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PA26.{8,10} | Pericardial Disease & Cardiac Tumours — SDL Guide (Part 3)

Cardiac Myxoma

Cardiac myxoma is the commonest primary tumour of the heart in adults.

Location: ~75% arise in the left atrium, attached to the interatrial septum near the fossa ovalis by a broad or pedunculated stalk. Right atrium ~20%; ventricles rare.

Gross appearance:
• Soft, gelatinous, glistening, translucent mass
• Surface may be smooth or papillary (friable — embolic risk)
• Size: 1–10 cm diameter
• Polypoid or sessile; pedunculated forms can prolapse through the mitral valve

Histology:
• Myxoma cells (stellate or globular cells) scattered within abundant myxoid (mucopolysaccharide-rich) stroma
• Cells embedded in a pale basophilic matrix (Alcian-blue positive)
• Thin-walled blood vessels; occasional smooth muscle, haematopoietic cells
• No cytological atypia (benign)

Split-panel medical diagram showing a left atrial myxoma attached at the fossa ovalis and its histology with stellate cells in pale myxoid stroma. — **Panel A:** Opened left atrium, gelatinous polypoid myxoma, stalk or pedicle, fossa ovalis attachment, mitral valve orifice, ball-valve obstruction. **Panel B:** Stellate myxoma cells, abundant pale myxoid stroma, thin-walled vessels, sparse tumour cellularity.

Clinical presentation (three mechanisms):
1. Obstruction — pedunculated myxoma intermittently occludes the mitral valve → syncope, dyspnoea that varies with posture ('ball-valve' obstruction); mimics mitral stenosis
2. Embolism — friable surface fragments detach → systemic emboli (stroke, limb ischaemia, renal infarcts)
3. Constitutional — fever, weight loss, elevated ESR, anaemia (interleukin-6 secretion by tumour cells)

Treatment: surgical excision — curative in most cases.

SELF-CHECK

A 52-year-old woman presents with syncopal episodes that occur when she bends forward, progressive dyspnoea, and an early diastolic 'tumour plop' on auscultation. Echocardiography shows a mobile left atrial mass attached near the fossa ovalis. Which histological feature is MOST characteristic of this tumour?

A. Sheets of small round cells with hyperchromatic nuclei and scanty cytoplasm

B. Multinucleated giant cells in an inflammatory stroma

C. Stellate cells within an abundant pale myxoid (mucopolysaccharide-rich) matrix

D. Intracytoplasmic vacuoles distending the cell (spider cells)

Reveal Answer

Answer: C. Stellate cells within an abundant pale myxoid (mucopolysaccharide-rich) matrix

The clinical picture — left atrial mass near the fossa ovalis, postural syncope, tumour plop — is classic for myxoma. Histologically it is defined by stellate/globular myxoma cells scattered in an abundant Alcian-blue-positive myxoid stroma with thin-walled vessels (option C, index 2). Option A describes small round blue-cell tumours (e.g., lymphoma); option B describes granulomatous inflammation; option D (spider cells with vacuoles) is characteristic of rhabdomyoma.

Other Primary Cardiac Tumours

A four-panel medical diagram compares the locations, gross features, histology, and clinical associations of rhabdomyoma, lipoma, papillary fibroelastoma, and angiosarcoma of the heart. — **Panel A:** Anterior heart cutaway showing ventricular rhabdomyomas, septal involvement, subepicardial/subendocardial lipoma, aortic valve papillary fibroelastoma, and right atrial angiosarcoma infiltrating pericardium.. **Panel B:** Rhabdomyoma histology showing large vacuolated spider cells, glycogen-distended myocytes, cytoplasmic strands, multiplicity, regression tendency, and tuberous sclerosis association.. **Panel C:** Lipoma with mature adipocytes and papillary fibroelastoma as a tiny sea-anemone-like valvular tumour with endothelial-lined papillae and avascular elastic core.. **Panel D:** Angiosarcoma histology showing anastomosing vascular channels, atypical endothelial cells, mitoses, haemorrhage, necrosis, right atrial origin, and poor prognosis..

