Utility of Cytokeratin7 Immunocytochemistry in the Cytopathological Diagnosis of Fibrolamellar Hepatocellular Carcinoma

OBJECTIVE: To distinguish fibrolamellar hepatocellular carcinoma (FL-HCC) variant from the conventional hepatocellular carcinoma (HCC) by cytology, immunocytochemistry, and morphometry. STUDY DESIGN: Retrospective detailed cytomorphological, immunocytochemical, and morphometric analysis was performed in 6 cases of FL-HCC reported on fine needle aspiration. Cell block immunocytochemistry (CB-ICC) for CK7 and CD68 was performed in four cases. Morphometry was carried out with Cell A software. Area of the cell, nucleus and nucleolus was measured in 50 nuclei per case in 6 cases each of FL-HCC and HCC. RESULTS: The mean age of patients with FL-HCC was 19 years and all had normal serum alpha-fetoprotein levels. Fine needle aspiration smears showed large polygonal cells with abundant cytoplasm, vesicular nucleus and prominent nucleolus, associated with variably cellular fibrous stromal fragments. Intranuclear inclusions, cytoplasmic eosinophilic inclusions, and bile were also noted. FL-HCC showed strong membrano-cytoplasmic CK7 positivity and cytoplasmic granular and canalicular positivity for CD68. In contrast, HCC showed weak focal positivity for CK7 and only canalicular CD68 positivity. Morphometry revealed that FL-HCC cells were 2.19 times the size of HCC. CONCLUSION: CK7 immunocytochemistry on cell blocks is useful for confirming and distinguishing it from HCC.