A tumor composed of granulation tissue resulting from injury or inflammation or infection WordNet 3.0 & Open English WordNet

A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. Wikipedia

An inflammatory nodule found in many diseases, consisting of histiocytes (macrophages) attempting to wall off substances they perceive as foreign but are unable to eliminate, such as certain infectious organisms as well as other materials such as suture fragments. Wiktionary