Signet Ring B Cell Lymphoma: A Potential Diagnostic Pitfall.

Signet ring B cell lymphoma is an unusual non-Hodgkin lymphoma. It is similar to signet ring cell carcinoma and liposarcoma in morphology which should be distinguished. We treated a 63-year-old male patient who suffered from abdominal pain for two months. Multiple enlarged lymph nodes were found in the retroperitoneum by CT scan. The needle biopsy showed neoplastic cells distributed uniformly with clear cytoplasm and the nucleus squeezed to the side mimicking the appearance of signet ring in morphology. By special staining, the neoplastic cells were positive for CD45, Vimentin, Bcl-2 and CD20 but negative for AE1/AE3, S-100, CD3, EMA, CD5, CD10, Bcl-6, MUM1 , Kappa, Lambda and PAS . Ki67 proliferation index was much more than 80%. Based on the histological characters, a diagnosis of signet ring B cell lymphoma was made. Although the patient received six courses of R-CHOP therapy, he died of tumor recurrence at the 34th month after diagnosis.