Selective Immunohistochemical Comparison of Polymorphous Low-Grade Adenocarcinoma and Adenoid Cystic Carcinoma

Polymorphous Adenocarcinoma: A Systematic Review of the Literature and Presentation of Two Cases in a Less-Considered Anatomical Site

BACKGROUND

Polymorphous adenocarcinoma (PAC) is the second-most common malignant tumour of the minor salivary glands. Although PAC predominantly affects the palate, it can also involve the buccal mucosa. This systematic review aims to investigate the literature data about PAC. Furthermore, we report two cases of patients affected by PAC in an infrequently considered anatomical site.

METHODS

According to PRISMA guidelines, a systematic review search was conducted on PubMed, Scopus, and Web of Science. Observational studies conducted on patients with a histological diagnosis of PAC were selected and analysed. Furthermore, two cases of patients with PAC affecting the buccal mucosa were reported.

RESULTS

Twenty-nine studies were included, and 143 patients affected by PAC were analysed (62 males, 75 females, and 6 undefined, with a mean age of 57.4 ± 14.5 years). The palate was the most affected site (99/143, 69.2%), followed by the buccal mucosa (12/143, 8.4%). Moreover, we report two cases of patients with PAC affecting the buccal mucosa (one male and one female, with a mean age of 70.5 ± 2.5 years).

CONCLUSIONS

The present study underscores the importance of considering the buccal mucosa as a possible location of minor salivary gland tumours; although it is a less-considered affliction, it is not uncommon.

Diagnostic reliability of c-KIT (CD117) in salivary gland tumours - A systematic review and meta-analysis

c-KIT is an important diagnostic marker in salivary gland tumours and is expressed in most adenoid cystic carcinomas. Histologically similar salivary gland tumours with variable immunohistochemical expression for c-KIT pose a challenge and make diagnostic reliability ambivalent. An electronic search was performed in MEDLINE by PubMed, Google Scholar, Scopus, Trip, Cochrane Library, and EMBASE up to 31 December 2023, without period restriction. The articles that investigated CD117 or c-KIT in salivary gland tumours were included for review. Sensitivity, specificity, and positive and negative predictive values of c-KIT immunohistochemical expressions were derived and subjected to meta-analysis using Open Meta analyst for Sierra software. The risk of bias in selected studies was analysed using the QUADAS-2 tool, and RevMan 5.4 was used to output the result. Forty-three articles were reviewed, and 2285 salivary gland cases were analysed. Adenoid cystic carcinoma had an overall expression of 84.9%. A similar expression was found in epimyoepithelial carcinoma (79.1%), lymphoepithelial carcinoma (75%), myoepithelial carcinoma (60.8%), monomorphic adenoma (94.1%), and pleomorphic adenoma (74.7%). The sensitivity, specificity, and positive and negative predictive values of c-KIT/CD117 for adenoid cystic carcinoma with other salivary gland tumours were 84.99%, 69.09%, 84.79%, and 69.41%, respectively. Current evidence shows that c-KIT, despite its sensitivity, is not specific and therefore cannot be a useful diagnostic marker for distinguishing adenoid cystic carcinoma from other salivary gland tumours. Further research on other salivary gland tumours that exhibit comparable expression is necessary to validate the diagnostic accuracy of c-KIT.

Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis

Polymorphous adenocarcinoma (PAC) is a rare variant of minor salivary gland tumors. Because of its architectural diversity, histological diagnosis of PAC can be difficult especially for small biopsies, and immunohistochemistry is of great help in differentiating it from its histologic mimics. The aim of this study is to conduct a systematic literature review to identify reliable immunohistochemical markers for PAC. We conducted an electronic literature search of the MEDLINE, ScienceDirect, SpringerLink, and Wiley Online Library databases, covering the literature published in the period between 1988 and 2021. The eligibility criteria included case reports and retrospective studies of PAC cases with details of immunohistochemical markers. Following the search and selection process, 32 studies with 409 cases were included in this systematic review. Overall, > 90% positivity was observed for pan-cytokeratin (CK) (97.3%), CK7 (96.8%), CK7/8 (97.4%), E-cadherin (90.0%), Vimentin (92.5%), S100 (97.0%), p63 (91.7%), and SOX10 (100%), while little to no positivity was observed for CK20 (0.0%), p40 (0.0%), and GFAP (5.0%). The average MIB-1 labeling index was 3.78%. The results of this systematic review indicate that CK7+/CK20-, p63+/p40-, S100+, Vimentin+, and GFAP- immunophenotype have diagnostic value for PAC. In addition, the use of S100, MSA, p40, and c-Kit provide additional layers of information helpful to differentiate PAC from adenoid cystic carcinoma, one of challenging differential diagnoses.

