Isolated (localized) idiopathic granulomatous vasculitis (IGV) is an uncommon, heterogeneous, and poorly defined group of disorders characterized by infiltration of the arterial wall caused by compactly grouped mononuclear phagocytes, with or without giant cells, in segmental distribution. We report on a 55-year-old woman with IGV limited to an intramuscular lipoma of the left thigh. The vasculitis was identified incidentally upon microscopic examination of the removed tumor. The IGV was centered on two medium-sized arteries, accompanied by narrowing of the lumens, and not associated with secondary changes such as infart or postinfart fibrosis. The inflammatory infiltrate was rich in T-lymphocytes and macrophages, with the presence of giant cells. The patient was asymptomatic and well in a follow-up period of 2 months, during which she was not treated. To our knowledge, this is the first report of lipoma involvement in localized IGV. It is important to distinguish cases of isolated intratumorous IGV from systemic disease, because the latter implies a poor prognosis and requires an aggressive treatment.