Yonago Acta medica 2001;44:125–130

Malignant Oncocytoma of the Parotid Gland: Report of a Case andReview of Literature
Katsuyuki Kawamoto, Kei Nakahara and Hiromi Takeuchi
Department of Oto-Rhino-Laryngology, Tottori University Faculty of Medicine, Yonago
683-0826 Japan
We reported a case of malignant oncocytoma arising from the right parotid glandthrough neck metastasis. In 1992, the patient was treated by surgical removal of alymph-node mass, diagnosed as malignant unclassified tumor. In 1995, a right parotid
gland tumor and right neck lymph-node masses occurred. We suspected the patient of
having a malignant tumor of the right parotid gland through neck metastasis, especiallyrecurrence of the previous clear-cell carcinoma. In July 1995, a right-side total parotidectomy and a neck dissection were carried out. A definite diagnosis was based on
histological findings of the resected tumor as malignant oncocytoma: large eosinophilic
granular cells were detected, and electron-microscopically, cytoplasms of tumor cells
were rich in mitochondria with no encapsulation, perineural and intravascular invasion,and metastases to the cervical lymph nodes. Additional therapy such as chemotherapy
and irradiation were not applied. To date, he has had no evidence of disease for 6years.
Key words: malignant oncocytoma; parotid gland; parotidectomy

Malignant oncocytoma is an extremely raretumor, especially when it arises in the major
salivary glands. To date, about 50 cases havebeen reported in the literature. Of them, mostarose in the parotid gland: 34 cases of parotid
gland malignant oncocytoma have been reported since the first report by Bauer and Bauer(1953). The oncocyte is a large eosinophilic
granular cell which can be seen in the glandular
tissue, especially in the major salivary gland.
There are no characteristic examinations
except for histological examinations for thisdisease due to its low incidence. Histologicalexaminations of specimens obtained by needle
aspiration biopsy and surgical removal arethought to be useful for diagnosis. The mostdesirable therapy is a curative operation, while
irradiation and chemotherapy are thought toexert poor effects. Several cases of distantmetastasis to the lung, liver and brain were reported, in which patients suffered a fatal outcome (Date et al., 1999). Long-term observa-tion is necessary in treating patients with malignant oncocytoma which spreads by distantmetastasis.

Patient report
In September 1992, a 70-year-old Japanese man
was referred to our clinic at the University Hospital with a 1-month history of a slowly enlarging mass in the right side of the neck. The mass
was about 4 × 3 cm in size: we highly suspected
its malignancy, and carried out a right-side neckdissection within the month. Histologicalexamination revealed the specimen as a malignant unclassified tumor, which was highly suspected of being a clear-cell carcinoma. Aftersurgery, we performed a detailed examination
with magnetic resonance imaging (MRI) andscintigraphy, and observed no abnormal findings in general. Additional treatments such as
chemotherapy or irradiation were not carried

Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging

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AB (upper right)
Fig. 1. Computed tomographic images showing
tumors (arrows in A and B) in the parotid gland andneck metastasis lymph node (arrow in C).

out. The primary site of this tumor was unknown at that time.
In June 1995, he noticed a painless swellingin the right parotid gland region, without facial
nerve paralysis. Examination by computed tomography (CT) with sialography showed 2masses about 1.8 cm and 1.4 cm in diameter at
the inferior and dorsal portion of the rightparotid gland, which were suspected of being
hypervascular tumors. CT with sialography
showed another mass about 1.2 cm in diameterin the right side of the neck, beyond the range ofthe previous operation (Figs. 1A–C). We suspected the patient of having a malignant tumorof the right parotid gland and neck metastasis:
especially, recurrence of the previous clear-cellcarcinoma. In July 1995, a right-side total
parotidectomy and a neck dissection werecarried out under general anesthesia. The 2
extirpated tumors were elastic hard, about 2 × 2
cm in size. Macroscopically, the cut surface
was black in color and homogenous. Microscopically, the tumor cells showed a solid,Ctrabecular or alveolar pattern (Fig. 2). The
nuclei of the tumor cells were round in shapeand relatively uniform in size. No encapsulation, perineural and intravascular invasion
were observed. The cytoplasm showed eosinophilia on hematoxylin and eosin stain (Fig. 3).
Observed under an electron microscope, thecytoplasm of tumor cells had rich amounts of126