52 year old with a remote history of a rare skin cancer, dermatofibrosarcoma protuberans (DFSP) now presenting with recurrent pneumothoraces and difficulty breathing.

Top: Frontal and lateral chest radiographs shows the lungs filled by numerous cysts of varying sizes. Some cysts have layering fluid in them forming fluid levels.

Bottom: Axial CT through the mid lungs shows the numerous cysts, some with layering fluid, some with wall thickening.

Differential diagnosis for cystic lung disease: airway disease (emphysema, bronchiectasis from various causes), infectious/inflammatory (abscesses, vasculitis), cellular proliferation (cystic metastases, papillomatosis, mesenchymal cystic hamartomas, eosinophilic granulomas, lymphangioleiomyomatosis), injury (traumatic cysts, old lung infarcts).

Final diagnosis: The history of a histiocytic skin cancer suggested an extremely rare entity for cystic lung disease called pulmonary cystic fibrohistiocytic tumor.

It is sort of unclear if the lung cysts represent metastases from the fibrous histiocytic skin cancer or a separate primary neoplasm. The disease has an indolent progressive course. There is no good treatment for this as far as I am aware. These patients also get pulmonary arteriovenous malformations that might need embolization - you can see this patient does have a few embo coils on the chest radiographs at the left lung base.