High‐grade mantle zone lymphoma

A 66‐year‐old man with a 6‐month history of sweating at night, generalized lymphadenopathy, hepatosplenomegaly, and paraproteinemia was diagnosed to have a Stage IV mantle zone lymphoma (MZL), which behaved aggressively. The neoplasm rapidly disseminated to extranodal sites—the skin, lungs, pleural cavity, and the central nervous system. The neoplasm did not respond to initial double‐agent chemotherapy, but it did partially respond to multi‐agent chemotherapy. In addition, the neoplasm had histopathologic features not reported previously in MZL—vascular invasion, massive extranodal infiltration, high mitotic count, and convoluted nuclei.