Bull's eye (target) inclusions in neoplastic cells in malignant serous effusions. A study of 289 cases

OBJECTIVE: To study the prevalence and significance of bull's eye (target) inclusions in neoplastic cells in malignant serous effusions. STUDY DESIGN: We reviewed malignant pleural, peritoneal and pericardial effusions from 289 patients who had proven cancer at known primary sites. The ages of the patients ranged from 5 to 72 years; 166 were male and 123 female. RESULTS: Bull's eye inclusions are an uncommon finding and appeared in only 13 cases of metastatic adenocarcinoma of the breast, stomach, colon, lung, ovary, pancreas and urinary bladder. They were positively stained with periodic acid-Schiff stain with diastase. The inclusions were not seen in cells of nonadenocarcinomatous neoplasms, such as squamous cell carcinoma, oat cell (small cell) carcinoma, neuroblastoma, lymphoma and germ cell tumors. CONCLUSION: Bull's eye inclusions are found in about 5% of malignant serous effusions containing cells of metastatic adenocarcinoma. The primary site of an adenocarcinoma cannot be deduced on the basis of the presence of inclusions.