Evaluation of Fine Needle Aspiration Cytology versus Culture for Laboratory Diagnosis of Subcutaneous Mycosis

Introduction: Subcutaneous swellings are commonly seen in clinical practice having varied pathology from epidermal inclusion cyst to malignancy. Subcutaneous mycosis is a fungal infection of subcutaneous tissue and dermis which is more prevalent in workers of rural, tropical, and subtropical regions. The subcutaneous infection mostly occurs due to minor trauma which goes unnoticed. Fine Needle Aspiration Cytology (FNAC) followed by microbiological analysis is a cost-effective and simple procedure and can be considered as one of the main modalities for early diagnosis. Moreover, it gives an early presumptive identification of fungus, which helps the clinician in a timely therapeutic approach. Aim: To study the efficacy of FNAC in the diagnosis of subcutaneous mycosis in comparison with culture method. Materials and Methods: A cross-sectional study, including clinically diagnosed cases of subcutaneous mycosis was evaluated between the periods of March 2019 to February 2021 in a tertiary care hospital in Northern Odisha. FNAC samples from all the cases of subcutaneous mycosis were studied cytologically and microbiologically. Cases were analysed and further evaluated on the basis of their age, sex, detailed clinical history, and presentation. FNAC showed the presence of fungal elements in 20 cases. Microbiological evaluation of these samples was carried out. Results: Out of the total 50 cases of subcutaneous mycoses, male (16): female (4) ratio was 4:1 and the commonest age group affected was 20-60 years of age (75%). The most common site of involvement was the lower limb (60%) followed by upper limb (30%). Almost all the cases were from rural areas with a history of trauma present in 11 cases (55%). Out of 50 clinically diagnosed cases, cytological examination revealed fungal element in 20 (40%) cases. The most common cytological diagnosis was abscess with neutrophilic infiltration seen in 13 cases (65%) followed by granuloma in 7 cases (35%). All the 20 samples were further evaluated in conventional methods like KOH mount and culture. Fungal agents were isolated in 13 (65%) cases. Cladosporium spp. was the commonest isolate in 5 cases (25%). Conclusion: Subcutaneous mycosis is a rare disease. FNAC can be used as a rapid and cost-effective screening tool in the diagnosis of such cases as it is more sensitive. Though culture is the gold standard test, it is less specific.