Comparison of p63 and p40 (ΔNp63) as Basal, Squamoid, and Myoepithelial Markers in Salivary Gland Tumors

Updates in head and neck cytopathology: Insights from European Congress of Pathology Short Course

Cytological specimens play a pivotal role in head and neck nodule/mass work up and diagnoses. The specimens´ importance has grown with the onset of personalized medicine and the routine use of molecular markers in the diagnostic work up. The Updates in Head and Neck Cytopathology Short Course ran during the 35th European Congress of Pathology held in Dublin, Ireland, in 2023 and brought together experts in cytopathology, pathology, and related fields to share their expertise and experience in the field of head and neck cytopathology and its future directions. Topics such as a one-stop clinic, the Milan System for Reporting Salivary Gland Cytopathology, next generation sequencing, and human papilloma virus detection in the head and neck area were covered during the short course. These topics are briefly summarized in the present review.

Proceedings of the 2024 North American Society of Head and Neck Pathology Companion Meeting, Baltimore, MD, March 24, 2024: Navigating Ancillary Studies in Basaloid/Blue Salivary Tumors

BACKGROUND

Basaloid salivary tumors can demonstrate significant morphologic overlap and be challenging to diagnose.

METHODS

A review of select ancillary studies in basaloid salivary tumors was performed.

RESULTS

A number of immunohistochemical stains, including PLAG1, HMGA2, β-catenin, MYB, and RAS Q61R, have been more recently incorporated into the diagnostic workup of basaloid salivary tumors.

CONCLUSIONS

Although reported variability in their performance has perhaps limited their widespread adoption, these immunohistochemical studies can nevertheless be useful in supporting pathologic diagnoses, particularly when considered in more specific differentials or when used as a panel with other markers.

Canalicular-Like Pleomorphic Adenoma of the Parotid Gland: A Recently Classified Tumor Highlighting the Use of Frozen Section Analysis and Surrogate IHC for Gene Rearrangement Defined Subtypes

Canalicular-like pleomorphic adenomas are a relatively recently described entity, that possess features of both canalicular adenomas and pleomorphic adenomas. The presence of unusual HMGA2-fusion partners (most commonly HMGA2::WIF1 gene fusions) has established canalicular-like pleomorphic adenoma as a distinct entity. The use of intraoperative frozen section analysis and surrogate HMGA2 IHC are 2 tools that can provide the surgical team with valuable insight into intraoperative decision making and final classification of rare tumors of the parotid gland, respectively. We present a case of canalicular-like pleomorphic adenoma and characterize its appearance on frozen section analysis. HMGA2 IHC staining was retroactively performed, assisting in the confirmation of the tumor subtype.

Recent developments in the pathology of primary pulmonary salivary gland-type tumours

Primary pulmonary salivary gland-type tumours are rare neoplasms that are thought to arise from seromucinous glands that are located in the submucosa of large airways. These neoplasms have clinical and pathologic features that are distinct from other pulmonary neoplasms. The majority of primary pulmonary salivary gland-type tumours are malignant, with the most common entities being mucoepidermoid carcinoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma. Less commonly seen are myoepithelial carcinoma, hyalinizing clear cell carcinoma, acinic cell carcinoma, secretory carcinoma, salivary duct carcinoma, intraductal carcinoma, and polymorphous adenocarcinoma. Benign salivary gland-type tumours of the lung include pleomorphic adenoma and sialadenoma papilliferum. Morphologic, immunophenotypic, and molecular features of these neoplasms are largely similar to salivary gland tumours elsewhere, and therefore the exclusion of metastatic disease requires clinical and radiologic correlation. However, the differential diagnostic considerations are different in the lung. The distinction of salivary gland-type tumours from their histologic mimics is important for both prognostication and treatment decisions. Overall, salivary gland type-tumours tend to have a more favourable outcome than other pulmonary carcinomas, although high-grade variants exist for many of these tumour types. Recent advances in our understanding of the spectrum of salivary gland-type tumours reported in the lung and their diversity of molecular and immunohistochemical features have helped to refine the classification of these tumours and have highlighted a few differences between salivary gland-type tumours of the lung and those primary to other sites.

