Fine-needle aspiration cytology in soft tissue tumors-5-year institutional experience

Fine-needle aspiration cytology (FNAC) forms one of the first-line investigations in the evaluation of tumors in modern era. Its role in diagnosing soft tissue tumors (STT) has been well established. However, the morphological overlap and biological heterogeneity of STT pose a morphological diagnostic challenge.

To evaluate the scope of FNAC in diagnosis and categorization of STT and to correlate the cytological features with histological findings wherever available, and to analyze the reasons for discordance, if any.

All FNAs of cytologically diagnosed STT during 5-year period were retrospectively analyzed. FNAC smears stained using May-Grünwald Giemsa, Pap- and hematoxylin and eosin, were evaluated and interpreted inconjunction with clinical details. Cellblock and immunocytochemistry (ICC) was done, wherever required to render the final diagnosis.

Of the total 15,844 FNAC done in 5 years, 1319 (8.3%) cases were diagnosed as STT. Benign tumors comprised the majority (94.2%), whereas 5.8% were diagnosed to be malignant. These were further grouped according to the cytomorphological features into adipocytic (82.2%), benign spindle cell lesions (10.8%), vascular (1.4%), spindle cell sarcoma/sarcoma NOS (2.2%), myxoid (0.3%), round cell tumors (0.9%), metastatic tumors (1.9%), and others (0.3%). The cytological findings were corelated with histopathological findings, which were available in 316 cases. The specificity and sensitivity calculated for detecting malignancy was 99.2% and 95.4%, respectively. The overall diagnostic accuracy for diagnosing malignancy was 98.7%. Among the group of non-adipocytic tumors, the sensitivity, specificity, PPV, NPV calculated for diagnosing a malignant tumor (irrespective of exact sub-categorization) is 95.2%, 100%, 100%, and 96.4%, respectively. The overall diagnostic accuracy in non-adipocytic tumors is 97.92%.

FNAC is a simple, cost effective, and minimally invasive method in diagnosing STT with good sensitivity and specificity. It is of utility not only in primary lesions, but also for metastatic tumors, and for the documentation of locally recurrent soft tissue neoplasms.