An unusual case of neurothekeoma of the arm in an adult.

Neurothekeomas are uncommon benign neoplasms with a peripheral nerve sheath origin. This tumor usually involves dermis and is described as a small, solitary, slow growing and reddish to flesh-colored nodule or papule. Neurothekeoma preferentially affects the central aspect of the face, the arms or shoulders of women in the second and third decades of life. This is the first case report of neurothekeoma involving the wrist developing from synovial tissue and with uncertain clinical behavior in an adult female. The tumor was completely excised under brachial plexus block. Histopathologically, the examination of the microscopic slides revealed the presence of a 20-mm diameter, well-circumscribed and multilobulated tumor composed of abundant myxoid stroma with cellular elements; with immunohistochemistry there was positivity to vimentin but S100-protein, epithelial membrane antigen, cytokeratin AE1-3, CD99 and CD34 were all negative. This pattern suggested a myxoid tumor form of neurothekeoma, mixed subtype. The patient had an atypical local recurrence and was re-operated after 3 months. After 12 months there was no evidence of clinical recurrences confirmed by magnetic resonance evaluation. Basically, our case report adds an important element in the correct clinical management of neurotecheomas: faced with a histological diagnosis with an unusual localization and mixed or hypercellular type, clinicians must consider the possibility of an early local recurrence, suggesting a close clinical and radiological follow-up.