Mucosa-associated lymphoid tissue-type lymphoproliferative lesion of the common bile duct.

Only a few cases of primary lymphoma of the common bile duct have been reported up to now. Here, we report a mucosa-associated lymphoid tissue (MALT)-type lymphoproliferative lesion of the common bile duct with some considerations about MALT lymphoma and benign lymphoproliferation. The patient, a 71-year-old woman, was admitted to our hospital because of progressive epigastric pain. Abdominal ultrasonography, magnetic resonance cholangiopancreatography, endoscopic retrograde cholangiopancreatography, and abdominal computed tomography showed a non-specific finding of stenosis of the common bile duct due to thickening of the wall. Angiography provided little diagnostic information. Bile duct carcinoma was diagnosed and pylorus-preserving pancreaticoduodenectomy was performed. Histological examination revealed that the common bile duct was occupied by full-thickness proliferation of lymphoplasma cells with many reactive lymph follicles. The histological features were somewhat consistent with those of MALT lymphoma. However, we could not determine the clonal proliferation of lymphoplasma cells in either immunohistochemical immunoglobulin light chain restriction of the plasma cells or in polymerase chain reaction based immunoglobulin heavy chain gene rearrangement. The present case may be categorized as a borderline lesion close to benign lymphoproliferation. To the best of our knowledge, there have been no reports of cases similar to the present case.