Head cheese sign (lungs)

Last revised by Henry Knipe on 19 Jun 2023

The head cheese sign, more recently called the three-density pattern, refers to a juxtaposition of regions with three (or sometimes more) different densities/regions of different attenuation within the lungs:

A mixed infiltrative (ground-glass opacity) and obstructive (mosaic attenuation) disease process can give rise to the head cheese sign. Less frequently, the superposition of a separate infiltrative and obstructive process causes this pattern. As the mosaic attenuation pattern is caused by airway narrowing/air trapping, these low attenuation areas may only be apparent on expiratory scans.

The head cheese sign is considered to be highly specific for hypersensitivity pneumonitis, although it can also be seen in other mixed infiltrative and obstructive processes (e.g. sarcoidosis) and atypical infections associated with bronchiolitis (e.g. Mycoplasma pneumonia3.

History and etymology

Head cheese, believe it or not, is not cheese and is often not made of the head. It is, in fact, a type of terrine, with bits of meat scavenged from various parts of various animals (including the head) usually from a calf or pig. The appearance of the cut surface of this dubious delicacy has been likened to the previously described pattern.

The three-density pattern has been proposed as an alternative name for this sign as familiarity with head cheese is regionally limited 5.

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Cases and figures

  • Figure 1: head cheese - photo
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  • Case 1: with hypersensitivity pneumonitis
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