Microsecretory Adenocarcinoma of Salivary Glands: An Expanded Series of 24 Cases

Microsecretory adenocarcinoma (MSA) is a recently described salivary gland tumor with a characteristic histologic and immunophenotypic profile and recurrent MEF2C-SS18 fusions. Because only six cases of MSA have been published, its complete clinicopathologic spectrum is unclear, and its biologic behavior has not been documented. Here, we present an updated and expanded experience of 24 MSA cases. All cases of MSA were obtained from the authors' files. Immunohistochemistry for S100, SOX10, p63, p40, SMA, calponin, and mammaglobin was performed. Molecular analysis was performed by targeted RNA sequencing, SS18 break apart fluorescence in situ hybridization, and/or reverse transcriptase polymerase chain reaction for MEF2C-SS18 fusion. Clinical follow-up was obtained from medical records. A total of 24 MSA cases were collected, from 13 women and 11 men, ranging from 17 to 83 years (mean 49.5 years). The vast majority (23 of 24) arose in the oral cavity, with the palate (n = 14) and buccal mucosa (n = 6) as the most frequent subsites. Tumors showed consistent histologic features including: (1) microcystic tubules, (2) flattened intercalated duct-like cells, (3) monotonous oval hyperchromatic nuclei, (4) abundant basophilic luminal secretions, (5) fibromyxoid stroma, and (6) circumscribed borders with subtle infiltration. The tumors were very consistently positive for S100 (24 of 24), p63 (24 of 24), and SOX10 (14 of 14) and negative for p40 (0 of 21), calponin (0 of 12) and mammaglobin (0 of 16), while SMA (4 of 20) was variable. MEF2C-SS18 fusion was demonstrated in 21 of 24 cases; in the remaining 3 cases with insufficient RNA, SS18 break apart FISH was positive. Treatment information was available in 17 cases, all of which were managed with surgery only. In 14 cases with follow-up (1-216 months, mean 30), no cases recurred or metastasized. MSA is a distinct salivary gland neoplasm with remarkably consistent clinical, histologic, immunophenotypic, and genetic features that generally behaves in an indolent manner following surgery alone. These observations solidify MSA as a unique, low-grade salivary gland carcinoma that warrants inclusion in the next version of the WHO classification of head and neck tumors.

Polymorphous Adenocarcinoma: A Rare Case Report with Unique Radiographic Appearance on CBCT

BACKGROUND

Polymorphous low-grade adenocarcinoma (PLGA) is a slow growing malignant tumor of minor salivary glands and is generally of indolent nature. However, according to the most recent WHO Classification of Salivary Gland Tumors (2017), the cancer is classified as Polymorphous AdenoCarcinoma (PAC). PAC presents as a less aggressive tumor, though it could on rare occasions demonstrate distant metastasis. Case Presentation. A 47-year-old man who was referred by a private practitioner for a CBCT scan in reference to a proliferative soft-tissue growth in the hard palate. The growth was mild and tender and there was Grade III mobility in relation to all the maxillary teeth. Panoramic radiograph taken previously had revealed evidence of alveolar bone loss in relation to the maxillary teeth and was inconclusive of any other findings. The CBCT scan revealed evidence of moth-eaten appearance of maxilla with destruction of medial and lateral walls and floor of maxillary sinus. There was also evidence of involvement of right eustachian tube, ethmoidal wall, and nasopalatine canal. An intraosseous malignancy of the palate was suspected, and a total maxillectomy was performed. The tissue sample was sent for histopathological assessment wherein changes diagnostic for polymorphous low-grade adenocarcinoma of the palate were observed.

CONCLUSION

PAC is a distinct, yet commonly occurring, minor salivary gland tumor with varied clinical and histologic appearance. This case report highlights the importance of CBCT in diagnosing the intraosseous involvement of such tumors which can help shed some light in enhancing our knowledge about the minor salivary gland malignancies like PAC.