Rhabdomyoma — commonest cardiac tumour in infants and children. Hamartomatous; strongly associated with tuberous sclerosis complex (~50% of patients with tuberous sclerosis have rhabdomyomas). Located in ventricular myocardium / septum. Histology: large, vacuolated spider cells (glycogen-distended myocytes with cytoplasmic strands extending to the cell membrane). Usually multiple, often regress spontaneously.

Lipoma — benign; subepicardial or subendocardial; mature adipocytes; usually asymptomatic incidental finding.

Papillary fibroelastoma — tiny, frond-like tumour on valve surface (aortic > mitral). Grossly resembles a sea anemone. Risk: embolism (stroke). On histology: papillary projections lined by endothelium; avascular elastic core.

Angiosarcoma (primary cardiac malignant)
• Commonest primary malignant cardiac tumour
• Usually right atrium; infiltrates pericardium early
• Haemorrhagic, necrotic mass
• Histology: anastomosing vascular channels lined by atypical endothelial cells; mitoses; necrosis
• Prognosis poor; usually presents late
• Note: angiosarcoma also occurs in soft tissue, liver (vinyl chloride exposure), breast, and skin (post-mastectomy lymphoedema — Stewart–Treves syndrome)

Vascular Tumours

Vascular tumours arise from the endothelium or pericytes of blood vessels. A brief but exam-relevant classification:

Benign vascular tumours

Haemangioma — commonest benign vascular tumour overall; often congenital.
• Capillary haemangioma: lobules of thin-walled capillaries; appears in skin/liver/mucosa; often involutes in childhood ("strawberry naevus")
• Cavernous haemangioma: large, thin-walled vascular spaces engorged with blood; liver is common site; risk of rupture + haemoperitoneum
• Lobular capillary haemangioma (pyogenic granuloma): polypoid, bleeds easily; gingiva, skin; associated with pregnancy ("pregnancy tumour")

Glomus tumour (glomangioma) — benign, derived from glomus body (arteriovenous thermoregulatory unit). Exquisitely painful. Subungual location (under fingernail) classic. Histology: nests of small round glomus cells (modified smooth muscle) around dilated vascular channels.

Malignant vascular tumours

Kaposi sarcoma — low-grade endothelial malignancy caused by Human Herpesvirus 8 (HHV-8). Four clinical forms:
1. Classic: elderly Eastern European men; lower limbs; indolent
2. AIDS-related (epidemic): most common AIDS-defining malignancy; skin, mucosa, viscera; aggressive
3. African endemic: children and young adults in sub-Saharan Africa
4. Iatrogenic: immunosuppressed transplant recipients
Histology: spindle cell proliferation + slit-like vascular spaces + red cell extravasation + haemosiderin.

Angiosarcoma — malignant tumour of endothelial cells. Can arise in liver (vinyl chloride, thorotrast), breast (post-irradiation), skin (post-mastectomy lymphoedema — Stewart–Treves), or heart (right atrium). Histology: irregular anastomosing channels lined by pleomorphic endothelial cells; haemorrhage; necrosis; mitoses. Aggressive; poor prognosis.

Three labelled histology panels compare cavernous haemangioma, Kaposi sarcoma, and angiosarcoma by their vascular spaces, spindle cells, red cell extravasation, and atypical endothelial channels. — **Panel A:** Cavernous haemangioma: large blood-filled vascular spaces, thin endothelial lining, flattened endothelial cells, thin fibrous septa, erythrocytes.. **Panel B:** Kaposi sarcoma: spindle cell proliferation, slit-like vascular channels, extravasated red blood cells, haemosiderin deposits, HHV-8 association.. **Panel C:** Angiosarcoma: irregular anastomosing vascular channels, atypical endothelial cells, hyperchromatic nuclei, endothelial multilayering, malignant invasion..

