Mucosa-associated lymphoid tissue (MALT) of the gallbladder: a clinicopathological correlation

Lymph follicles are frequently found on histological examination of a surgically removed gallbladder. The significance of these lymph follicles is not clearly understood. The aim of this study was to examine the clinicopathological correlation between the lymph follicles in the gallbladder morphologically and the mucosa-associated lymphoid tissue (MALT) in the gut.

The gallbladders were fixed and cut serially. The tissue slices were processed in the routine manner for a histological examination. The histological criteria for MALT in this study was defined as the presence of lymph follicles with germinal centers in the lamina propria mucosae in approximately equal numbers in all portions of the gallbladders from the neck to the fundus. Biliary bile obtained at surgery was cultured for a bacteriological examination in the hospital laboratory. The types of gallstones were classified according to the Classification of Gallstones by the Japanese Society of Gastroenterology.

Of the 1341 patients, 158 (11.8%) patients fulfilled the histological criteria, including 64 men and 94 women with an average age of 64.2 years. Gallstones were present in 89.2% of the patients, and 74.5% of these were calcium bilirubinate gallstones. Cultures of the bile were positive in 95.4% of the patients. A variety of bacterial species were thus found, most commonly Escherichia coli and Klebsiella spp. Grossly, the gallbladders usually showed a granular appearance of the mucosa.

The MALT in the gallbladder is not a rare condition and is frequently encountered in clinical practice. This lymphoid tissue may represent a mucosal and morphological immune phenomenon for infection rather than a substrate for the development of low-grade B-cell lymphoma.