A septated trabeculated tan lesion, with glistening areas reflecting the glandular component, is seen in the gallbladder fundus. The fundus is the most common area in the gallbladder for adenomyomas.
Within wall of gallbladder, dilated irregular glandular structures are seen with surrounding stroma.
Within the stroma are intervening bands of smooth muscle. The glands appear cytologically benign.
Some areas show numerous glands of various sizes, yielding an appearance of adenosis.
Adenomyoma of the gallbladder is in fact a diverticular process composed of invaginated glandular elements. These glands represent exaggerated Rokitansky-Ashoff sinuses and are surrounded by hypertrophied smooth muscle. Rokitansky-Ashoff sinuses and adenomyomas arise from chronic irritation to the mucosa and thus are features of chronic cholecystitis (Iacobuzio).
They are important to recognize as both may mimic invasive carcinoma as the glands are displaced into and beyond the muscular layer. Occasionally, an adenomyoma may form a discrete mass (Rosai).
Iacobuzio-Donahue CA, Montgomery EA. Gastrointestinal and Liver Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elsevier; 2005: 439.
Rosai, J. Rosai and Ackerman's Surgical Pathology. 9th Ed. Philadelphia, PA: Elsevier; 2004: 1042.