LOW-GRADE B-CELL LYMPHOMA OF MUCOSA-ASSOCIATED LYMPHOID-TISSUE ARISING IN THE KIDNEY

We describe a malignant lymphoma arising in the kidney that exhibited clinical and histologic features of low-grade B-cell lymphoma of mucos a-associated lymphoid tissue (MALT). Clinically, the neoplasm involved the kidney and one perirenal lymph node (stage IIE) and did not recur or disseminate following nephrectomy, lymphadenectomy, and local radi ation therapy. Histologically, the neoplasm recapitulated the features of low-grade B-cell lymphomas of MALT at other sites. The neoplastic cells resembled centrocyte-like cells, some of which formed lymphoepit helial lesions with renal tubules, and reactive lymphoid follicles wer e scattered within the neoplasm. The neoplastic cells expressed monoty pic cytoplasmic Igkappa. Low-grade B-cell MALT lymphomas arising in th e kidney are rare. Their occurrence further demonstrates the diversity of anatomical sites that may be involved by MALT lymphomas. In additi on, this neoplasm also had histologic and cytologic features resemblin g those of monocytoid B-cell lymphoma, supporting the hypothesis that low-grade B-cell lymphomas of MALT and monocytoid B-cell lymphomas are closely related and may be two morphological manifestations of the sa me neoplasm.