Application of anti-leukocyte common antigen and anti-cytokeratin antibodies to the biopsy diagnosis of gastric large cell lymphoma.

Definitive diagnosis of gastric large cell lymphoma and its distinction from anaplastic carcinoma in endoscopic biopsy material may be problematic. To assess the utility of immunohistochemical studies in routinely processed, paraffin-embedded tissue in this situation, we applied immunostaining for leukocyte common antigen (LCA) and cytokeratin in 17 cases diagnosed on biopsy as undifferentiated malignant tumor but proved on resection to be primary gastric large cell lymphoma. Clinical and endoscopic features failed to distinguish lymphoma from carcinoma in these cases. Immunoreactivity for LCA occurred in 15 cases (88 per cent) and was correctly and readily interpreted on blinded evaluation. Open review increased the yield to 16 cases (94 per cent). Tumor cells were uniformly negative for cytokeratin; however, staining of adjacent epithelium for cytokeratin provided additional confirmation of the lymphoid nature of the tumor. The one case in which excessive background staining precluded interpretation consisted of a single biopsy specimen of necrotic tumor. We conclude that antibodies to LCA and cytokeratin are sensitive, specific, and reliable diagnostic adjuncts that are useful in the definitive biopsy diagnosis of gastric large cell lymphoma.