A Rare Case of Humerus Metastasis From Acinic Cell Carcinoma of Parotid Gland

Seventy-five percent of salivary gland tumors occur in parotid tumors. These tumors are mainly (75% to 85%) benign and around 25% turn out to be malignant. The most common cases of malignancy are mucoepidermoid carcinoma and adenoid cystic carcinoma (they totally represent half of the malignant tumors). Acinic cell carcinoma (ACC) is not of high incidence and is often seen in major salivary glands, particularly parotid gland. ACC makes up for 1-3% of salivary gland tumors and 3% of total parotid tumors. It is a low-grade malignant tumor with metastatic and invasive ability. Advanced stage, painful and fixed tumor, desmoplasia, anaplasia and differential character of the tumor, high mitosis, and necrosis, and nerve invasion, incomplete removal of the tumor, large size, and invasion to the deeper lobe of parotid worsen the prognosis of this tumor. We present a case report of a 52-year-old man with ACC metastasis to superior left humerus 15 years after surgery.