Basal cell adenoma of the parotid gland. Case report with ultrastructural observations

Monomorphic (basal cell) salivary adenoma of ovary: report of a case

A pregnant 26-year-old woman presented with an asymptomatic 10-cm left ovarian mass diagnosed at 19 weeks gestation. On removal, the tumor was shown to be a cribriform variant of basal cell salivary adenoma with no other teratomatous or germ cell tumor elements present. The pregnancy continued uneventfully to term and the patient remains symptom-free 10 months after diagnosis. Tissues of salivary type are occasionally observed within mature cystic teratomas of the ovaries and are presumed to have given rise to the present lesion, which is thought to be the first reported case of a neoplasm of salivary type arising in the ovaries.

Basal cell adenocarcinoma of the submandibular gland

Basal cell adenoma is a well recognized histopathologic variant of monomorphic adenoma of salivary gland, but in recent years there have been occasional reports of malignant basal cell tumors of major salivary glands. We present a case report of one such basal cell adenocarcinoma arising in the submandibular gland and discuss the differential diagnosis and distinction from a basal cell adenoma. We also review the published literature on basal cell adenocarcinoma. This is the first case of basal cell adenocarcinoma to be studied in detail by both immunohistochemistry and electron microscopy. There has been debate in the past as to the cell of origin of salivary gland basal cell tumors and specifically as to whether myoepithelial differentiation occurs in these tumors. The immunohistochemical and ultrastructural features of this case provide evidence for a dual population of ductal and myoepithelial cells. A flow cytometric analysis of nuclear deoxyribonucleic acid content showed the presence of DNA aneuploidy within one tissue block.

Myoepithelium of salivary glands

In salivary glands and other exocrine organs, there are starfish-shaped cells that lie between the basal lamina and the acinar and ductal cells. These have structural features of both epithelium and smooth muscle cells, and so are called myoepithelial cells. Their functions include contraction when the gland is stimulated to secrete, compressing or reinforcing the underlying parenchymal cells, thus aiding in the expulsion of saliva and preventing damage to the other cells. They also may aid in the propagation of secretory and other stimuli. Their common developmental origin with the basal cells of the larger ducts is displayed in the mature glands by shared structural and immunohistochemical features, but most such basal cells do not have the distinguishing features of myoepithelial cells, such as myofibrils. Although myoepithelial cells can be identified by light microscopy through enzyme histochemistry and special stains and immunohistochemistry for their myofibrils, these techniques can be misleading in salivary gland neoplasms. Thus, the most reliable means of identifying neoplastic myoepithelial cells is with a combination of histochemistry and electron microscopy. The extent to which these cells are derived from undifferentiated stem cells in both normal and neoplastic growth is controversial. The presentation here of transmission electron microscopy (TEM) of well-differentiated myoepithelial cells in mitotic division indicates that stem cells are not necessarily the only source of myoepithelial cells in the later stages of salivary gland development or in neoplasia.

Canalicular adenoma: report of five cases with ultrastructural observations

Canalicular adenomas from five patients were examined by light and electron microscopy. All patients were over 50 years of age; 4 of the lesions were from the upper lip, 4 were cystic, 2 showed capsular invasion and 1 was multifocal. Histopathologically there were epithelial duct-like or canalicular structures cut at various angles and epithelial islands surrounded by hyalinized and mucinous connective tissue that contained little collagen. Ultrastructurally the epithelial islands contained many small lumina and connective tissue islands. The characteristic epithelial cell was columnar or cuboidal, extended from the lumina to the connective tissue, had almost straight lateral cell boundaries with desmosomes that predominated near the lumina, and possessed gap junctions and a small number of tight junctions. Their main cytoplasmic constituents were ribosomes, mitochondria, rough-surfaced endoplasmic reticulum and microfilaments. These findings show that canalicular adenomas are truly monomorphic and support the concept that they are derived from the cells of excretory ducts.

Basal cell adenocarcinoma of the parotid gland: a case report and review of the literature

Basal cell adenocarcinoma is a rare salivary gland tumour. A DNA diploid parotid gland basal cell adenocarcinoma, with a low mitotic rate, in a 78-year-old female patient is described. Total removal of the affected salivary gland without sacrificing the facial nerve gave a good therapeutic result.

