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

Abstract

Introduction 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. Aims 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. Materials and Methods 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. Results 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%. Conclusion 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.

Cytomorphology of mesenchymal lesions in a tertiary care centre and its correlation with histopathology

“…and Rakheja et al , who found benign tumours to be 93.5%, 95.3%, 82.3% and 94.2% respectively. [ 7 - 9 , 12 ]…”

“…who observed a sensitivity, specificity, PPV, NPV and diagnostic accuracy of 95.2%, 100%, 100%, 96.4% and 97.9% respectively. [ 12 ] Soni et al . observed an accurate characterization in 77.14% cases between the cytological and final histopathological diagnosis.…”

Pitfalls in soft tissue cytopathology

“…There is a substantial volume of literature establishing the utility of FNAB in differentiating benign from malignant tumours, with a sensitivity varying from 84% to 100%, a specificity varying from 83% to 98% and a positive predictive value ranging from 84% to 99%. However, there is considerable variation in the attitude among pathologists and clinicians regarding the role of FNAB as a primary diagnostic modality for the evaluation of clinically or radiologically “suspicious” soft tissue masses 1–9 . The reasons for this include the growing number and complexity of soft tissue tumour types, including sarcomas, with overlapping morphological, immunohistochemical (IHC) and occasionally molecular features 10 .…”

“…However, there is considerable variation in the attitude among pathologists and clinicians regarding the role of FNAB as a primary diagnostic modality for the evaluation of clinically or radiologically "suspicious" soft tissue masses. [1][2][3][4][5][6][7][8][9] The reasons for this include the growing number and complexity of soft tissue tumour types, including sarcomas, with overlapping morphological, immunohistochemical (IHC) and occasionally molecular features. 10 In contrast to core needle and excision biopsy specimens, there has been a tendency to utilise direct FNAB smears and cell blocks less frequently for these ancillary techniques, leading to a lower percentage (reported as 25% to 47%) of tumours being precisely subtyped.…”

“…12 While in histopathology, soft tissue tumours are classified based on lineage, in FNAB cytopathology they are initially classified based on their cytomorphological patterns, which include round cell, predominant spindle cell, adipocytic, epithelioid, pleomorphic and myxoid. 9,[13][14][15][16] It is crucial that cytopathologists are aware of the various recognised challenging pitfalls that are present when using FNAB for the diagnosis of a soft tissue mass, which may show one of these patterns, or in some cases, a less distinctive or mixed pattern. The pattern recognition approach serves as a foundation for a judicious ancillary work-up, including IHC and molecular genetic studies (Table 1).…”