Useful Application of Immunostaining to Malignant Pleural Effusion among Lao People in Vientiane Capital, Lao PDR.

Background: Pathology and laboratory medicine (PALM) services are limited in low-resource countries, such as Lao PDR. Patients with malignant pleural effusion (MPE) are not properly diagnosed and treated in these situations. The purpose of this study is to confirm the usefulness of immunocytochemistry in MPE to identify the histological type and probable primary site of cancer of MPE and to discuss its usefulness in low-resource countries, such as Laos. Methods: We retrospectively reviewed glass slides of pleural effusion sent to the Department of Pathology at the University of Health Sciences from the central hospitals for cytological screening from January 2012 to December 2016. The cytological review, cell transfer and immunocytochemical staining were performed at Tokyo Medical and Dental University. Among 81 cases of MPE from Laos, 66 cases of malignant tumors that contained enough tumor cells were included in this study, and the slides were screened with 14 primary antibodies to classify the histological type and identify the probable primary site of carcinoma. Results: Among the 66 cases, 34 cases (52%) were of female patients, and 32 cases (48%) were of male patients. The patients’ ages ranged from 28 to 88 years with an average of 58 years. The immunocytochemical study identified 32 cases (49%) of primary lung adenocarcinoma, two cases (3%) of malignant mesothelioma, one case (1.5%) of breast/gynecological carcinoma, one case (1.5%) of T cell lymphoma, and one case (1.5%) of B cell lymphoma. Twenty-nine cases (43.5%) were classified as carcinoma not otherwise specified. Pulmonary small cell carcinoma/squamous cell carcinoma and metastatic colon, prostate, and liver carcinoma were not identified among the cases. Conclusions: Immunocytochemistry is a useful ancillary method in MPE diagnostics. This method could be applied in the pathological laboratories in low- or middle-resource countries, such as Laos.