Primary Cutaneous Mucinous Carcinoma: A Review of the Literature

BACKGROUND

Primary cutaneous mucinous carcinoma (PCMC) is an exceedingly rare, low-grade tumor that histologically resembles mucinous carcinoma from other primary sites, such as the breast, gastrointestinal tract, and lungs.

OBJECTIVE

The purpose of this article was to review the current literature on PCMC as it relates to epidemiology, clinical presentation, histopathology, immunohistochemistry, treatment, and prognosis.

MATERIALS AND METHODS

An extensive literature review was conducted using PubMed and Ovid MEDLINE to identify articles related to PCMC.

RESULTS

Several hundred cases have been reported in the medical literature, and surgical resection, whenever feasible, is the standard of care.

CONCLUSION

The diagnosis of primary cutaneous mucinous carcinoma is one of exclusion, requiring a metastatic work-up to rule out distant primary. Mohs micrographic surgery is a tissue sparing technique that allows complete margin control of these rare neoplasia.

J, Rajagopal, Sarada. Huge Recurrent Mucoepidermoid Carcinoma of Parotid - a Rare Presentation

Mucoepidermoid carcinoma is the commonest primary malignant salivary gland tumor in both children and adults and constitutes around 2.8-16% of all salivary gland tumors. There is a wide age range of 3 to 95 years with a mean age of 47 years. We reported a case of 85 years old female patient, who presented to the department of Surgical Oncology, Srinivasan Medical College and Hospital, Trichy, with history of right parotid swelling for past 25 years, who had undergone Superficial parotidectomy 10 years back, followed by recurrence of tumor with huge increase in size, around 20 cm in greatest dimension. Right Completion Radical Parotidectomy with Modified Radical neck dissection type 1 with Cervical Rotation Flap cover was done and histopathological examination of the surgical specimen confirmed as high grade Mucoepidermoid carcinoma. Following surgery, the patient's outcome is better, uneventful with periodic regular follow-up.

MYB RNA detection by in situ hybridisation has high sensitivity and specificity for the diagnosis of adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is one of the most common primary salivary gland cancers. ACC has several benign and malignant mimics amongst salivary gland neoplasms. An accurate diagnosis of ACC is essential for optimal management of the patients and their follow-up. Upregulation of MYB has been described in 85-90% of ACC, but not in other salivary gland neoplasms. In ACC, MYB upregulation can occur as a result of a genetic rearrangement t(6;9) (q22-23;p23-24), MYB copy number variation (CNV), or enhancer hijacking of MYB. All mechanisms of MYB upregulation result in increased RNA transcription that can be detected using RNA in situ hybridisation (ISH) methods. In this study, utilising 138 primary salivary gland neoplasms including 78 ACC, we evaluate the diagnostic utility of MYB RNA ISH for distinguishing ACC from other primary salivary gland neoplasms with a prominent cribriform architecture including pleomorphic adenoma, basal cell adenoma, basal cell adenocarcinoma, epithelial myoepithelial carcinoma, and polymorphous adenocarcinoma. Fluorescent in situ hybridisation and next generation sequencing were also performed to evaluate the sensitivity and specificity of RNA ISH for detecting increased MYB RNA when MYB gene alterations were present. Detection of MYB RNA has 92.3% sensitivity and 98.2% specificity for a diagnosis of ACC amongst salivary gland neoplasms. The sensitivity of MYB RNA detection by ISH (92.3%) is significantly higher than that of the FISH MYB break-apart probe (42%) for ACC. Next generation sequencing did not demonstrate MYB alterations in cases that lacked MYB RNA overexpression indicating high sensitivity of MYB RNA ISH for detecting MYB gene alterations. The possibility that the sensitivity may be higher in clinical practice with contemporary samples as compared with older retrospective tissue samples with RNA degradation is not entirely excluded. In addition to the high sensitivity and specificity, MYB RNA testing can be performed using standard IHC platforms and protocols and evaluated using brightfield microscopy making it a time and cost-efficient diagnostic tool in routine clinical practice.

