Fine-needle aspirates of adenocarcinoma/metastatic carcinoma that resemble hepatocellular carcinoma - Correlating cytologic features and performance in the College of American Pathologists Nongynecologic Cytology Program

Context.-The cytologic features of adenocarcinoma/ metastatic carcinoma in liver fine-needle aspirates are well described. We review the cytologic findings from 16 aspirates of adenocarcinoma/metastatic carcinoma that were frequently misclassified as hepatocellular carcinomas and compare them with 17 cases that were rarely misclassified. Objective.-To compare the cytologic features of adenocarcinoma/metastatic carcinoma in fine-needle aspiration specimens of the liver that were frequently misclassified as hepatocellular carcinoma with those of aspirates that were rarely misclassified. Design.-We reviewed a total of 1712 interpretations from 33 different cases of adenocarcinoma/metastatic carcinoma tumor in liver fine-needle aspiration specimens in the College of American Pathologists Nongynecologic Cytology Program and correlated the cytologic features with performance in the program. Results.-Overall, cases that were frequently misclassified as hepatocellular carcinoma were misclassified on average 26% of the time (range, 13%-54%), while infrequently misclassified cases were interpreted as hepatocellular carcinoma on average 0.7% of the time (range, 0%-3 %). The difference was statistically significant (P < .001). On review, cases that were frequently misclassified most often had moderate amounts of granular cytoplasm (16/16 cases) and round nuclei with even chromatin (13/16 cases). Trabeculae (3/16 cases), bare nuclei (2/16 cases), and endothelial wrapping (1/16 cases) were also occasionally present. In contrast, cases that were rarely misclassified were more likely to have areas with cells showing scant cytoplasm that were crowded and overlapped or molded (13/17 cases) and contained dark hyperchromatic chromatin (13/17 cases) compared to cases that were frequently misclassified (P < .001 and P = .002, respectively). Trabeculae (2/17) and bare nuclei (2/17 cases) were also rarely present. Conclusion.-Cases of adenocarcinoma/metastatic carcinoma with moderate amounts of granular cytoplasm and round nuclei with even chromatin are frequently misclassified as hepatocellular carcinoma. Recognition of this problem, attention to cytologic criteria, and frequent use of immunohistochemical studies and core biopsy may help avoid this pitfall.