Oncocytic myoepithelioma and pleomorphic adenoma of the salivary glands

 Twenty oncocytic myoepitheliomas (MEs) and pleomorphic adenomas (PAs) were composed of interlacing fascicles of swollen spindle-shaped or/and epithelioid oncocytic myoepithelial cells showing intense finely granular immunoreactivity with anti-mitochondrial antibody. Focal vacuolation of the cytoplasm of oncocytic myoepithelial cells and their gradual transition into sebaceous metaplasia were observed in 3 cases. Another unusual feature found in 5 cases was the presence of slit-like adenomatoid spaces lined with double-layered oncocytic myoepithelium closely resembling Warthin’s tumour. The nuclei of oncocytic cells were characterized by enlargement, hyperchromasia and polymorphism, which should not be confused with malignancy. Oncocytic change in myoepithelial cells in MEs and PAs can cause pitfalls in the differential diagnosis of salivary gland tumours. We describe some unusual histological features associated with onococytic metaplasia in benign myoepithelial cell-derived salivary gland tumours, hoping to help to avoid the overdiagnosis of malignancy. Received: 24 September 1998 / Accepted: 31 January 1999     

Myoepithelial tumours of the salivary glands

Myoepithelial cells are a normal constituent of the salivary acini and smaller ducts, and are found between the epithelial cells and the basement membrane. They can be recognized with various immunohistochemical markers, although none is specific or reliable in every case. Neoplastic myoepithelial cells in both benign and malignant tumours can take several forms, including epithelioid, spindle, plasmacytoid and clear, and this variability largely accounts for difficulties in histopathological diagnosis. Benign salivary adenomas form a spectrum with widely differing proportions of luminal, basal and myoepithelial cells and stroma. Whilst clinically similar, benign myoepithelioma differs from basal cell adenoma and pleomorphic adenoma only by being composed almost exclusively of myoepithelial cells, but the very different morphology justifies separation of the entity. Myoepithelial carcinoma is a rare but probably underrecognized malignancy typically with a multinodular architecture. It too can display a wide variety of cytological appearances, and often a most useful diagnostic clue is the presence of plentiful hyaline and/or myxoid stromal material. Its behaviour is variable, and histology is a relatively poor predictor of clinical outcome. Myoepithelial cells are also found in greater or lesser numbers in a few other carcinomas, and are an integral part especially in epithelial–myoepithelial carcinoma.     

Oncocytic tumours

 Oncocytic tumours represent a distinctive set of lesions with distinctive granular cytoplasmic eosinophilia of the neoplastic cells. These cells are called oncocytes because of the ”swollen” appearance they have as the result of a striking accumulation of mitochondria. Although generally uncommon, oncocytic tumours are by no means rare and have been reported, with different frequencies, in virtually every organ. A variety of biochemical and molecular changes have been identified, and the aberrant biogenesis of mitochondria in oncocytic cells bears intriguing similarities to that of a group of degenerative disorders known as mitochondrial encephalomyopathies. Although the relationship between the accumulation of mitochondria and the occurrence of tumours is unknown, investigation into the cellular alterations of oncocytes may further our knowledge of a variety of important biological processes such as proliferation, energy production and ageing. Received: 27 October 1997 / Accepted: 19 January 1998     

Oncocytic hyperplasia in the human minor salivary glands: A post-mortem study

Oncocytic hyperplasia in the human labial salivary glands was sought in a series of 217 post-mortem subjects. Oncocytic change occured in 183 subjects and hyperplasia was found in 19 of those (the overall incidence being 8.8%), ranging in age from the third deacde to the ninth. The sex distribution showed a significantly greater rate in males (16 of 139 males, 11.5%; 3 of 78 females, 3.8%). Oncocytic hyperplasia occurred in the duct system, and not in the acinar regions; it was frequently seen in the interlobular and intralobular ducts. Oncocytic hyperplasia was classified into four types; focal hyperplasia of the duct wall resulting in partial thickening of the duct wall; marked hyperplasia resulting in thickening of the duct wall, extending over half of the circumference; marked hyperplasia extending to the whole duct wall and intralobular adeno-tubular hyperplasia with or without cystic dilatation. About half of the subjects with oncocytic hyperplasia showed a few hyperplastic foci in one gland. The changes increased in severity in older subjects.     

Papillary tumours of the minor salivary glands.

