**2.6 Necrotizing sarcoid granulomatosis (NSG)**

Infectious granulomatosis should also be differentiated from NSG. Some characteristics of the latter are likened to those seen in polyangiitis with granulomatosis. NSG is characterized by the interstitial necrosis, which is often eosinophilic, but

#### **Figure 9.**

*Rheumatoid arthritis: Extensive necrosis with rims of histiocytes at the periphery and lymphoid infiltration of vessel wall. H&E.*

**55**

**Figure 10.**

*Necrotizing sarcoid granulomatosis: Granulomatous vasculitis. H&E.*

*Pathology of Sarcoidosis and Differential Diagnostics of other Granulomatous Diseases*

sometimes may contain cellular debris. However, necrosis in NSG is combined with the non-necrotizing sarcoid-type granulomas, consisting mainly of epithelioid and giant multinucleated cells with just a small number of lymphocytes. These granulomas tend to merge and are often located near blood vessels or in its walls, but not causing vasculitis (**Figure 10**) [6]. The following symptom triad is obligatory for the NSG diagnosis: sarcoid-type granulomas, granulomatous vasculitis, and necrotiz-

Since necrosis in infectious granulomatosis may be of a coagulation type, pulmonary infarction should also be a part of the differential diagnosis. In the stage of organization, infarction may be surrounded by fibroblasts and inflammatory cells, resembling granulomatous inflammation. As a rule, in lung resection specimens with pulmonary infarction, thrombi can be detected in the branches of the pulmo-

Fungi that cause deep mycoses, as a rule, do not form granulomas in the lungs.

Histoplasmosis is caused by *H. capsulatum* (North America, river valleys) and *H. duboisii* (Africa), which are budding yeast cells with a diameter of 2–4 μm. Microorganisms are found in the cytoplasm of macrophages, histiocytes, and necrotic debris. Its capsule is stained with Giemsa or PAS reaction. Both organisms

In most cases, fungi such as *Aspergillus, Candida*, and some others cause local mycetoma, diffuse invasive mycosis, or allergic reactions (allergic bronchopulmonary aspergillosis/mycosis). The granulomatous response in these fungi infections

nary artery that caused the development of a pulmonary infarction [13].

**2.7 Granulomatous inflammation caused by infectious agents**

*DOI: http://dx.doi.org/10.5772/intechopen.90693*

ing inflammation.

*2.7.1 Fungi*

is rare [14].

*2.7.1.1 Histoplasmosis*

### *Pathology of Sarcoidosis and Differential Diagnostics of other Granulomatous Diseases DOI: http://dx.doi.org/10.5772/intechopen.90693*

sometimes may contain cellular debris. However, necrosis in NSG is combined with the non-necrotizing sarcoid-type granulomas, consisting mainly of epithelioid and giant multinucleated cells with just a small number of lymphocytes. These granulomas tend to merge and are often located near blood vessels or in its walls, but not causing vasculitis (**Figure 10**) [6]. The following symptom triad is obligatory for the NSG diagnosis: sarcoid-type granulomas, granulomatous vasculitis, and necrotizing inflammation.

Since necrosis in infectious granulomatosis may be of a coagulation type, pulmonary infarction should also be a part of the differential diagnosis. In the stage of organization, infarction may be surrounded by fibroblasts and inflammatory cells, resembling granulomatous inflammation. As a rule, in lung resection specimens with pulmonary infarction, thrombi can be detected in the branches of the pulmonary artery that caused the development of a pulmonary infarction [13].
