fibrous cap
The fibrous cap is a layer of fibrous connective tissue, which is thicker and less cellular than the normal intima, found in atheromatous plaques. The fibrous cap contains macrophages and smooth muscle cells.{{cite journal|last=Hansson|first=Göran K.|author2=Libby, Peter|title=The immune response in atherosclerosis: a double-edged sword|journal=Nature Reviews Immunology|date=July 2006|volume=6|issue=7|pages=508–519|doi=10.1038/nri1882|pmid=16778830}}
The fibrous cap of an atheroma is composed of bundles of muscle cells, macrophages, foam cells, lymphocytes, collagen and elastin. An atheroma with a cap is termed a fibrous cap atheroma.
Rupture
File:Histopathology of progressive atherosclerotic lesions.jpg
The rupture of a fibrous cap can lead to a stroke, or a heart attack either of which has the potential to be fatal.{{cite web |last1=Wissing |first1=T. B. |last2=Van der Heiden |first2=K. |last3=Serra |first3=S. M. |last4=Smits |first4=A. I. P. M. |last5=Bouten |first5=C. V. C. |last6=Gijsen |first6=F. J. H. |title=Tissue-engineered collagenous fibrous cap models to systematically elucidate atherosclerotic plaque rupture |url=https://www.nature.com/articles/s41598-022-08425-4 |website=Scientific Reports |access-date=27 March 2025 |pages=5434 |language=en |doi=10.1038/s41598-022-08425-4 |date=31 March 2022}}
The fibrous cap is prone to rupture and ulceration which can lead to thrombosis. In advanced lesions, further complications may arise including calcification of the fibrous cap.{{cite journal|last=Swirski|first=F. K.|author2=Nahrendorf, M.|title=Leukocyte Behavior in Atherosclerosis, Myocardial Infarction, and Heart Failure|journal=Science|date=10 January 2013|volume=339|issue=6116|pages=161–166|doi=10.1126/science.1230719|url= |pmid=23307733|pmc=3891792|bibcode=2013Sci...339..161S }}