Participation by Adjacent Tissues in the Formation of the Capsule of Benign Parotid Gland Pleomorphic Adenoma

Abstract

From June 1984 to March 1991, 25 patients with benign parotid gland pleomorphic adenoma were treated surgically in my department of otolaryngology. Histological study was done to clarify the important factors participating in the formation of the capsule of benign parotid gland pleomorphic adenoma. In the tissues surrounding the capsule of the tumor, atrophy of acinal cells, lipoid degeneration, increase of the connective tissues around the lobules and dilatation of the interlobular ducts, which seemed to be due to compression by the tumor itself, were found. In the capsule wall and/or just outside it, normal duct tissues were seen and in constricted parts of the capsule, vessels were sometimes recognized. In some parts, the increased connective tissues around the lobules were combined with the tumor capsule. Small defects of the capsule were seen in a few cases of Seifert's type 2 tumor (stromal component rich type), and in all such cases newly formed cnnective tissue membranes were seen a little outside such parts. These findings suggest that the parotid gland tissue around the tumor participate in the formation of the tumor capsule.