Ominous lung cavity “Tambourine sign”

Table 1 Confounding factors leading to delay in diagnosis in the index case

Young age of presentation

Lack of significant soft tissue component and thin walls initially

Multifocality favoured a systemic infection/disease (vasculitis) rather than primary lung malignancy

Increase in wall thickness in second CT was suspicious, but interpretation was confounded by heavy growth of streptococcus.

Waxing and waning symptoms.

Repeated negative BAL and FOB

CT: Computed tomography; BAL: Bronchoalveolar lavage; FOB: Fiberoptic bronchoscopy.

Table 2 Learning points

IMAC is more common in non-smokers and females and has poor prognosis

It has lower lobe predominance and is frequently multifocal

IMAC may be missed on repeated cytology and biopsies due to relative paucity of malignant cells and large amount of mucin

“Tambourine” sign in appropriate clinical setting identifies lung cavity suspicious for malignancy, especially IMAC

IMAC may show unusual slow growth and only mild uptake on PET

IMAC: Invasive mucinous adenocarcinoma; PET: Positron emission tomography.