Pulmonary mass and air meniscus sign in a 19-year-old man

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

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.

Ectopic Anterior Mediastinal Pathology in the Chest: Radiologic-pathologic Correlation of Unexpected Encounters with the "Terrible Ts"

The complex embryology of the anterior mediastinum makes it home to an array of primary neoplasms tied to the presence of the thyroid and thymus glands in that compartment. While the occurrence of ectopic thyroid deposits in the extramediastinal thorax has not been convincingly established, the other three “Ts” of the classic “4T” mnemonic for the differential diagnosis of an anterior mediastinal mass have occurred in the lung parenchyma, pleural space, and endobronchially as primary tumors. Finding any of the three lesions – thymoma, teratoma, or B-cell lymphoma – in the chest outside the mediastinum is very unusual, but that possibility exists. Herein, we illustrate examples of this rare phenomenon.