Trabecular and solid-cribriform types of basal cell adenoma. A morphologic study of two cases of an unusual variant of monomorphic adenoma

Monomorphic adenomas are a morphologically complex group of salivary gland tumors. Two unusual examples, one a trabecular and the other a solid form of basal cell adenoma, reveal the development of a cribriform growth pattern focally in the former example and diffusely in the latter. They illustrate the potential for cellular differentiation within this subgroup, organization of synthetic products by the tumor cells, and the histologic criteria useful for the distinction of basal cell adenoma from adenoid cystic carcinoma.

Immunohistochemical characterization of basal cell adenomas of the salivary gland

Seven cases of basal cell adenomas of the salivary gland were analyzed by immunohistochemical methods with a broad panel of routinely used antibodies. Histologically the epithelial elements were classified as tubuloglandular, trabecular and solid patterns. The authors' results indicated the following: 1) The duct lining cells of tubuloglandular and trabecular patterns have distinct epithelial features with cytokeratins (KL 1, PKK 1, *PKK 2 and PKK 3), alpha-one-antichymotrypsin (alpha 1-ACT), carcinoembryonic antigen (CEA) and S-100 alpha subunit positivity. 2) The basaloid cells in the trabecular and solid patterns expressed two immunophenotypes: one had actin, neuron-specific enolase (NSE), S-100 protein and S-100 beta subunit patterns typical of myoepithelial cells in normal glands. The other basaloid cells had vimentin and S-100 protein patterns. The former cell type could be found in 4 of 7 cases and the latter was found in 7 cases. This represents a minor participation of the myoepithelial cells in the basal cell adenoma. 3) The basement membrane and stromal connective tissue around the neoplastic cells were positive for alpha-one-antitrypsin (alpha 1-AT). This antibody is a good marker in identifying the basement membrane-like material.

The cellular composition of basal cell adenoma of the parotid gland: an immunohistochemical analysis

Four cases of basal cell adenoma of the parotid gland were examined immunohistochemically to characterize their cellular composition. In all cases epithelial membrane antigen and keratin were detected in the inner luminal cells; some cells also showed positive staining for secretory functional markers, indicating their differentiation toward secretory epithelium. In tubular and trabecular types the outer cells consistently displayed an intense staining for vimentin and some were also positive for actin, indicating their myoepithelial nature. In the solid type, most tumor cells resembled the ductal cells or basal cells of larger ducts in normal gland with regard to their immunoreactivity. Our results may suggest that the proportion and arrangement of heterogeneous tumor cells are responsible for different histologic patterns of the salivary basal cell adenoma.

Basal cell adenocarcinomas of the major salivary glands

Basal cell adenoma of salivary gland has become an established variant of monomorphic adenoma since its segregation from pleomorphic adenoma in 1967. Although there have been many comprehensive reports about benign basal cell adenomas, only rare case reports of malignant basal cell type neoplasms have appeared in the literature. Described in this report are the clinicopathologic features of 29 cases labeled basal cell adenocarcinomas that had morphologic characteristics of basal cell adenomas but infiltrative, perineural, and intravascular growth features that indicated a malignant potential. With limited follow-up, seven tumors are known to have recurred, and three of these metastasized to lymph nodes and lung. One patient died with extensive local spread of the tumor. All patients were adults. The peak incidence was in the sixth decade of life, and there was no gender predilection. The parotid gland was the predominant site. A solid type growth configuration was most frequent; membranous, trabecular, and tubular types were less frequent, in that order. Three patients also had dermal cylindromas, perhaps indicative of a salivary gland-skin adnexal diathesis that has been previously reported.

Monomorphic adenomas of the salivary glands. A clinico-pathologic study of 12 cases with immunohistochemical observation

Twelve cases of monomorphic adenoma of the salivary glands were histologically reclassified and their immunohistochemical reactivity for S-100 and cytokeratin was correlated. All patients underwent a benign clinical course. Individual tumors were well encapsulated and frequently showed a focal cystic change. Histologically, 9 cases were of the epithelial basaloid cell type and 3 cases were of the myoepithelioma variant. About one half of the epithelial type featured a mixture of trabecular and tubular patterns. The immunoreactivity to S-100 and cytokeratin varied. All basaloid cell adenomas were positive for cytokeratin, while S-100 positivity was found mostly in the stroma along with the varied reaction and intensity in the epithelial nests. In myoepitheliomas, cytokeratin was totally negative and S-100 was positive in 2 of 3 cases. The above findings suggest that the degree of participation of myoepithelial cells determines the phenotypic expression of monomorphic adenomas, and supports the hypothesis that the basaloid cell and myoepithelial types may be located on extreme ends of the same tumor spectrum with a wide range of pleomorphic adenoma in-between.

