glycogen and Adenoma--Oxyphilic

A case of multifocal nodular oncocytic hyperplasia (MNOH) of the bilateral parotid gland is presented. An 80-year-old woman was admitted to hospital because of painless swellings in bilateral parotid regions. Histologically, the nodular lesion had incomplete capsules and engulfed the surrounding parotid gland at the periphery. The lesions were mostly composed of clear cells, while the peripheries of the lesions had typical oncocytic cells with abundant fine granules. The histological existence of the clear cell component in the lesions led to misdiagnoses of other clear cell neoplasms. However, this case had multiple nodules in bilateral glands. No evidence of malignant histological findings was found. Moreover, the clear cells, as well as the oncocytic cells, were demonstrated to have mitochondria and glycogen in their cytoplasm using special staining. Based on these findings, the diagnosis of this case was MNOH in the parotid gland. We also discuss the differential diagnosis for clear cell lesions.

Topics: Adenoma, Oxyphilic; Aged, 80 and over; Diagnosis, Differential; Female; Glycogen; Humans; Hyperplasia; Mitochondria; Oxyphil Cells; Parotid Diseases; Parotid Gland; Parotid Neoplasms; Treatment Outcome

Nosologically, the designation clear cell oncocytoma seems illogical and contradictory when the definition of an oncocytoma relies on mitochondrial-rich cells; its relationship to the granular (mitochondrial-rich) oncocytoma needs further clarification. Electron microscopy of six examples of oncocytoma from five patients allowed assessment of cellular features in three clear cell variants, two typical oncocytomas and one with a roughly equal proportion of clear and granular tumor cells. Ultrastructurally, in the clear cell types of oncocytoma, a considerable to extensive portion of the central cytoplasm was occupied by monoparticulate glycogen with margination of mitochondria and other organelles. The degree of extraction of the glycogen during fixation and processing accounts for variation in the extent of the clear cell component as phosphotungstic acid-hematoxylin staining reveals considerable mitochondria in many of the tumor cells in the clear cell variant of oncocytoma. Ultrastructural findings further support an interrelationship between clear and granular cells, as some typical oncocytes are evident in the clear cell variant of oncocytoma, and one oncocytoma in this series had a roughly equal number of glycogen-rich and mitochondrial-rich tumor cells both of which took part in the formation of microlumens. The designation clear cell oncocytoma is appropriate within the oncocytoma subgroup of salivary gland tumors.

Topics: Adenoma, Oxyphilic; Glycogen; Granular Cell Tumor; Humans; Microscopy, Electron; Mitochondria; Parotid Neoplasms