[Clinicopathologic and molecular features of myoepithelial tumors of salivary glands].

Objective: To investigate the clinicopathological, and molecular characteristics of myoepithelial tumors (MTs) of salivary glands. Methods: A total of 37 MTs cases including 13 malignant epithelial tumors (MMTs) and 24 benign epithelial tumors (BMTs) of salivary glands were identified from the archives of the Department of Pathology, General Hospital of Eastern Theater Command, dating from 2006 to 2016. Clinical features, histological patterns, immunohistochemical characteristics and status of EWSR1 gene rearrangement by fluorescence in situ hybridization (FISH) analysis were reviewed in all cases. Results: Clinically, 37 MTs cases mainly occurred in the parotid glands, when most of the patients presented with painless masses. Of the 13 MMTs cases, male to female ratio was 7∶6, and the median age was 62 years old. Of the 24 BMTs cases, male to female ratio was 5∶7, and the median age was 54 years old. Immunohistochemically, 37 MTs cases were positive for CKpan, and at least one myoepithelial marker. Twenty six of 37 MTs cases were analyzable for the EWSR1 gene break by FISH. Based on the previous evaluation criterion, the EWSR1 translocation was detected in 4 cases of 11 MMTs, and 4 cases of 15 BMTs. According to the main histological composition of tumor cells, 4 EWSR1-positive MMTs covered 2 clear-cell cases and 2 epithelioid-cell cases, when 4 EWSR1-positive BMTs covered 2 clear-cell cases, 1 plasmacytoid-cell case, and 1 spindle-cell case. Conclusions: Males and females are affected equally. MTs express immunoreactivity for CKpan, and at least one myoepithelial marker. The EWSR1 rearrangement is present in a subset of MTs, with variable morphological characteristics, and has no statistical significance on clinical behavior.

Transcription factors related to chondrogenesis in pleomorphic adenoma of the salivary gland: a mechanism of mesenchymal tissue formation.

In salivary gland pleomorphic adenoma, expression of extracellular matrix (ECM) substances indicates that tumor epithelial cells are becoming chondrogenic and will produce cartilage-like mesenchymal tissues. Sox9, the master transcription factor of chondrogenesis, is expressed in mouse salivary gland cells. To clarify the mechanism behind chondrogenesis in tumor epithelial cells, we examined the expression of transcription factors related to chondrogenesis in tumors and salivary glands. Reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative real-time RT-PCR, and immunostaining were performed on pleomorphic adenoma tissues, salivary gland tissues, and human submandibular gland (HSG) cells. The mRNAs of essential transcription factors for chondrogenesis-Sox9, Sox6, and Sox5-were detected in both tumor and salivary gland tissues. The mRNAs of aggrecan and type II collagen-cartilage-specific ECM substances-were detected only in tumors. Sox9 and Sox6 proteins were colocalized in many epithelial cells in tumors and salivary glands. Tumor epithelial cells also possessed aggrecan protein and occasionally type II collagen protein. Moreover, mRNAs for transcription repressors of chondrogenesis δEF1 and AP-2α were detected in both tumors and salivary glands, whereas Twist1 mRNA was detected only in salivary glands and was at significantly low-to-undetectable levels in tumors. Twist1 protein was localized in the Sox9-expressing salivary gland cells. HSG cells expressed Sox9, Sox6, and Twist1, but not aggrecan or type II collagen, and thus were similar to salivary gland cells. Twist1 depletion by Twist1 siRNA led to the upregulation of aggrecan and type II collagen mRNA expression in HSG cells. In contrast, forced expression of Twist1, using Twist1 cDNA, resulted in the downregulation of both these genes. Taken together, these results indicate that salivary gland cells have a potential for chondrogenesis, and Twist1 depletion concomitant with neoplastic transformation, which would permit tumor epithelial cells to produce cartilage-like mesenchymal tissues in salivary gland pleomorphic adenoma.

Mammary analog secretory carcinoma, low-grade salivary duct carcinoma, and mimickers: a comparative study.

