Cytokeratin expression and epithelial differentiation in Warthin's tumour and its metaplastic (infarcted) variant

In Vitro Characteristics of Canine Primary Tracheal Epithelial Cells Maintained at an Air-Liquid Interface Compared to In Vivo Morphology

Culturing respiratory epithelial cells at an air-liquid interface (ALI) represents an established method for studies on infection or toxicology by the generation of an in vivo-like respiratory tract epithelial cellular layer. Although primary respiratory cells from a variety of animals have been cultured, an in-depth characterization of canine tracheal ALI cultures is lacking despite the fact that canines are a highly relevant animal species susceptible to various respiratory agents, including zoonotic pathogens such as severe acute respiratory coronavirus 2 (SARS-CoV-2). In this study, canine primary tracheal epithelial cells were cultured under ALI conditions for four weeks, and their development was characterized during the entire culture period. Light and electron microscopy were performed to evaluate cell morphology in correlation with the immunohistological expression profile. The formation of tight junctions was confirmed using transepithelial electrical resistance (TEER) measurements and immunofluorescence staining for the junctional protein ZO-1. After 21 days of culture at the ALI, a columnar epithelium containing basal, ciliated and goblet cells was seen, resembling native canine tracheal samples. However, cilia formation, goblet cell distribution and epithelial thickness differed significantly from the native tissue. Despite this limitation, tracheal ALI cultures could be used to investigate the pathomorphological interactions of canine respiratory diseases and zoonotic agents.

Cytopathology and diagnostics of Warthin's tumour

Warthin's tumour (WT) is a benign epithelial salivary tumour, one type of salivary adenoma. Histologically, WT is structured of two components, epithelial tissue that often lines cystic formations and lymphoid tissue in the tumour stroma. FNA is a reliable diagnostic approach in the diagnosis of salivary gland lesions allowing a highly accurate categorization of benign tumour-like lesions, benign tumours and malignant tumours. In the proposed Milan reporting system of salivary gland lesions, WT is categorized in the IVA group of benign neoplasms. Accurate cytological diagnosis is straightforward when three characteristic components are present: oncocytes, either isolated or associated in clusters, lymphocytes and lymphoid cells and often an inflammatory/necrotic-like substance. Also, specific features of scintigraphy and radiological imaging contribute to the diagnosis of WT. WT is categorized according to Seifert G. et al in 4 types, depending on the proportions of the epithelial component and lymphoid stroma. Differential cytopathological and pathohistological diagnosis include other salivary gland lesions with lymphoid, oncocytic epithelial and cystic components. In some cases, such as the metaplastic WT variant, there are additional cytopathological and histological diagnostic difficulties. Moreover, bilateral, multicentric or multiple and infrequently seen extra-salivary localizations of WT are associated with further cytopathological diagnostic difficulties. Also, a rare possibility of malignant transformation of the epithelial or lymphoid component of WT as well as possible association with other primary tumours remains a challenge in accurate cytopathological and histological diagnosis of WT.

[Patterns of xanthogranulomatous reaction in salivary glands. Histomorphological spectrum and differential diagnosis]

Xanthogranulomatous inflammation is an uncommon subtype of chronic inflammatory processes that has been mainly reported in the kidneys, gallbladder and other less common sites. Due to the presence of tumefactive mixed inflammatory infiltrates with variable involvement of surrounding soft tissues, this benign condition is often mistaken for a malignancy on clinical examination. In the salivary glands xanthogranulomatous inflammation is rare and mainly represents reactive changes secondary to a preexisting lesion, in particular infarcted Warthin tumors as well as ruptured ductal cysts and other sialectatic ductal changes. A special type of xanthogranulomatous salivary gland disease is represented by the rare primary (idiopathic) xanthogranulomatous sialadenitis without identifiable predisposing parenchymal or ductal lesions. The histological differential diagnosis is mainly based on the dominant histological pattern and encompasses among others inflammatory pseudotumors of various etiologies (e.g. inflammatory myofibroblastic tumor, IgG4-related disease and sarcoidosis), neoplastic and paraneoplastic xanthogranulomatosis, malignant lymphoma and carcinoma with secondary xanthogranulomatous reactions. Thus, identification of the underlying lesion is necessary for correct classification and to avoid overlooking more serious neoplastic or autoimmune diseases.

