Monomorphic adenomas of salivary glands. Trabecular-tubular, canalicular, and basaloid variants

An unusual case report of basal cell adenoma: A Diagnostic Enchanter

Oral lesions show a wide range of biologic behaviours. There are various lesions which may mimic others and present in such an unusual manner thus making them very difficult to diagnose clinico-pathologically. An accurate diagnosis is not only important for correct treatment planning but also for determination of prognosis. Thus, it is very important for a surgical pathologist to be aware of the various atypical presentations of the lesions. The present unusual case report of basal cell adenoma occurring on upper lip with frank areas of calcifications and abundant inspissated mucoid secretions is an example of one such case. BCA is an uncommon benign epithelial salivary gland neoplasm. It is one of the nine subcategories of salivary gland epithelial tumours according to WHO 2005 classification of salivary gland tumors. It is composed of basaloid cells organized with a prominent basal cell layer and distinct basement membrane-like structure and no myxochondroid stromal component as seen in pleomorphic adenomas. To our best knowledge, no case in English literature has been reported BCA with exuberant inspissated mucoid secretions and frank areas of calcifications to such a large extent and this is the first case to report the same.

Key words: Basal cell adenoma, calcifications, diagnosis, inspissated mucoid secretions, surgical pathologist.

Canalicular adenoma: a clinicopathologic and immunohistochemical analysis of 67 cases with a review of the literature

There is a lack of a comprehensive immunohistochemical (IHC) analysis of canalicular adenoma (CanAd), especially when combined with a description of the unique histologic features. Given the usual small biopsies, IHC may be useful in distinguishing CanAd from other tumors in the differential diagnosis. Retrospective. The patients included 54 females and 13 males (4.2:1), aged 43-90 years, with a mean age at presentation of 69.9 years. Clinical presentation was generally a mass (n = 61) slowly increasing in size (mean 38.5 months), affecting the upper lip (n = 46), buccal mucosa (n = 17) or palate (n = 4), involving the right (n = 29), left (n = 24) or midline (n = 9), without any major salivary gland tumors. The tumors ranged in size from 0.2 to 3 cm (mean 1.2 cm). Most tumors were multilobular or bosselated (76 %), often surrounded by a capsule. Histologically, the tumors were characterized by cystic spaces, tumor cords with beading, tubule formation, and by the presence of luminal squamous balls (n = 41). The cells were cuboidal to columnar with stippled chromatin. Mitoses were inconspicuous. A myxoid stroma (n = 64), sclerosis (n = 42), luminal hemorrhage (n = 51), and luminal microliths (calcifications) (n = 33) were characteristic. Nine (13.4 %) were multifocal. CanAd showed the following characteristic immunohistochemistry findings: CK-pan and S100 protein (strong, diffuse reaction); peripheral or luminal GFAP reaction; CK5/6 and p16 luminal squamous ball reaction; SOX10 nuclear reaction; cytoplasmic p63 reaction. CanAd are unique minor salivary gland tumors showing a distinct architecture and phenotype. They predilect to older women, with the majority multilobulated and affecting the upper lip, multifocal in 13 %; no major salivary gland tumors were identified. S100 protein, CK-pan, GFAP and SOX10 are positive, with luminal squamous balls highlighted by CK5/6 or p16.

Canalicular adenoma--search for the cell of origin: ultrastructural and immunohistochemical analysis of 7 cases and review of the literature

Canalicular adenoma (CA) is a rare, benign epithelial neoplasm of the salivary glands. Historically considered to be a variant of basal cell adenoma, this "monomorphic" adenoma has a distinct clinical, morphologic, and immunohistochemical profile. The putative cell of origin remains a topic of debate. A combination of morphology, immunohistochemistry, and ultrastructural analyses have been employed to determine histogenesis, but the interpretations of these studies have implicated multiple different cell types along the salivary gland duct as the cell of origin. The authors sought to further characterize CA using electron microscopy, immunohistochemistry, and special and immuno-stains on 7 cases. Their morphologic, immunohistochemical, and ultrastructural findings support a cell of origin demonstrating features of both the intercalated duct cells and the striated duct luminal epithelial cells.

A PATHOLOGICAL STUDY OF BENIGN AND MALIGNANT TUMOURS OF SALIVARY GLANDS

Interest in the knowledge of salivary gland tumours is highlighted. A sample of 315 cases, collected over a period of 25 years in a busy pathology centre, is analysed both on total and individual aspects of tumours. The findings are compared to earlier works on the subject and also with contemporary literature.

