Amyloid deposition in extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue: A clinicopathologic study of 5 cases.

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) is the most common subtype of marginal zone lymphoma (MZL), with stomach being the most frequent primary site, followed by salivary gland, lung and ocular adnexa. Although clinically indolent, MALT lymphoma has the potential of local recurrence and systemic spread. Amyloid deposition is a very unusual complication of MALT lymphoma. In this study, we report clinicopathologic features of 5 cases of MALT lymphomas with associated amyloid deposits. One case showed amyloid deposits in the primary lesion; the other four cases showed amyloid deposits only in recurrences. Previous studies suggest that the amyloid deposits do not implicate worse prognosis. In our study, although amyloid deposits were focal and organ confined, one patient had extensive deposits of amyloid in the large bowel wall leading to bowel perforation and another patient developed significant peripheral neuropathy due to amyloid deposits in the brachial plexus. In conclusion, amyloid deposits in MALT lymphomas are rare and organ/tumour confined. However, complications can be critical and cause considerable morbidity. Therefore, pathologists should be aware of the association between MALT lymphoma and amyloid deposition, and clinical follow up is warranted.