An Atypical Behavior of Metastatic Lung Disease in a Young Woman With Osteosarcoma: A Case Report.

Osteosarcoma is an aggressive primary malignant bone tumor with frequent local or metastatic recurrence after surgery. Lungs are the most common site of metastasis. Although the majority of relapses will occur within five years of the initial diagnosis of osteosarcoma, lung metastases may appear a long time after initial presentation. This mechanism is known as late-relapse metastasis, in which dormant metastatic cells undergo reactivation and give rise to metastatic outgrowths. We report a case of a 29-year-old woman diagnosed with osteosarcoma of the left distal tibia. Chest CT performed at the initial presentation showed no metastasis. The patient underwent two cycles of neoadjuvant chemotherapy prior to surgery. Routine follow-up chest CT revealed a lung nodule five years later. A sudden increase in the size of the lung nodule was observed two years later. Histopathological analysis of the lung nodule confirmed osteosarcoma lung metastasis. A better understanding of the various types of aspects and atypical behaviors of osteosarcoma metastases could have a significant impact on the prognosis of the patients.