Aims. We performed a systematic literature review to define features of patients, treatment, and biological behaviour of multicentric giant cell tumour (GCT) of bone. Methods. The search terms used in combination were “multicentric”, “giant cell tumour”, and “bone”. Exclusion criteria were: reports lacking data, with only an abstract; papers not reporting data on multicentric GCT; and papers on multicentric GCT associated with other diseases. Additionally, we report three patients treated under our care. Results. A total of 52 papers reporting on 104 patients were included in the analysis, with our addition of three patients. Multicentric GCT affected predominantly young people at a mean age of 22 years (10 to 62), manifesting commonly as metachronous tumours. The mean interval between the first and subsequent lesions was seven years (six months to 27 years). Synchronous lesions were observed in one-third of the patients. Surgery was curettage in 63% of cases (163 lesions); resections or amputation were less frequent. Systemic treatments were used in 10% (n = 14) of patients. Local recurrence and distant metastases were common. Conclusion. Multicentric GCT is rare, biologically aggressive, and its course is unpredictable. Patients with GCT should be followed indefinitely, and referred promptly if new symptoms, particularly pain, emerge. Denosumab can have an important role in the treatment. Cite this article: Bone Joint J 2022;104-B(12):1352–1361

Multifocal osteolytic lesions of the skeletal system are a challenge regarding diagnosis especially when multi-nucleated giant cells which are not specific for a tumour entity are found in the histological specimen. Therefore multiple differential diagnosis have to be considered such as metastases, primary malignant bone tumours, multicentric giant cell tumour of bone and brown tumours of primary hyperparathyroidism. A 49 year old woman underwent medical investigation in an external surgical department due to right hip pain after a fall. The radiologic skeletal status surprised with multiple osteolytic pelvic lesions and one tumour in the left scapula and first histological diagnosis described a giant cell tumour of bone with malignant aspects. After confirmation of this diagnosis by a second histopathological inquiry accomplished by a bone tumor specialist the patient was transferred to our tumour centre. To exclude the differential diagnosis of brown tumours a close look on the parathormon level was done which revealed an exorbitantly high serum amount of 922.7 pg/ml (normal 15–65 pg/ml). Further examination confirmed a parathyroid adenoma. After its extirpation serum levels of parathormon decreased and two months after therapy with high dose calcium substitution radiologic controls show a decline of osteolysis with bone consolidation. Brown tumours of hyperparathyroidism have always to be considered as a rare differential diagnosis of multiple giant cell containing tumours. The disease cannot be distinguished by the histological pattern but can very easily be excluded by normal parathormon levels. First step of therapy in brown tumours should be surgical extirpation of parathyroid adenomas or carcinomas followed by an endocrinological regime. Only failure of this treatment requires further surgical stabilisation of the bone lesions