Soft tissue lesions represent a widely diverse group of non-epithelial extra-skeletal structures derived from embryonic mesoderm, including adipose tissue, skeletal muscle, smooth muscle, blood vessels, peripheral nerves, and fibrous tissue [1,2]. Their clinical presentation varies from benign indolent subcutaneous nodules to highly aggressive malignant sarcomas. Diagnostic triaging is essential for therapeutic planning [3,4]. Fine-needle aspiration cytology (FNAC) has gained widespread acceptance as a first-line diagnostic investigation for superficial and deep-seated soft tissue masses [5,6]. It is a simple, quick, minimally invasive, outpatient-based technique that provides rapid provisional diagnostic results without requiring regional or general anaesthesia [7,8]. The cytological assessment of soft tissue masses presents diagnostic challenges due to the morphologic overlap across diverse pathological conditions [9]. Broad cytomorphological sub-categorisation (e.g., spindle cell, myxoid, pleomorphic, round cell, and lipomatous) serves as an effective diagnostic triage system [10,11]. This retrospective study evaluates the spectrum and relative distribution of cytologically diagnosed soft tissue lesions at Agartala Government Medical College & GBP Hospital, providing regional data from Northeast India [12]. OBJECTIVES • To document the cytomorphological spectrum and distribution of soft tissue lesions presented for FNAC over a 1.5-year study period. • To categorise soft tissue FNAC aspirates into broad non-neoplastic, benign, and malignant subtypes to aid therapeutic decision-making

Study Design & Setting This retrospective observational study was conducted in the Department of Pathology at Agartala Government Medical College & Govind Ballabh Pant (GBP) Hospital, Agartala, Tripura, India. Study Period & Sample Size The study period spanned 1.5 years (18 months). A total of 40 consecutive patients presenting with clinical soft tissue swellings referred for diagnostic FNAC were included. Inclusion & Exclusion Criteria Inclusion Criteria: All patients of all age groups with clinically palpable or ultrasonographically localised soft tissue masses who gave informed consent and underwent FNAC. Exclusion Criteria: Primary bone tumours, fluid-only or non-diagnostic/inadequate cytological aspirates lacking cellular details, and non-mesenchymal lymph node swellings. Procedure & Sample Preparation Standard aseptic precautions were observed. FNAC was performed using 22–24 gauge disposable needles attached to 10 mL disposable syringes. Air-dried slides were stained with Giemsa/Leishman stain, while wet-fixed slides (fixed in 95% ethyl alcohol) were stained with Papanicolaou (PAP) stain. Cytomorphological Evaluation Cytological slides were evaluated under light microscopy by experienced pathologists. Lesions were characterised by cytomorphological features (e.g., cell arrangement, nuclear/cytoplasmic ratio, chromatin pattern, background components) and subclassified into lipomatous, neurogenic, fibroblastic/myofibroblastic, inflammatory, vascular, and sarcomatous categories.

A total of 40 soft tissue cases were evaluated during the 1.5-year study period. Table 1 summarises the cytomorphological spectrum and relative diagnostic breakdown. Cytological Findings Summary Benign Mesenchymal & Non-Neoplastic Lesions: Comprised the vast majority of cases (82.5%). Lipoma was the single most common entity (30.0%), presenting cytologically as mature adipocytes arranged in cohesive fragments. Epidermal inclusion cysts (12.5%) showed an abundance of anucleated squames and keratin debris. Schwannomas (10.0%) demonstrated cohesive clusters of spindle-shaped cells with wavy, buckled nuclei and Verocay body formation. Intermediate & Locally Aggressive Entities: Nodular fasciitis (5.0%) and Fibromatosis (5.0%) were categorised within the fibroblastic/myofibroblastic spectrum. Malignant Tumours: Soft tissue malignancies accounted for 17.5% of the total cohort, including Spindle-cell sarcoma NOS (5.0%), MPNST (2.5%), Rhabdomyosarcoma (2.5%), Synovial sarcoma (2.5%), Liposarcoma (2.5%), and Metastatic carcinoma (2.5%). Table 1. Diagnostic Spectrum of Soft-Tissue Lesions on FNAC (N = 40) Diagnosis Number (n) Percentage (%) Lipoma 12 30.0% Epidermal inclusion cyst 5 12.5% Schwannoma 4 10.0% Abscess/inflammatory lesion 3 7.5% Benign fibrous histiocytoma 2 5.0% Fibromatosis 2 5.0% Nodular fasciitis 2 5.0% Spindle-cell sarcoma, NOS 2 5.0% Malignant peripheral nerve sheath tumour (MPNST) 1 2.5% Haemangioma 1 2.5% Metastatic carcinoma 1 2.5% Rhabdomyosarcoma 1 2.5% Granular cell tumour 1 2.5% Dermatofibroma 1 2.5% Synovial sarcoma 1 2.5% Liposarcoma 1 2.5%

