Partial hydatidiform mole can evolve into a metastatic trophoblastic tumor. A 36-year-old, multiparous woman, pregnant with a 22-week embryonic hydatidiform mole, having spontaneously expelled. Histopathological examination showed a non-invasive partial mole. During biological monitoring, a trophoblastic tumor was diagnosed with pulmonary metastasis on CT-scan and myometrial invasion by MRI. Authors opted for a monochemotherapy with a good evolution. The potential risk of malignant transformation of the partial hydatidiform mole requires an adequate therapeutic strategy with strict monitoring.