The mural nodule in cavitary opportunistic pulmonary aspergillosis.

Abstract
A common radiographic feature of opportunistic pulmonary (human) aspergillosis is a rounded, cavitary lesion with a nodule projecting into it. This appearance has been given a variety of names, including air crescent, meniscus, target, bull''s eye and peninsula. These signs merely represent different radiographic projections of the cavitary lesion and mural module. Similar lesions may also be encountered in other conditions.