Role of Cytology for Diagnosis of Appendageal Tumours and Comparison with Histopathology: A Cross-sectional Study

Abstract

Introduction: Skin adnexal neoplasms are quite rare in routine pathology practice, yet the domain of Fine Needle Aspiration Cytology (FNAC) remains relatively unexplored. This current study explored different Adnexal Tumours (ATs) through FNAC, emphasising the efficacy of cytological diagnosis as a safe, simple, quick, and cost-effective tool with high sensitivity and specificity for diagnosing skin ATs. Aim: To diagnose various appendageal tumours through cytological examination, confirm and categorise them (benign/ malignant) via histopathological examination, and identify any cytohistological discrepancies. Materials and Methods: This retrospective cross-sectional study was conducted over a five-year period (January 2016- December 2021) at the Department of Pathology, Nil Ratan Sircar Medical College and Hospital (NRSMCH) in Kolkata, West Bengal, India, following ethical approval. Patients underwent history and physical examination followed by FNAC. ATs were diagnosed cytologically in 78 out of 23,852 FNAC cases. The results were compared with histopathological diagnosis to assess concordance or discordance based on predefined criteria. Leishman-Giemsa (L&G) stain was used for cytological examination, and Haematoxylin and Eosin (H&E) stain for histopathology. Results: Cytologically, ATs were diagnosed in 78 cases (0.33%), with the majority being benign 69 (88.46%). There was a female preponderance (49, 62.82%) with a male-to-female ratio of 1:1.7. Nodular Hidradenoma (NH) was the most common diagnosis (16/48=33.33%). Out of 59 biopsy-confirmed lesions, 55 showed cytohistological concordance (93.22%), with only four discordant cases (6.78%). The sensitivity, specificity, positive predictive value, and negative predictive value for detecting malignancy in this series were 70%, 97.90%, 87.50%, and 94.10%, respectively. Conclusion: FNAC should be the primary choice for detecting skin ATs due to its safety, reliability, high predictive value, and low chance of discordance. Although occasional cytohistological discrepancies may occur, proper clinical correlation, aspiration from multiple sites, expert cytopathologists, and high-quality staining are essential to avoid misdiagnosis.