Middle aged male patient with a 2-cm liver mass. The mass was biopsied twice before with a diagnosis of "atypical cells", not further specified.
The aspirate is cellular composed of two populations of cells: benign loosely cohesive liver cells and these branching cohesive ductal cells. These ducts are composed of bland uniform cells with minimal cytologic atypia.
Diagnosis:
Biliary duct hamartoma (von Meyenburg complexes)
This is a diagnostic pitfall, especially in patients with known malignancy. The architectural feature (branching ducts) may be confused as architectural complexity and misdiagnosed as metastatic adenocarcinoma.
The key feature is bland cytology with minimal atypia.
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