The clinical and histological features of oncocytic adenomatous hyperplasia, papillary adenoma, and papillary adenocarcinoma of the oral cavity are described, and the literature is reviewed. Histological features which may be of value in distinguishing between benign and malignant variants are described, and in view of the slow growth rate of most of these tumours, the importance of long-term follow-up is stressed.     

Immunoreactive prolactin in lesions and tumours of salivary glands

The prolactin binding in obstructive lesions and tumours of salivary glands was described by use of the immunohistochemical PAP technique. Normal salivary glands had prolactin binding cells in the striated ducts only. Chronic obstructive lesions of submandibular glands showed negative immunoreaction for prolactin binding in ductal cells, but positive staining of the luminal surface of ductal segments. In pleomorphic adenomas, occasional neoplastic cells located along the luminal borders of tubular, ductal, or of duct-like epithelial structures were strongly reactive with anti-prolactin and 26.5% of cases pleomorphic adenoma were positive for anti-prolactin. Adenoid cystic carcinoma exhibited positive prolactin binding on the luminal surface of some of tumour foci, but not in the rest of the tumour. Warthin's tumour was devoid of detectable prolactin binding.     

Basal membrane associated substances in human salivary glands and salivary gland tumours

Human salivary gland tissue was analysed with respect to the distribution of basal membrane associated substances. Collagen type IV and laminin were studied on the basis of monoclonal antibodies, fibronectin was analysed with polyclonal antibodies. The structure of the basal membrane was well preserved in normal salivary gland tissue. There was a continuous staining of the basal membrane around the acini and the ducts. The labelling for these substances appeared to be associated with the myoepithelial cells. Pleomorphic adenomas exhibited a heterogeneous pattern for the basal membrane substances. Focally, there was an augmentation of collagen IV and laminin, as well as of fibronectin. This was observed in the neighbourhood of myoepithelial like cells. Other parts of pleomorphic adenomas showed an interruption of the basal membrane. Adenoid cystic carcinomas displayed a clear staining of the basal membrane associated substances in the pseudocysts. Stromal trabeculae were stained in an irregular manner. Acinic cell tumours, adenocarcinomas, mucoepidermoid tumours and squamous cell carcinomas (for comparison taken from other regions in the head and neck area) presented a clear destruction of the basal membrane as visualized by antibodies against collagen IV and laminin. The study of the basal membrane substances may be helpful for identifying special features of salivary gland tumours and for grading the amount of invasive behaviour in the malignant tumours.     

Oncocytic adenomas and oncocytic hyperplasia of salivary glands: a clinicopathological study of 26 cases

Twenty-six benign oncocytic lesions of the salivary glands, excluding Warthin's tumours, have been reviewed and criteria for their classification as oncocytoma, multifocal nodular oncocytic hyperplasia, diffuse oncocytosis, pleomorphic adenoma with oncocytic change or oncocytic monomorphic adenoma have been proposed. The histological and clinical features of this heterogeneous group of lesions are discussed. This analysis suggests that the majority of lesions initially categorized as oncocytomas were, in fact, either non-neoplastic or, alternatively, oncocytic change in other types of adenoma.     

The expression of different intermediate-sized filaments in human salivary glands and their tumours

The intermediate-sized filaments can be divided into several groups which are characteristic of different types of tissues (e.g.: epithelial, mesenchymal, muscle, astrocytic and neural origin). Antibodies specific for some of these filament types have been used to analyse a group of salivary gland tumours. Prekeratin-positive cells were seen in the normal gland, cystadenolymphomas, mucoepidermoid tumours, and squamous cell carcinomas which are all tumours of epithelial origin. The pleomorphic adenomas showed the presence of some cells which appeared to contain both prekeratin and vimentin. The results are discussed with respect to their histogenetic implications.     

