The usefulness of the reticulin stain in the differential diagnosis of liver nodules on fine-needle aspiration biopsy cell block preparations.

We reviewed fine-needle aspiration biopsy (FNAB) cell blocks of hepatocellular carcinoma (HCC) (n = 16) and benign hepatic processes (n = 16) to evaluate the significance of reticulin staining (Gomori stain) in combination with standard cytomorphologic and architectural criteria. We analyzed the staining pattern using semiquantitative grading: normal, variable, decreased, or virtually absent. Also, we graded the cell thickness of the hepatic trabeculae as greater than or less than three cells. Fourteen of 16 biopsy specimens of benign processes demonstrated a normal reticulin framework, with staining outlining hepatic trabeculae less than three cell layers in thickness. Staining was markedly decreased in one case of steatosis and virtually absent in one case of cirrhosis. In contrast, all of the 16 HCCs demonstrated either a virtually absent (7 of 16), decreased (6 of 16), or variable (3 of 16) reticulin staining pattern, with thickened trabeculae greater than three cell layers. We conclude that the reticulin stain is a useful adjunct in the differential diagnosis of liver nodules on FNAB cell block preparations and that it is particularly useful in distinguishing HCC from benign hepatic processes. Virtually absent or decreased reticulin staining and staining outlining trabeculae greater than three cells in thickness support the diagnosis of HCC. Normal reticulin staining outlining well-defined hepatic trabeculae less than three cell layers in thickness supports the diagnosis of a benign hepatic process.