Free Tissue Flaps: A mass of tissue that has been cut away from its surrounding areas to be used in TISSUE TRANSPLANTATION.Surgical Flaps: Tongues of skin and subcutaneous tissue, sometimes including muscle, cut away from the underlying parts but often still attached at one end. They retain their own microvasculature which is also transferred to the new site. They are often used in plastic surgery for filling a defect in a neighboring region.Esophageal Diseases: Pathological processes in the ESOPHAGUS.Reconstructive Surgical Procedures: Procedures used to reconstruct, restore, or improve defective, damaged, or missing structures.Seroma: Tumor-like sterile accumulation of serum in a tissue, organ, or cavity. It results from a tissue insult and is the product of tissue inflammation. It most commonly occurs following MASTECTOMY.Microsurgery: The performance of surgical procedures with the aid of a microscope.Veins: The vessels carrying blood away from the capillary beds.Head and Neck Neoplasms: Soft tissue tumors or cancer arising from the mucosal surfaces of the LIP; oral cavity; PHARYNX; LARYNX; and cervical esophagus. Other sites included are the NOSE and PARANASAL SINUSES; SALIVARY GLANDS; THYROID GLAND and PARATHYROID GLANDS; and MELANOMA and non-melanoma skin cancers of the head and neck. (from Holland et al., Cancer Medicine, 4th ed, p1651)Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Flap Endonucleases: Endonucleases that remove 5' DNA sequences from a DNA structure called a DNA flap. The DNA flap structure occurs in double-stranded DNA containing a single-stranded break where the 5' portion of the downstream strand is too long and overlaps the 3' end of the upstream strand. Flap endonucleases cleave the downstream strand of the overlap flap structure precisely after the first base-paired nucleotide, creating a ligatable nick.