Lymphangioma is a congenital anomaly in which abnormal lymphatic drainages localize to form a benign mass, but it has the tendency to grow in size and the potential to infiltrate surrounding structures, causing devastating effects and leading to severe morbidity. The most common site of lymphangioma is the neck region (cystic hygroma colli), whereas lymphangioma in the lower limbs is very rare, accounting for only 2% of cases. Accordingly, the prenatal diagnosis of lymphangioma of the lower limbs has been scarcely reported. This study describes two cases of lymphangioma of the lower limbs, focusing on unique sonographic features and the natural course of rapidly progressive changes, which is different from nuchal lymphangioma. Based on previous isolated case reports together with our two cases, lymphangioma of the lower limbs usually develops in the second trimester, tends to have rapidly progressive changes, and is unlikely to be associated with aneuploidy and structural anomalies. Diagnoses can be made by using sonographic findings pertaining to the subcutaneous complex and multi-septate anechoic cystic lesions in the lower limbs, the latter of which can infiltrate visceral structures. Prenatal detection can be helpful in laying the groundwork for providing counseling to the parents and the planning of management strategies, i.e., opting to terminate the pregnancy, revising delivery plans, and looking towards the postnatal management of the infant.