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 eosino‐philic and often foamy cytoplasm and eccentric small nuclei with apparent nucleoli. They contained periodic acid‐Schiff‐reactive granules, and were further immunoreactive for lysoryme and α1‐antttrypsin. 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.