Sarcoidosis-Like Cancer-Associated Granulomatosis: Characteristics and a Case-Control Comparison with Sarcoidosis

(1) Background: Systemic granulomatosis developed in a context of malignancy has already been reported. Our objective was to describe the clinical, radiological, functional, biological, and evolutive characteristics of sarcoidosis-like cancer-associated granulomatosis (SLCAG) and to compare them to those of sarcoidosis. (2) Methods: 38 patients with a biopsy-proven SLCAG developed after a diagnostic of malignancy were included. The control group consisted of sarcoidosis patients matched for age, sex, and radiologic stage. Clinical, biological, physiological, radiological, and outcome data were collected. (3) Results: The mean age of SLCAG patients was 51 ± 14 years. They were diagnosed within 15 ± 14 months of the cancer diagnosis (breast cancer most frequently). All SLCAG patients presented a thoracic involvement, extrathoracic locations were observed in 32% of subjects. SLCAG was more often asymptomatic than sarcoidosis (p < 0.0001). During follow-up, systemic treatment was less often required in SLCAG than in sarcoidosis (58% vs. 32%, p = 0.04 respectively) and SLCAG were characterized by a significantly less severe progression profile according to the Sarcoid Clinical Activity Classification, with a complete recovery more frequent at 5 years (p = 0.03). (4) Conclusion: This case-control study shows that SLCAG differs from sarcoidosis with a significantly more benign course. These results might argue for true differences in the physiopathology, which remain to be elucidated.