Pathology quiz case 1. Oncocytic lipoadenoma of the parotid gland.

A 38-YEAR-OLD MAN PRESENTED WITH A 3-month history of a painless, slowgrowing mass of the left parotid gland, without any inflammatory cutaneous signs or facial weakness. He had no history of smoking or alcohol use. Physical examination revealed a 4.0 3.5-cm nontender, soft, mobile mass in the preauricular region of the left parotid gland. There was no evidence of adhesion to the overlying skin or palpable lymph nodes. Facial mobility was normal. The findings of cervical ultrasonography supported a diagnosis of hemangioma. A computed tomographic scan with contrast showed a 3.8 3.2 2.2-cm well-circumscribed parotid mass of the left superficial lobe, with intense, nearly homogeneous enhancement (Figure 1) and only a small focus of low-density fat in the deep portion of the tumor. Magnetic resonance imaging with gadolinium demonstrated a heterogeneous mass with massive enhancement, consistent with a vascular tumor of the superficial parotid lobe. A fine-needle biopsy specimen showed oncocytic cells exclusively (Figure 2). The patient underwent a left total parotidectomy with preservation of the facial nerve after the mass was located in the deep lobe of the gland. The definitive specimen is shown with regular staining in Figure 3 and with phosphotungstic acid–hematoxylin staining in Figure 4. What is your diagnosis?