Basal cell adenomatosis of minor salivary glands of the upper lip

The basal cell adenoma is one of the more commonly occurring types of salivary tumors in the upper lip. A case with multiple (five) tumors is presented and the literature reviewed. This lesion would be more correctly designated as an adenomatosis. In spite of its frequent multicentricity, recurrence is unusual following surgical removal.

Normal and neoplastic myoepithelial cells in salivary glands: an immunohistochemical study

To determine the difference between normal and neoplastic myoepithelial cells, we performed immunoperoxidase staining for contractile proteins (actin and myosin) and intermediate filament proteins (vimentin and 55- to 57-kilodalton keratin) on paraffin sections from salivary gland tumors. Normal myoepithelial cells were positive for actin and myosin but negative for vimentin and keratin. Outer tubular cells of organoid double-layered tubular structures seen in pleomorphic and monomorphic adenoma and adenoid cystic carcinoma, and "cyst"-lining cells and outermost cells of adenoid cystic carcinoma were occasionally positive for actin and myosin. These outer tubular cells, "cyst"-lining cells, and outermost cells were considered to be neoplastic myoepithelial cells. However, their stainability was much lower than that of normal myoepithelial cells. On the other hand, these neoplastic myoepithelial cell were always positive for vimentin. "Mesenchymal" cells and hyaline cells of pleomorphic adenoma and indifferent cells of adenoid cystic carcinoma were negative for both actin and myosin but positive for vimentin and occasionally also positive for keratin. The significance of vimentin staining in neoplastic myoepithelial cells and the coexpression of vimentin and keratin in some tumor cells is discussed.

The intraoral basal cell adenoma

The histological and clinical behaviour of nine intraoral salivary basal cell adenomas is described. Despite problems in classification, this study confirms the impression that these are all benign salivary gland tumours which respond well to localized excision only.

Basaloid-squamous carcinoma of the tongue, hypopharynx, and larynx: report of 10 cases

Ten cases of an unusual form of carcinoma involving the mucosa and underlying tissue of the tongue, hypopharynx, and larynx are described. All ten of the tumors were evaluated by light microscopy; five were also studied by electron microscopy. The major histopathologic feature is carcinoma with a basaloid pattern in intimate association with squamous cell carcinoma, carcinoma in situ, or focal squamous differentiation. The basaloid tumor consists of small crowded cells with hyperchromatic nuclei, scant cytoplasm, small cystic spaces, and foci of tumor necrosis. Prominent hyalinosis is evident. Ultrastructurally, the basaloid epithelial cells possess rare tonofilaments and varying amounts of desmosomes. The cystic spaces contain either loose stellate granules or replicated basal lamina arranged in parallel stacks or globoid masses. This unique tumor was found to be highly malignant, with histologically proved metastases in 80 per cent of the cases. Most of the patients were treated by radical surgery supplemented with radiation and/or chemotherapy. It is concluded that tumors with these characteristic features constitute a distinct histopathologic entity, not previously described, for which basaloid-squamous carcinoma is an appropriate term.

Adenoid cystic (cylindromatous) carcinoma of the trachea: an ultrastructural study

Adenoid cystic (cylindromatous) carcinoma of the trachea is a rare tumour. The histological features in previously reported cases have been widely variable; only one previous ultrastructural study has been undertaken. Three cases are reported in the present study and the ultrastructural findings are reviewed. The tumours were composed of two types of cells, mature ductal and immature myoepithelial. The cylindromatous stroma appeared as a fibrillar substance which was also found between the undifferentiated myoepithelial cells and appeared to be a product of these cells.

Ultrastructural similarities of adenoid cystic carcinoma and pleomorphic adenoma

Ultrastructural examination of five adenoid cystic carcinomas, three breast and two salivary gland, reveals identical patterns of tumour cell differentiation, organization and distribution of cellular products (Zaloudek, Oertel & Orenstein 1984). In both sites, there is proliferation of two populations of cells, one with characteristics and organization of duct-type luminal epithelial cells and a second that forms the principal proliferating component and has the overall organization and appearance that would suggest that they represent modified myoepithelial cells. Recent ultrastructural studies also indicate that tumour cell types and histological organization similar to those described for adenoid cystic carcinoma occur during histodifferentiation of salivary gland pleomorphic adenoma (Dardick et al. 1983a, b). The characteristic histological pattern of adenoid cystic carcinoma is dependent on the formation of pseudolumina containing proteoglycans and reduplicated basal lamina. Similar, but smaller, lumina of like organization and contents are evident in some cases of pleomorphic adenoma. Both the ultrastructural similarities of the tumour cell types and their organization, in adenoid cystic carcinoma and pleomorphic adenoma, suggest that these tumours have a similar histogenetic basis. The fact that one lesion is malignant and the other benign does not preclude common types of tumour cells and developmental processes.