SELF-CHECK

A 34-year-old HIV-positive man develops multiple purplish skin nodules on his lower limbs and palate. Histology shows spindle cell proliferation with slit-like vascular spaces and haemosiderin deposits. Which virus is the primary aetiological agent?

A. Human Herpesvirus 8 (HHV-8)

B. Epstein-Barr virus (EBV)

C. Human papillomavirus (HPV)

D. Hepatitis B virus (HBV)

Reveal Answer

Answer: A. Human Herpesvirus 8 (HHV-8)

Kaposi sarcoma is caused by Human Herpesvirus 8 (HHV-8), also called Kaposi sarcoma-associated herpesvirus (KSHV). The clinical picture — AIDS, violaceous skin/mucosa nodules, spindle cells with slit-like spaces and haemosiderin on histology — is diagnostic. EBV causes lymphomas and nasopharyngeal carcinoma; HPV causes cervical and oropharyngeal carcinomas; HBV is associated with hepatocellular carcinoma.

CLINICAL PEARL

A useful exam framework: when asked about 'cardiac tumour' remember the 3-2-1 rule. 3 categories of primary benign tumours to know in detail (myxoma, rhabdomyoma, papillary fibroelastoma). 2 malignant cardiac associations (angiosarcoma = primary; any carcinoma/lymphoma = metastatic). 1 key ratio: metastases outnumber primary tumours 20–40:1. In any clinical scenario where a cardiac mass is found in a patient with known extracardiac malignancy, metastasis is always the first diagnosis to consider.

Complications — Summary Table

A seven-panel medical infographic summarises complications of pericarditis, cardiac tamponade, constrictive pericarditis, cardiac myxoma, angiosarcoma, visceral Kaposi sarcoma, and cavernous liver haemangioma. — **Panel A:** Acute fibrinous pericarditis showing fibrinous exudate, pericardial effusion, organisation, and adhesive pericarditis.. **Panel B:** Cardiac tamponade showing tense pericardial fluid, compressed right-sided chambers, reduced ventricular filling, obstructive shock, and cardiac arrest risk.. **Panel C:** Constrictive pericarditis showing rigid thickened pericardium with chronic venous hypertension, hepatic congestion, protein-losing enteropathy, and cachexia.. **Panel D:** Cardiac myxoma showing left atrial tumour, ball-valve mitral obstruction, systemic embolism, stroke, peripheral embolus, and rare infective endocarditis on tumour surface.. **Panel E:** Angiosarcoma showing right atrial malignant vascular tumour, haemopericardium, cardiac tamponade, lung and liver metastasis, and fatal arrhythmia.. **Panel F:** Visceral Kaposi sarcoma showing gastrointestinal bleeding, pulmonary involvement with dyspnoea and haemoptysis, and rare cardiac involvement.. **Panel G:** Cavernous haemangioma of liver showing cavernous vascular spaces, rupture, haemoperitoneum, Kasabach-Merritt syndrome, and consumptive coagulopathy in giant infantile haemangioma..

Condition	Key Complications
Acute fibrinous pericarditis	Pericardial effusion; organisation → adhesive pericarditis
Cardiac tamponade	Obstructive shock; cardiac arrest if untreated
Constrictive pericarditis	Chronic venous hypertension; hepatic congestion (cardiac cirrhosis); protein-losing enteropathy; cachexia
Cardiac myxoma	'Ball-valve' mitral obstruction; systemic embolism (stroke, peripheral); rarely infectious endocarditis on tumour surface
Angiosarcoma	Haemopericardium; cardiac tamponade; metastasis (lung, liver); fatal arrhythmia
Kaposi sarcoma (visceral)	GI bleeding; pulmonary involvement (dyspnoea, haemoptysis); rarely cardiac involvement
Cavernous haemangioma (liver)	Rupture → haemoperitoneum; Kasabach-Merritt syndrome (consumptive coagulopathy in giant haemangiomas in infants)