耳下部に発生した筋肉内脂肪腫例

Abstract

The patient was a 64-year-old man with an infra-auricular mass. Since the tumor was strongly adherent to the angle and the posterior aspect of the mandible, part of the medial pterygoid muscle, masseter muscle, and parotid gland, it was bluntly dissected and resected en bloc. The resected tumor was measured 65×50×13 mm, and weighed 31 g. The tumor was histopathologically diagnosed as an intramuscular lipoma, presumably arising from the sternocleidomastoid or masseter muscle. The reported recurrence rate of non-infiltrating lipoma is less than 5%, whereas that of infiltrating lipoma ranges from 3 to 62.5%. Since intramuscular lipoma is characterized by an infiltrating growth pattern, it cannot always be completely resected. To reduce its recurrence, it is necessary to perform a wide en-bloc resection of the adjacent normal muscle, while considering the degree of residual muscle dysfunction, including muscle weakness.