Mammary analog secretory carcinoma (MASC) is a recently recognized low-grade salivary carcinoma characterized by a specific ETV6 rearrangement. We describe 14 new MASCs and examine their immunophenotypic and genetic profiles in the context of look-alikes, namely, low-and high-grade salivary duct carcinoma and acinic cell carcinoma. ETV6 rearrangement, and robust expression of mammaglobin and S100, were demonstrated in 11/11, 14/14, and 12/14 MASCs, respectively. All low-grade salivary duct carcinomas coexpressed S100/mammaglobin (6/6); none harbored ETV6 rearrangements (0/5). Given that S100/mammaglobin coexpression and absence of zymogen granules are features of both MASC and low-grade salivary duct carcinoma, these two are best distinguished histologically. The former is predominantly an extraductal neoplasm with bubbly pink cytoplasm, whereas the latter is a distinct intraductal micropapillary and cribriform process. Querying ETV6 gene status may be necessary for difficult cases. No acinic cell carcinoma expressed mammaglobin (0/13) or harbored an ETV6 rearrangement (0/7); only 1/13 acinic cell carcinomas weakly expressed S100. DOG1 expression was limited or absent among all tumor types, except acinic cell carcinoma which expressed DOG1 diffusely in a canalicular pattern. Therefore, histology and immunohistochemistry (mammaglobin, S100, DOG1) suffices in distinguishing acinic cell carcinoma from both MASC and low-grade salivary duct carcinoma. HER2 (ERBB2) amplification was detected in only 1/10 acinic cell carcinomas, but none of the MASCs or low-grade salivary duct carcinomas tested. High-grade salivary duct carcinomas frequently expressed mammaglobin (11/18) and harbored HER2 amplifications (13/15); none harbored ETV6 rearrangements (0/12). High-grade salivary duct carcinomas can easily be distinguished from these other entities by histology and HER2 amplification.

Label-free determination of lipid composition and secondary protein structure of human salivary noncancerous and cancerous tissues by Raman microspectroscopy.

The applications of optical spectroscopic methods in cancer detection open new possibilities in oncological diagnostics. Raman spectroscopy and Raman imaging represent noninvasive, label-free, and rapidly developing tools in cancer diagnosis. In the study described in this paper Raman microspectroscopy has been employed to examine noncancerous and cancerous human salivary gland tissues of the same patient. The most significant differences between noncancerous and cancerous tissues were found in regions typical for the vibrations of lipids and proteins. The detailed analysis of secondary structures of proteins contained in the cancerous and the noncancerous tissues is also presented.

A study on the inhibition of VEGF expression in salivary gland adenoid cystic carcinoma cells via iNOS gene RNAi in vitro.

In this study, we aimed to explore the effect of inducible nitric oxide synthase (iNOS) on vascular endothelial growth factor (VEGF) expression in salivary gland adenoid cystic carcinoma (SACC). Using RNAi, we transfected chemically synthesised iNOS siRNA into ACC-M cells (a highly metastatic adenoid cystic carcinoma cell line) and detected the change in the gene and protein expression levels of iNOS and VEGF by qRT-PCR and Western blotting. A transwell invasiveness assay was used to examine the changes in invasive ability of ACC-M cells. Cell growth was determined using a CCK-8 assay. Apoptosis and cell-cycle phases were detected by flow cytometry. We found that silencing iNOS down-regulated the expression of VEGF and then inhibited cell growth and invasiveness of SACC cells, while it increased apoptosis. Therefore, we concluded that iNOS can regulate VEGF expression and iNOS may be a therapeutic target.

A comparative immunohistochemistry study of diagnostic tools in salivary gland tumors: usefulness of mammaglobin, gross cystic disease fluid protein 15, and p63 cytoplasmic staining for the diagnosis of mammary analog secretory carcinoma?

