*Requires 10 sections to exclude;<ref>KC. 1 October 2010.</ref> sections should include right ventricle and left ventricle.
**It is often missed with five.<ref name=pmid9559966>{{Cite journal | last1 = Kubo | first1 = N. | last2 = Morimoto | first2 = S. | last3 = Hiramitsu | first3 = S. | last4 = Uemura | first4 = A. | last5 = Kimura | first5 = K. | last6 = Shimizu | first6 = K. | last7 = Hishida | first7 = H. | title = Feasibility of diagnosing chronic myocarditis by endomyocardial biopsy. | journal = Heart Vessels | volume = 12 | issue = 4 | pages = 167-70 | month = | year = 1997 | doi = | PMID = 9559966 }}</ref>
===Microscopic===
Features:
*Inflammation.
*Myocyte necrosis (disputed<ref name=pmid16449736>{{Cite journal | last1 = Baughman | first1 = KL. | title = Diagnosis of myocarditis: death of Dallas criteria. | journal = Circulation | volume = 113 | issue = 4 | pages = 593-5 | month = Jan | year = 2006 | doi = 10.1161/CIRCULATIONAHA.105.589663 | PMID = 16449736 }}</ref>).
====Classification====
Classified by the inflammatory cells present:<ref name=emedicine1612533>[http://emedicine.medscape.com/article/1612533-overview http://emedicine.medscape.com/article/1612533-overview]</ref>
*Eosinophilic - ''hypersensitivity myocarditis'' - most common.
**May be assoc. with peripheral blood eosinophilia.<ref name=pmid20181108>{{cite journal |author=Amini R, Nielsen C |title=Eosinophilic myocarditis mimicking acute coronary syndrome secondary to idiopathic hypereosinophilic syndrome: a case report |journal=J Med Case Reports |volume=4 |issue= |pages=40 |year=2010 |pmid=20181108 |pmc=2830978 |doi=10.1186/1752-1947-4-40 |url=}}</ref>