Granulomatous inflammation : A histopathological study

Correspondence: Dr. Ram Chandra Adhikari, MD Consultant Pathologist, Department of Pathology, Om Hospital & Research Centre, Chabhil, Kathmandu, Nepal E-mail: rcadhikari@hotmail.com Background: Granulomatous inflammation is a special type of chronic inflammation that is being a manifestation of many infective, toxic, allergic, autoimmune and neoplastic diseases and also conditions of unknown etiology.

transformed macrophages which are formed with the help of the CD 4+ T cells is required.The CD 4+ T cells secrete various mediators such as IL 2, IFγ, TNF and lymphotoxin for the transformation of the macrophages into epithelioid cells and giant cells. 2 Causes of granuloma include bacterial, metal-induced, fungal, viral, chlamydial, helminthic, foreign body and unknown cause. 3Other causes of granulomatous inflammation are tumor associated, BCG-instillation, sarcoidosis, Crohn's disease, protozoal (toxoplasma, leishmaniasis) & chalazion.
There is often no single histologic feature that distinguishes infectious necrotizing granulomas from other granulomas. 5ncillary studies like special stains (Ziehl-Neelsen, Grocott methamine silver), real-time PCR, In situ hybridization can be performed to find the cause of granuloma. 5However, some granulomas remain unexplained even with ancillary studies and in these instances, good clinical history and clinicopathological correlation are essential in making a final diagnosis.
Hence, this study was undertaken to find the frequency and cause of granulomatous lesions.

MATERIALS AND METHODS
The study was done from January 2010 to December 2012 in the department of pathology, Tribhuvan University Teaching Hospital, Kathmandu, Nepal.This study included a total of 418 granulomatous lesions, diagnosed on Hematoxylin & eosin stain from all sites.Special stains like Ziehl-Neelsen (ZN), Periodic Acid Schiff (PAS) and Fite-Faraco were used whenever required.The clinical history, other laboratory investigations are radiological findings were collected from the medical records.

RESULTS
The median age of the patients with granulomatous lesion was 29 years with a range of 1 to 83 years.The majority of the patients were in the age group of 20-29 years.There was slight male predominance with male to female ratio of 1.2:1 (Table 1).Majority of granulomas were seen in lymph nodes (41.1%), followed by skin & sub cutis (22%) and bone & joints (11.5%).Other sites were respiratory system, gastrointestinal tract, urinary system, pericardium, male genital system, eye & ocular adnexae, omentum, oral cavity & oropharynx, breast & brain (Table 2).
Granulomas of different etiologies were seen and tabulated in table 3. Tuberculosis (fig. 1) was the most common cause of granuloma with 258 (61.7%) cases, followed by fungal infections, foreign body reaction, parasites and toxoplasmosis.Other causes are leprosy, sarcoidosis, catscratch disease, Crohn's disease, leishmaniasis, tumors, BCG-instillation and chalazion.Final diagnosis was made based on histomorphology, special stains, other laboratory parameters, clinical & radiological findings and even patient's response to therapy.In 121 (28.9%) cases, histomorphology, special stains, other laboratory parameters and clinic-radiologic findings could not establish the cause of granulomatous inflammation, so, they were just labeled as granulomatous lesion.
In tuberculosis, ZN stain was done in 90 cases, out of which 10 cases were ZN positive (fig.2).Out of 258 cases of tuberculosis, lymph nodes were involved in 140 (54.26%)cases, followed by bone & joints (12.79%), respiratory system (5.42%),gastrointestinal system (4.65%) and female genital system (3.10%).Fungal elements were demonstrated  in five cases with PAS stain, which was performed in 13 cases.Out of five cases, three were aspergilloma (fig.3) and two were sporotrichosis.Lung was the site of aspergilloma and skin revealed sporotrichosis.
The most common type of granuloma was epithelioid (83.5%), followed by epithelioid with suppuration and mixed inflammatory (fig.4).In 97.3% cases of tuberculosis, the granuloma was epithelioid type.However, fungal infection showed epithelioid granuloma with suppuration in 76.9% cases.Histiocytic granulomas were seen in fungal and parasitic infections, whereas mixed inflammatory granulomas were seen in parasitic infestation, tuberculosis, chalazion and leishmaniasis (Table4).Necrobiotic granulomas were not seen in this study.

