Cytomorphological profile of neoplastic effusions: An audit of 10 years with emphasis on uncommonly encountered malignancies

CONTEXT: The diagnosis of metastatic cancer in fluids is of capital importance as, in most such instances, a rapid fatal outcome of the disease is anticipated. AIM: To determine the spectrum and cytomorphological features of the common and unusual malignancies presenting with effusions. METHODS AND MATERIALS: A total of 11,562 effusion samples received for cytopathological examination over a 10-year period were analyzed retrospectively. Cytomorphological features of neoplastic effusions were studied. Special stains and immunocytochemistry (ICC) were performed to aid the diagnosis in difficult cases. OBSERVATIONS: The effusion samples comprised of pleural (5018), peritoneal (6340) and pericardial (204) fluids. A definitive diagnosis of classifiable malignancy could be given in 836 (7.3%) of these cases (5.7% adenocarcinomas and 1.6% uncommon malignancies). Adenocarcinoma was the most frequent cause of malignant pleural (70%) and peritoneal effusions (86.9%). The most common primary site for pleural metastasis was lung (35.7%), while for peritoneal metastasis, it was the ovary (54.3%). Among the uncommon neoplastic effusions, hematopoeitic malignancies were the most frequent, followed by squamous cell carcinomas. Primary malignant mesotheliomas were the most challenging to diagnose on effusion cytology. ICC was useful to arrive at a definitive diagnosis in difficult cases. CONCLUSIONS: Cytology is a useful tool to detect malignant effusions. However, in uncommon malignancies presenting as effusions, a detailed clinical history and ancillary investigations are often required to make a correct diagnosis.