Tumefaction arising lately after latissimus dorsi flap harvest are rare and observed in 1 or 2% of the cases. These lesions are frequently related to kystic sero-hematoma and are easily and efficiently treated with surgical excision. In some rare circumstances, a tumoral evolution can mimic a kystic sero-hematoma. We will discuss one case of desmoid tumor arising from a latissimus dorsi flap donor-site scar. The subject was a 45 years old woman who had a breast reconstruction following mastectomy. A dorsal tumefaction, with a benign aspect, was observed during the follow-up period. The biopsy showed an extra-abdominal desmoid tumor. The patient was treated with a large excision of the lesion and reconstructed using two opposing local cutaneous advancing flaps. No radicalization was necessary. No sign of recurrence has been observed at 4 years follow-up.