Challenging Metastatic Melanoma to the Lung With p40 Expression: A Diagnostic Pitfall, Case Report

p40 immunohistochemistry is a cornerstone of histopathological examination for non-small cell lung carcinoma. p40 is an isoform of p63 and is reported to be highly specific for the diagnosis of squamous cell carcinoma. Very rare pitfalls are reported for this antibody, and p40 is typically negative in melanoma. A 66-year-old patient was admitted for multiple hemorrhagic brain tumors evocative of secondary tumors. On imaging, a 26 mm lung tumor was detected, and a biopsy of the lung tumor was performed. The tumor was stained by melanic markers and diffusely stained by p40 and p63. Molecular analysis found a somatic p.Asn581Ser (c.1742A>G) point mutation in exon 15 of BRAF and a p.Arg80Ter (c.238C>T) germline variant of CDKN2A , a predisposing mutation to melanoma. This case report highlights the importance of clinical, pathologic, and molecular correlation.

Expression of p40 in Primary Cutaneous Mucinous Carcinoma Versus Primary Mucinous Carcinomas of the Breast and Colon

BACKGROUND

The transcription factor p63 is a homolog of p53, expressed in basal layers of epithelia and myoepithelial cells. Some studies have suggested that p63 may provide utility in differentiating primary versus metastatic mucinous carcinoma of the skin, given its preferential expression in primary adnexal neoplasms. There have been few studies investigating the expression patterns of p40, an isoform of p63, in primary cutaneous mucinous carcinomas.

METHODS

An immunohistochemical panel including p40, CK7, CK20, estrogen receptor, and progesterone receptor was applied to primary mucinous carcinomas of the skin, breast, and colon.

RESULTS

Only a small subset (25%) of primary cutaneous mucinous carcinomas displayed focal positive staining with p40, similar to what has been reported in the literature for p63. All primary mucinous carcinomas of skin and breast labeled positively with CK7, estrogen receptor, and progesterone receptor. Primary colon mucinous carcinomas were only positive for CK20.

CONCLUSIONS

Based on these results, p40 seems to be an insufficient marker for distinguishing primary versus metastatic mucinous carcinoma due to its low rate of positivity in primary cutaneous mucinous carcinomas.

Practical immunohistochemistry in the classification of salivary gland neoplasms

Diagnosis of salivary gland neoplasms can be challenging for surgical pathologists due to low incidence of tumors as well as overlapping histologic features. On small biopsy, the most important information to be conveyed for clinical management is the distinction between a benign/low grade tumor and a high grade carcinoma. This review will discuss the differential diagnosis of salivary gland tumors based on four broad morphologic patterns: basaloid/tubular/cribriform, (micro)cystic/secretory/mucinous, solid-nested/clear-spindled, and oncocytic/oncocytoid. With the assistance of immunohistochemistry, demonstration of the number of cell types (mainly epithelial versus myoepithelial/basal) can further subclassify tumors within these morphologic categories. Additional tumor-specific immunomarkers are useful in some cases. Underlying tumor-specific genetic anomalies can be of value, however, immunohistochemical correlates are only available for some. When used judiciously, in the correct morphologic context, and with knowledge of their limitations, immunohistochemical stains can aid in differentiating tumors with similar morphology.

Classic polymorphous adenocarcinoma: Fine needle aspiration cytopathology of eight cases

INTRODUCTION

The cytopathology and diagnostic accuracy of salivary gland (SG) polymorphous adenocarcinoma (PAC) is the subject of a limited number of reports. We undertook a review of our experience with fine needle aspiration (FNA) biopsy and PAC.

MATERIALS AND METHODS

A search was made of our cytopathology files for PAC cases that also had histopathological confirmation. FNA biopsy smears and cell-blocks were performed and examined using standard techniques.

