Kittisak Wongchansom M.D.
Department of Anatomical Pathology, Army Institute of Pathology, Bangkok, Thailand
Objective: Metastatic lung adenocarcinoma is commonly presented with effusions. The cytologic examination of the fl uid is one of the fi rst diagnostic techniques attempted in these patients. Identifi cation of the cancer cells in pleural fl uid specimens, using minimal, less invasive and cost effective intervention is crucial especially for the early diagnosis and also for the staging, prognosis and management of the malignant neoplasms. This study compares the cytologic features of metastatic lung adenocarcinoma in malignant pleural effusion and benign pleural effusion. We evaluated the accuracy and specifi city of cytological pleural effusions, based on morphological criteria alone.
Methods: We collected 76 pleural effusion specimens from the archives of army institute of pathology. Smears were routinely stained with and Papanicolau. All the cases were confi rmed by immunohistolochemical studies (TTF-1 for metastatic lung adenocarcinoma and WT-1 for benign mesothelial cells). Thirty-fi ve preparations were obtained from benign effusions of 18 males and 17 females (aged 37–83, mean age 62). Forty-one slides were from metastatic lung adenocarcinoma (21 males and 20 females, aged 30–98, mean age 60). All cytologic slides were examined for cytologic features by random sampling with blinding in original clinical and pathological data. All statistical analysis was performed using statistical packet for social science (SPSS). sensitivity, specifi city, positive predictive value and negative predictive value were calculated.
Results: The fi ve cytologic features, which were most useful to distinguish between metastatic lung adenocarcinoma in pleural effusion and benign pleural effusion, included three-dimensional cell groups (85.53% accuracy and 88.57% specifi city), acini/glands formation (82.89% accuracy and 85.71% specifi city), irregular nuclear membrane (81.58% accuracy and 62.86% specifi city), signetring cells (77.63% accuracy and 71.43% specifi city) and intranuclearpseudoinclusion (75% accuracy and 91.42% specifi city). The cytologic features, which commonly were found in benign pleural effusion were monolayer aggregation (83%) and peripheral vacuoles (73%).
Conclusion: There are several overlapping features between metastatic lung adenocarcinoma in pleural effusion and benign pleural effusion. Although there are several features that can help distinguish between benign and malignant process having been described in the literatures, ancillary techniques such as cell block preparation or immunohistochemical studies may also add some values in making a more confi dent defi nitive diagnosis.