We report an observation of a macro- and micro-cystic lymphatic malformation located in the right upper limb. This was a 5-year-old girl with no previous pathological history, followed since the age of 11 months for a congenital subcutaneous, painless and soft swelling of the right upper limb. Ultrasound of the soft tissue and magnetic resonance imaging (MRI) allowed the diagnosis of macro- and micro-cystic lymphatic malformation of the right upper limb. There is little epidemiological data on cystic lymphatic malformations (CLM). Superficial MLKs are more numerous than deep MLKs; of the superficial MLKs, nearly 75% are located in the head and neck, with an estimated incidence of 1.2 to 2.8 per 1000 births, and in the axillary hollows in 20% of cases. They affect equally males and females and different ethnic backgrounds. Involvement of the upper limb and particularly the arm is very rare. MRI plays an important role in the diagnosis and assessment of the tumor’s boundaries. Treatment can be difficult because of the location of the tumor and its extension into the surrounding tissue.