Cannonball metastases refer to well-defined spherical nodules scattered over both lungs, being a classical presentation of hematogenous tumor spreading. Striking progression of lung metastases without established primary malignancy can raise a diagnostic challenge. We herein report three cases with cannonball metastases at initial presentation. Two patients ended up having a choriocarcinoma but no awareness of the presence of primary tumors, and the third had abrupt lung metastases of endometrial cancer while she was being asymptomatic. Relentless progression was illustrated by clinical and radiographic changes. Ectopic expression of human chorionic gonadotropin (hCG) would seemingly go some way responsible for fulminant cancer spreading associated with poor prognosis in our patients. The goal of this presentation is to raise awareness of ectopic hCG expression in patients presenting with similar astonishing scenarios.