Pitfalls in the cytological classification of borderline leprosy in the Ridley-Jopling scale

This is a blinded, retrospective, correlative study of classification of leprosy by cytomorphology, clinical examination, and bacterial density. One hundred consecutive adequate aspirates from skin lesions of leprosy were studied. The Ridley-Jopling (R-J) five-group classification system was used. May-Gruenwald-Giemsa (MGG) and Ziehl-Neelsen (Z-N) stains were employed. Complete clinical, cytological, and bacteriological concordance was found in 88 patients. One-step mismatch in classification was seen in 12 patients with cytomorphological features of borderline-borderline (BB/mid-borderline) leprosy. Cytomorphological features of BB leprosy in aspirates from skin lesions should alert the cytopathologist to the possibility that the bacteriological index (BI) may vary widely. Appropriate steps must be taken to ensure accurate reporting of BI.