Ki-67 expression as a diagnostic biomarker in odontogenic cysts and tumors: A systematic review and meta-analysis

Ki-67 is a marker of cell proliferation, used as an important diagnostic marker in the pathologic differentiation of various lesions. It is also relevant for developing targeted molecular therapies. We carried out a systematic review to assess the Ki-67 labeling index (LI) in odontogenic cysts and tumors. Databases were searched, including PubMed (MEDLINE), Scopus, CINHAL, PsycoInfo, the Cochrane Library, and Proquest. The meta-analysis was carried out based on the data of 608 lesions. When a 5% cut-off point was set, ki-67 LI of all benign odontogenic tumors dropped below this point. All the malignant tumors demonstrated an LI of over 15.3%; a significantly higher Ki-67 LI in malignant odontogenic lesions (17.59±2.80) was observed. Among benign tumors, the largest and the smallest Ki-67 LIs were seen in ameloblastoma (4.39±0.47) and adenomatoid odontogenic tumor (0.91±1.71). The mean values of Ki-67 LI in tumors and cysts were 4.23 (0.38) and 1.04 (0.07), respectively. Among odontogenic cysts, the highest Ki-67 LI was found in odontogenic keratocyst (OKC) (3.58±0.51), and the lowest in the radicular cyst (1.29±0.62%). Ki-67 LIs in all odontogenic cysts were <3%, except for OKC. This controversial lesion seems to have a profile more similar to a tumor, and a treatment plan similar to tumors might be suggested. We found that odontogenic lesions have diverse proliferative activities that help differentiate between various lesions and suggest therapeutic plans.

SOX10 and GATA3 in Adenoid Cystic Carcinoma and Polymorphous Adenocarcinoma

Differentiating between adenoid cystic carcinoma (AdCC) and polymorphous adenocarcinoma (PAC) can be difficult on small biopsies and cytologic specimens. As such, further characterization of their immunophenotype may aid in distinction. Previous studies have found AdCC to be SOX10+/GATA3 variable and PAC to be GATA3 negative. SOX10 expression in PAC has, as yet, not been established. We performed GATA3 and SOX10 immunohistochemistry on whole sections of 25 cases each of AdCC and PAC (including both classic PAC and the cribriform variant) to assess whether these markers are of diagnostic utility in distinguishing between these entities. SOX10 was found to be positive in 100% of PAC and AdCC whereas GATA 3 was immunoreactive in 45% of AdCCs and 20% of PAC. While this is the first series to compare SOX10 and GATA3 staining in these two tumor types, their frequent expression and similar staining patterns render them of limited value in discriminating between these neoplasms.

MiR-455-3p, miR-150 and miR-375 are aberrantly expressed in salivary gland adenoid cystic carcinoma and polymorphous adenocarcinoma

BACKGROUND

Adenoid cystic carcinoma (AdCC) and polymorphous adenocarcinoma (PAC) are included among the most common salivary gland cancers. They share clinical and histological characteristics, making their diagnosis challenging in specific cases. MicroRNAs (miRNA) are short, non-coding RNA sequences of 19-25 nucleotides in length that are involved in post-transcriptional protein expression. They have been shown to play important roles in neoplastic and non-neoplastic processes and have been suggested as diagnostic and prognostic markers.

METHODS

This study, using quantitative RT-PCR, investigated miR-150, miR-455-3p and miR-375 expression, in order to identify a possible molecular distinction between AdCC and PAC.

RESULTS

miRNA-150 and miRNA-375 expression was significantly decreased in AdCC and PAC compared with salivary gland tissue controls, whilst miRNA-455-3p showed significantly increased expression in AdCC when compared to PAC, (P < 0.05). miR-150, miR-357 and miR-455-3p expression in AdCC, PAC and control was not associated with age, gender nor with anatomic site (major and minor salivary glands) (P > 0.05).

CONCLUSION

MiR-455-3p could be used as a complimentary tool in the diagnosis of challenging AdCC cases.

Utility of smooth muscle actin and CD117 as reliable markers in the diagnosis of salivary gland neoplasms

Objective:

The aim of this study is to analyze the utility of immunohistochemical markers such as CD117 and smooth muscle actin (SMA) in the diagnosis of various benign and malignant salivary gland neoplasms.

Materials and Methods:

The study comprises 17 samples categorized into three groups: Group I consisted of 5 histopathologically normal salivary gland tissue; Group II comprised 7 cases, of which 3 cases were pleomorphic adenoma, 3 cases were myoepithelioma and 1 case was Warthin's tumor; and Group III consisted of 5 cases, of which 1 was mucoepidermoid carcinoma and 4 cases were adenoid cystic carcinoma. The selected cases were subjected to immunohistochemistry (IHC) procedure to assess the expression pattern of CD117 and SMA.

