Reticular and microcystic schwannoma: a distinctive tumor of the gastrointestinal tract.

Reticular/microcystic schwannoma is a rare variant of schwannoma with a predilection for viscera, especially the gastrointestinal tract. Of the 9 cases reported thus far, 7 have occurred in female patients. The average age of presentation is 67 years. They are usually small, asymptomatic lesions ranging in size from 0.85 to 2.2 cm with a mean size of 1.35 cm. They usually occur in the stomach, small bowel, and proximal large intestine. It differs from usual schwannomas of the gastrointestinal tract by lacking the peripheral cuff of lymphocytes. The histologic appearance of slender bipolar spindle cells in a lace-like reticular pattern set within a myxoid stroma raises a wide differential diagnosis including gastrointestinal stromal tumor, perineurioma, and in more epithelioid examples, even carcinoma. Awareness of the entity and an immunohistochemical panel of markers will ensure that the correct diagnosis is made.