CD68+ reactive histiocytosis complicating early gastric cancer.

A peculiar form of reactive, non-granulomatous proliferation of CD68+ histiocytes was demonstrated, for the first time, in the submucosal layer just beneath the IIa-type early gastric adenocarcinoma that focally invaded submucosal lymphatics. The histiocytic cells possessed plump eosinophilic and often foamy cytoplasm and eccentric small nuclei with apparent nucleoli. They contained periodic acid-Schiff-reactive granules, and were further immunoreactive for lysozyme and alpha 1-antitrypsin. The infiltration was ill-defined, and partly involved the tunica muscularis mucosae and the proper muscle layer. Markers of epithelial cells, Langerhans' histiocytes, smooth muscle cells and myofibroblasts were all negative.