Results:

In SMA, 85.8% showed severe-to-moderate intense expression among the tumor cells in benign salivary gland tumor. All the 5 malignant tumors showed the expression of SMA and 3 cases demonstrated severe expression among the tumor cells. An intense expression pattern of SMA was observed in both benign and malignant neoplasms in the periphery and stromal components of the tumor. Only two cases were positive for CD117, and connective tissue components were completely negative in both malignant and benign salivary gland neoplasms.

Conclusion:

Alpha-SMA can be utilized as reliable IHC markers for salivary gland neoplasms due to its diagnostic importance in tumors with myoepithelial origin indicative of the histogenesis of salivary gland tumors.

Immunohistochemical study of salivary gland tumors in a tertiary institution in South-South Region of Nigeria

Aim:

The aim of this study was to see the usefulness of immunohistochemistry in diagnosing salivary gland tumors found in a tertiary health institution.

Materials and Methods:

Twenty-six formalin-fixed paraffin embedded salivary gland tumors were accessioned, and 2 μm were sectioned and processed using Streptavidin-Biotin immunoperoxidase method.

Results:

Adenoid cystic carcinoma (ADCC) was positive to alpha-smooth muscle actin (α-SMA) while mucoepidermoid carcinoma (MEC), polymorphous low-grade adenocarcinoma (PLGA), squamous cell carcinoma (SCC) and oncocytic carcinoma (OCC) were all negative to it. MEC, PLGA, ADCC and the only pleomorphic adenoma (PA) were positive to Ki-67 while both SCC and OCC were negative to it. All the tumors except PA were positive to p63.

Conclusion:

It appears that α-SMA may be used to distinguish ADCC from MEC and PLGA, but Ki-67 cannot be used for this purpose. Furthermore, p63 cannot help in the diagnosis of ADCC, MEC or PLGA. It was concluded that immunochemistry can be used as adjunct to routine H and E stain in the diagnosis of the various salivary gland tumors.

Polymorphous adenocarcinoma of the salivary glands: reappraisal and update

Although relatively rare, polymorphous adenocarcinoma (PAC) is likely the second most common malignancy of the minor salivary glands (MiSG). The diagnosis is mainly based on an incisional biopsy. The optimal treatment comprises wide surgical excision, often with adjuvant radiotherapy. In general, PAC has a good prognosis. Previously, PAC was referred to as polymorphous low-grade adenocarcinoma (PLGA), but the new WHO classification of salivary gland tumours has also included under the PAC subheading, the so-called cribriform adenocarcinoma of minor salivary glands (CAMSG). This approach raised controversy, predominantly because of possible differences in clinical behaviour. For example, PLGA (PAC, classical variant) only rarely metastasizes, whereas CAMSG  often shows metastases to the neck lymph nodes. Given the controversy, this review reappraises the definition, epidemiology, clinical presentation, diagnostic work-up, genetics, treatment modalities, and prognosis of PAC of the salivary glands with a particular focus on contrasting differences with CAMSG.

Polymorphous low-grade adenocarcinoma of the head and neck

Polymorphous low-grade adenocarcinomas are rare tumors that can arise from many areas of the head and neck. We reviewed the pertinent literature pertaining to the incidence, diagnostic evaluation, and treatment strategies for this malignancy. Histopathologic diagnosis always involves careful analysis of tissue and especially characteristic immunohistochemical staining patterns. Common differential diagnoses include adenoid cystic carcinoma, pleomorphic adenoma, and other benign or malignant salivary gland neoplasms. Although the ideal treatment is debated, surgical resection at times combined with adjuvant radiation therapy is preferred by many physicians. Further research will be needed to delineate optimal management.

Review and Updates of Immunohistochemistry in Selected Salivary Gland and Head and Neck Tumors

Context

Immunohistochemistry is a useful tool for diagnosing salivary gland and head and neck tumors.

Objective

To review immunohistochemical markers, which can aid in the diagnosis of selected salivary gland and head and neck tumors.

Data Sources

Literature review and authors' personal practice experience.

Conclusions

Salivary gland and head and neck tumors include a large diverse group of tumors with complex and overlapping histologic features. Immunohistochemistry plays an important role in resolving the differential diagnosis of some salivary gland and head and neck tumors and can provide information for the prognosis of certain tumors.

Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma

Polymorphous low grade adenocarcinoma (PLGA) is a tumor of minor salivary glands that exhibits considerable morphologic overlap with adenoid cystic carcinoma and cellular pleomorphic adenoma, especially in small biopsy specimens. Unlike these other tumor types. PLGAs do not harbor a myoepithelial component, yet their frequent positivity for p63 diminishes the usefulness of this particular myoepithelial marker as a discriminating immunostain. p40 is an antibody that recognizes ΔNp63, a p63 isoform that is more specific for true myoepithelial differentiation. As such, p40 immunostaining could help distinguish PLGAs from adenoid cystic carcinomas and pleomorphic adenomas. In this study, p63 and p40 immunohistochemistry was performed on paraffin embedded, formalin fixed tissue from 11 PLGAs, 101 adenoid cystic carcinomas, and 31 pleomorphic adenomas. All 11 PLGAs (100 %) were positive for p63 but completely negative for p40. Among adenoid cystic carcinomas, 91 of 101 (90 %) were positive for p63 and 90/101 (89 %) were positive for p40. The single discordant p63+/p40- adenoid cystic carcinoma exhibited solid architecture and high grade features not typically seen in PLGA. Among pleomorphic adenomas, 21/31 (68 %) were positive for p63 and 13/31 (42 %) were positive for p40. For the pleomorphic adenomas, the discordant p63+/p40- staining pattern was seen only in the overtly mesenchymal chondromyxoid stroma. The cellular epithelial component of the pleomorphic adenomas demonstrated concordant p63+/p40+ or p63-/p40- immunophenotypes. PLGA consistently exhibits a p63+/p40- immunophenotype that can help distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma, tumors that characteristically demonstrate concordant p63 and p40 immunostaining patterns. A p63/p40 immunohistochemical panel can provide a valuable tool for making the distinction between these morphologically similar but clinically divergent entities.

Evaluation of c-kit protein (CD117) expression in common salivary gland neoplasms

BACKGROUND

Adenoid cystic carcinoma (AdCC) is a malignant salivary gland neoplasm with poor long-term prognosis. Differentiating between AdCC and other salivary gland neoplasms can be a diagnostic challenge, particularly in examining tissues obtained from small incisional biopsies.

AIM

The aim of this study was to evaluate c-kit expression in four common benign and malignant salivary gland neoplasms.

MATERIALS AND METHODS

Immunohistochemical techniques were used to analyze the level of c-kit expression in normal salivary gland (n = 10) and four different types of salivary gland tumors: Pleomorphic adenoma (PA) (n = 17), AdCC (n = 9), polymorphous low-grade adenocarcinoma (PLGA) (n = 4) and mucoepidermoid carcinoma (MEC) (n = 6). Samples were immunostained using monoclonal antibody against c-kit.

RESULTS

The immunoreactivity for c-kit was found in all cases of AdCC, PLGA and MEC and majority of PAs. Positive reactivity was observed in more than 50% of the tumor cells of AdCC and less than 50% in PLGA. PA did not show strong immunostaining and c-kit was predominantly localized to the cell membrane. Furthermore, the difference in the expression of c-kit between the benign and malignant neoplasms was not statistically significant.

CONCLUSIONS

CD117 expression itself cannot be used as a marker in differential diagnosis of salivary gland neoplasms. However, the percentage of the CD117 immunoreactive cells and the staining intensities appeared to be important factors in distinguishing AdCC from PLGA and PA.

Polymorphous Low-Grade Adenocarcinoma (PLGA) in an 18-Year-Old Male

Polymorphous low-grade adenocarcinoma (PLGA) is a minor salivary gland tumor with a low malignant potential. It is twice more common in females, with a mean age of presentation at 59 years. It is a very slow-growing tumor with mean duration of symptoms that range from 27 months to as long as 40 years. We report a case of a male patient who was found to have PLGA with symptoms since birth. The patient was treated with wide local excision with good results. The lip is a rare location for PLGA, and its occurrence in adolescent age groups is even rarer.

Immunohistochemical features of lacrimal gland epithelial tumors

PURPOSE

To investigate the immunohistochemical features of ocular adnexal pleomorphic adenoma and adenoid cystic carcinoma.

DESIGN

Retrospective clinicopathologic study.

METHODS

Clinical records and microscopic slides of 7 cases of each tumor type were reviewed. Immunohistochemical probes for Ki-67 and p53, and newer nuclear markers MYB for adenoid cystic carcinoma and PLAG1 for pleomorphic adenoma, were employed.

