A case of Epstein-Barr virus-associated smooth muscle tumor of the posterior interosseous nerve mimicking schwannoma.

Here we report a case of Epstein-Barr virus (EBV)-associated smooth muscle tumor (SMT) of the peripheral nerve in a young man seropositive for human immunodeficiency virus (HIV). Initially, the lesion was clinically and radiologically confused with a schwannoma of the forearm's posterior interosseous nerve. The diagnosis was corrected by histological examination, which revealed a well-defined tumor consisting of eosinophilic spindle cells, positive for α-smooth muscle actin on immunohistochemistry and positive for EBV-encoded early RNA (EBER) on in situ hybridization. EBV-associated SMTs are well described in the literature; they are frequently multiple and arise in many organs. They occur preferentially in young adults with poorly controlled and chronic HIV infection. The prognosis is influenced by the complications of immunodeficiency. To our knowledge, this is the first description of a peripheral nerve location. Because EBV-associated SMT should be considered in the differential diagnosis of a tumor in the peripheral or central nervous systems in immunocompromised patients, EBV should be tested in these locations. Thus, a cause of immunodeficiency should be identified when the diagnosis of EBV-associated SMT is made.