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URBANA ATLAS OF PATHOLOGY

Image Number 32 - Lung, tuberculosis

Tuberculosis is caused by Mycobacterium tuberculosis. This disease is on the rise and the causative agent is gaining resistance to current medications. The characteristic lesion of TB is a caseating (cheesy) granuloma. Caseous material is not seen in this particular slide. In general, a granuloma is characterized by an aggregation of modified macrophages, called epithelioid cells because of their resemblance to squamous epithelial cells. Epithelioid cells may fuse to form a giant cell (Langhan's cell). A Langhan's cell is seen in the bottom left hand corner of this slide-the large pink cell with about 20 nuclei arranged in a horseshoe shape. Granulomas are found in many diseases-sarcoidosis for example. However, caseating granulomas are found in relatively few diseases e.g. TB and some of the fungal infections.

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