RESULTS

Pleomorphic adenomas were asymptomatic, whereas adenoid cystic carcinomas were painful. No pleomorphic adenomas recurred; 4 adenoid cystic carcinomas recurred, resulting in 3 deaths. Unusual histopathologic variants for which immunohistochemistry proved useful included a myoepithelioma, an atypical pleomorphic adenoma, tubular and solid/basaloid variants of adenoid cystic carcinoma, and a morphologically heterogeneous adenoid cystic carcinoma of a Wolfring gland. For the pleomorphic adenomas, the average Ki-67 proliferation index was 3.8%; p53 was weakly staining, with an average positivity of 18.5%; PLAG1 was strongly positive in all cases; MYB was negative in 5 cases and weakly focally positive in 2 cases. For the adenoid cystic carcinomas, the average Ki-67 proliferation index was 29.1%; p53 stained positively and strongly with an average of 39%; none stained positively for PLAG1; and 6 out of 7 were MYB positive.

CONCLUSIONS

Between pleomorphic adenoma and adenoid cystic carcinoma, there was no overlap in Ki-67 positivity. Positivity for p53 showed overlap in only one lesion of each type. PLAG1 and MYB positivity were highly discriminating between pleomorphic adenoma and adenoid cystic carcinoma. Immunohistochemical analysis should be investigated further for its role in the evaluation of pleomorphic adenoma and adenoid cystic carcinoma.

Mammaglobin and S-100 immunoreactivity in salivary gland carcinomas other than mammary analogue secretory carcinoma

Mammary analogue secretory carcinoma (MASC) is a recently described salivary gland tumor that has morphologic features similar to secretory carcinoma of the breast and that also harbors the same ETV6 translocation. Diffuse mammaglobin and S-100 immunoreactivity are used to differentiate MASC from its morphologic mimics, especially acinic cell carcinoma and adenocarcinoma, not otherwise specified. However, the combination of mammaglobin and S-100 immunoreactivity has not been well studied in other types of salivary gland carcinomas that may have focal areas reminiscent of MASC. Here we evaluated mammaglobin and S-100 immunoreactivity in 15 cases each of polymorphous low-grade adenocarcinoma, adenoid cystic carcinoma and mucoepidermoid carcinoma, and also in 2 cases of adenocarcinoma, not otherwise specified, and 1 mucinous adenocarcinoma. Cases with significant co-expression of mammaglobin and S-100 (moderate or strong immunoreactivity in >25% of tumor cells) were further analyzed by fluorescence in situ hybridization using the ETV6 (12p13) break-apart probe. Nine cases (60%) of polymorphous low-grade adenocarcinoma and two (13.3%) of adenoid cystic carcinoma met the criteria for significant co-expression of mammaglobin and S-100. All were negative for the ETV6 translocation by fluorescence in situ hybridization. Although mammaglobin and S-100 positivity was seen in the majority of polymorphous low-grade adenocarcinomas and a minority of adenoid cystic carcinomas, none were positive for the ETV6 translocation characteristic of MASC. This indicates a need for caution in the use of immunohistochemistry for diagnosing MASC, especially in the absence of cytogenetic confirmation.

Immunohistochemical clue for the histological overlap of salivary adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

It remains difficult to distinguish adenoid cystic carcinoma (ACC) from polymorphous low-grade adenocarcinoma (PLGA). Although these neoplasms exhibit nearly similar histologic patterns, their biologic behavior is significantly different. This study was carried out in an attempt to overcome the histological overlap between these tumors using immunohistochemical method for c-kit and galectin-3 proteins on twenty cases of salivary gland tumors including twelve ACC and eight PLGA. Results revealed positive cytoplasmic reactivity for c-kit in 100% of ACC cases and only in 25% of PLGA. On the other hand, galectin-3 expression was observed in 100% of both ACC and PLGA cases. Moreover, solid variant of ACC showed overexpression of both proteins than cribriform and tubular subtypes. Significant positive correlation between the two studied proteins in ACC and PLGA was also observed (p < 0.05). Upon these results, over expression of c-kit and galectin-3 in ACC cases supports the concept of solid variant as a high-grade tumor. Moreover, c-kit may be used as a helpful marker to distinguish ACC from PLGA in cases where the diagnosis can be challenging.

Polymorphous low-grade adenocarcinoma of maxillary alveolus metastasising to the abdomen: the role of immunomarkers in diagnosis

Polymorphous low-grade adenocarcinoma (PLGA) originating mostly in the minor salivary glands of the posterior hard and soft palate is characterised by its indolent growth and a slower rate of metastasis. Seldom does the PLGA present an aggressive behaviour and demonstrate distant metastasis, as in the present case where a 73-year-old female patient with a swelling in the maxillary alveolus was diagnosed as PLGA exhibiting high-grade transformation, subsequently metastasizing to the abdomen and lungs. The importance of immunomarkers, c-kit and ki-67 in deciphering the clinical behaviour of this PLGA is highlighted. Distant metastasis to the abdomen has not yet been reported; hence, this case of PLGA emphasises the importance of immunohistochemistry in assessing its aggressiveness and understanding a novel aspect of its pathogenesis.