The congenital basal cell adenoma of salivary glands Contribution to the differential diagnosis of congenital salivary gland tumours

Congenital epithelial tumours of the salivary glands are very rare. The Salivary Gland Registry maintained in the Department of Pathology, University of Hamburg, contains only three cases among a total of 6,646 salivary gland tumours from the years 1965–1994. The three cases were classified as congenital basal cell adenoma, two of the parotid gland and one of the submandibular gland. Histologically, the three adenomas were similar in structure to the adult counterpart of basal cell adenoma with solid, trabecular or tubular (duct-like) patterns. In some cystic spaces of the duct-like structures PAS- and Astra blue-positive substances were secreted. On immunocytochemistry, the luminal duct-like cells showed membranous expression of cytokeratins 3, 5, 6, 7, 13 and 19. In the isomorphic basaloid cells of the solid and trabecular cell nests few cells expressed cytokeratin. On the outside of the solid cell nests there were smaller elongated myoepithelial-like cells, which expressed cytokeratin 14 and vimentin. Cytokeratins 1, 2, 4 and 18 were not expressed. The pattern of expression reflects the different stages of maturity of the tumour cells and is related to the development of the salivary glands until the end of the 3rd embryonal month with an arrest of further cell differentiation. No acinic cells, invasive growth, recurrence or metastases were observed. The differential diagnosis includes other congenital salivary gland tumours, such as hybrid basal cell adenoma-adenoid cystic carcinoma, sialoblastoma or embryoma, carcinoma, hamartoma and teratoma.     

Undifferentiated tumours of salivary glands. Immunocytochemical investigations and differential diagnosis of 22 cases

22 undifferentiated tumours of the Salivary Gland Register (University of Hamburg) were studied by conventional light microscopical and immunocytochemical methods to elucidate the heterogeneity of this tumour group. The following observations were made in this collective: 18 tumours displayed one or more markers for the epithelial character and were classified as carcinomas. 10 carcinomas were considered as primary ones and 8 were considered as secondary ones (metastatic or invasive "per continuitatem"). Primary carcinomas were subclassified as poorly differentiated variants of a distinctive type of salivary gland tumours, as follows: 6 cases of carcinoma in pleomorphic adenoma, and one case each of mucoepidermoid tumour, adenocarcinoma, salivary duct carcinoma and epidermoid carcinoma. Secondary carcinomas were subclassified as follows: 3 epidermoid carcinomas, 3 nasopharyngeal carcinomas and 2 bronchial carcinomas. One tumour positive for S-100 protein and NSE (Neuron-specific enolase) was classified as a metastatic melanoma. Another tumour positive for vimentin and actin was classified as a rhabdomyosarcoma of the periglandular tissue. Two tumours lacked any markers studied here and were regarded as a malignant paraganglioma and an undifferentiated lymphoma, respectively. The differential diagnosis of the undifferentiated tumours of salivary glands and the special problems of this tumour group are discussed.     

Immunohistochemical study of carbonic anhydrase in mixed tumours from major salivary glands and skin

Summary Immunohistochemical distribution of carbonic anhydrase isoenzyme I and II was studied in mixed tumours of major salivary glands and skin. The normal salivary glands displayed strong carbonic anhydrase activity in both ductal epithelium and serous acinar cells and the serous demilune cells in the submandibular glands, including the eccrine ducts. Pleomorphic adenoma salivary gland origin exhibited positive staining in the innerlayer of epithelial cells of tubular, duct-like and glandular structures. No enzymatic staining was noted in the outer layer of tumour cells in these structures. Spindle tumour cells or the fibroblast-like cells with long cytoplasmic processes identified in the adjacent hyalin and myxomatous stroma were rarely positive, while chondroidal and osteo-chondroidal cells were highly reactive. Mixed tumours of eccrine gland origin showed the most reactive staining cells scattered throughout neoplastic epithelium in all tissues examined. Immunohistochemical stainability was usually higher for carbonic anhydrase II than I for both normal and tumour tissues. The biological roles of the distribution profiles of carbonic anhydrase are discussed.This investigation was supported partially from Miyata Research fund     

涎腺嗜酸细胞性脂肪腺瘤二例

报道2例罕见的发生于腮腺的涎腺嗜酸细胞性脂肪腺瘤。大体观察:2例均包膜完整,1例呈多结节状,1例呈哑铃状。镜下观察:2例肿瘤均被覆薄的纤维性包膜,由不同比例的脂肪组织和大小不等的嗜酸性细胞巢混合构成。免疫组织化学染色:2例嗜酸性细胞均表达人低分子量细胞角蛋白,部分表达细胞角蛋白(CK)7、CK5/6、CK19、p63、上皮细胞膜抗原(EMA),不表达S-100蛋白、Calponin、DOG1,Ki-67阳性指数约1%~2%。2例分别随访4和5个月,均未见复发。