Soft tissue tumours pose significant diagnostic challenges due to overlapping histological and cytological profiles. FNAC is an indispensable initial diagnostic tool, allowing clinicians to distinguish non-neoplastic and benign masses from malignancies requiring radical surgical intervention or neoadjuvant therapy [13,14]. In this study of 40 soft tissue cases over 1.5 years at Agartala Government Medical College, benign lesions far outnumbered malignant cases. Lipoma was identified as the most frequent soft tissue lesion, comprising 30.0% of cases. This observation aligns with established literature emphasising lipomas as the most common benign mesenchymal tumour in clinical practice [15]. Non-neoplastic cystic and inflammatory lesions accounted for 20.0% combined (Epidermal inclusion cysts at 12.5% and Abscess/inflammatory lesions at 7.5%). FNAC offers rapid diagnostic confirmation for these conditions, avoiding unnecessary surgical biopsies [16]. Neural sheath lesions, specifically Schwannoma (10.0%) and Malignant Peripheral Nerve Sheath Tumour (MPNST, 2.5%), were identified. Cytological identification of classical Verocay bodies, bipolar spindle cells with pointed nuclei, and fibrillary backgrounds aids in neurogenic tumour diagnosis [17]. Malignant soft tissue lesions comprised 17.5% of cases. Spindle-cell sarcoma, NOS (5.0%) represented the most frequent malignant cytological subcategory. Sarcomas such as synovial sarcoma, Rhabdomyosarcoma, and Liposarcoma each represented 2.5%. Cytological subtyping into broad morphological groups (spindle, pleomorphic, round, or lipomatous cell types) guides subsequent immunohistochemical panels on cell blocks or tissue biopsies [18,19].

FNAC is a simple, cost-effective, safe, and accurate preliminary modality for evaluating soft tissue lesions. It reliably differentiates benign, inflammatory, and malignant lesions, facilitating patient triaging and preoperative planning in tertiary care settings. While cytological evaluation accurately screens soft tissue masses, definitive subtyping of complex sarcomas benefits from histological examination and immunohistochemical correlation.

1. Layfield LJ, Schmidt RL, Samborski W, Hirschowitz SL. Fine-needle aspiration cytology of soft tissue tumors: A single-institution experience. Diagn Cytopathol. 2018;46(8):651-7. 2. Rosai J. Rosai and Ackerman’s Surgical Pathology. 11th ed. Philadelphia: Elsevier; 2018. 3. Dey P. Fine-needle aspiration cytology of soft tissue tumors: Utility, limitations, and diagnostic pitfalls. J Cytol. 2018;35(4):201-7. 4. Goldblum JR, Folpe AL, Weiss SW. Enzinger and Weiss's Soft Tissue Tumors. 7th ed. Elsevier; 2019. 5. Fletcher CDM, Bridge JA, Hogendoorn PCW, Mertens F, eds. WHO Classification of Tumours of Soft Tissue and Bone. 5th ed. IARC Press; 2020. 6. Kulkarni MM, Joshi AR, Anand AS. Cytomorphological evaluation of soft tissue tumors and correlation with histopathology: A 3-year study. Ind J Pathol Oncol. 2019;6(2):189-94. 7. Garg S, Gupta S, Agarwal R. Accuracy of fine needle aspiration cytology in the diagnosis of soft tissue lesions. J Clin Diagn Res. 2019;13(5):EC01-5. 8. Singh A, Sharma M, Rani S. Cytomorphological spectrum of soft tissue masses on fine needle aspiration cytology in a tertiary care institute. Int J Med Res Health Sci. 2019;8(3):45-52. 9. Verma N, Sharma A, Gupta P. Role of FNAC in soft tissue lesions with histopathological correlation: A retrospective study. J Med Acad. 2020;3(1):15-9. 10. Patel G, Shah M, Patel V. Cytomorphological broad categorization of soft tissue tumors on fine needle aspiration cytology. Acta Cytol. 2020;64(3):210-8. 11. Roy S, Ghosh B, Das S. Fine needle aspiration cytology of soft tissue lesions: A diagnostic approach. Indian J Diagnostic Cytopathol. 2020;5(2):88-94. 12. Sharma P, Kumar A, Meena N. Utility of FNAC in diagnostic triaging of soft tissue swellings: An institutional study. J Cytopathol Mol Med. 2021;7(1):32-8. 13. Das S, Debbarma S, Debnath A, Saha S. Diagnostic accuracy of fine needle aspiration cytology (FNAC) in soft tissue tumors of extremities. Healthcare Bulletin. 2023;11(9):4286. 14. 14 Roy S, Manna A, Pathak S, Guha D. Evaluation of fine needle aspiration cytology and its correlation with histopathological findings in soft tissue tumours. J Cytol. 2007;24(1):37 40. 15. Padmanabhan A, Saraf SR, Singh V, Patel NA. Utility of fine needle aspiration cytology (FNAC) in the diagnosis of soft tissue tumors and tumor like lesions. Indian J Pathol Oncol. 2018;5(2):277 82. 16. 16 Jain V, Agarwal T. Role of FNAC in soft tissue tumors and its histopathological correlation. Int Surg J. 2017;4(8):2632 6. 17. 17 Rekhi B, Gorad BD, Kakade AC, Chinoy RF. Diagnostic accuracy of FNAC in soft tissue tumors: Correlation with histopathology in 115 cases. CytoJournal. 2007;4:20. 18. 18 Rakheja G, Handa U, Punia RS, Attri AK. Fine needle aspiration cytology in soft tissue tumors—5 year institutional experience. Diagn Cytopathol. 2022;50(10):463 70. 19. 19 Kumar H, Patni A, Kumari L, Katara HC. Diagnostic efficacy of fine needle aspiration cytology in soft tissue tumors and cytohistological correlation. Int J Res Med Sci. 2023;11(8):2956 60.