a very rare case of metachronous multicentric giant cell tumor of bone with benign lung metastasis in form of a very large mass lesion

Giant cell tumour (gct) is a benign, locally aggressive tumour of the bone that accounts for 5% of primary bone tumors and 21% of benign bone tumours. this tumour more commonly presents as a single (solitary) lesion; however, it may appear with multiple (multicentric) lesions in less than 1% of the cases. according to the literature, 1-9% of solitary gcts metastasizes to the lung, more commonly in cases with local recurrence. there are limited case reports on multicentric gct (mcgct) in the literature. the mcgct can be synchronous or metachronous depending upon the time interval between the two lesions. herein, we presented a very rare case of metachronous mcgct with benign lung metastasis in form of a huge lung mass.