CD79A and lymphoma: MRI brain: mild periventricular white matter ischemic changes of aging. No sign of acute infarction or enhancing lesions. No intracranial hemorrhage; bone marrow biopsy: small clonal population of B cells; brain biopsy: striking infiltration of lymphoma cells within the lumina of intramuscular blood vessels; immunocytochemical identification of CD20, CD79a, CD5 positive atypical large B-cell population in clumps