Sarcoidosis is a multiorgan granulomatosis of unknown origin that involves thoracic sites in most cases. Our objective was to identify the unusual and potentially confusing thoracic CT features in this disease.

Thoracic high-resolution CT examinations of 965 consecutive patients who underwent CT in our center for confirmed thoracic sarcoidosis were reviewed. CT were evaluated by consensus of two radiologists. CT features were considered as unusual if observed in less than 5% of patients.

209 patients (22%) had one or more unusual CT features. Unusual features were equally observed in women (n=98 patients) and men (n=111 patients), with a mean age of 47 years old (min/max: 16-78) and 37% of patients older than 50 years old. No difference between these patients and patients with typical features were observed for sex (p=0.14) and age>50 years old (p=0.12). Unusual features were observed more frequently in radiographic stage 2 (n=78;37%), and 4 (n=76; 36%). Unusual manifestations in lung parenchyma (17.5% of patients) included atypical features in the distribution or shape of nodules (n=25) and micronodules (n=20), cavitation other than mycotic (n=48), atelectasis or air trapping (n=24), bronchiectasis (n=15) and basal reticulation (n=11). Other unusual features were noted regarding lymph nodes (4.9% of patients), pleura (2.7% of patients), vascular compression (2.2% of patients).

Unusual CT features are frequently noted in this large series with a wide spectrum of manifestations. Awareness of these atypical radiological features is essential for differential diagnosis.