BACKGROUND: Mammary analog secretory carcinoma (MASC) of the salivary gland has been recently described according to morphological, immunohistochemical, and molecular (ETV6-NTRK3 translocation) similarities with the mammary secretory carcinoma. The most important differential diagnostic considerations of MASC are low-grade adenocarcinoma not otherwise specified (NOS), cystadenocarcinoma, and acinic cell carcinoma (AciCC). These tumors may share an overlapping morphology with MASC, and additional immunohistochemical studies are required to reinforce the diagnosis. Mammaglobin, GCDFP-15, and p63 staining have been reported in MASC. Our study was designed to check the specificity of these antibodies in MASC compared to other frequent tumors of salivary glands. METHODS: A series of 62 salivary gland tumors [10 MASCs, 5 adenocarcinomas NOS and 2 cystadenocarcinomas with MASC features and without ETV6 rearrangement, one low-grade cribriform cystadenocarcinoma (LGCCC), 9 AciCCs, 10 MECs, 10 adenoid cystic carcinomas (AdeCCs), 5 polymorphous low-grade adenocarcinomas (PLGAs), and 10 pleomorphic adenomas (PAs)] was analyzed by immunohistochemistry with mammaglobin, GCDFP-15, and p63 antibodies. RESULTS: Positivity for mammaglobin was observed in all MASCs, cystadenocarcinomas, LGCCC, and PLGAs, in some adenocarcinomas NOS, PAs, and MECs, rarely in AciCCs and never in AdeCCs. Positivity for GCDFP-15 was observed in most of the tumor types except in AdeCCs. Interestingly, cytoplasmic positivity for p63 was observed in most of MASCs and PLGAs while rarely in adenocarcinomas NOS and PAs, and never in the other tumor types. CONCLUSION: Our study revealed the usefulness of mammaglobin and p63 cytoplasmic staining to define which tumors are worth to be screened for ETV6 rearrangement.

A unique case of a cutaneous lesion resembling mammary analog secretory carcinoma: a case report and review of the literature.

Mammary analog secretory carcinoma (MASC) is a rare type of salivary gland tumor named for its morphological and genetic similarity to secretory carcinoma of the breast. These tumors are most often found in the parotid gland but have been described in several other mucosal locations of the head and neck. In this case report, a cutaneous lesion most closely resembling MASC was found in a neck mass of a 64-year-old male patient without evidence of a primary salivary gland or oral tumor. The lesion was excised, and the patient remains disease free to date. This case depicts a rare tumor in the skin most closely mimicking MASC and brings additional awareness to dermatopathologists of this tumor.

Searching for mammary analogue [corrected] secretory carcinoma of salivary gland among its mimics.

Mammary analog secretory carcinoma of salivary gland is a recently described entity with unique morphologic, clinical, and genetic characteristics, including the characteristic t(12;15)(p13;q25) with ETV6-NTRK3 translocation found in secretory carcinomas of the breast. Before their initial description, these salivary gland tumors were generally diagnosed as acinic cell carcinoma or adenocarcinoma. For the purpose of this study, all cases of salivary gland acinic cell carcinoma, cribriform cystadenocarcinoma, and adenocarcinoma, not otherwise specified (NOS), diagnosed over a 10-year period were retrieved from our surgical pathology files. There were a total of 11 cases diagnosed as acinic cell carcinoma, 10 cases of adenocarcinoma, NOS, and 6 cases of cribriform cystadenocarcinoma. All slides were reviewed by two pathologists (AP, CGF) and tumors that show morphologic features of mammary analog secretory carcinoma according to the recent literature were selected. This process narrowed down the initial number to six cases originally diagnosed as acinic cell carcinoma, three cases originally diagnosed as adenocarcinoma, NOS, and one case originally diagnosed as cribriform cystadenocarcinoma. The 10 cases were subjected to immunohistochemistry for S-100, mammaglobin, and ANO1, as well as fluorescence in situ hybridization analysis for t(12;15)(p13;q25) with ETV6-NTRK3 fusion rearrangement. The ETV6-NTRK3 gene rearrangement was detected in three tumors. These three tumors, initially diagnosed as acinic cell carcinomas, stained positive for S-100 and mammaglobin, and negative for ANO1 by immunohistochemistry. Two of the three patients were male (2/3). In summary, mammary analog secretory carcinoma is a newly described diagnostic entity that should be in the differential diagnosis of salivary gland tumors that morphologically mimic other neoplasms, mainly acinic cell carcinomas. They differ from conventional acinic cell tumors immunohistochemically and molecularly. Positivity for mammaglobin and S-100, and negativity for ANO1 are useful screening tools before confirmatory molecular studies.