Canalicular adenoma: not a basal cell adenoma

The evidence that canalicular adenomas and basal cell adenomas are separate entities is presented in this article. The clinical features were studied in a series of 13 previously unreported salivary gland tumors (5 canalicular adenomas and 8 basal cell adenomas) and 99 examples derived from the literature (68 canalicular adenomas and 31 basal cell adenomas). Representative tumors from the new cases and from 66 referred cases were studied by histologic, histochemical, and electron microscopic techniques. The two tumors differ significantly with respect to the age range of affected patients, site of predilection, and morphologic and histochemical features.

The use of the terms monomorphic adenoma, basal cell adenoma, and canalicular adenoma as applied to salivary gland tumors

There is considerable confusion in the literature concerning the terms monomorphic adenoma, basal cell adenoma, and canalicular adenoma. This article traces the history of these terms as applied to the pathology of salivary gland tumors and attempts to clarify their usage. It is recommended (1) that monomorphic adenoma be used, as it was originally intended, as a nosologic grouping for all benign epithelial salivary gland tumors that are not pleomorphic adenomas, (2) that basal cell adenoma be used to identify a specific entity that is one component of the monomorphic adenoma group and exhibits a number of histologic subtypes, and (3) that canalicular adenoma be used to describe another entity, distinct from basal cell adenomas but also belonging to the monomorphic adenoma group.

Monomorphic adenomas of the parotid glands. Their ultrastructure and histogenesis

Three cases of monomorphic basal cell adenoma of the parotid glands were studied with light microscopy. In one patient, fresh tissue was available for electron microscopic observations. On the basis of ultrastructural findings it was concluded that myoepithelial cells play little, if any, role in the histogenesis of this lesion. The tumor originates from the undifferentiated stem cells analogous to the cells seen at the "end bud" stage of salivary gland morphogenesis prior to their further cytodifferentiation and functional maturation into secretory and myoepithelial cells. In fully developed salivary glands such undifferentiated stem cells reside as "reserve" cells in the intercalated ductal system.

Basal cell adenoma with acinic differentiation

A case of basal cell adenoma in the left parotid region of a 45 years old male was reported. The tumor measured 1.1 cm X 0.9 cm, was spherical and covered with a fibrous capsule. Histologically, it was a monomorphic adenoma, forming solid, trabecular, tubular and acinic structure. The tumor cells secreted PAS-positive substance. Electron microscopically, the tumor consisted of three kinds of cells - secretory cells containing electron-dense secretory granules, non-secretory cells, and myoepithelial cells. The acinus was formed of single-layered secretory cells, in the base of which myoepithelial cells were observed. The tubulus was formed of both secretory and non-secretory cells, and myoepithelial cells were found in the base of the tubules. The interstitium was narrow, and was composed of a small amount of collagen fibers, myoepithelial cells, and basement membrane-like substance.

Histopathologic studies of basal cell adenoma of the parotid gland

Five-hundred-thirty-one cases of primary epithelial tumors of the parotid gland were examined. The incidence of basal cell adenomas was 7.5% (40 cases). The tumors could be classified histologically into these subtypes: basal cell (21/40; 42.5%); tubular, (13/40; 32.5%); trabecular (4/40; 10.0%); and papillary (2/40; 5.0%). The pattern of classic basal cell adenoma predominated in the basal-cell type but was also seen in varying degrees in the latter three types with a reciprocal transition. Accordingly, it could be suggested that tubular, trabecular, and papillary types are variants of basal cell adenoma. The higher incidence of basal cell adenomas in our survey could be accounted for by this categorization. Histologically, basal cell adenomas presented various features; (1) cystic formation (26/40; 65.0%), being most frequently seen in tubular and trabecular types; (2) adenoid cystic pattern (4/40; 10.0%); (3) elastosis in the stromal tissues (2/40; 5.0%). Basal cell adenomas were clinicopathologically compared with 291 cases of pleomorphic adenomas. Basal cell adenomas were seen more often in female patients, (60.0%), as were pleomorphic adenomas (68.4%). They were observed more frequently in patients over 50 years of age and the average was ten years higher than for pleomorphic adenoma. The tumor size tended to be smaller (below 2 cm at the greatest diameter) than pleomorphic adenomas.