RESULTS

Eight FNA biopsy cases of histologically proven PAC from 7 patients [F:M = 1.3:1, age 39-75 years, mean = 58] met study inclusion. Metastatic aspirates were most common (4), followed by 3 primary cases and 1 locally recurrent neoplasm. Primary FNA sites included hard palate (1 case), lip (1), and lateral tongue (1); all metastatic sites were in the neck. A precise cytologic diagnosis was made in 38% of cases; however, when applying the Milan classification system, 100% could be categorised as either malignant or of uncertain malignant potential. Ancillary immunohistochemical testing performed in 44% of the cases was non-specific. Cytologic smears showed cellular uniformity and structural variety of cell groups with tubular, branching, cribriform, and convex patterns as well as variable, but occasionally abundant globular myxoid stroma leading to confusion with adenoid cystic carcinoma.

CONCLUSION

The imitative cytopathology of PAC with other SG neoplasms as well as its infrequency in routine FNA biopsy practice makes specific interpretation difficult, but using a classification system allows for appropriate patient management. Molecular testing in future specimens holds promise for enhancing diagnostic accuracy.

The Decline of Salivary Adenocarcinoma Not Otherwise Specified as a Tumor Entity: Reclassification Using Contemporary Immunohistochemical Profiling and Diagnostic Criteria

The classification of salivary gland carcinomas has become increasingly specific over the last decade with the definition of new tumor types, documentation of novel molecular and immunohistochemical findings, and development of more refined diagnostic criteria. In this setting, it is unclear how many salivary tumors still cannot be easily categorized-and whether such tumors represent undifferentiated malignancies or include additional definable entities. Relying largely on current classification schemes and contemporary immunohistochemical panels, we reassessed salivary tumors previously diagnosed as adenocarcinoma, not otherwise specified (ACA NOS) from 2 large academic medical centers. Fifty-seven ACA NOS (72%) could be reclassified as more specific entities including 31 salivary duct carcinomas (39%), 7 polymorphous adenocarcinomas (9%), 5 epithelial-myoepithelial carcinomas (6%), 4 myoepithelial carcinomas (5%), 4 secretory carcinomas (5%), 1 acinic cell carcinoma (1%), 1 basal cell adenocarcinoma (1%), 1 intraductal carcinoma (1%), and 1 clear cell carcinoma (1%) as well as 2 metastatic squamous cell carcinomas (3%). Of reclassified cases, 21 (37%) represented variant histologies within these categories. ACA NOS comprised 11% of salivary malignancies before reclassification, but only 4% after reclassification. The remaining 22 ACA NOS demonstrated heterogeneous features, with an association between histologic grade and clinical outcome. In effect, ACA NOS is becoming a bygone entity as modern classification schemes and ancillary techniques now permit more specific typing of a majority of these tumors, potentially facilitating more specific prognostication and treatment. Additional distinctive entities such as mucinous adenocarcinoma may still be definable within the ACA NOS category.

Diagnostic utility of p63/p40 in the histologic differentiation of salivary gland tumors: A systematic review

OBJECTIVE

Salivary gland tumors are a heterogeneous group of neoplasms with complex clinicopathologic behavior. These tumors often show an extremely diverse morphology and significant histologic patterns, making diagnosis a difficult task. Owing to the considerable differences in prognosis, treatment, and follow-up, accurately distinguishing these histologic mimickers is imperative. The aim of the present systematic review was to establish the diagnostic utility of p63/p40 immunostaining in histologic differentiation of salivary gland tumors.

STUDY DESIGN

An electronic search was carried out using MEDLINE by PubMed, Scopus, Google Scholar, Trip, Cochrane Library, and EMBASE databases. Articles in which both p63 and p40 immunohistochemical expressions were assessed were included for systematic review and their sensitivity and specificity were calculated. Risk of bias was analyzed for each study using the Quality Assessment of Diagnostic Accuracy Studies tool.

RESULTS

Ten eligible articles were included in the quantitative synthesis, which revealed a concordant positivity of p63 and p40 by nearly all cases of adenoid cystic carcinoma, pleomorphic adenoma, and mucoepidermoid carcinoma and most polymorphous adenocarcinomas showed discordant immunohistochemical expression (p63+/p40-).

