The Air-Cleft Sign: Imaging and Histopathologic Findings in 7 Cases of Pulmonary Benign Metastasizing Leiomyomatosis

Benign metastasizing leiomyomatosis (BML) is a rare complication of uterine leiomyoma and most often develops following uterine surgery. Pulmonary BML usually follows a benign clinical course and is often encountered incidentally, but may manifest clinical symptoms or even hypoxic respiratory failure in patients with large tumor burdens. In this paper, we present the "air-cleft sign," a potentially useful and previously unreported CT finding in pulmonary BML patients with larger pulmonary nodules.

We queried the electronic medical record and picture archiving and communication system at our institution and identified a total of 7 cases of biopsy-confirmed pulmonary BML over the last 25 years. A team of 4 chest radiologists and a surgical pathologist reviewed these cases for key imaging and pathology findings.

All 7 patients in our cohort had a history of uterine surgery or intervention before developing lung nodules. Most of the patients had nodules that demonstrated either very slow growth or long-term stability. Six of these 7 patients had nodules containing crescentic or oblong-shaped air-density clefts, and we observed these air clefts mostly in the larger nodules (average diameter 63 mm). At pathology, the air clefts corresponded to normal entrapped respiratory epithelium and are thus distinct from true cavitation.

Establishing a diagnosis of pulmonary BML is difficult, given the rarity of the disease. In this small cohort of patients with pulmonary BML, we report a previously undescribed finding, the air-cleft sign, which can potentially help radiologists recognize pulmonary BML in women with multiple pulmonary nodules.