Cavities

The term “cavity” is used to describe nodules, masses, or consolidations with an air-filled central space (synonyms: cavern, cavitary nodule). They are formed following bronchial drainage of necrotic material from the center of a lesion, resulting in the necrotic cavity manifesting as an air-filled hollow space on imaging.

Differential diagnosis varies in accordance with the number of nodules (solitary or multiple) and the nodule size (▶Table 22.1).

The probability of malignancy of large cavities increases in line with the thickness and irregularity of the cavity wall. But there are also adenocarcinomas that present as very thinwalled, smoothly marginated cavities, with a virtually cyst-like appearance.

Table 22.1 Differential diagnosis of solitary and multiple cavitary lesions

Diagnoses	Solitary	Multiple	Remarks
Lung cancer	++	(+)	Squamous cell carcinoma: solitary, thick-walled Adenocarcinoma: thin-walled, occasionally multifocal
Metastasis	(+)	++	Thin-walled, usually small nodules; common primary tumors: bladder cancer, pulmonary adeno- and squamous cell carcinomas, sarcomas
Abscess	++	+	Generally clinical and paraclinical inflammatory symptoms
Septic embolism	–	++	Generally severe inflammatory symptoms
Tuberculosis	++	++	Postprimary tuberculosis. Concomitant findings: consolidations, bronchial wall thickening, tree-in-bud pattern
Rheumatoid nodules	(+)	++	In known rheumatoid arthritis: cavitary and solid nodules, usually smoothly marginated
Granulomatous polyangiitis	–	++	Positive c-ANCA, furthermore, diffuse alveolar hemorrhage (ground-glass opacities and consolidations)
Langerhans cell histiocytosis	–	++	Small nodules, of which some solid with apical predominance, sparing the costophrenic angles
Necrotizing sarcoid granulomatosis	–	++	Rare; multiple nodules or largish masses, some cavitary
Bronchocentric granulomatosis	–	++	Rare; consolidations and liquefying nodules
Abbreviation: c-ANCA, cytoplasmic antineutrophil cytoplasmic antibodies.