CONCLUSIONS

The current evidence supports that integrated immunostaining of p63/p40 is a valuable adjunct for discerning enigmatic salivary gland tumors with true myoepithelial and/or squamous differentiation.

MYB RNA In Situ Hybridization Facilitates Sensitive and Specific Diagnosis of Adenoid Cystic Carcinoma Regardless of Translocation Status

Adenoid cystic carcinoma (AdCC) can demonstrate histologic and immunohistochemical (IHC) overlap with a wide range of salivary and nonsalivary tumors, especially in small biopsy specimens. While MYB fluorescence in situ hybridization (FISH) frequently is used to confirm the diagnosis of AdCC, the pathognomonic MYB-NFIB fusion is only present in 40% to 70% of cases. Likewise, although MYB RNA overexpression is seen in the vast majority of AdCC regardless of translocation status, MYB IHC has shown suboptimal specificity for this diagnosis. In this study, we sought to determine whether a novel chromogenic RNA in situ hybridization (ISH) platform could directly detect MYB RNA overexpression and offer a rapid diagnostic adjunct for AdCC. We performed MYB RNA ISH on 84 cases of AdCC as well as 128 other salivary tumors and 108 basaloid and sinonasal carcinomas that mimic AdCC. MYB RNA ISH was 92% sensitive for AdCC, including 97% of cases with MYB rearrangement and 83% without MYB rearrangement by FISH. It was also 89% specific for AdCC overall, with 95% specificity among other salivary tumors and 81% specificity in basaloid and sinonasal carcinomas. In contrast, MYB IHC was 94% sensitive but just 54% specific for AdCC. Overall, MYB RNA ISH provides superior sensitivity for the diagnosis of AdCC compared with MYB FISH and superior specificity compared with MYB IHC. This assay could provide a useful tool for rapidly confirming the diagnosis of AdCC in formalin-fixed, paraffin-embedded specimens.

Emerging Entities in Salivary Pathology: A Practical Review of Sclerosing Microcystic Adenocarcinoma, Microsecretory Adenocarcinoma, and Secretory Myoepithelial Carcinoma

In recent years, increased molecular testing and improved immunohistochemical panels have facilitated more specific classification of salivary gland carcinomas, leading to recognition of several novel tumor types and unique histologic variants. Sclerosing microcystic adenocarcinoma, microsecretory adenocarcinoma, and secretory myoepithelial carcinoma are three such recently described entities that demonstrate low-grade cytology, production of prominent secretory material, and variable amounts of sclerotic stroma. This review provides a practical overview of these important and overlapping emerging entities in salivary gland pathology with a focus on distinctive histologic features and helpful ancillary studies that differentiate them from a wide range of familiar morphologic mimics.

p63 expression in human tumors and normal tissues: a tissue microarray study on 10,200 tumors

Background

Tumor protein 63 (p63) is a transcription factor of the p53 gene family involved in differentiation of several tissues including squamous epithelium. p63 immunohistochemistry is broadly used for tumor classification but published data on its expression in cancer is conflicting.

Methods

To comprehensively catalogue p63 expression, tissue microarrays (TMAs) containing 12,620 tissue samples from 115 tumor entities and 76 normal tissue types were analyzed.

Results

p63 expression was seen in various normal tissues including squamous epithelium and urothelium. At least occasional weak p63 positivity could be detected in 61 (53%) of 115 different tumor types. The frequencies of p63 positivity was highest in squamous cell carcinomas irrespective of their origin (96–100%), thymic tumors (100%), urothelial carcinomas (81–100%), basal type tumors such as basal cell carcinomas (100%), and various salivary gland neoplasias (81–100%). As a rule, p63 was mostly expressed in cancers derived from p63 positive normal tissues and mostly not detectable in tumors derived from p63 negative cancers. However, exceptions from this rule occurred. A positive p63 immunostaining in cancers derived from p63 negative tissues was unrelated to aggressive phenotype in 422 pancreatic cancers, 160 endometrium cancers and 374 ovarian cancers and might be caused by aberrant squamous differentiation or represent stem cell properties. In 355 gastric cancers, aberrant p63 expression occurred in 4% and was linked to lymph node metastasis (p = 0.0208). Loss of p63 in urothelial carcinomas - derived from p63 positive urothelium - was significantly linked to advanced stage, high grade (p < 0.0001 each) and poor survival (p < 0.0001) and might reflect clinically relevant tumor dedifferentiation.