MAML2 rearrangement in Warthin's tumour: a fluorescent in situ hybridisation study of metaplastic variants

BACKGROUND

Warthin's tumour (WT) is a common benign lesion of the major salivary glands. The nature of WT remains controversial, with particular regard to the presence of clonal chromosomal abnormalities, including the t(11;19) translocation involving the CRTC1 and MAML2 genes, that have been identified in both WT and mucoepidermoid carcinoma. In this study, we focused our attention on metaplastic WT variants, and we conducted a fluorescent in situ hybridisation (FISH) analysis for the presence of MAML2 gene rearrangement.

METHODS

Dual-colour FISH analysis was performed on paraffin-embedded sections of eight WTs showing metaplastic changes (five with squamous metaplasia, two with mucinous metaplasia and one with both) using a MAML2 break-apart probe.

RESULTS

Presence of split signals indicative of gene rearrangement was identified in a subset of cells in areas of squamous metaplasia in two samples of WT. No rearrangement was observed in the oncocytic epithelium, in lymphocytes and in areas of mucinous metaplasia.

CONCLUSIONS

The presence of a small subpopulation of cells carrying MAML2 rearrangement in areas of squamous metaplasia within WT could predispose these lesions to malignant transformation in mucoepidermoid carcinoma and could represent a molecular link between the two entities.

Rare Malignant and Benign Salivary Gland Epithelial Tumors

Although at least 24 distinct histologic salivary gland carcinomas exist, many of them are rare, comprising only 1% to 2% of all salivary gland tumors. These include epithelial-myoepithelial carcinoma, (hyalinizing) clear cell carcinoma, basal cell adenocarcinoma, cystadenocarcinoma, low-grade salivary duct carcinoma (low-grade cribriform cystadenocarcinoma), oncocytic carcinoma, and adenocarcinoma not otherwise specified. Few tumors (clear cell carcinoma and basal cell adenocarcinoma) have unique molecular correlates. Benign tumors, although histologically less diverse, are far more common, with pleomorphic adenoma and Warthin tumor the most common salivary gland tumors. Many benign tumors have malignant counterparts for which histologic distinction can pose diagnostic challenge.

Expression of podoplanin in Warthin tumours

PURPOSE

Warthin tumour is the second most common benign tumour of the parotid gland. This study was designed to investigate the lymphatic vessels in Warthin tumours in an effort to understand better its pathogenesis.

MATERIALS AND METHODS

Tissue specimens of 31 patients (19 men and 11 women; mean age 57 years, median size of the tumours 2.86 cm) were analysed by means of immunohistochemistry applying the monoclonal antibody D2-40.

RESULTS

We found numerous D2-40-positive sinus-like vessels particularly at the inner layer of the capsule.

CONCLUSIONS

Since subcapsular sinuses are a major morphological feature of lymph nodes in general, the finding of podoplanin expression in the large majority of subcapsular vessels in Warthin tumours confirms the view that this tumour has its origin in regional lymph nodes.

Warthin adenocarcinoma: analysis of 2 cases of a distinct salivary neoplasm

Carcinomas arising in or from the epithelial component of preexisting parotid Warthin tumors (WTs) are rare; the other histologic types of carcinoma found to arise from WTs are adenocarcinoma not otherwise specified, undifferentiated, mucoepidermoid, squamous cell, and oncocytic. The aim of this study is to describe the clinicopathologic features of a distinct salivary gland neoplasm, previously undescribed, with a striated duct phenotype arising from WT. We have designated this neoplasm "Warthin adenocarcinoma" (WA). In this retrospective study, we searched the surgical pathology files of the Department of Pathology at The University of Texas M.D. Anderson Cancer Center for cases of malignant WT and salivary adenocarcinoma not otherwise specified diagnosed from January 1, 1985, through December 31, 2006, and evaluated patients' medical records and pathologic material. We obtained tissue sections and immunohistochemically stained them with antibodies against p63; Bcl-2; cytokeratin (CK)903, CK7, CK14, and CK18; antimitochondrial antibody (AMA); smooth muscle actin; calponin; S-100; and Ki-67. We identified 2 cases of WA; both patients were women, 44 and 60 years of age, with 4.0- and 4.5-cm tumors in the left parotid gland. Histologically, the tumors were composed of bilayered duct-like structures: The inner layer was formed by a single row of columnar oxyphilic cells expressing CK7, CK14, CK18, and AMA. The outer layer was composed of multiple layers of small round dark cells with scanty cytoplasm that expressed p63, Bcl-2, and CK903 and were focally positive for AMA and negative for myoepithelial markers. The Ki-67 proliferative indices were 20%; and 25%. A residual WT with transition to carcinoma was identified in both cases. Treatment had consisted of total parotidectomy with postoperative irradiation. Patients were free of disease 1 and 3 years after treatment. Warthin adenocarcinoma is a unique salivary gland carcinoma representing the malignant epithelial counterpart of WT. The identification of additional cases would help to better elucidate the line of differentiation of the tumor and further define its natural history.

