Signet ring cell “lymphoma”: mimicking the appearance of signet ring cell carcinoma

Excerpt

A 70-year-old man presented with a 1-month history of intermittent epigastric pain. Emergency upper endoscopy revealed acute gastric ulcer. Abnormal findings of blood analysis included anemia (hemoglobin level: 8.1 g/dL), thrombocytopenia (platelet count: 29000/μL), high levels of lactase dehydrogenase (LDH: 983 IU/L), hypercalcemia (11.8 mg/dL) and renal failure (serum creatinine: 2.8 mg/dL). 18-Fluoro-2-deoxyglucose (FDG) positron emission tomography scan showed marked FDG uptake in the angular incisure, and in the systemic lymph nodes and bones (Fig. 1a, b). A second upper endoscopy biopsy was performed to obtain samples for pathological analysis, which showed diffuse infiltration by a “signet-ring”-like tumor (Fig. 2a, c). These tumor cells had round and large cytoplasmic vacuoles, and compressed atypical nuclei in a crescent shape. The initial impression was signet ring cell carcinoma, primary gastric tumor and its metastasis. Immunohistochemical staining, however, demonstrated that the tumor cells were positive for CD10, CD 20, bcl-2, and MUM-1, leading to a diagnosis of diffuse large B cell lymphoma (Fig. 2d). The cytoplasmic vacuoles were negative for PAS (periodic acid-Schiff) staining. The same tumor cells were also found in bone marrow biopsy specimen. Subsequently he received systemic chemotherapy (R-THP-COP therapy; combinations of rituximab, pirarubicin, cyclophosphamide, vincristine, and prednisolone), but died from primary disease progression after 3 months.

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