Usefulness of Fine needle aspiration cytology in diagnosis of soft tissue tumors and its correlation with histopathological features

Objective: Fine needle aspiration cytology (FNAC) is a standard diagnostic tool and has several advantages which are specific to soft tissue tumors (STT). STT arises from non-epithelial and extra-skeletal tissue of the body, excluding the reticuloendothelial system, glia, and supporting tissues of organs. Primary STTs are very rare and encompass a wide range of different tumor types; therefore, the classification and diagnosis remain complex. If the tumor is diagnosed as benign, surgery may not be necessary. However, in the case of malignancy, a cytological diagnosis allows for the initiation of palliative treatment. This study was conducted to evaluate the role of FNAC in the diagnosis of STT by sub classifying them based on their cytology features and finally correlating their FNAC findings with histopathological results with special reference to immunohistochemistry (IHC) in diagnostic challenging cases. Material and Methods: It was a hospital-based retrospective study conducted in a tertiary care center, over a period of 2 years, i.e., from July 2016 to May 2018. After obtaining approval from the ethics committee of the institution, the study was carried out. All STT cases subjected to FNAC followed by incisional, excisional, or core needle biopsy or complete resection for histopathological examination were studied. The slides of these patients were retrieved and reviewed to establish a proper diagnosis. IHC was carried out in most cases whenever there was a diagnostic dilemma. Results: In our study, among Fifty patients who presented with STT, forty were benign, and ten were malignant. The median age of incidence was forty-one, and male-to-female ratio was 0.85:1. The most common site was the trunk. There were four discordant cases, and the final evaluation of all results showed sensitivity, specificity, positive predictive value of tests, and negative predictive value of tests of FNAC as 100%, 76.92%, 92.5%, and 100%, respectively. Conclusion: In STT, most were benign tumors, with lipomas being the most common among them. While benign and malignant were easy to diagnose, intermediate spindle cell tumors were often missed on cytology. These intermediate tumors represent the diagnostic “grey zone.” With increasing experience, STT can be diagnosed more accurately. FNAC is therefore a standard pre-operative diagnostic tool and a reliable alternative to open biopsy for diagnosing STT.