Phenotypes in canalicular adenoma of human minor salivary glands reflect the interplay of altered secretory product, absent neuro-effector relationships and the diversity of the microenvironment

AIMS

Uncertainty about the factors influencing phenotypes in salivary canalicular adenoma prompted the present investigation.

METHODS AND RESULTS

Specimens of canalicular adenoma from 15 patients were examined with the use of histology, histochemistry for protein, mucosubstances and pigments, nerve staining and immunocytochemistry for cytoskeleton components. The tumours consisted largely of simple cells lining tubules that were occasionally cystic or branching and budding, and were set in loose, vascular and often haemorrhagic stroma. Other phenotypes recognized were mucous cells, apocrine-like cells, pigmented cells, microliths and stromal macrophages, detected in 26.6%, 20%, 33.3%, 20% and 53. 3% of the patients, respectively. Simple cells showed moderate levels of -SH groups and strong immunoreactivity for 'simple' epithelial phenotype cytokeratin. The simple cells lining cystic tubules showed additional immunoreactivity for 'stratified' epithelial phenotype cytokeratin, possibly an adaptation to mechanical pressure. Lumina showed variable levels of neutral and carboxylated glycoproteins, and chondroitin sulphate. Stroma showed high levels of chondroitin sulphate and hyaluronic acid. Mucous cells showed high levels of -SS- groups and nonsulphated glycoproteins. Apocrine-like cells contained lipofuscin. Pigmented cells contained haemosiderin, possibly a consequence of localized iron overload. Microliths contained mucosubstances. Macrophages often contained lipofuscin. No nerves were found in relation to the tumours.

CONCLUSIONS

The results suggest that, contrary to popular belief, phenotypes in canalicular adenoma do not reflect histogenetic concepts but rather may derive from the interplay between an altered secretory product, consisting of glycosaminoglycan and an immature form of glycoprotein, the lack of neuro-effector relationships and the different microenvironments throughout the tumour.

Pathology of the salivary glands: the contribution of electron microscopy

Electron microscopy has a limited role in the diagnosis of primary salivary gland tumors, although it can be helpful in metastatic lesions of possible salivary gland origin. The diversity of subtypes in salivary gland tumors, as well as the range of histomorphology within any one subtype, is unparalleled in any other human tumor. This and their relative infrequency causes diagnostic problems for pathologists. Ultrastructural techniques have been of major importance in determining the inter-relationship of these tumors for classification purposes, revealing the subtle variations in common cellular differentiation pathways, determining the organization of tumor cells, and displaying the importance of extracellular matrix materials in establishing diagnostic criteria for each of the many subtypes. Electron microscopy has also been valuable in non-neoplastic salivary gland disease and has an increasing role in experimental studies involving tissue from human and animal salivary parenchyma.

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.

Basaloid monomorphic adenomas

Monomorphic adenomas can be divided into basaloid and nonbasaloid type. With the exception of the canalicular adenoma, the basaloid monomorphic adenomas are preponderantly tumors of the major salivary glands, most often the parotid gland. The dermal analogue monomorphic adenomas, so named because of their histologic similarity to eccrine tumors of the skin, are a unique subset of the basaloid adenomas. They are often multifocal, recur frequently, may undergo malignant change, and can be part of a salivary-cutaneous tumor diathesis.

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.

Monomorphic adenomas of the major salivary glands: clinicopathological study of 44 cases

We report 44 cases of monomorphic adenoma (MA) of the major salivary glands observed during the years 1979-1989. All of these tumours were reviewed and classified on the basis of the World Health Organisation (WHO) criteria. Histological type, site, sex and age were considered. 34 cases of adenolymphoma were observed, all of them located in the parotid glands; 10 MA without lymphoid stroma were located in both parotid and submandibular glands. Distinctive histological and clinico-pathological features of the latter group of tumours are discussed, as well as the diagnostic criteria in distinguishing these tumours from pleomorphic adenoma and adenoid-cystic carcinoma.