Polymorphous low-grade adenocarcinoma: an analysis of epidemiological studies and hints for pathologists

Background

This study is an analysis of the prevalence of polymorphous low grade adenocarcinoma (PLGA) in epidemiological surveys of salivary tumors published in the English language from 1992 to 2012.

Methods

These surveys included studies from different researchers, countries and continents. The 57 surveys for which it was possible to calculate the percentage of PLGAs among all malignant minor salivary gland tumors (MMSGT) were included in this review.

Results

The statistical analyses show significant differences in the PLGA percentage by time period, country and continent in the studies included in this review. The percentage of PLGAs among MMSGTs varied among the studies, ranging from 0.0% to 46.8%. PLGA rates have varied over the period studied and have most recently increased. The frequency of reported PLGA cases also varied from 0.0% to 24.8% by the country in which the MMSGT studies were performed. The PLGA percentages also varied significantly by continent, with frequencies ranging from 3.9% in Asia to 20.0% in Oceania

Conclusion

Based on these results, we concluded that although the accuracy of PLGA diagnoses has improved, they remain a challenge for pathologists. To facilitate PLGA diagnoses, we have therefore made some suggestions for pathologists regarding tumors composed of single-layer strands of cells that form all of the histological patterns present in the tumor, consistency of the cytological appearance and uniformly positive CK7, vimentin and S100 immunohistochemistry, which indicate a single PLGA phenotype.

Virtual slide

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1059098656858324

The Molecular Pathology of Salivary Gland Tumors with Translocations

Presented here are the salivary gland tumors now recognized to have significant and highly prevalent translocations. These include both common and uncommon malignancies: mucoepidermoid carcinoma, adenoid cystic carcinoma, mammary analog secretory carcinoma, and clear cell carcinoma. These mutations have potential diagnostic applications, particularly in difficult and challenging variant morphologies are unusually challenging differential diagnoses. Practical applications of the molecular pathology of these tumors is discussed. The mutational assessment may also prove to have therapeutic importance, as targeted therapies may be generated for these tumors in the future.

Common Malignant Salivary Gland Epithelial Tumors

Malignant salivary gland epithelial tumors are histologically diverse with at least 24 recognized distinct entities. In general, malignant tumors account for 15% to 30% of parotid tumors, 40% to 45% of submandibular tumors, 70% to 90% of sublingual tumors, and 50% of minor salivary tumors. Common malignancies include mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma, salivary duct carcinoma, carcinoma ex pleomorphic adenoma, polymorphous lowgrade adenocarcinoma, and myoepithelial carcinoma. Each tumor type has its own unique histologic variants and prognostic pathologic features, and only mucoepidermoid carcinomas have a formalized grading system. The molecular pathogenesis of certain tumors, such as mucoepidermoid carcinoma and adenoid cystic carcinoma, has recently begun to be elucidated.

Molecular biology of adenoid cystic carcinoma

BACKGROUND

Adenoid cystic carcinoma (ACC) is an unusual salivary gland malignancy that remains poorly understood. Standard treatment, including surgery with postoperative radiation therapy, has attained reasonable local control rates, but the propensity for distant metastases has limited any improvement in survival over time. Our understanding of the molecular mechanisms driving ACC is quite rudimentary, due to the infrequent nature of its occurrence.

METHODS

An extensive literature review was performed on salivary gland ACCs and basic science research findings.

RESULTS

This review highlights many findings that are emerging about the carcinogenesis of ACC including cytogenetics, tumor suppressor genes, oncogenes, epigenetic alterations, mitochondrial alterations, and biomarker studies.

CONCLUSION

Although there have been many discoveries, much still remains unknown about this rare malignancy. © 2011 Wiley Periodicals, Inc. Head Neck, 2011.

An update on molecular diagnostics of squamous and salivary gland tumors of the head and neck

CONTEXT

Molecular testing in anatomic pathology is becoming standardized and can contribute valuable diagnostic, therapeutic, and prognostic information for the clinical management of patients. In head and neck pathology, recent advances in molecular testing have provided important targets in several different diagnostic areas, with particular emerging clinical applications in squamous and salivary gland pathology. In squamous mucosal-derived lesions, human papilloma virus has emerged as an important pathogenic etiology in a subset of oropharyngeal squamous cell carcinomas. Within the category of salivary gland tumors, 3 tumors have recently been recognized that contain oncogenic translocations.