Monomorphic adenomas of the major and minor salivary glands. Report of twenty-one cases and review of the literature

Monomorphic adenomas are benign salivary gland tumors that have a predilection for development in the upper lip and parotid gland. Typically, patients are older persons (mean age, 61 years), but a broad age range (32 to 87 years) has been reported in the literature. Adequate treatment consists of superficial or total parotidectomy (depending on extent and location of the tumor) for parotid lesions and excision with a limited border of normal tissue for minor gland tumors. Uniform cellularity, lack of myxoid or chondroid features, and a tendency for multicentric origin are features which separate these tumors from pleomorphic adenomas. Monomorphic adenomas have been mistakenly diagnosed and treated as adenoid cystic carcinomas. Close attention to cytologic detail, histomorphology, and growth pattern at the periphery are important in separating these tumors.

Basal cell adenomas of the minor salivary glands. A clinicopathologic study of seventeen new cases and a review of the literature

The basal cell adenoma (BCA) is a benign monomorphic salivary gland tumor. Those of minor gland origin tend to occur within or adjacent to the upper lip (80 percent). The BCA is an encapsulated, slow-growing lesion which most commonly affects older persons. Several different histologic patterns can be noted, and often a combination of these variations is present within the same tumor. Simple surgical excision appears to be adequate treatment.

Canalicular adenoma of the upper lip: an electron microscopic study

Canalicular adenoma is composed of a row of tall columnar cells adjacent to canalicular lumina and a row of conical cells adjacent to connective tissue stroma. It differs from basal cell adenoma, of the parotid by the lack of well developed desmosomes associated with bundles of tonofilaments; by the presence of moderate numbers of cellorganelles; by a single, inconspicuous basal lamina instead of multi-layering; and by the presence of mucoid material in the stroma. Results suggest that this type of tumor should be considered a specific benign entity of the salivary glands. Cytologic features also suggest that it originates in excretory duct cells of minor salivary glands.

Tumours of the salivary glands: a histological and clinical review

The aim of this paper is to try to identify points of correlation between the histological appearance and the clinical behaviour of minor salivary gland tumours. To this end 62 well-documented minor salivary gland tumours have been followed up for at least five years or until recurrence. The discussion is limited to the adenoidcystic carcinoma, the pleomorphic adenoma and the basal cell adenoma, since only these three tumours were represented in sufficient numbers to be analysed. For each tumour a number of histological pointers to prognosis are reviewed. In the case of the basal cell adenoma, a recently recognised tumour, the possibility of confusion with the adenoidcystic carcinoma is discussed.

Ultrastructural features of monomorphic adenoma of the parotid gland

A monomorphic adenoma of the parotid gland (basaloid type) was studied with the electron microscope. In general, the tumor consisted of a single cell type, except in areas of squamous metaplasia. The cells were polygonal with prominent nuclei and scant cytoplasmic organelles. Intercellular junctions and plasmalemmal projections (filopodia) were conspicuous. Myoepithelial cells and secretory granules were absent. On the basis of these ultrastructural features, it is proposed that the interlobular duct, rather than the intercalated duct, is the probable site of origin of this tumor.

Adenoid cystic carcinoma of the salivary gland and its histologic variants. A clinicopathologic study of thirty cases

Thirty adenoid cystic carcinomas were seen among 384 salivary gland tumors during the 24-year period from 1952 to 1975. They caused the most difficulty in diagnosis, as they showed a spectrum of histologic appearances. In addition to tumors with the typical cribriform pattern of uniform dark cells, there were some with a more solid basaloid pattern resembling basal-cell carcinomas of the skin. Others manifested both cribriform and basaloid patterns in juxtaposition. A shorter duration of symptoms in lesions with a basaloid component suggests a more rapid growth rate in such tumors. Ultrastructural examination of a tumor with a typical cribriform pattern showed spaces of two types; the more frequent type was bounded by cells with straight plasma membranes and contained filamentous and basement-membrane-like material, and the less frequent type was surrounded by cells with numerous microvilli and contained nonfilamentous homogeneous material. The filamentous and basement-membrane--like material corresponded to connective tissue mucin and the non-filamentous material to epithelial mucin in the light microscopic sections.