Conclusion

The high prevalence of p63 expression in specific tumor types makes p63 immunohistochemistry a suitable diagnostic tool. Loss of p63 expression might constitute a feature of aggressive cancers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40364-021-00260-5.

Basal Cell Adenoma and Basal Cell Adenocarcinoma

Basal cell adenoma (BCA) and basal cell adenocarcinoma (BCAC) are uncommon biphasic salivary gland tumors having morphologic similarities to other biphasic salivary gland neoplasms having differentiation toward the intercalated ducts of the salivary gland. Both tumors show mixtures of trabecular, tubular, solid, and membranous solid patterns. BCAC is separated from BCA primarily by the presence of invasion in the former. The diagnosis of BCA and BCAC is best carried out with hematoxylin and eosin-stained sections and careful attention to detail of tumors in the differential diagnosis, including adenoid cystic carcinoma, pleomorphic adenoma, and epithelial myoepithelial carcinoma.

Carcinoma Showing Thymus-Like Differentiation (CASTLE) Arising in the Sublingual Gland

Carcinoma showing thymic-like differentiation (CASTLE) is a rare tumor most commonly occurring in the thyroid and soft tissues of the neck. We report the first case of CASTLE occurring in the sublingual gland. The patient, a 35-year-old healthy man, presented with a submucosal lesion located in the anterior right floor of the oral cavity and an ipsilateral neck mass. The lesion had been previously investigated by neck computed tomography and ultrasound-guided fine needle aspiration cytology and diagnosed as metastatic squamous cell carcinoma. After oral cavity magnetic resonance imaging, positron emission tomography, and a non-diriment, fine needle aspiration cytology of the sublingual mass, the patient was treated as affected by a sublingual gland malignancy with removal of primary tumor and neck dissection. Morphological and immunohistochemical findings were diagnostic for primary sublingual gland CASTLE. The patient received adjuvant radiotherapy and is free of disease 2 years after treatment. We describe the pathological features of the lesion and discuss the possible differential diagnoses.

Navigating small biopsies of salivary gland tumors: a pattern-based approach

Diagnosis of salivary gland tumors on small biopsy can be difficult because of overlapping morphology, limited tissue availability, and technical artifact. Although a specific diagnosis is not feasible in all cases, a cautious and thoughtful approach to the differential diagnosis and a keen awareness of clinical consequences can facilitate the most complete and useful classification possible. In this review, we present a general strategy for the evaluation of small salivary biopsies, including consideration of clinical and radiographic information, systematic assessment of histologic patterns, and judicious use of immunohistochemistry and molecular studies. We then focus on the distinctive differential diagnoses raised by 6 specific histologic patterns: tubular and cribriform architecture, squamous differentiation, mucin and other secretions, high-grade cytology, epithelial and lymphoid elements, and oncocytic features. Throughout this systematic and pattern-based approach, we focus on practical and cost-effective strategies to overcome the most common diagnostic challenges in limited material.

Adamantinoma-like Ewing Sarcoma of the Salivary Glands: A Newly Recognized Mimicker of Basaloid Salivary Carcinomas

