Modified fine‐needle aspiration technique for diagnosis of granulomatous skin lesions with special reference to leprosy and cutaneous tuberculosis

Abstract

Skin infections are commonly assessed by slit skin or scrape methods. Fine-needle aspiration biopsy (FNAB) is highly effective especially with blanching of skin to ensure good yield and reduced bleeding. The aim of this study was to assess usefulness of cytology, especially modified FNAB technique, in diagnosis of leprosy and cutaneous tuberculosis and to identify specific cytological characteristics for diagnosis and classification. The study was conducted on 40 patients-25 cases of leprosy and 15 cases of cutaneous tuberculosis. Smears were prepared using modified FNAB technique, slit skin, and scrape methods (depending on type of lesion). Cytological diagnosis was confirmed by histopathology where the Ridley-Jopling system was used to classify cases of leprosy. A similar attempt was made for diagnosis and classification of leprosy on cytology. Diagnoses rendered by both modalities were compared to assess the efficacy of cytological examination. Cytological diagnosis was made in 23 cases of leprosy and 12 cases of cutaneous tuberculosis. The smears showed good cellularity. A broad division into tuberculoid and lepromatous leprosy could be made fairly accurately on cytology. Maximum agreement among clinical, cytological, and histopathological diagnosis was observed in cases of tuberculoid leprosy. Smears of cutaneous tuberculosis were characterized by epithelioid cell granulomas with caseation. Overall accuracy of diagnosis was 92% in leprosy and 80% in tuberculosis. FNAB is an inexpensive and accurate procedure for diagnosis of leprosy and cutaneous tuberculosis. The modified technique yields good results. However, clinical correlation, acid-fast staining, and culture are essential as they provide valuable supportive information.

Cytomorphological spectrum and immunochemistry of cutaneous tuberculosis

“…Katuria et al found similar correlation of 94.8% in scrofuloderma, 88.9% in lupus vulgaris and an overall correlation of 92.9% on cytopathology compared to histopathology with 30 cases using modified FNA technique . Mehdi et al also found a correlation of 80% with a sample size of 11 cases . Hence doing FNA is advantageous in cutaneous tuberculosis as it shows high correlation to histopathology, it is less time consuming, more compliant and cost effective.…”

“…Mehdi et al also concluded that distinguishing various subtypes of cutaneous tuberculosis is difficult on the basis of cytology alone. Clinical correlation is essential to arrive at a final diagnosis …”

“…This method was first described by Singh et al in their study of cytomorphology of leprosy . Later this method was used by Mehdi et al in Cutaneous Tuberculosis …”

“…23 Mehdi et al also found a correlation of 80% with a sample size of 11 cases. 17 Hence doing FNA is advantageous in cutaneous tuberculosis as it shows high correlation to histopathology, it is less time consuming, more compliant and cost effective.…”

“…This may be explained by the fact that Clinical correlation is essential to arrive at a final diagnosis. 17 Immunochemistry is a widely used confirmatory and ancillary test in various tumors, but it has received little attention for diagnosis of tuberculosis. Polyclonal antibody against BCG, combination of three recombinant antigens (38 kDa, Ag16 and Ag 85B) and Monoclonal antibodies MPT64, 38 kDa have been used.…”