Granulomas are organized conglomerates of histiocytes, a specialized white blood cell 1. They form by the process of granulomatous inflammation, which is a specific type of chronic inflammation that occurs following cellular injury as a response to the mediators that are released. A broad range of insults, including infections, autoimmune, foreign bodies, allergens and neoplastic disease, may trigger the formation of granulomas. This inflammatory response is seen at all ages and in all body tissues.
Terminology
It is important to not confuse granuloma with granulation tissue, the latter describes the new tissue that forms as part of the healing of an injury.
Two lesions of the oral cavity that are commonly called granuloma are misnomers:
- pyogenic granuloma is an angiomatous lesion rather than a true granuloma 3
- periapical granuloma consists of chronic granulation tissue 4
For historical reasons, a number of diseases bear "granuloma" in their name despite not having any granulomas.
- granuloma annulare
- Eosinophilic granuloma (also known as Langerhans cell histocytosis)
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