Cardiophrenic Angle Mass

Jud W. Gurney, MD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Pericardial Cyst
Pericardial Fat Pad
- Lipomatosis
- Pericardial Fat Necrosis
Morgagni Hernia
Adenopathy

Less Common

Thymoma
Right Middle Lobe Collapse
Pectus Deformity

Rare but Important

Fibrous Tumor of Pleura
Impending Cardiac Volvulus

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Mnemonic: FAT PAD
- Fat
- Pericardial cyst, Adenopathy, Diaphragmatic hernia

Helpful Clues for Common Diagnoses

Pericardial Cyst
- Benign disorder due to anomalous outpouching of parietal pericardium
- 5-10% of all mediastinal masses
- Location: Cardiophrenic angle
  - Right (70%), left (10-40%)
- Size: 2-30 cm in diameter
- Morphology: Round, sharp margins
- Unilocular in 80%, 20% multiloculated
- Wall imperceptible, noncalcified
  - No internal enhancement or enhancing rim
Pericardial Fat Pad
- Common normal finding can mimic pneumonia on radiographs
- Lipomatosis
  - Exuberant deposition of unencapsulated adipose tissue in mediastinum
  - CT: Homogeneous fat attenuation, mass does not compress or invade adjacent structures
  - Does not enhance with contrast
  - May have enlarged pericardial fat pads
- Pericardial Fat Necrosis
  - Rare benign condition of unknown etiology
  - Patients usually present with acute pleuritic chest pain
  - Imaging and pathologic features similar to those of fat necrosis in epiploic appendagitis
Morgagni Hernia
- Rare, 2% of all diaphragmatic hernias
- Congenital defect through anterior parasternal hiatus between diaphragm muscle and ribs (space of Larrey)
- Location: Primarily right-sided (heart limits herniation on left)
- Smooth and sharply marginated
- Commonly contains omental fat; may contain bowel, particularly transverse colon
  - Omentum contains vessels (compared to fat pads, which have sparse vessels)
  - Air in mass should suggest hernia
- If there is pleural effusion, suspect strangulation of bowel in hernia sac
Adenopathy
- Lymphadenopathy from lymphoma most common cause in this location
  - Metastases from tumors of thorax or abdomen may also affect these nodes
- Mantle radiation therapy: Cardiac blocker used to protect heart, area undertreated
  - “Recurrent fat pad” sign: Enlarging recurrent nodes from lymphoma in undertreated pericardial lymph nodes
  - Nodes may be irradiated since field was blocked initially
  - Appearance or enlargement of “fat pad” heralds development of adenopathy

Helpful Clues for Less Common Diagnoses

Thymoma
- Most common primary anterior mediastinal mass
- Oval or lobulated mass
- Homogeneous enhancement is common with small tumor, more heterogeneous enhancement for larger tumors
- 1/3 have calcification present on CT, usually thin and linear within capsule
- Cystic regions and necrosis are common (1/3), especially with larger tumors, and may be a dominant feature
- Paraneoplastic syndromes in 40%
  - Myasthenia gravis (35%), pure red cell aplasia (5%), hypogammaglobulinemia (10%)
Right Middle Lobe Collapse
- Right middle lobe smallest of all lobes
  - Indirect signs from collapse uncommon; hilar shift infrequent
  - Lobe collapses medially toward right heart border
- Right middle lobe syndrome: Cicatrizing atelectasis of RML due to prior pneumonia and poor collateral drift
  - RML bronchus is small, susceptible to compression from adjacent lymphadenopathy
Pectus Deformity
- Pectus excavatum: 1 in 300-400 births, most common chest wall abnormality (90%)
- Right heart border frequently obliterated because depressed sternum replaces aerated lung at right heart border
- Heart displaced to left and rotated, may cause spurious cardiomegaly

Helpful Clues for Rare Diagnoses

Fibrous Tumor of Pleura
- Uncommon primary mesenchymal tumor of pleura
  - 80-85% benign, 15-20% malignant
  - Most common location: Inferior hemithorax
  - Often large (> 7 cm), grow very slowly over years
  - Lobulated, sharply marginated mass with longitudinal axis paralleling chest wall
  - Pedunculated lesions change location with position, a characteristic imaging feature
  - Rarely, pedicle may twist and detach tumor
  - Pleural effusion (20%), more common with malignant lesions
  - Calcification in 5%; calcification in malignant tumors more common (20%)
  - Tumors often enhance with contrast
  - Hypertrophic osteoarthropathy in 17-30%
  - Hypoglycemia rare (5%), known as Doege-Potter syndrome
  - Recurrence may occur even with benign tumors, requires long-term surveillance
Impending Cardiac Volvulus
- Herniation of heart into hemithorax
- Generally takes 3 days for adhesions to form between cut edge of pericardium and heart
- Usually occurs in immediate postoperative period
- Most commonly presents with sudden shock
- Prior to herniation, there may be a tight, spherical, cardiac bulge (like top of snow cone) as heart begins to herniate through pericardial defect