STAG2 loss of expression is rare in aneuploid malignant salivary gland neoplasms.

BACKGROUND: STAG2 depletion leads to loss of centromere cohesion in vitro, and some human neoplasms have been shown to lose expression of this protein. As a result, STAG2 loss has been shown to cause chromosomal instability and aneuploidy in human cancer cell lines. METHODS: We tested the hypothesis that aneuploid salivary gland tumours lose immunoexpression of STAG2 compared with diploid tumours using image cytometry to determine DNA ploidy and immunohistochemistry to assess STAG2 protein expression in 30 malignant salivary gland neoplasms. RESULTS: There was no difference in the immunoexpression of STAG2 between aneuploid (n = 9) and diploid (n = 21) samples. In all but two samples, more than 50% of cells stained for STAG2. CONCLUSION: Aneuploidy in human salivary gland carcinomas is not driven by loss of expression of STAG2.

Canalicular adenoma immunoprofile: a case report.

OBJECTIVES: To report a case of canalicular adenoma (CA) and discuss the use of immunohistochemistry to better address the diagnosis given some unusual characteristics in this patient. BACKGROUND: CA is an uncommon benign neoplasm that can develop in minor salivary gland duct tissues throughout the oral cavity. At histology, it shares several features with other salivary tumors. Immunohistochemistry can be useful in the differential diagnosis. MATERIALS AND METHODS: The clinical presentation consisted in a nodule on the left upper lip of an 85-year-old man. The patient's main complaint was upper denture instability secondary to soft tissue changes. The nodule was excised under local anesthesia and underwent histological and immunohistochemical examination to rule out any malignancy. RESULTS: Histological findings, cytokeratin positivity and the absence of any reactivity to specific markers of myoepithelial differentiation confirmed the epithelial nature of the lesion. CONCLUSION: The histological diagnosis of benign salivary tumors such as CA can be confirmed by immunohistochemistry.

Evaluation of cell proliferation marker CDC-7 in salivary adenoid cystic carcinoma.

BACKGROUND: Adenoid cystic carcinoma (AdCC) is considered one of the most common destructive types of malignant salivary gland tumor that have high affinity to perineural invasion (PNI). This study was conducted to access different histological features of AdCC, and assessment of the immunohistochemical expression of CDC-7. METHODS: Thirty formalin-fixed paraffin incorporated tissue blocks of AdCC were classified according to the WHO histopathological types. The immune-expression of CDC-7 positive area was evaluated according to percentage area as following: Negative = 0 %, Weak = 1-10 %, Moderate = 11-49 %, and Strong = 50-100. The correlations between expression of the marker and different clinico-pathological variables were investigated using Chi-square (χ2) test. The P-value ≤ 0.05 was considered statistically significant. RESULTS: The expression of CDC-7 revealed statistical significant difference between the different tumor types (p ≤ 0.05). CONCLUSION: The biological behavior of AdCC can be predicated from the expression of CDC-7.

PON3::LCN1 and HTN3::MSANTD3 Gene Fusions With NR4A3/NR4A2 Expression in Salivary Acinic Cell Carcinoma.

