Artifactual signet-ring-like cells in endoscopic biopsy of gastric lymphoma.
OBJECTIVE: To describe the morphologic characteristics of neoplastic lymphocytes with shrinkage artifact of cytoplasm secondary to formalin fixation and/or necrosis, which simulate carcinoma signet-ring cells in endoscopic biopsy. DESIGN: Sixty-eight endoscopic biopsies with gastric lymphoma were studied retrospectively. We selected those biopsies in which artifactual signet-ring-like cells were the main histologic feature and were confused with adenocarcinoma. Mucin stains were performed on all specimens. To support their B-cell phenotype, immunohistochemical study with leukocyte common antigen (CD45), pan B-cell marker L26, keratin, and carcinoembryonic antigens were performed. The diagnosis of gastric lymphoma was confirmed in gastrectomy specimens. SETTING: The distinction between poorly differentiated adenocarcinoma and gastric lymphoma in endoscopic biopsies is sometimes difficult owing to the morphologic similarities that these neoplasias can share and the small amount of tissue obtained by this technique. An additional factor that may contribute to this confusion is the presence of artifactual lymphocytes resembling signet-ring cells. RESULTS: Three (4%) of the 68 biopsies showed artifactual lymphocytes in most or all the tissue fragments that resembled carcinoma signet-ring cells. These biopsies showed massive substitution of gastric glands by lymphomatous infiltrate. Crush artifact of neoplastic lymphocytes was observed in many fields. Necrosis, inflammation, and epithelial erosion were prominent findings. Mucin stains were negative, and immunohistochemical studies were positive for leukocyte common antigen and B-cell marker L26 in two of the three cases. CONCLUSIONS: We conclude that if a poorly differentiated neoplasm consistent with signet ring adenocarcinoma is found in an endoscopic biopsy with artifactual changes, the diagnosis of gastric lymphoma must be excluded using histochemical and immunohistochemical studies.