Chest X-ray Anatomy
Soft tissues

Key points

  • Assess the soft tissues on every chest X-ray
  • Thick soft tissue may obscure underlying structures
  • Black within soft tissue may represent gas

Whenever you look at a chest X-ray, have a look at the soft tissues, especially around the neck, the thoracic wall, and the breasts.

If a patient has very thick soft tissue due to obesity, underlying structures such as the lung markings may be obscured. Large breasts may obscure the costophrenic angles, giving the impression of the presence of pleural effusions.

Breast asymmetry

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Breast asymmetry

  • Here the breasts are asymmetric. The underlying lung markings (white boxes) appear denser on the left than the right. This should not be mistaken for underlying lung disease.
  • Breast asymmetry is very common, even to the extent that no breast tissue is visible on one side. It should not be assumed that the patient has had a mastectomy, unless this is known from the history.

Nipple markings

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Nipple markings

  • The nipples are clearly seen on this chest X-ray, but care is needed whenever there is a chance that the markings may represent underlying lung nodules. If there is any doubt then a repeat chest X-ray should be performed, with metallic markers used to indicate the position of the nipples.

Pseudo-blunting of the costophrenic angle

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Pseudo-blunting of the costophrenic angle

  • At first glance the left costophrenic angle appears blunt. This is because the patient was in a rotated position when the X-ray was taken. This has resulted in a greater thickness of breast overlying the costophrenic angle on the left, compared to the right.
  • If you are not careful you may be misled into thinking there is a pleural effusion or other pathology causing costophrenic angle blunting.

Soft tissue fat

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Soft tissue fat

  • This close-up demonstrates a normal fat plane between layers of muscle. Fat is less dense than muscle and so appears blacker.
  • Note that the edge of fat is smooth. Irregular areas of black within the soft tissues may represent air tracking in the subcutaneous layers (surgical emphesyma).

Assessing the soft tissues

The X-ray appearances of soft tissues of the chest can be misleading. As well as hiding genuine pathology, normal soft-tissues may mimic disease.

If you are in doubt, the first thing to do is to re-examine the patient. If you are still uncertain about the X-ray appearances, then discuss the image with a radiologist.