Cytological diagnosis of lepromatous leprosy: A report of two cases with review of literature.

The "gold standard" for the diagnosis and classification of leprosy to date, is histological examination of skin biopsy in correlation with the bacteriological indices. These are, however, time-consuming. An attempt was made to diagnose leprosy using fine needle aspiration cytology (FNAC) which is a simple, safe, cost-effective and time-saving procedure with minimal trauma and complications. This case report highlights the role of FNAC in rapid diagnosis and early management, in patients of leprosy.

Introduction

Cytology is a widely accepted diagnostic procedure for a large variety of malignant and inflammatory lesions. Skin-slit smear technique stained with Ziehl-Neelsen stain has been conventionally used for the assessment of the bacterial index and morphological index in lesions of leprosy.

Studies have been undertaken to evaluate the utility of fine needle aspiration cytology (FNAC) in reactional and nonreactional leprosy lesions.[1] Utility of FNAC in the classification of leprosy has also been assessed.[23]

We report two cases of lepromatous leprosy where FNAC aided in early diagnosis of the lesions, later confirmed by histopathology.

Case Reports

Case 1

A 46-year-old woman presented with a swelling on the left wrist of 3-week duration. The swelling was 1.5 cm in diameter and a clinical diagnosis of “ganglion” was made. The patient was a known case of lepromatous leprosy on treatment. FNAC of the lesion yielded whitish aspirate and slides were prepared and stained with Giemsa stain.

Case 2

A 60-year-old man presented with multiple erythematous, raised, painful nodules over the back of 7-day duration along with type II deformity of the nose and hand. He was a known case of BL leprosy on treatment. A clinical diagnosis of erythema nodosum leprosum (ENL) type II reaction was made. FNAC was done from one of the lesions and slides were stained with Giemsa stain.

In both cases, one slide each was stained with Ziehl-Neelsen stain.

Cytological findings

Aspirates from both the cases revealed cellular smears composed of large number of foamy macrophages with intracellular and extracellular “negative” images, scattered lymphocytes and histiocytes in a fatty background [Figure 1]. Ziehl-Neelsen staining showed bundles of intracellular and extracellular acid fast bacilli (AFB) in both cases (B.I.6+) [Figure 1, inset]. In the second case, cytological features of ENL in the form of intact and degenerated polymorphonuclear leucocytes and fragmented AFB were not found.

Figure 1

Microphotograph revealing abundant foamy macrophages with intracellular and extracellular negative images and interspersed lymphocytes in a fatty background (Giemsa, ×400). Inset reveals bundles of intracellular and extracellular acid-fast lepra bacilli (ZN stain, ×400)

Histopathology of both the lesions was done and the diagnosis of lepromatous leprosy was confirmed.

Discussion

Leprosy, or Hansen's disease, is a slowly progressive infection caused by Mycobacterium leprae, affecting the skin and peripheral nerves and resulting in disabling deformities.[4] The Ridley-Jopling (RJ) classification currently in use classifies leprosy into five clinically and histologically recognizable groups and helps predict the prognosis and possible complications.

Laboratory diagnosis of leprosy by skin-slit smears and skin biopsy is simple but both techniques have their limitations. Skin-slit smears are negative in paucibacillary cases whereas, skin biopsy is an invasive procedure and leads to biopsy scar.

FNAC is a simple and safe technique and has been described as a useful tool for the diagnosis of leprosy in skin lesions and nerves.[5] It has been observed that FNA smears, in contrast to skin-slit smears, are free from confounding epidermal squamous cells and are therefore better suited for evaluating cell morphology.[6] Additionally, the skin-slit smears can only mention about the presence or absence of acid-fast bacilli whereas, FNA can also help classify the lesion.

Singh et al.[6] in 1995 attempted the cytological diagnosis and classification of leprosy and found 100% cytohistological concordance. Rao et al.[2] also evaluated the utility of FNAC in the classification of leprosy and found 90% concordance in cases of tuberculoid leprosy and 93.75% concordance was observed in lepromatous leprosy. They, however, observed difficulty in differentiating tuberculoid leprosy (TT) from borderline tuberculoid leprosy (BT) and borderline lepromatous leprosy (BL) from lepromatous leprosy (LL) on cytology.

Nigam et al.[1] found a fairly good correlation (77.3%) of cytomorphological features with clinicopathological diagnosis in patients of leprosy. They attributed the poor correlation in 22.1% cases to incorrect site selection. They also advocated aspiration from multiple sites for better concordance as was observed by Singh et al.[6]

Cytological criteria for subclassification of leprosy as defined by Singh et al.[6] [Table 1] have been used in various studies for evaluation of FNAC in leprosy.[23] A study by Prasad et al.[3] included various types of skin lesions such as macules, papules, plaques and nodules. They observed macules in 42.5% cases which gave poor cellularity in cytology as was also observed by Singh et al.[6] This is a diagnostic limitation of FNAC in leprosy.

FNAC has also been used in the follow-up of patients with lepromatous leprosy.[7] Malik et al.[8] in 1999 have defined cytomorphological features of reactions in leprosy with significant correlation in both type of reactions.

Our case report, hence emphasizes the role of FNAC, which due to its rapidity and simplicity, can be used for early diagnosis and prompt management of cases of leprosy.