The beta subunit of human chorionic gonadotropin lacks specificity for malignant cells in serous effusions

The cytologic diagnosis of malignancy is frequently straightforward. For difficult cases, multiple immunostains and immunostain panels have been investigated without consensus. beta-human chorionic gonadotropin (hCG) has been reportedly expressed in malignancies, but not in normal tissue. HCG also has been reported as a specific marker of metastases in serous fluids when detected with laboratory assays. We investigated the clinical utility of hCG in this cytologic setting. A total of 97 cases of benign and malignant effusions were studied. Each case was immunostained with monoclonal hCG using the avidin-biotin technique and diaminobenzidine as a chromogen. Additionally, a mucicarmine stain was performed on most cases. Cases were evaluated for hCG expression and mucin in a blinded fashion. After the cases were reviewed, the diagnoses were unblinded and staining patterns were evaluated. Of the 47 benign cases studied, 23 (49%) exhibited immunoreactivity to hCG in at least 5% of mesothelial cells present. In contrast, 28 of 44 (64%) adenocarcionomas exhibited a similar degree of immunostaining. In all, 21 (48%) of the adenocarcinomas were also positive for mucin; five of these mucin-positive cases were negative for hCG. The combination of mucin and hCG detected 33 of 44 (75%) adenocarcinomas. We conclude that hCG lacks the specificity for malignant cells to be of clinical use in effusion cytology.