Nipple shadows

Last revised by Dr Daniel J Bell on 14 Oct 2020

Nipple shadows refer to the silhouettes of the nipples on frontal chest radiographs, which may mimic solitary pulmonary nodules (SPNs).

Nipple shadows are apparent on ~7.5% (range 3.5-11%) of frontal chest x-rays 1.

It has been proposed by Miller et al. that solitary pulmonary nodules that reach some or all of the following criteria be considered nipple shadows 2:

  • bilateral and symmetric
  • "fuzzy" margins or radiolucent "halo"
  • sharp lateral border and poorly defined medial border (may be present only on PA projections 3)
  • nodules are in a characteristic position:
    • male: between the 5th and 6th ribs anteriorly
    • female: at the inferior aspect of the breast shadow
  • were not present on a very recent film
  • prominent nipples may be visible on a lateral projection

However, if there is doubt whether a nodular opacity represents a nipple shadow or not, a repeat chest x-ray with nipple markers should be performed 4, albeit at a financial cost and further radiation dose to the patient.

There is always the rare occurrence of a real solitary pulmonary nodule being overshadowed by a nipple shadow.

On chest radiograph the following features are present:

  • nipple shadows are nodular opacities that are consistent in shape, size and position 1,2:
    • oval or round
    • 5-15 mm in diameter
    • between the 9th and 10th ribs posteriorly or the 5th and 6th ribs anteriorly
  • tend to have incomplete margins due to their attachment to the chest wall 4

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Cases and figures

  • Case 1: solitary pulmonary nodule (right)
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  • Case 1: with nipple markers
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  • Case 2: bilateral nipple shadows
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  • Case 3: bilateral nipple shadows
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