Acinic cell carcinoma of the salivary gland (AciCC) is a low-grade carcinoma characterized by the overexpression of the transcription factor nuclear receptor subfamily 4 group A member 3 (NR4A3). AciCC has been the subject of a few molecular research projects. This study delves into AciCC's molecular landscape to identify additional alterations and explore their clinical implications. RNA sequencing and immunohistochemical staining for markers NR4A3/NR4A2, DOG-1, S100, and mammaglobin were utilized on 41 AciCCs and 11 secretory carcinoma (SC) samples. NR4A3 was evident in 35 AciCCs, while the residual 6 were NR4A3-negative and NR4A2-positive; SC samples were consistently NR4A3-negative. A novel fusion, PON3 exon 1- LCN1 exon 5, was detected in 9/41 (21.9%) AciCCs, exhibiting a classical histologic pattern with serous cell components growing in solid sheets alongside the intercalated duct-like component. Clinical follow-up of 39 patients over a median of 59 months revealed diverse prognostic outcomes: 34 patients exhibited no disease evidence, whereas the remaining 5 experienced poorer prognosis, involving local recurrence, lymph node, and distant metastasis, and disease-associated death, 4 of which harbored the PON3::LCN1 fusion. In addition, the HTN3::MSANTD3 fusion was recurrently identified in 7/41 AciCC cases. SC patients lacked both fusions. Immunohistochemistry uncovered differential expression of DOG-1, S100, and mammaglobin across samples, providing nuanced insights into their roles in AciCC. This study accentuates PON3::LCN1 and HTN3::MSANTD3 fusions as recurrent molecular events in AciCC, offering potential diagnostic and prognostic utility and propelling further research into targeted therapeutic strategies.

Detection of claudin-4 in salivary gland neoplasms (a study utilizing RT-PCR and immunohistochemistry).

BACKGROUND: Claudins are transmembrane proteins of tight junctions emerging as targets for diagnosis, prediction of prognosis, disease recurrence, and metastasis. Our goal was to evaluate expression of claudin-4 in the most common benign and malignant salivary gland neoplasms. METHODS: Claudin-4 gene levels and protein expression were determined by real-time polymerase chain reaction (PCR), and immunohistochemistry in a total of 30 specimens containing normal salivary tissue, pleomorphic adenoma, Warthin's tumor, mucoepidermoid carcinoma, and adenoid cystic carcinoma. RESULTS: We identified down-regulation of claudin-4 gene levels and protein expression from normal control to benign salivary gland neoplasms and reached their lowest values in the malignant salivary gland neoplasms. CONCLUSIONS: Low claudin-4 expression could be considered as a sign of increasing cellular disorientation and invasion of salivary gland tumors.

Intraoral exophytic lesion in an adolescent: A case report of myoepithelioma with unique clinical presentation.

Myoepithelioma is an infrequent benign tumor of the salivary glands, characterized by its composition of myoepithelial cells which can show different shapes and be arranged in various patterns with a well-circumscribed or encapsulated growth. This tumor commonly presents in adults as an asymptomatic swelling of the parotid gland, very rarely in minor salivary glands of children or adolescents, and even rarer in the buccal mucosa, with only six cases reported to date and only one of them presented in an adolescent. We present an additional case of myoepithelioma in the buccal mucosa of a 16-year-old male, with a novel clinical presentation as a non-submucosal exophytic mass. Immunohistochemically, neoplastic cells were positive for CK, S100, p63, and GFAP. The tumour was treated surgically, and the patient showed satisfactory evolution at 1 year of follow-up. The clinical and histopathological characteristics of the reported cases are discussed.

Clear-cell Variant of Mucoepidermoid Carcinoma Presenting as a Palatal Mass in a 10-Year-old Boy.

