Case 6 -

Bile Duct Adenoma Linda D. Ferrell, M.D. Wendy L. Frankel, M.D.

Clinical history: 40 year old man with cirrhosis who underwent a liver transplantation. The explant liver contained a 1 cm tan firm nodule in that appeared different from the surrounding nodules. Case 6 - Figure 1 - Cirrhotic liver with a nodular proliferation of ducts in a fibrotic area, low power Case 6 - Figure 2 - Ductular structures with a tubular appearance in a fibrotic stroma with some lymphocytes, medium power Case 6 - Figure 3 - Ducts with no cytologic atypia, high power Pathologic findings: Cirrhotic liver with a nodular proliferation of ducts in a fibrotic area. Ductular structures with a tubular appearance and no cytologic atypia in a fibrotic stroma with some surrounding lymphocytes. Diagnosis- Bile Duct Adenoma Comment Bile Duct Adenoma Clinical features. Bile duct adenoma (BDA) is a less common lesion than biliary hamartoma. The designation of "adenoma" may be a misnomer as most feel this lesion does not not represent a true neoplasm, but rather represents a localized ductular proliferation at a site of previous injury or a form of peribiliary gland hamartoma. The lesions are usually discovered as incidental findings, and may be biopsied at time of surgery (often for frozen section) to exclude metastatic disease. Gross features. BDAs are small lesions, usually less than 2 cm in diameter, firm, white to grey-tan, and well-circumscibed. Typically, they are noted in a subcapsular location, but they can be located deep in the parenchyma. BDAs can be single or multifocal. Microscropic features. The ductules in BDA are more uniform in size without the appearance of dilatation and with less intervening fibrous stroma than the ductules in hamartomas. Although the fibrous stroma is typically not as pronounced as that in hamartoma, the amount of collagenization may vary considerably, and focal zones of dense collagen can be present. The ductules tend to have tubular or curvilinear shapes and are lined by cuboidal epithelium with bland round to oval nuclei without mitotic activity. Mucinous metaplasia of the epithelium, alpha-one-antitrypsin droplets, and neuroendocrine differentiation may be seen in the tubular lining cells. Typically, residual portal tracts are often preserved within or near the edge of the lesion and small aggregates of lymphocytes are present at the periphery. Biliary Hamartoma Clinical features. Biliary hamartoma (BH), or the von Meyenburg complex, is thought to represent a ductal plate malformation, and so these lesions are often seen as part of the spectrum of polycystic disease in the liver and other organs. Gross features. BH is a small (usually less than 0.5 cm), grey to white, irregularly shaped lesion; multifocality is common. Microscopic features. BH consists of numerous small to medium-sized ductules, which are typically more dilated than normal ducts, and are separated by dense collagen. They typically are located within and at the edge of a portal zone. The ductules are lined by small, cuboidal to flattened epithelium with round to oval nuclei, are also more irregularly shaped than normal ducts, and may contain eosinophilic debris or inspissated bile.