Lymphocytic Myocarditis: Seaport Criteria for Non-Biopsy Specimens

Vocabulary flashcards based on the Seaport consensus criteria for the histopathologic diagnosis and classification of lymphocytic myocarditis in surgical and autopsy specimens.

Lymphocytic myocarditis

A myocardial inflammation predominantly composed of lymphocytes, accompanied by myocyte injury not attributable to other causes (e.g., ischemia, trauma, foreign body, or amyloid).

Dallas Criteria

Histopathologic findings established in 1987 to define lymphocytic myocarditis on endomyocardial biopsy specimens.

Seaport criteria

The 2025 expert consensus guidelines for the diagnosis and classification of lymphocytic myocarditis specifically in non-biopsy ventricular myocardial specimens.

LIUS (Lymphocytic Infiltrate of Uncertain Significance)

A term recommended for cases where a lymphocytic infiltrate is identified within the myocardium but myocyte injury cannot be confidently identified.

Active lymphocytic myocarditis

The specific diagnostic term invoked when myocardial lymphocyte-predominate inflammation is present alongside identifiable myocyte injury.

Focal (Extent)

A classification used when a single focus of lymphocytic myocarditis is identified that involves $< 50\%$ of the area of myocardium on the examined tissue section.

Multifocal (Extent)

A classification used when two or more non-contiguous foci are identified, but the areas collectively involve $< 50\%$ of the area of the examined tissue section.

Diffuse (Extent)

A classification used when $\ge 50\%$ of the area of a single tissue section is involved by active lymphocytic myocarditis.

Myocytolysis

A feature of myocyte injury characterized by the overt breakdown of myocyte structure and disruption of the sarcolemma.

Sarcolemmal scalloping

A histopathologic finding where a lymphocytic infiltrate imparts sharp and irregular borders to the sarcolemma, often associated with hypereosinophilia.

Acute lymphocytic myocarditis

A temporal qualifier used when active lymphocytic myocarditis is present and no granulation tissue is observed.

Subacute lymphocytic myocarditis

A temporal qualifier used when active lymphocytic myocarditis is present and granulation tissue is identified.

Chronic lymphocytic myocarditis

A temporal qualifier used when active lymphocytic myocarditis is present and mature, replacement-type interstitial fibrosis is observed.

Autopsy sampling requirements

A recommended minimum of six full-thickness (endocardium to epicardium) sections of ventricular myocardium should be evaluated to reasonably exclude lymphocytic myocarditis.

Septal myectomy sampling requirements

The evaluation of these surgical specimens should generally include a minimum of two cassettes or blocks of myocardium.

Apical core resection requirements

These specimens, typically derived during ventricular assist device installation, should be entirely submitted as cross-sections to visualize epicardium, myocardium, and endocardium.

IHC (Immunohistochemistry)

An ancillary technique that may increase diagnostic yield by counting lymphocytes, though not currently mandated in the Seaport criteria due to cost and accessibility issues.

Nuclear pyknosis

A sign of myocyte injury characterized by nuclear shrinkage with chromatin condensation.

Karryorrhexis/Karyolysis

Forms of myocyte injury involving nuclear fragmentation or dissolution.

Vacuolar degeneration

A myocytologic change indicative of injury where prominent vacuoles are contained within the cytoplasm of the myocytes.