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 adenoma with myoepithelial cell-derived "stroma": a new major salivary gland tumor entity

The light microscopic, immunohistochemical, and ultrastructural features of a unique variant of tubular-trabecular basal cell adenoma are described. The unusual feature of the six examples reported is the richly cellular "stroma" composed of spindle cells coursing between the anastomosing cords of epithelial tumor cells. Immunohistochemistry of all six cases and electron microscopy of two examples illustrated the biphasic differentiation of the epithelial portion of this form of basal cell adenoma, with a central core of duct luminal cells bordered on either side by one or more layers of modified myoepithelial cells. By light microscopy, the features and arrangement of cells in "stromal" regions of this tumor convey a fibroblastic derivation. However, this population of cells stains strongly for S-100 protein, ultrastructurally displays excessive external lamina production, intercellular junctions, and a growth pattern unlike fibroblasts, and is involved in the formation of extracellular mucinous materials. Such aspects indicate a second population of neoplastic myoepithelial cells in this tumor. Thus, this form of tubular-trabecular basal cell adenoma displays tricellular differentiation and, perhaps, may be considered either a hybrid basal cell adenoma and myoepithelioma or a cellular pleomorphic adenoma.

Tubuloalveolar adenoma of salivary gland

An unusual monomorphic salivary gland adenoma, occurring in a 57-year-old woman, is described. The lesion was histologically similar to the so-called tubular adenoma; however, occasional microscopic foci of serous (acinar cell) differentiation were present. The term tubuloalveolar adenoma is proposed to describe salivary gland tumors that are histologically benign and composed of cells resembling those of normal intercalated ducts and secretory units (acini).

Dermal cylindromas (turban tumour) and eccrine spiradenomas in a patient with membranous basal cell adenoma of the parotid gland

A patient with coexisting dermal cylindromas (Turban tumour), eccrine spiradenomas and a variant of basal cell adenoma of the parotid gland characterized by prominent focal deposition of hyaline (membranous basal cell adenoma of parotid gland) is reported. The microscopic appearance of the cutaneous and parotid gland tumours was very similar. This rare association of analogous tumours of sweat and parotid glands has been described only in 5 previous cases. It is hypothesized that the occurrence of the 3 different tumours found in this individual may be explained by the multipotential reserve cell concept and these tumours perhaps could be considered as different expressions of a single genetic disorder.

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.

Eccrine spiradenoma and dermal cylindroma

The homologous nature and morphological similarities between cutaneous and salivary gland tumors have been well documented. This is especially true of the monomorphic adenoma, eccrine spiradenoma and cylindroma. Prior to the first full clinical and pathological description, about twenty-five years ago, the lesion of eccrine spiradenoma had been given multiple synonyms. This report is of a patient with an eccrine spiradenoma in the buttock and dermaltype cylindroma of the parotid gland. This may represent the transformation of pleuripotential basal cells originating in the parotid and eccrine sweat gland.

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.

Dermal analogue tumours of major salivary glands

Monomorphic adenomas of the major salivary glands manifest a histologic spectrum whose diversity rivals that of pleomorphic adenomas. In nearly all forms of monomorphic adenomas there are histologic features which recall stages in the embryonic development of salivary glands and/or adenexae of skin. A close histogenetic relationship between certain monomorphic adenomas and certain adenexal tumours of skin is suggested by the findings of this report. Within the diversity of expression found in monomorphic adenomas are subsets of tumours which are analogous and nearly homologous with dermal appendage tumours, especially the dermal eccrine cylindroma. The analogous relationship is carried further by a proposed diathesis in which patients exhibit histologically similar tumours in their salivary glands and skin.

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.

Sebaceous differentiation in adenoid cystic carcinoma of the parotid gland

The first reported case of sebaceous differentiation in adenoid cystic carcinoma is presented. The tumor arose in the superficial lobe of the left parotid gland of a 48-year-old white man, had a predominantly solid histologic pattern, and manifested focal sebaceous differentiation in each of three recurrences over a two-year period. Review of the medical literature suggests that sebaceous differentiation is a normal property of some salivary ducts and may be found in any type of salivary gland neoplasm which has a ductal component. The differential diagnosis of sebaceous and clear cell lesions of salivary glands is discussed.

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.

A case report of basal cell adenoma showing elastic fiber (elastin-basement membrane complex) formation of the submandibular gland

A biopsy case of basal cell adenoma of the submandibular gland was reported in a 15-year-old boy. The tumor was pigeon's egg-sized, spherical in shape and encapsulated by fibrous tissue, and its cut-surface was grayish white. Histologic feature of this neoplasm was a trabecular or tubular monomorphic adenoma with well-developed elastic fibers (elastin-basement membrane complex) in the interstitial tissue. Electron microscopy disclosed 4 kinds of tumor cells, that is, secreting cells, squamous cell-like cells with tonofibrils and tonofilaments, clear cells with a few filaments, and myoepithelial cells. The interstitium contained elastin, collagen fibrils and basement membrane-like substance. Possible production of elastic fibers by the myoepithelial cells of this adenoma was 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.

