Gastric carcinoma with osteoclast-like giant cells. Lymphoepithelioma-like carcinoma with Epstein-Barr virus infection is the predominant type.

Osteoclast-like giant cells (OGC) are rare in gastric carcinomas. Histopathological study of seven gastric carcinomas with OGC demonstrated three distinct types: lymphoepithelioma-like carcinoma (LELC), non-LELC, and giant cell tumor (GCT) types. LELC is a poorly differentiated adenocarcinoma with prominent lymphoid stroma. The LELC type (n = 4) showed similar histology to LELC of the stomach, except that they were accompanied by OGC and granulomatous reaction. Epstein-Barr virus (EBV) infection was demonstrated by EBV-encoded RNA (EBER) in situ hybridization (ISH) in all the neoplastic cells. The non-LELC type (n = 2) consisted of EBV-negative carcinoma cells with inflammatory infiltrates. OGC and granulomas were frequently observed in the glandular lumens with accumulated mucus. The GCT type (n = 1) was a neuroendocrine carcinoma, containing many OGC with metaplastic bone formation, which showed typical morphological features of OGC in GCT of the bone. In all three types, OGC expressed CD68, but not cytokeratin, indicating that OGC had a reactive histiocytic lineage. Both LELC and non-LELC types are included in the differential diagnosis of isolated granulomatous gastritis, and EBER-ISH was useful for the identification of LELC type. Both LELC and no-LELC types were also suggested to have better prognoses, but the behavior of the GCT type needs to be further characterized.