BACKGROUND Rosai-Dorfman disease (RDD) is a rare benign proliferative disease whose etiology is not clear and may be related to infection or unexplained immune dysfunction. The authors present a case of RDD with lung involvement in a 10-year-old patient. CASE SUMMARY A 10-year-old girl found that her left cervical lymph nodes were enlarged for more than 7 mo, and the largest range was about 6.5 cm × 5.9 cm × 8.1 cm. Cervical magnetic resonance imaging showed multiple masses in the left neck, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. A malignant tumor, with a high possibility of lymph node metastasis, was initially considered. At the same time, lung computed tomography showed multiple nodules of different sizes scattered on both sides of the lung, with uniform internal density. Thus, a possible metastatic tumor was considered. Finally, RDD was diagnosed by pathology and immunohistochemistry. According to the antibiogram, clindamycin was administered for 2 wk, and prednisone acetate was administered for 7 wk. Nine months later, the ulcer in the left neck was better than before, but the imaging showed that the lesion was not controlled. CONCLUSION The diagnosis of RDD cannot be made by a single tool and its treatment is a long-term exploratory process. Follow-up is necessary.

Background: Rosai-Dorfman disease (RDD) is a rare benign proliferative disease whose etiology is not clear and may be related to infection or unexplained immune dysfunction. The authors present a case of RDD with lung involvement in a 10-year-old patient.\\ Case description: a 10-year-old female found that the left lymph node was enlarged for more than 7 months, the larger range was about 6.5-5.9-8.1cm, and the cervical MR was considered as: malignant tumor, the possibility of lymph node metastasis was high. At the same time, lung CT conclusion: multiple nodules in both lungs, it is possible to consider metastatic tumor. Finally, RDD was diagnosed by pathology and immunohistochemistry.\\ Discussion: RDD involving the lung is very rare in clinic, and lung RDD clinical symptoms and imaging have no obvious specific manifestations, clinically easy to be misdiagnosed as malignant tumor, the final need for pathological diagnosis. The pathological manifestation of this case is typical, CD68, CD163 and Smur100 are all positive, and no other lesions are found in clinical and laboratory examination, so it is considered as the possibility of RDD involving the lung.\\ Conclusion: The simple use of imaging methods for diagnosis RDD is easy to lead to misdiagnosis, we need to comprehensively consider the use of different diagnostic methods; and according to the epidemiological characteristics of RDD, long-term follow-up of cases is necessary.