Adamantinoma-like Ewing sarcoma (ALES) is a rare tumor that demonstrates the EWSR1-FLI1 translocation characteristic of Ewing sarcoma despite overt epithelial differentiation including diffuse expression of cytokeratins and p40. Most cases of ALES described to date have occurred in the head and neck where they can mimic a wide range of small round blue cell tumors. Because distinguishing ALES from basaloid salivary gland carcinomas can be particularly difficult, we analyzed a series of 10 ALESs that occurred in the salivary glands with the aim of identifying features that allow for better recognition of this entity. The salivary ALESs included 8 parotid gland and 2 submandibular gland tumors in patients ranging from 32 to 77 years (mean: 52 y). Nine were initially misclassified as various epithelial neoplasms. Although these tumors displayed the basaloid cytology, rosette formation, infiltrative growth, and nuclear monotony characteristic of ALES, peripheral palisading and overt keratinization were relatively rare in this site. Salivary ALESs not only displayed positivity for AE1/AE3, p40, and CD99, but also demonstrated a higher proportion of synaptophysin reactivity than has been reported for nonsalivary ALESs. These morphologic and immunohistochemical findings make ALES susceptible to misclassification as various other tumors including basal cell adenocarcinoma, adenoid cystic carcinoma, squamous cell carcinoma, NUT carcinoma, large cell neuroendocrine carcinoma and myoepithelial carcinoma. Nevertheless, monotonous cytology despite highly infiltrative growth and concomitant positivity for p40 and synaptophysin can provide important clues for consideration of ALES, and identification of the defining EWSR1-FLI1 translocations can confirm the diagnosis.

Challenges in Minor Salivary Gland Biopsies: A Practical Approach to Problematic Histologic Patterns

Evaluation of minor salivary gland biopsy can be fraught with a wide range of problems, including technical limitations due to the small size and distorted nature of tissue received and interpretive difficulties navigating the considerable morphologic and immunohistochemical overlap between widely disparate entities. As such, common pathologic findings can evoke a perplexing differential diagnosis that encompasses malignant, benign, and non-neoplastic processes. This review will present the diagnostic considerations that arise from four histologic patterns that are frequently encountered on minor salivary gland biopsies: squamous differentiation, tubular and cribriform growth, mucin production, and myxoid stroma. The discussion herein will emphasize practical strategies and priorities for navigating these differential diagnoses in a clinically-relevant and cost-effective manner.

Comparison of p63/p40 Expression With Myoepithelial Markers in Minor Salivary Gland Tumors

The present study aimed to compare the expression of p63/p40 with smooth muscle actin (SMA) and vimentin (VIM) by myoepithelial cells in minor salivary gland tumors. Fifty-two formalin-fixed paraffin-embedded samples of minor salivary gland tumors derived from intercalated duct (pleomorphic adenoma [PA], adenoid cystic carcinoma [ACC], epithelial-myoepithelial carcinoma [EMC], polymorphous adenocarcinoma [PAC], and secretory carcinoma [SC]) and 3 samples of minor salivary gland tumors derived from excretory duct (mucoepidermoid carcinoma [MEC]) were evaluated by means of immunohistochemistry. The data were analyzed qualitatively. The results indicated that p63 and p40 expression were detected in myoepithelial cells present in PA, ACC, and EMC. However, both proteins were also observed in squamous areas of PA and all cases of MEC. SMA were noticed in some myoepithelial cells of PA, ACC, and EMC. Expression of SMA was negative in the other salivary gland tumors evaluated. VIM was constantly expressed by myoepithelial cells in PA, ACC, and EMC. VIM was also observed in cells of PAC and SC, but not in squamous areas of PA and MEC. In conclusion, p63 expression is almost comparable with VIM in detecting myoepithelial cells, an immunolabeling pattern not followed by p40, and consequently, caution has to be taken during the interpretation of salivary gland tumor exhibiting an p63/p40 phenotype in order to avoid a misdiagnosis.

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.

Sialadenoma Papilliferum: Analysis of Seven New Cases and Review of the Literature

