Soft tissue neoplasms with features of both
schwannoma and
perineurioma (hybrid
schwannoma-
perineurioma) have been increasingly recognized in recent years. To date, only a single case of this entity has been documented in the gastrointestinal tract (sigmoid colon). We herein describe 2 new cases of this entity. For comparison, we reevaluated 12 classic gastrointestinal
schwannomas for the perineurial cell component. The 2 hybrid
schwannoma-
perineuriomas were detected incidentally in the gastric antrum and the vermiform appendix in a 50-year-old woman and a 17-year-old man during surgery for gastric GIST and
appendicitis-like symptoms, respectively. None of the patients had
neurofibromatosis 1 or 2. Patients were alive with no evidence of recurrence or new
tumors at 8 and 12 months, respectively. The
tumors measured 1.2 cm and 1.5 cm in size. Histologically, they showed prominent storiform, lamellar, and fascicular patterns. Notably, both lacked peripheral lymphoid cuffs and the trabecular pattern of gastrointestinal
schwannomas. Both
tumors coexpressed
protein S100 (≥80%), CD34 (80%), and the perineurial cell markers (20% to 40% of
tumor cells). The perineurial cell component formed alternating fascicles with S100-positive cells throughout the
neoplasm. Reevaluation of 12 classic gastrointestinal
schwannomas showed isolated
claudin-1/
epithelial membrane antigen-positive cells. However, 4
schwannomas (33%) strongly expressed
glucose transporter-1 in most of the
tumor cells indicating its limited specificity in this setting. Compared with gastrointestinal
schwannomas, CD34 expression was stronger and more diffuse in hybrid
schwannoma-
perineuriomas. We conclude that hybrid
schwannoma-
perineuriomas are distinct from gastrointestinal
schwannoma, both histologically and immunohistochemically.