BACKGROUND: The clear-cell variant of mucoepidermoid carcinoma (MEC) involving minor salivary glands is extremely rare in children. CASE REPORT: We report a case of clear-cell variant MEC in the minor salivary gland in a 10-year-old boy who presented with a mass of the right hard palate. Fine-needle aspiration showed features suggestive of clear-cell variant of MEC. Microscopically, the tumor cells showed predominant clear cells and scattered mucous cells. There was increased mitotic activity (6/mm2). No tumor necrosis or nuclear pleomorphism was identified. The tumor cells were positive for cytokeratin 7 (CK7), tumor protein p63, P40 (ΔNp63), CK5/6 and mucicarmine. Rearrangement of mastermind-like transcriptional coactivator 2 (MAML2) (11q21) gene was present in the tumor cells by fluorescence in situ hybridization, supporting the diagnosis of an intermediate-grade clear-cell variant of MEC. A right infrastructure maxillectomy for palate carcinoma with negative margins was performed. Grossly, the tumor was a 2.1 cm well-circumscribed, friable, pale tan mass with focal areas of cystic change. The final pathological diagnosis was clear-cell variant of MEC, intermediate grade, pT2. Post surgery, the patient recovered and was doing well, with no tumor recurrence or metastasis at the 6-month follow-up. CONCLUSION: To the best of our knowledge, this is the first documented case of clear-cell variant MEC in a child. Due to low to intermediate tumor grade, an overtly aggressive treatment should be avoided in a child.

Lymphadenoma of the salivary gland: clinicopathological and immunohistochemical analysis of 33 tumors.

Lymphadenomas (LADs) are rare salivary gland tumors. Their clinicopathologic characteristics and etiopathogenesis are poorly understood. We examined 33 LADs in 31 patients (17 women and 14 men) aged 11-79 years (median 65 years). There were 22 sebaceous LADs in 21 patients (9 women and 12 men) and 11 non-sebaceous LADs in 10 patients (8 women and 2 men). Two patients had synchronous double tumors. Twenty-six tumors (79%) arose in parotid, three in the neck, and two each in submandibular gland and oral cavity. Extraparotid tumors were seen in 2 of 21 (10%) patients with sebaceous and 4 of 10 (40%) patients with non-sebaceous LADs. Seven of twenty-three (30%) patients had immunosuppressive therapy for unrelated diseases. The tumors were well circumscribed, encapsulated (n=28, 84%) painless masses, varying in size from 0.6 to 6 cm (median 2.2). The cut surfaces were gray-tan to yellow, homogeneous and multicystic (n=24, 72%). The epithelial cells were basaloid, squamous and glandular, forming solid nests, cords, tubules, and cysts. Sebaceous differentiation was restricted to sebaceous lymphadenoma. The epithelial cells expressed basal cell markers (p63, 34BE12, and/or CK5/6, 18/18, 100%) and the luminal glandular cells expressed CK7 (12/12, 100%). Myoepithelial cells were absent (n=10/16, 63%) or focal. The lymphoid stroma was reactive, with germinal centers in 28 (84%). There was no evidence of HPV (0/11), EBV (0/7), and HHV-8 (0/8). Malignant transformation to sebaceous and basal cell adenocarcinoma was seen in one patient each. None of the 11 patients with follow-up (1-8 years) recurred. In summary, sebaceous and non-sebaceous LADs are benign, encapsulated, solid and cystic tumors affecting older adults. Non-sebaceous LADs affect women and extraparotid sites more frequently than sebaceous LADs. Altered immune status may have a role in their etiopathogenesis. Multiple synchronous tumors, origin in buccal mucosa, and malignant transformation may rarely occur.

Expression of ERBB3 binding protein 1 (EBP1) in salivary adenoid cystic carcinoma and its clinicopathological relevance.

