Amyloidosis is characterized by progressive deposition of amyloid substances in various tissues. A 67-year-old man was referred to our department because of a massive hematoma of the lower lip. On examination,another hematoma appeared on the left buccal mucosa. The patient had a history of deep venous thrombosis and had been receiving anticoagulant therapy for about 3 months. A biopsy of the clinically normal buccal mucosa revealed diffuse deposition of amyloid substances in the mucosal and submucosal stroma, excluding the vessel walls. The massive hematomas in this patient were attributed to the frailty of the oral mucosa caused by amyloid deposition, as well as the effect of anticoagulant therapy.