Sweat gland differentiation in mammary adenoid cystic carcinoma

A breast tumor is described which presented as an exophytic mass, and which by both light and electron microscopic examination had a biphasic histologic composition. In the superficial area adjacent to the epidermis, it showed tubular differentiation similar to a cutaneous tubular apocrine adenoma and salivary basal cell adenoma, and, in the deeper portion, it had the characteristic features of adenoid cystic carcinoma. Their possible interrelationships are discussed, and mammary adenoid cystic carcinoma is briefly reviewed.

The pathology of head and neck tumors: salivary glands, part 3

The term adenoma is applied to a rather wide variety of histopathologic entities in the salivary glands. These include tumors derived from the ductal epithelium and/or from myoepithelial cells and other salivary-gland elements, such as the sebaceous glands. Within the categories of mixed tumor (pleomorphic adenoma), monomorphic adenoma, clear-cell tumor, and sebaceous lesions, there are also several subtypes, each of which lends further credence to the germinative potential of the salivary tissues. Presented in this report is a clinicopathologic and histogenetic analysis of these lesions. Specifically discussed are mixed tumor, monomorphic adenoma, carcinoma ex-pleomorphic adenoma, clear-cell tumor, sebaceous lymphadenoma, and sebaceous carcinoma.

The hyaline cell: a distinctive feature of "mixed" salivary tumours

We have identified and described a distinctive type of cell which is characteristic of the "mixed" salivary tumour. This "hyaline cell" or plasmacytoid cell is particularly common and conspicuous in "mixed" tumours of the palate and other sites in the mouth. It occurs also in tumours of the major glands, but with much lesser frequency. The hyaline cell is found in "mixed" salivary-type tumours in other sites, e.g. the skin. It is not present in the other types of salivary tumour, notably adenoid cystic carcinoma, adenolymphoma, mucoepidermoid and acinic tumour. Ultrastructural study suggests that the hyaline cell is an indicator of myoepithelial differentiation. Current concepts of the acceptable pathways of myoepithelial differentiation in "mixed" tumours are discussed briefly. The specificity of the hyaline cell will probably prove valuable in separating "mixed" tumours from monomorphic adenomas, thus retaining the identity of the latter. The hyaline cell is almost as distinctive a feature of "mixed" tumours as is myxochondroid tissue and its specificity is of practical value in the diagnosis and classification of salivary tumours.

Multicentric dermal-type cylindromas of the parotid glands in a patient with florid turban tumor

Dermal-type cylindromas of parotid glands in a patient with turban tumor, and various adnexal tumors, represent a rare diathesis, apparently not reported previously. A Caucasian man, born in 1916, had a scalpectomy for turban tumor in 1957. In 1957, 1960, and 1974, dermal type cylindromas were excised from portions of both parotid glands, developing from intercalated and striated ducts; they were considered benign, based on long term followup. Adrexal tumors included multiple dermal cylindromas, trichoepitheliomas, eccrine spiradenomas, and Bowen's disease, and occurred on almost all skin surfaces. In November, 1976, a portion of a right parotidectomy included a 3.5 X 3-cm malignant tumor having the characteristics of an invasive poorly differentiated spindle cell epidermoid carcinoma, which showed no evidence of originating from a malignant basal cell tumor. Several encapsulated and developing benign basal cell tumors were included in the specimen. Dermal-type cyclindromas of the parotid gland are considered to be a variant of basal cell ademona, or monomorphic adenoma, basal cell type, since they consist of similar cell components, although of somewhat different arrangement and with prominent focal deposition of hyaline. Dermal-type cylindromas should be excised conservatively as they appear. They must be differentiated from adenoid cystic carcinoma, which is an infiltrating neoplasm and requires a radical surgical approach.

Pleomorphic adenomas of the parotid gland resembling mesenchymal tumors

Two cases of unusual pleomorphic adenoma of the parotid gland are described. Each showed marked palisaded zones. Distinction from smooth muscle tumors, neurofibromas, and other spindle-cell neoplasms is described.