BACKGROUND: ERBB3 binding protein 1 (EBP1) gene transfer into human salivary adenoid cystic carcinoma cells has been shown to significantly inhibit cell proliferation and reduce tumor metastasis in mouse models. In the current study, to evaluate if EBP1 is a novel biomarker capable of identifying patients at higher risk of disease progression and recurrence, we examined the EBP1 expression profile in adenoid cystic carcinoma (ACC) patients and analyzed its clinicopathological relevance. To understand the underlying anti-metastatic mechanism, we investigated if EBP1 regulates invasion-related molecules. METHODS: We performed immunohistochemical analysis on 132 primary adenoid cystic carcinoma and adjacent non-cancerous tissues using commercial EBP1, MMP9, E-cadherin and ICAM-1 antibodies. Results were correlated to clinicopathological parameters, long-term survival and invasion-related molecules by statistical analysis. Cell motility and invasiveness of vector or wild-type EBP1-transfected ACC-M cell lines were evaluated using wound healing and Boyden chamber assays. MMP9, E-cadherin and ICAM-1 proteins in these cell lines were detected using western blot assay. RESULTS: The expression of EBP1 was significantly higher in non-cancerous adjacent tissues compared with corresponding cancer tissues. The intensity and percentage of cells that reacted with EBP1 antibodies were significantly higher in cases with tubular pattern than those with solid pattern (P<0.0001). We also found adenoid cystic carcinoma with local lymphatic metastasis had significantly lower EBP1 expression than ACC with no local lymphatic node metastasis (P<0.0001). Similar findings were observed in ACC with lung metastasis compared with cases with no lung metastasis (P<0.0001), in particular, in cases with perineural invasion compared with cases with no perineural invasion (P<0.0001). Furthermore, a decrease in EBP1 expression was positively associated with a reduction in overall survival of ACC patients. Of note, EBP1 inhibits migration and invasiveness of ACC cells by upregulating E-cadherin but downregulating MMP9. In clinical adenoid cystic carcinoma patients, higher EBP1 expression was positively correlated with E-cadherin levels (P<0.001) but negatively correlated with MMP9 expression (P=0.0002). CONCLUSIONS: EBP1 expression is reduced in adenoid cystic carcinoma, indicating unfavorable prognosis of ACC patients. Its regulation of MMP9 and E-cadherin protein levels suggests a critical therapeutic potential.

Lysosomal and cytoskeletal events in epithelial salivary tumours as assessed by imunohistochemistry for CD63 and HSP27.

Little attention has been paid to immunohistochemically assessed, lysosomal activities in salivary neoplasia. In an attempt to remedy this, the present investigation applied immunohistochemistry for CD63 antigen (a lysosomal membranous protein) and HSP27 (a molecular chaperone with roles in intracellular homeostasis) to archival paraffin-embedded surgical specimens of 101 benign and malignant, epithelial salivary tumours. Diffuse cytoplasmic CD63 immunoreactivity was seen in serous cells in acinic cell carcinoma, and mucous cells in mucoepidermoid carcinoma, pleomorphic adenoma (PA) and Warthin tumour. Apical rims or bands of CD63 immunoreactivity were also seen in simple cells lining tubular structures in PA, acinic cell carcinoma, mucoepidermoid carcinoma and polymorphous (low-grade) adenocarcinoma; and, occasionally, oncocytic luminal cells in Warthin tumour. HSP27 immunoreactivity was usually seen in non-luminal cells of PA, basal cells of oncocytic tumours, epidermoid cells of mucoepidermoid carcinoma and PA, and cells outlining aggregates or pseudolumina of adenoid cystic carcinoma. Expression of CD63 is preferentially associated with differentiated or simple luminal cell phenotypes in epithelial salivary tumours and possibly reflects autophagy of secretory granules or absorption of luminal material. Expression of HSP27 is preferentially associated with non-luminal cells and possibly reflects remodelling of the cytoskeleton.

Primary Mucoepidermoid Carcinoma of the Lacrimal Apparatus.

