Papillary thyroid carcinoma (PTC) is typically an indolent disease characterized by slow growth and a favorable prognosis. In rare instances, this disease may metastasize to the pleura and manifest as a malignant pleural effusion. We report 3 female patients of Japanese/Okinawan ancestry with a history of PTC who presented with hydrothorax. Cytologic examination in conjunction with immunohistochemical staining enabled a definitive diagnosis of metastatic PTC. Molecular analysis of the mitogen activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways demonstrated the presence of the v-raf murine sarcoma viral oncogene homolog B (BRAF)(V600E) mutation in 2 of our 3 patients, with the absence of any other clinically significant mutations in all cases. Further investigation is necessary to elucidate the molecular and environmental mechanisms involved in this aggressive manifestation of PTC.
Keywords: BRAFV600E mutation; effusion cytology; metastatic papillary thyroid carcinoma; pleural metastasis.