|Year : 2012 | Volume
| Issue : 3 | Page : 141-143
Histoid leprosy: Role of fine needle aspiration cytology in the diagnosis
Sunita Y Patil1, Rajeev A Malipatil2
1 Department of Pathology, J.N.Medical College, Belgaum, India
2 Department of General Medicine, J.N.Medical College, Belgaum, India
|Date of Web Publication||11-Jan-2013|
Sunita Y Patil
Department of Pathology, J.N.Medical College, Belgaum
Source of Support: None, Conflict of Interest: None
Histoid leprosy is a distinct variant of lepromatous leprosy. It presents clinically as well demarcated cutaneous and subcutaneous nodules similar to dermatofibroma. A 40 year old male, presented with multiple progressive skin lesions on buttock, trunk, face, back and extremities of six months duration. Examination findings revealed multiple, irregular, bilateral, symmetrical shiny cutaneous nodules over the above mentioned sites. Radial, ulnar, radial cutaneous and lateral popliteal nerve thickening was seen. Fine needle aspiration cytology (FNAC) showed features of histoid leprosy, which was confirmed by histopathology. Modified Ziehl-Neelsen stain for Acid fast bacilli was positive. Bacterial index was 6+. Histoid leprosy is an unusual variant of lepromatous leprosy. The identification of histoid leprosy and differentiation of it from lepromatous leprosy helps to facilitate the follow up of patients with regards to the drug sensitivity, relapse and reaction. We present here the role of FNAC in the diagnosis of histoid leprosy.
Keywords: Fine needle aspiration cytology, histoid leprosy, nodule
|How to cite this article:|
Patil SY, Malipatil RA. Histoid leprosy: Role of fine needle aspiration cytology in the diagnosis. J Sci Soc 2012;39:141-3
| Introduction|| |
Histoid Leprosy is a distinct and rare variant of lepromatous leprosy, having characteristic skin lesions, histopathology and bacterial morphology. The term histoid leprosy was introduced by Wade in 1963. It presents clinically as a well demarcated, cutaneous and subcutaneous nodules similar to dermatofibroma.  It occurs in patients with Dapsone monotherapy earlier or incompletely treated leprosy with multidrug therapy. It may also occur due to de novo infection with drug resistant bacilli.  Reports of Primary cytodiagnosis of leprosy lesions by FNAC from skin, nerve and lymph nodes are very few in the literature.  Fine needle aspiration cytology (FNAC) is safe and comparatively non-invasive procedure. The first recorded utilization of this technique is available from St. Bartholomew's hospital in the year 1833. In 1989 Ridley used Zeihl-Neelsen (Z-N) Stain to study the nature of exudates and to study their cytology.  In 1994 Singh et al., used FNAC to diagnose a case of nodular lepromatous leprosy.  Cytodiagnosis of histoid leprosy on FNAC was only recently described for the first time by Bhake AS et al. in 2001. 
| Case Report|| |
A 40 year old male presented with multiple progressive skin lesions on the trunk, back, buttocks, face and extremities of six months duration. There was history of having received incomplete treatment for leprosy in the past few months. Examination findings revealed irregular multiple bilateral symmetrical shiny cutaneous nodules over the above mentioned sites. Nodules were raised relative to the skin surface. One nodule over the left hand showed an umbilicated lesion and measured 0.5 × 0.5 cm. [Figure 1] Radial, ulnar, radial cutaneous and lateral popleteal nerve thickening was seen. FNAC was done from the lesion on left hand which produced thick, white material. Slit skin smears were also taken and studied.
