Multifocal adenomatous oncocytic hyperplasia of the parotid gland

Abstract

Multifocal adenomatous oncocytic hyperplasia (MAOH) is a non-neoplastic lesion that is classified as oncocytosis. MAOH is a rare entity of the parotid gland and accounts for approximately 0.1% of salivary gland lesions. Here, we report a case of MAOH of the parotid gland. The patient was a 71-year-old woman who presented with discomfort at the left side of her neck. Fine-needle aspiration cytology of the parotid gland revealed a loose sheet-like cluster of round to polygonal cells with granular cytoplasm against a hemorrhagic background. The cells had round to oval, centrally located nuclei with granular chromatin and without distinct nucleoli. Histologically, the lesion was formed of many variable-sized nodules, comprising oncocyte-like cells with small round nuclei and eosinophilic granular cytoplasm that was positive for mitochondrial antibodies. The diagnosis of MAOH is difficult to make by cytology alone, because the findings overlap with those of other oncocytic lesions. In particular, the cytological findings of MAOH have not been sufficiently reported to date. A correlation of cytology and histology was expected.

Keywords: Cytology; Histology; Multifocal adenomatous oncocytic hyperplasia; Oncocytes; Parotid gland.

Fig. 1

Fine-needle aspiration findings. a Direct preparation of smear findings. Polygonal cells with abundant granular cytoplasm were seen. b LBC preparation findings. The cytoplasm showed small vacuoles compared with the cells that underwent direct preparation. Papanicolaou staining. ×400.c Granules were observed clearly by Papanicolaou staining. MGG staining. ×400.

Fig. 2

a The cut surface of the resected lesion revealed a milky-white lobular mass with an unclear border. Histological findings of the parotid lesion. b Many variable-sized nodules were observed. H&E staining. ×100. c The lesion comprised oncocyte-like cells with granular cytoplasm. H&E staining. ×400.d Cells were strongly positive for mitochondrial antibodies. Immunohistochemical staining. ×400.e p63-positive cells appeared around the rim of the nodules. The findings suggest a transition from existing tissue. Immunohistochemical staining. ×400.