Mass-like or tumefactive hypertrophic cardiomyopathy is a morphological variant or phenotype of hypertrophic cardiomyopathy (HCM).

Epidemiology

Mass-like or tumefactive hypertrophic cardiomyopathy is rare and accounts for less than 2% of cases ^1-4.

Associations

Mass-like or tumefactive hypertrophic cardiomyopathy can be sometimes associated with left ventricular outflow obstruction if the affected segment is located in the basal region near the left ventricular outflow tract ¹.

Pathology

This phenotype is characterised by asymmetric focal left ventricular thickening simulating a cardiac tumour but with otherwise typical features of hypertrophic cardiomyopathy.

Microscopic appearance

Microscopically the hypertrophic segment is characterised by the following features ¹:

• cardiomyocyte hypertrophy

• myocardial fibre disarray

• interstitial fibrosis or replacement fibrosis

• bizarre enlarged nuclei nuclear hyperchromasia and pleomorphism

Radiographic features

Mass-like hypertrophic cardiomyopathy is characterised by a focally thickened segment.

Ultrasound

Echocardiography

Echocardiography might serve as a first-line imaging modality for the detection of the lesion ⁴.

Speckle tracking echocardiography can be used to assess cardiac contractility which might be variable but should be present.

CT

On cardiac CT the cardiac segments affected by mass-like hypertrophic cardiomyopathy should look like the remainder of the myocardium with similar contrast enhancement and without calcifications ².

MRI

Cardiac MRI characteristics of mass-like hypertrophic cardiomyopathy feature a similar signal intensity as the normal uninvolved myocardium and relative preservation of myocardial contractility unlike real cardiac tumours which need to be distinguished from the condition ^1-5:

• cine imaging: focal mass-like thickening

• cardiac strain imaging: variable contractility

• cardiac tissue characterisation​

  • T2/STIR black blood: should look like normal myocardium

  • T1 mapping: mildly increased native T1 values

  • ECV: mildly increased

• perfusion imaging: normal first-pass perfusion

• IRGE/PSIR:

  • fan-shaped or patchy mesocardial late gadolinium enhancement

  • indicating replacement fibrosis or myocardial scarring

Radiology report

The radiological report should include a description of the following:

• location, extent, contractility and contrast enhancement of the hypertrophic wall segment

• cardiac volumes and measurements including left ventricular mass

• cardiac wall motion abnormalities

• presence of myocardial crypts

• signs of myocardial fibrosis, focal replacement fibrosis or myocardial fibre disarray

• mitral annular plane systolic excursion (MAPSE)

• left ventricular outflow obstruction

• systolic anterior movement of the mitral valve

Differential diagnosis

Conditions that might mimic the clinical presentation or imaging appearance of mass-like or tumefactive hypertrophic cardiomyopathy include ^1-5:

• cardiac tumours (e.g. fibroma, rhabdomyoma, lymphoma)

• asymmetric hypertrophic cardiomyopathy

• midventricular hypertrophic cardiomyopathy

• apical hypertrophic cardiomyopathy (Yamaguchi syndrome)

• cardiac sarcoidosis