PURPOSE: In this study, we evaluated the clinicopathologic and molecular characteristics of lacrimal apparatus mucoepidermoid carcinoma (MEC) to define its typical diagnostic features. DESIGN: Retrospective observational case series. METHODS: Institutional pathology records between 2011 and 2021 were searched for all cases of lacrimal apparatus MEC. RESULTS: A total of 2 male and 6 female patients ranging in age from 18 to 83 years (median 56, mean 54) were included. Six lacrimal apparatus MECs were found in the lacrimal gland, and 2 cases occurred in the lacrimal sac and nasolacrimal duct. Histologically, there were 6 cases of conventional MEC, 1 clear-cell variant of MEC, and 1 oncocytic variant of MEC for a total of 8 cases. There were 3 low-grade cases and 5 high-grade cases. All 8 cases were evaluated via immunohistochemistry, and the results were positive (scores 1-4) for pankeratin, 34betaE12, p63, p40, CK7, CK8, and CK19, with a relatively higher expression of p63 observed in high-grade MEC. The presence of human papillomavirus (HPV) type 6 DNA was found in 4 patients. MAML2 fluorescence in situ hybridization was positive for MAML2 rearrangement in 3 lacrimal gland tumors (2 low-grade and 1 high-grade). Six tumors were managed with radical resection, and 2 patients underwent orbital exenteration. Postoperative radiation therapy was delivered to 6 patients, and chemotherapy was administered to 1 patient. CONCLUSIONS: MECs of the lacrimal apparatus are rare tumors, and the rate of MAML2 translocations is lower than that in salivary MECs. Lacrimal gland and lacrimal sac MECs may not be of the same subtypes intrinsically because of the difference in MAML2 translocation, anatomy, and clinical course. The etiologic function of HPV type 6 infection should be explored in lacrimal apparatus MECs. Radical surgery is the treatment of choice. The description of these unique findings may assist in the definitive diagnosis of and improve our understanding of lacrimal apparatus MEC.

HMGA2-WIF1 Rearrangements Characterize a Distinctive Subset of Salivary Pleomorphic Adenomas With Prominent Trabecular (Canalicular Adenoma-like) Morphology.

Most of salivary gland neoplasms (benign and malignant) are characterized by recurrent gene fusions. Pleomorphic adenoma (PA), the most frequent salivary gland tumor, is driven by chromosomal rearrangements involving PLAG1 mapped to 8q12 and HMGA2 mapped to 12q13-15 in most cases. Multiple fusion partners have been identified including CTNNB1, FGFR1, LIFR, CHCHD7 and TCEA for PLAG1 fusions and NFIB, WIF1 and FHIT for HMGA2 fusions. To date, no data exist on the morphology of the few reported HMGA2-WIF1-rearranged PAs. We present 28 major salivary gland adenomas displaying distinctive trabecular and canalicular morphology associated with recurrent genotype. Patients were 15 females and 13 males aged 43 to 87 (median: 65). All tumors originated from the parotid. Their size range was 1 to 4 cm (mean: 2.3). Histologically, all tumors showed elongated or columnar cells arranged into bilayered to multilayered communicating and branching strands and trabeculae in a manner similar to canalicular adenoma of minor salivary glands or trabecular myoepithelioma with variable solid confluent intercalated duct-like areas. Fifteen tumors were exclusively canalicular/trabecular while 13 had intermingled or well-demarcated conventional (chondromyxoid) PA component comprising 5 to >50% of the tumor. The monomorphic areas expressed uniformly CK7 (28/28), vimentin (21/21), S100 (24/24), SOX10 (16/17) and variably p63 (8/21) and mammaglobin (6/16) but were negative with p40 (0/24), smooth muscle actin (0/24) and MUC4 (0/16). Targeted RNA sequencing revealed HMGA2 fusions in 14/16 (87%) assessable cases. Fusion partner was WIF1 (12), RPSAP52 (1) and HELB (1). Separate testing of the 2 components in 1 hybrid tumor showed same HMGA2/WIF1 fusion. HMGA2 immunohistochemistry was homogeneously positive in all cases including the 2 fusion-negative cases. A control cohort of 12 genuine canalicular adenomas revealed no HMGA2 fusions (0/4) and lacked HMGA2 immunoreactivity (0/12). This study highlights a distinctive variant in the spectrum of PA characterized by prominent trabecular and canalicular adenoma-like morphology. Our data confirm that canalicular adenomas in major salivary glands (either monomorphic or part of hybrid tumors) are distinct from canalicular adenoma of minor salivary glands. Their uniform genotype irrespective of presence or absence of a conventional PA component argues for classifying those tumors lacking a conventional PA component as "monomorphic variants of PA" rather than canalicular/basal cell adenomas, intercalated duct adenoma, trabecular myoepithelioma or true hybrid tumors.