This case report presents a 57 years-old woman treated for a squamous cell carcinoma of the anal canal by radiochemotherapy and brachytherapy. The particularity of this case lays on the fact that she presented a mediastinal and pleural metastatic evolution three years later, which was also treated by radiochemotherapy, leading to a complete remission of 50 months. This observation is interesting for its curative treatment in metastatic cancer of the anal canal. It also illustrates the radiosensibility of anal canal cancers, including metastatic situations, and raises the contribution of PET-scanner to evaluate the response to treatment and detect a recurrence.