Gallbladder osseous metaplasia mimicking a focal lesion on ultrasound: a case report of a rare benign condition.

Focal gallbladder wall thickening may raise suspicion for inflammatory, hyperplastic, or malignant processes. We report a rare case of chronic cholecystitis associated with adenomyosis and osseous metaplasia in a 43-year-old woman with multiple comorbidities. The patient presented with right upper quadrant abdominal pain. Ultrasonography revealed focal gallbladder wall thickening without calculi. She underwent uneventful laparoscopic cholecystectomy. Gross and microscopic pathological examination demonstrated chronic cholecystitis with mucosal hyperplasia, intramural diverticula consistent with adenomyosis, and areas of osseous metaplasia, with no evidence of dysplasia or malignancy. The postoperative course was uncomplicated. Awareness of such rare benign lesions is essential, as they may clinically and radiologically mimic more aggressive disease.