Benign histiocytosis X of stomach. Previously undescribed lesion

Histiocytosis X of the stomach of a 47-year-old Japanese woman, who underwent subtotal gastrectomy following a clinical diagnosis of scirrhous carcinoma, was studied by light and electron microscopy as well as by immunohistochemistry. The histiocytoid cells proliferated monotonously in the lamina propria mucosae of the atrophied mucosa covering the body and fornix. They were arranged in a sheet- or pavement stone-pattern and included some giant cells. The histiocytoid cells had a reniform to irregularly indented nucleus and conspicuous cytoplasm. Ultrastructurally, they were characterized by interdigitating cytoplasmic extensions and abundant tubulovesicular structures including Langerhans granules. S-100 protein, alpha 1-antitrypsin, and alpha 1-antichymotrypsin were immunohistochemically identified in the cytoplasm. Endoscopic biopsies of the extragastric digestive tract, a biopsy of the lymph node, and bone marrow aspiration excluded a systemic disorder. The case is regarded as benign localized histiocytosis X of the stomach, a previously undescribed gastric lesion.