Evaluation of Sensitivity, Specificity, and Risk of Malignancy in Patients with Pleural Effusion and Prior History of Breast Cancer

Summary: Introduction: This study intends to evaluate the diagnostic performance of cytology and assess the risk of malignancy of different cytologic categories in patients with history of breast cancer who presented with pleural effusion. Materials and Methods: We retrospectively evaluated patients with a prior breast cancer diagnosis who had pleural fluid cytology performed at an academic institution in the USA from 01/01/2010-12/30/2015. Two cytospins were prepared from 100 ml of fluid and then stained with Diff-Quik or PAP stain, and a cell block was prepared from the remainder. Immunohistochemistry was performed when necessary. We used diagnostic categories identical to those of the international system (TIS). Cytologic results were compared to pleural biopsies as the gold standard; sensitivity and specificity were calculated for cytology diagnosis at atypical and above. Risk of malignancy (ROM) for each category was calculated. We compared the performance of cytology for those with metastatic breast vs non-breast cancer in patients with a history of breast cancer. Results: In the study period, there were 295 patients (mean (SD) age of 65.5 (15.5) years, 196 (66.4%) were white, 75 (25.4%) African American, and 24 (8.13%) other. On cytology, 146 (49.5%) were negative, 31 (10.5%) were atypical, 9 (3.05%) suspicious, and 109 (36.95%) were positive. On biopsy, 125 (42.37%) were negative, 42 (14.24%) patients had metastatic breast carcinoma, 122 (41.36) had other metastatic neoplasms of a known origin, and 6 (2.03%) had metastasis of unknown origin. The sensitivity was 85.3%, 75.6%, and 78.3% in the breast, non-breast, and total cohort. The specificity was 86.4% for all. (Tables 1-3). Conclusions: In this group, most malignant pleural effusions in patients with breast cancer history are not breast-related. The diagnostic performance for breast cancer (CI 95% 0.74-0.96) is not significantly different from non-breast cancer (CI 95% 0.67-0.82). ROM was similar to what is reported by TIS (Table 4).