OBJECTIVE

To describe the current state of information about the molecular alterations in squamous lesions and in salivary gland tumors of the head and neck.

DATA SOURCES

Published literature on squamous and salivary gland tumors of the head and neck.

CONCLUSIONS

The different approaches to identification of viral-associated tumors include assays using polymerase chain reaction, in situ hybridization, and immunohistochemistry. Most mucoepidermoid carcinomas harbor MECT1-MAML2 gene rearrangement. The MYB-NFIB translocations have recently been identified in adenoid cystic carcinomas. Finally, a newly described tumor of salivary gland, mammary analogue secretory carcinoma, harbors the ETV6-NTRK3 translocation. Although these translocations are just emerging as diagnostic targets, future roles may evolve as potential therapeutic targets.

Polymorphous low-grade adenocarcinoma: a review regarding an unusual presentation as infected odontogenic cyst

The World Health Organisation (WHO) classified polymorphous low-grade adenocarcinoma (PLGA) in 1990 as a low-grade malignancy; ICD-O 8525/3 being the assigned international code. It has been frequently described as occurring in hard- or soft-palate accessory salivary glands: some cases being described in the tongue and in major salivary glands. We present an extensive literature review about PLGA and the most common diagnostic pitfalls. We also report the first case where it was seen surrounding an impacted maxillary tooth and discuss it in regard to our review.

Hierarchical cluster analysis of myoepithelial/basal cell markers in adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

Distinguishing adenoid cystic carcinoma from polymorphous low-grade adenocarcinoma of the salivary glands is important for their management. We studied the expression of several myoepithelial and basal/stem cell markers (smooth muscle actin, calponin, smooth muscle myosin heavy chain, metallothionein, maspin, and p63) by immunohistochemistry in 23 adenoid cystic carcinoma and 24 polymorphous low-grade adenocarcinoma, to identify the most useful marker or combination of markers that may help their diagnoses. The results were analyzed using hierarchical cluster analysis and chi(2) test for trend. We noted diffuse expression of smooth muscle actin in 20 adenoid cystic carcinoma vs one polymorphous low-grade adenocarcinoma (P<0.0001), calponin in 15 adenoid cystic carcinoma vs one polymorphous low-grade adenocarcinoma (P<0.0001), smooth muscle myosin heavy chain in 15 adenoid cystic carcinoma vs one polymorphous low-grade adenocarcinoma (P=0.001), metallothionein in 22 adenoid cystic carcinoma vs eight polymorphous low-grade adenocarcinoma (P<0.001), maspin in 22 adenoid cystic carcinoma vs 14 polymorphous low-grade adenocarcinoma, and p63 in 21 adenoid cystic carcinoma vs 14 polymorphous low-grade adenocarcinoma. Hierarchical clustering of smooth muscle actin, calponin, smooth muscle myosin heavy chain, and metallothionein was virtually identical (kappa< or =0.0035), suggesting no significant advantage to their use in combination than individually. Diffuse smooth muscle actin expression showed the highest accuracy (91.5%) and positive predictive value (95.2%) for adenoid cystic carcinoma. Thus, diffuse expression of smooth muscle actin, calponin, smooth muscle myosin heavy chain, and metallothionein was highly predictive of adenoid cystic carcinoma, whereas maspin and p63 were frequently expressed in both tumors. In differentiating adenoid cystic carcinoma from polymorphous low-grade adenocarcinoma, smooth muscle actin as a single ancillary test in support of the histological findings, appears to be as efficient as multiple immunohistochemical tests.

Immunohistochemical expression of vimentin, calponin and HHF-35 in salivary gland tumors

Myoepithelial cells present a complex immunophenotype, with the expression of proteins varying according to the stage of normal or neoplastic differentiation of the cell. In order to evaluate the immunohistochemical markers expressed by these cells, a panel of antibodies composed of vimentin, calponin and HHF-35 was applied to 28 salivary gland tumors. The results demonstrated a higher percent sensitivity of vimentin and calponin compared to HHF-35. However, calponin and HHF-35 presented a focal labeling pattern in contrast with the diffuse distribution of vimentin. The cells predominantly stained by all tested antibodies included nonluminal cells in duct-like and tubular structures, such as those seen in pleomorphic adenomas and adenoid cystic carcinomas, as well as cells in the cords and nests of polymorphous low-grade adenocarcinomas and peripheral cells of sheets and nests of myoepitheliomas. In conclusion, the combination of calponin and vimentin is suggested for the identification of myoepithelial cells in salivary gland tumors.