If you look at the slide and you see in the dermis collections of epithelioid histiocytes plus or minus surrounding lymphocytes or giant cells or neutrophils in the centre of these lesions, then you have granulomas.
Granulomas are sub-classified into about four types. They can be tuberculoid, sarcoidal, pallisading or infectious. Various diseases present as different types of granulomas. The sarcoidal granuloma is sometimes called the naked granuloma because basically you just have a collection of histiocytes without any surrounding lymphocytes or neutrophils. In a tuberculoid granuloma you will have histiocytes but you will also have some central caseous necrosis. In the pallisading granuloma you will find that the cells are surrounding denatured collagen and it goes under the name of necrobiosis or sometimes there is mucin or foreign body material at the centre of a pallisading granuloma. A suppurative granuloma has centrally numerous neutrophils and they are part of an infected abscess.
The granuloma is the body's immune attempt at isolating this infective process. The common granulomatous diseases we see will be sarcoidosis, granuloma annulare, actinic granuloma, granulomatous rosacea, necrobiosis lipoidica, tuberculosis of the skin and leprosy. The other condition we have to watch out for is the deep fungal infection which will have an infective granuloma.