DISCUSSION
Granulomatous is a distinctive pattern of chronic inflammation encountered in infectious and noninfectious conditions.In this study, granulomatous lesions were common in 3 rd decade of life with slight male predominance and this finding corresponds to the finding of other studies. 6,7The commonest site was lymph node, followed by skin & subcutis, bone & joints, respiratory system and gastro-intestinal tract.In a study of Permi HS et al 6 the most common site of granulomatous lesion was skin & subcutis.
The most common cause of granuloma in this study and other studies was tuberculosis.However, the second most common cause is fungal in this study, whereas it is leprosy in study of Pawale JS et al 7 and Permi HS et al 6 .Rare causes of granulomatous lesion in this study were chalazion, BCG-instillation, tumor-associated, leishmaniasis, Crohn's  [6][7][8] The low sensitivity of ZN stain may be due to technical reason.The most common fungal infection is aspergillosis, which is comparable to other studies.Parasitic granulomas were due to cysticercosis and hydatid cyst in this study.In these cases, in addition to granuloma, parasitic structures were demonstrated.
In this study, epithelioid granuloma was the most common type of granuloma, followed by epithelioid with suppuration, mixed inflammatory, histiocytic and foreign body granulomas.Similar to this study, epithelioid type granuloma was most common type in other studies. 6,7owever, in contrast to this study, the second most common is either foreign body type or histiocytic type in these studies.
Epithelioid granulomas were seen in tuberculosis (97.3%), toxoplasmosis, fungal, Crohn's disease, leprosy, sarcoidosis, BCG-instillation and tumor associated.In our study, urothelial carcinoma of urinary bladder, testicular seminoma, Hodgkin lymphoma, mature cystic teratoma and adenocarcinoma of lung showed granulomatous inflammation.In a study of Permi HS et al, granulomas were seen in squamous cell carcinoma of skin, infiltrating ductal carcinoma of breast, papillary carcinoma of thyroid gland, dysgerminoma, Hodgkin lymphoma, seminoma, ameloblastoma and benign cystic teratoma. 6Tumor associated granulomatous reaction has largely been attributed to the cytokine milieu of the main tumor or the other cells of the background. 9pithelioid granulomas with suppuration were seen in fungal infection (76.9%), tuberculosis, cat-scratch disease and leishmaniasis.Histiocytic granulomas were found in parasitic infestation and fungal infections.Foreign body granulomas were seen as a reaction to foreign body.The causes of mixed inflammatory granulomas were parasitic infestation, tuberculosis, leishmaniasis and chalazion.
Most of the epithelioid granulomas were necrotizing.As per study of Aubry MC et al 5 , the most common cause of necrotizing granulomatous inflammation is infectious and even with ancillary studies, cause of few necrotizing granulomas remain unexplained.Ulbright TM et al 10 suggested that these cases represent infectious granuloma in which micro-organisms have been killed and/or removed by the inflammatory process.Alternative stains i.e. auramine / auramine-rhodamine using fluorescence technique 11 , in-situ hybridization 12 and real-time polymerase chain reaction 13 are useful tools to find the cause of granulomatous inflammation.
In significant number of cases (28.9%), the cause of granuloma was not known in this study.It may be due to    limited special stains and unavailability of PCR or ISH like techniques.The use of auramine / auramine-rhodamine using fluorescence technique, in-situ hybridization and realtime PCR may provide specific diagnosis.

CONCLUSION
The granulomatous lesion is common in third decade of life with slight male predominance.The commonest site is lymph node with tuberculosis being the most common cause and epithelioid being the most common type of granuloma.

Table 3 : Causes of granuloma
ZN stain demonstrated acid fast bacilli only in 11.11% cases in this study, whereas it was 20.74% in a study of Permi HS et al, 22.62% in a study of Pawale JS et al and 71% in a study ofKrishnaswamy H et al.