Often submitted for frozen section to rule out metastasis
Microscopic
• Uniformly sized tubules and acini with rounded outlines
• Single layer of cuboidal to columnar cells that lack atypia, hyperchromasia, mitoses
• Fibrous stroma either scant or dense and hyalinized
• Bile is not present, and ducts do not communicate with biliary tree
• Variant features include clear cell change, mucinous metaplasia, neuroendocrine differentiation, and α-1-antitrypsin globules
• Circumscribed outline and lack of cytologic atypia are most important features to distinguish from adenocarcinoma
Ancillary Tests
• Ki-67 typically < 10%
• p53 weak and patchy
• DPC4 is intact in contrast to most of metastatic pancreatic ductal adenocarcinomas
Top Differential Diagnoses
• Biliary microhamartoma (von Meyenburg complex)
• Intrahepatic cholangiocarcinoma
• Metastatic adenocarcinoma
• Neuroendocrine tumor
Well-Circumscribed Lesion Bile duct adenomas are well circumscribed but unencapsulated. Note the fibrous stroma and evenly distributed glands. An adjacent normal portal tract is present.
Loose Fibrous Stroma Most bile duct adenomas have a scant compact stroma, while others may show abundant loose fibrous stroma with admixed chronic inflammation . The stroma tends to be more prominent toward the center of the lesion. The tubular glands are lined by a single layer of cuboidal epithelium with uniform nuclei.
Subcapsular Location Most bile duct adenomas are located in the subcapsular region. These are often noted intraoperatively during abdominal surgery and can mimic metastatic disease.
Cytoplasmic Globules Some bile duct adenomas contain eosinophilic cytoplasmic globules composed of α-1-antitrypsin . Note the lack of nuclear atypia, mitoses, or nuclear hyperchromasia in the lining epithelium of small rounded glands.
TERMINOLOGY
Abbreviations
• Bile duct adenoma (BDA)
Synonyms
• Bile duct adenoma, cholangioma, cholangioadenoma
Definitions
• Small, benign epithelial tumor composed of glands that resemble bile ducts
ETIOLOGY/PATHOGENESIS
Molecular Changes
• BRAF V600E mutations in > 50% of cases
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is present.
. The stroma tends to be more prominent toward the center of the lesion. The tubular glands are lined by a single layer of cuboidal epithelium with uniform nuclei.
. Note the lack of nuclear atypia, mitoses, or nuclear hyperchromasia in the lining epithelium of small rounded glands.
