multifocally 25% and p53 protein over expression was present in 50% of nuclei. Following excision with free margins the tumor locally recurred after 16 months. The recurrence was morphologically identical to the original lesion. Recognition of the clinical and morphological characteristics of this rarely encountered benign neoplasm will facilitate in diagnosing this entity.