Locally Aggressive Giant Cell Tumor of Bone With Pulmonary Distant Metastasis and Extrapulmonary Seeding in Pregnancy.

Giant cell tumor of bone (GCTB) is a locally aggressive benign neoplasm that is associated with a large biological spectrum ranging from latent benign to highly recurrent and occasionally metastatic tumor. In this article, we present a case of a 26-year-old woman who presented with swelling at the left lower ribs during pregnancy. Surgical excision was done, and histopathology showed tumor with features consistent with GCTB. MRI preformed after delivery revealed recurrence of the mass with extensive growth reaching 17 cm with two subcutaneous satellite nodules in the adjacent abdominal wall. positron emission tomography-computed tomography (PET-CT) scan revealed bilateral fluorodeoxyglucose (FDG)-avid lung nodules. Surgical resection was done, and histopathology showed no evidence of malignant transformation. Few months later, the tumor recurred again, with peritoneal deposits. The patient underwent wide massive resection of the recurrent mass and then started on denosumab therapy. Molecular analysis of the tumor detected H3F3A G34W mutation with no copy number alterations. We are presenting this case of GCTB with pulmonary distant metastasis and extrapulmonary seeding to upsurge awareness among clinicians about the possible extreme aggressive biological behavior of GCTB that can mimic the presentation of malignant bone tumor and also to discuss the possible predictive factors of such aggressive behavior.