Reply: Teratoma: another cause of the air-crescent sign.

We read with great interest the well-written article by Tseng and Chen, 1 who described the case of a 65-year-old woman who presented with hemoptysis and a cavitary lesion in the right lung with an air crescent sign and an intracavitary fungus ball-like mass. The final diagnosis was lung carcinoma. The authors highlighted the importance of cavity wall thickness for the differential diagnosis, reporting that cavity lung cancer rarely presents with a thin-walled cavity. We would like to report the case of a 22-year-old woman who also presented with hemoptysis and a thick-walled cavitary lesion on chest X-ray. She had received therapy for pulmonary tuberculosis for 1 year from other institution, in the absence of laboratory evidence of Mycobacterium tuberculosis. Chest-computed tomography revealed a thick-walled cavity in the left upper lobe with an air crescent sign and an intracavitary mass (Figure 1). The final diagnosis was a mature teratoma. The air crescent sign is a collection of air in a crescentic shape that separates the wall of a cavity from an inner mass. This sign is often considered to be characteristic of Aspergillus colonization of pre-existing cavities or the retraction of infarcted lung in angioinvasive aspergillosis. 2 Because Aspergillus spp. are the most commonly implicated fungi, these fungal masses are also called aspergillomas. 3 Although Aspergillus is the most frequent cause of the air crescent sign, this finding has been reported in association with a variety of other conditions, including tuberculosis (blood clot or Rasmussen an-eurysm), hydatic cysts, lung cancer, bacterial lung abscess, other fungal or fungal-like conditions (coc-cidioidomycosis, actinomycosis, nocardiosis, can-didiasis), and intracavitary hematoma. 1–4 In conclusion, teratoma should be considered in the differential diagnosis of the air crescent sign. References 1. Tseng YY, Chen CH. Air crescent sign: not always due to fungal infection. Reply: Teratoma: another cause of the air-crescent sign Dear editor Dr Edson reported another interested case with air-crescent sign due to mature teratoma. This case is also a thick-wall cavity lesion but not Figure 1. A chest-computed tomography image revealed a thick-walled cavity in the left upper lobe of the lung with an air crescent sign (arrows) and an intracavitary mass (asterisk).