Biliary Hamartoma: Incidentally Discovered Lesions on Frozen Section

Introduction

Biliary duct hamartomas, often known as 'Von Meyenburg complexes,' are benign bile duct malformations.1 Polycystic liver and polycystic kidney disease patients are much more likely to have them.2 Their estimated frequency on autopsy ranges from 0.6% to 5.6% and is around 1% on imaging.3,4 However, they occur sporadically as well. Bile duct hamartomas are normally small (<0.5cm), grey to white, irregularly shaped lesions. They are often multiple and draw the surgeon's attention during surgeries that prompts the intraoperative consultation. Here, we present a case of bile duct hamartoma which was an incidental intraoperative finding in a patient being operated for cholelithiasis

Case Report

A 64-year-old male patient presented with acute abdominal pain. Ultrasound (USG) abdomen was suggestive of cholecystitis with cholelithiasis, for which mini-laparoscopic cholecystectomy was planned. Intraoperatively, multiple micronodules, approximately 0.4cm in size, were present in both lobes of the liver, raising suspicion of a metastatic tumour. A biopsy was taken from a nodule on the right lobe of the liver and sent for intraoperative frozen section.

A single, greyish-white, solid, soft tissue piece measuring 0.4x0.3x0.2cm was received in the histopathology laboratory. On frozen section, the tissue showed many small to medium-sized, irregularly shaped dilated bile ducts lined by bland cuboidal cells with prominent intervening collagenous stroma (Figure 1A). The frozen biopsy was reported as bile ductular proliferation. Sections from the biopsy on permanent haematoxylin and eosin (H&E) stained histopathology slides also revealed small and medium-sized, irregularly shaped dilated ducts seen at the periphery of portal tracts with intervening collagenous stroma (Figure 1B). The ducts were lined by cubo-columnar cells with minimal atypia. Mitotic activity was not identified (Figure 1C). Few ducts contained inspissated bile (Figure 1D).

Figure 1: Small to medium-sized, irregularly shaped dilated bile ducts (A; Frozen section); Small and medium-sized, irregularly shaped dilated ducts with intervening collagenous stroma. The ducts were lined by cubo-columnar cells with minimal atypia (B,C; H&E stain); Duct containing inspissated bile (D; H&E stain).

Discussion

Bile duct hamartomas, although a common incidental finding in liver surgical specimens and autopsies, need to be distinguished from malignant neoplasms in the liver such as metastatic adenocarcinoma or cholangiocarcinoma, especially during frozen section consultation. Microscopically, bile duct hamartomas consist of numerous small to medium-sized ductules, which are typically more dilated than normal ducts and usually separated by dense collagen. These lesions are usually located in and at the periphery of portal tracts. The ductules are lined by small cuboidal or flattened cells, with round to oval nuclei and may also contain eosinophilic debris or inspissated bile. They are benign lesions with no malignant potential, and no specific treatment is necessary for these lesions.5 The typical luminal dilatation with bile is a helpful feature that distinguishes bile duct hamartomas from metastatic adenocarcinoma. Additionally, the epithelial cells of bile duct hamartoma are typically bland and lack the malignant features seen in adenocarcinoma, including pleomorphism, hyperchromasia, and mitoses.6