Infectious and Non-Infectious Diseases Causing the Air Crescent Sign: A State-of-the-Art Review

Abstract

Aspergilloma, also known as mycetoma or fungus ball, is characterized by a round or oval mass with soft-tissue attenuation within a preexisting lung cavity. The typical computed tomography (CT) aspect of an aspergilloma is a mass separated from the wall of the cavity by an airspace of variable size and shape, resulting in the air crescent sign, also known as the meniscus sign. This CT feature is non-specific and can be simulated by several other entities that result in intracavitary masses. This review describes the main clinical and imaging aspects of the infectious and non-infectious diseases that may present with fungus-ball appearance, including pulmonary hydatid cyst, Rasmussen aneurysm, pulmonary gangrene, intracavitary clot, textiloma, lung cancer, metastasis, and teratoma, focusing on the differential diagnosis.

Chest

“…However, in reports in the literature, air crescent sign can also occur in other fungal infections, tuberculosis, actinomycosis, lung abscess and a small number of lung cancers [70]. Differential diagnosis should be based on characteristic imaging findings such as cavity thickness, enhanced performance, nodular mobility, and intracomponent attenuation [71]. The aspergillus ball is a soft-tissue attenuation mass, which is parasitic in the cavity of the lung and is easily secondary to the tuberculous cavity.…”

Giant Rasmussen’s aneurysm

“…A excisão cirúrgica é recomendada apenas quando a intervenção radiológica especializada não está disponível ou na presença de processo destrutivo considerável no pulmão. (4,5) Em resumo, embora o aspergiloma seja a causa mais comum de nódulo intracavitário em pacientes com tuberculose, o diagnóstico diferencial deve ser feito com outras afecções, especialmente o AR. A precocidade no diagnóstico possibilita o emprego de terapêutica adequada, reduzindo riscos de morte por sangramento maciço.…”

“…Surgical excision is recommended when specialized radiological procedures are unavailable or when there is considerable lung destruction. 4 , 5 …”

Radiological approach to cavitary lung lesions

“…Rasmussen’s aneurysm is a specific form of pulmonary artery pseudoaneurysm, which develops in pulmonary tuberculosis. 71…”