Ultrastructure of gastric myxofibroma with intracytoplasmic collagen.

Electron microscopy of a small mass removed from the stomach of a 65-year-old women demonstrated a myxofibroma composed of a pure population of fibroblasts, many of which contained intracytoplasmic, membrane-bound collagen fibers similar to those found in a few other human tumors and in certain experimental conditions. This ultrastructural documentation supports the hypothesis that pure fibrous neoplasms of the stomach do occur. Electron microscopy of gastric mesenchymal tumors almost always allows for confident differentiation among fibrous, neural, and smooth muscle neoplasms.