|Figure 1: (a) Nodule on the face. (b) An umbilicated lesion on the dorsum of the left hand. (c) Nodules over back. (d) Nodules on the chest|
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FNAC smears stained with Heamatoxylin and Eosin (H and E), Papanicolaou (PAP) and Giemsa stains showed cell rich aspirate with numerous macrophages. Macrophages were elongated to spindle shaped with dense cytoplasm and elongated blunt vesicular nuclei with fine regular chromatin. The cells were arranged in multilayered groups and bundles with nuclear palisading. Few lymphocytes were also seen scattered amidst these spindle shaped histiocytes. Intercellular stroma between these cells was nearly absent. Modified Zeihl-Neelsen stain for Acid fast bacilli (AFB) was positive with a high bacterial index (6+), based on Ridley's logarithmic scale. Slit skin smear examination also showed presence of AFB with high index of 5+. These findings were confirmed by histopathology which showed a circumscribed granuloma in the dermis separated from epidermis by a narrow, clear subepidermal zone. The granuloma consisted of thin spindle shaped cells forming interlacing bands and whorls. Fite Faraco stain showed the cells containing AFB, with a high Bacterial index of 6+. There was mild infiltration by lymphocytes and plasma cells [Figure 2].
|Figure 2: (a) Fine needle aspiration cytology Smears show spindle macrophages with lymphocytes (H and E, ×400). (b) Smears showing AFB with high index (Modified Z-N, ×400). (c) Histopathology showing a subepidermal clear zone and granuloma with spindle cells in dermis. (H and E, ×200). (d) Histopathology: Granuloma containing spindle cells in whorled pattern. (H and E ×400). Inset shows Fite-Faraco stain with index of 6+ (Fite-Faraco, ×400)|
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Rare variants of leprosy pose a diagnostic challenge even to astute clinicians and histoid leprosy is one such form of disease with unique clinical and histopathological features.  Histoid leprosy is an unusual variant of lepromatous leprosy with an incidence of 1.2-8.7% in various studies.  Histoid lesion, a variety of lepromatous leprosy, is due to alteration in the growth pattern of Mycobacterium leprae, possibly due to loss of immunity in localized areas. 
Cytodiagnosis of Histoid leprosy by FNAC has certain advantages over reporting by excision biopsy. The technique is simple, less traumatic and it is possible to obtain tissue material from lesions in different locations which adds to the value of sampling.  Morphologically cells can be visualized more or less their normal shape, since they undergo less shrinkage and distortion.  In our case the cell morphology was clear and evident. The arrangement of cells seen in the smears reflects the architectural patterns of histoid leprosy i.e., spindle cells arranged in bundles. Modified Z-N stain revealed the bacterial index of 6+ and Fite Faraco stain on histology sections also revealed high bacterial index.
Histoid leprosy was first described by Wade in 1963 to distinguish a relatively unusual form of lepromatous leprosy with characteristic clinical and histological features. The cellular morphology has been subsequently confirmed by several workers  essentially, the lesion is circumscribed, clearly separated by a pseudocapsule from the conventional granuloma of lepromatous leprosy. The cells of the histoid lesion are distinct from the cells of conventional lepromatous granuloma found just adjacent to it. The macrophages in the histoid type are thin and spindle-shaped, with poor evenly staining cytoplasm. They contain numerous tightly packed acid fast bacilli. The macrophages of the conventional lepromatous lesion, on the other hand, are large, and irregular, with abundant cytoplasm that is highly vacuolated. Acid fast bacilli in `globi' are found in the cytoplasm. 
Another important significance of histoid leprosy is that, its characteristic histologic features resemble those of fibrohistiocytoma and Z-N stains for AFB are mandatory in resolving the diagnostic dilemma. 
De novo histoid lesions, i.e., lesions of histoid leprosy developing without evidence of lesions of other types of leprosy in the Ridley - Jopling classification are also seen in about 12.5% of patients.  As the bacillary load is very high in these patients, they can form a potential reservoir of the infection in the community especially in the post-leprosy elimination era.  Hence the distinction of histoid lesion from other forms of leprosy is very important.
| Conclusion|| |
FNAC of histoid lesions is useful in reaching a rapid and accurate diagnosis. The identification of histoid leprosy and differentiating it from conventional lepromatous leprosy helps to facilitate the follow up of patients with regards to drug sensitivity, relapse and reaction. FNAC plays an important role, as it is a simple, less traumatic procedure and aids in rapid and accurate diagnosis of histoid leprosy. 
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[Figure 1], [Figure 2]