A closer look at Warthin tumors and the t(11;19)

The translocation t(11;19)(q21;p13) has been described in mucoepidermoid carcinoma (MEC) and rarely in Warthin tumors (WT), both tumors of the salivary gland. The translocation creates a fusion gene in which exon 1 of CRTC1 is linked to exons 2-5 of MAML2. To verify the translocation in WT, we performed nested reverse transcriptase-polymerase chain reaction using RNA from 48 WTs. This revealed the t(11;19)(q21;p13) translocation and expression of the chimeric gene in two metaplastic WT samples, but in none of the remaining ordinary 46 WTs. On review, the two positive cases were classified as tumors highly suspect for MEC. Indeed, our experience and published observations of the t(11;19)(q21;p13) translocation in WT reveal that only a small subset of WTs are positive, and that these tumors are often classified as infarcted or metaplastic WT, known to overlap considerably with MEC on purely morphological grounds. We therefore conclude that the presence of the t(11;19)(q21;p13) rearrangement favors a diagnosis of MEC.

Non-sebaceous lymphadenoma of the salivary gland: case report with immunohistochemical investigation

Non-sebaceous lymphadenoma (NSL) is a rare, recently described, benign salivary gland tumor characterized by a dense lymphoid infiltrate and absence of sebaceous differentiation. To our knowledge, only seven previous cases have been reported. In this paper, we describe an additional example of NSL along with an extensive analysis of its keratin (CK) profile. The patient was a 50-year-old woman presenting with a slowly growing painless mass in the right parotid gland. The tumor was encapsulated and measured 3 x 2 x 2 cm. Microscopically, the tumor comprised islands of epithelial cells with centrally located duct-like structures within a dense lymphoid stroma. Immunohistochemically, the tumor regularly expressed CKs 7, 8/18, and 19, which are typical for columnar differentiation and CKs 17 and 5/6, which are most typically expressed in basal cells of complex epithelia. CK14 was only expressed in rare scattered cells and eventually in groups of cells. The expression of CK10/13, which correlates with squamous differentiation, was negative. Additionally, immunostaining for smooth muscle actin, vimentin, and S-100 was also performed. The immunohistochemical findings in the neoplastic epithelial component of our case suggest a differentiation of "intercalated duct phenotype" without myoepithelial cell participation.

Immunohistochemical detection of the expression of the cell adhesion molecules E-cadherin, desmoglein-2, beta4-integrin, ICAM-1 and HCAM (CD44s) in Warthin's tumour of the parotid gland

The study of the expression of cell adhesion molecules (CAMs), E-cadherin, desmoglein-2, beta4-integrin, HCAM (CD44s) and ICAM-1 in Warthin's tumours. Twenty formalin--fixed, paraffin--embedded parotid Warthin's tumours were studied using an Envision/HRP immunohistochemical technique. Beta4-integrin was strongly expressed in all cell-basement membrane and intercellular contacts of the epithelium, E-cadherin and desmoglein-2 in cell-cell contacts, but not in basal cell-basement membrane connections and on columnar cells' luminal surfaces, HCAM (CD44s) in intercellular contacts of both luminal (mainly), basal cells and also in the periphery of monocytic-lymphocytic stroma, and ICAM-1 was weak to moderate expressed in both luminal and basal epithelial cells and strongly in the germinal lymphocytic centres. CAM expression suggests a bilayered excretory ductal structure of the neoplastic epithelium in Warthin's tumour, as a result of hyperplastic process of the glandular epithelium that interacts with the excessive lymphoid tissue of the stroma.

Tissue that has lost its track: Warthin's tumour

The origin of cystadenolymphoma (Warthin's tumour) of the parotid gland is unknown. According to the most favoured hypothesis, Warthin's tumour results from the proliferation of salivary gland ductal cells that were entrapped in parotid lymph nodes during embryonal life. If this is correct, and the almost total lack of recurrence and malignant transformation of this lesion lends credence to this view, Warthin's tumour is correctly classified in the group of tumour-like lesions and should not be considered to be a monomorphic adenoma.