Periampullary Epstein-Barr virus-associated myopericytoma.

Although myopericytoma occurs predominantly in the extremities, a wider anatomical distribution, malignant variant, and association with Epstein-Barr virus have been recognized recently. However, benign, malignant, or Epstein-Barr virus-myopericytoma has not been documented in the gastrointestinal tract to date. We report a periampullary Epstein-Barr virus-myopericytoma in a patient with AIDS who presented with obstructive jaundice. The tumor contained round, oval, and plump spindle cells arranged around and between slit-like, dilated, and staghorn vessels. A malignant variant was favored based on the presence of cellular pleomorphism, 23 mitoses per 10 high-power fields, necrosis, and lymphovascular involvement. Immunohistochemistry confirmed a myoid immunophenotype with h-Caldesmon positivity and desmin negativity. Epstein-Barr virus-encoded RNA was demonstrated by in situ hybridization. Heightened awareness of Epstein-Barr virus-myopericytoma and occurrence in the periampullary location are critical to diagnostic workup and differentiation of myopericytoma from other mesenchymal tumors and pseudotumors especially in small biopsies and in patients with AIDS.