Extranodal malignant lymphoma arising from mucosa-associated lymphoid tissue

TLDR

MALT-derived lymphomas are typically localized, responsive to local therapy, and histologically show noninvasive lymphoplasmacytic infiltrates with follicle center cells invading epithelium, highlighted by monotypic cytoplasmic immunoglobulin in plasma cells. The study proposes that the common clinical, histopathologic, and immunohistochemical features of these extranodal lymphomas arise from a shared MALT histogenesis. Four extranodal malignant lymphomas arising in stomach, salivary gland, lung, and thyroid were described, all sharing similar clinical, histopathologic, and immunohistochemical features suggestive of a common MALT origin.

Abstract

Four cases of extranodal malignant lymphoma, one each arising in the stomach, salivary gland, lung, and thyroid, are described. These cases have many clinical, histopathologic, and immunohistochemical features in common, and it is proposed that this is because they share a common pattern of histogenesis from mucosa-associated lymphoid tissue (MALT). Clinical features of MALT-derived lymphomas include a tendency to remain localized for prolonged periods, and, thus, to be responsive to locally directed therapy. Histologically, this group of tumors is characterized by a noninvasive lymphoplasmacytic infiltrate within which foci of follicle center cells (FCC) can be seen invading epithelial structures, forming lymphoplasmacytic infiltrate lesions. Immunohistochemistry reveals monotypic cytoplasmic immunoglobulin (CIg) in the plasma cells serving to highlight the CIg-negative lymphoepithelial lesions. The clinical and histopathologic features of these lymphomas can be understood in the context of the behavioral characteristics and morphology of MALT.