Sialadenoma papilliferum (SP) is a rare benign salivary gland neoplasm that comprises from 0.4 to 1.2% of all salivary gland tumors. The tumor is so named because of its microscopic resemblance to the syringocystadenoma papilliferum, an uncommon benign tumor of sweat gland origin. The purpose of this paper is to report the clinical and microscopic features of seven new cases of SP and combine them with cases previously reported in the English language literature to further define this unusual lesion. Combining our cases with acceptable cases from the literature, the palate (especially the hard palate) was the most common site, with 80% of the cases occurring in this location. Other locations in decreasing order were buccal mucosa, upper lip, retromolar pad, and parotid gland. Age at diagnosis ranged from 18 to 87 years with a peak in the 6th decade and an average age of 56.4 years. Microscopically, the lesions demonstrated a papillary surface morphology, and the papillary projections varied from long and pointed to short and blunted. The supporting connective tissue contained a variable number of convoluted ductal structures, which often fused with the overlying surface epithelium. The ductal structures exhibited papillary infoldings and were lined by a double layer of epithelium consisting of basal cell layer and a luminal layer of cuboidal-to-columnar ductal cells. Immunohistochemical reactivity with p63 and p40 indicated that the basal cell layer was comprised predominantly of neoplastic myoepithelial cells. The luminal cells were immunoreactive with epithelial membrane antigen characteristic of ductal cell differentiation. Conservative surgical treatment was accomplished in most cases and appears to be adequate treatment as only two recurrences were documented. Several case reports of purported malignant transformation in SP have been reported in the literature, but in our opinion, there is insufficient evidence in the publications to unequivocally determine whether any of the malignancies truly originated within a pre-existing SP.

Mucoepidermoid carcinoma of the sublingual gland harboring a translocation of the MAML2 gene: A case report

Among tumors of the major salivary glands, tumors in the sublingual gland are rare. Although mucoepidermoid carcinoma (MEC) represents a histological type of salivary gland tumor, it is occasionally difficult to diagnose due to its histological variation. The present study reports a case of MEC harboring a mastermind-like transcriptional coactivator 2 (MAML2) gene translocation in the sublingual gland. A 76-year-old Japanese woman with a mass in the left submandibular region was referred to Kurume University Hospital (Kurume, Japan). Computed tomography scans revealed that the tumor was predominantly located in the sublingual gland, and tumor resection was performed. Histologically, the tumor was composed of cells that exhibited low-grade nuclear atypia and clear and/or granular eosinophilic cytoplasm, and that were proliferating in solid patterns. Periodic acid-Schiff and alcian blue staining revealed a small number of mucinous cells in the tumor. Immunohistochemically, the tumor cells were positive for p40 and p63. Fluorescence in situ hybridization (FISH) analysis revealed a MAML2 gene split. The definitive pathological diagnosis was low-grade MEC, as the case lacked any factors indicative of high-grade malignancy. To the best of our knowledge, this is the first report of MEC in the sublingual gland with MAML2 gene translocation confirmed by FISH.

Divergent Schwannoma-Like Phenotype in a Pleomorphic Adenoma

The schwannoma-like pleomorphic adenoma is a rare histopathological variant of the pleomorphic adenoma. Five previous reports with seven cases exist in English language literature. These tumors present in the parotid gland most commonly. Intraparotid schwannomas of the facial nerve and schwannomas with glandular differentiation have also been reported. A 60-year-old male presented with an asymptomatic swelling over the left angle of the mandible. The swelling had been present for about 12 years with a recent increase in size. CT imaging showed a hyperdense circumscribed mass of the superficial lobe of the parotid. The working diagnosis was that of a benign tumor of salivary gland or soft tissue origin. The mass was excised with careful preservation of the facial nerve. The 3.5 cm mass was submitted for histopathological examination. The well-circumscribed, encapsulated mass showed a predominant sheet-like proliferation of Antoni type A-like tissue, Foci of glandular differentiation with duct-like structures were also seen. Cytological atypia or mitotic activity were not seen. Nuclei of lesional cells diffusely and strongly expressed reactivity to p63. The final diagnosis was a schwannoma-like pleomorphic adenoma. No recurrence has been reported in the 15 months since the removal. Facial nerve function is unimpaired with a House Brackmann facial nerve function score of one. The potential for misdiagnosis in fine needle aspirate and incisional biopsies is real in cases of schwannoma-like pleomorphic adenoma. The diagnostic pitfalls include the schwannoma and leiomyoma. Schwannomas with glandular differentiation have also been reported and therefore a misdiagnosis may potentially occur in excised specimens. Careful application of immunohistochemistry may help in the differentiation of these lesions.

Oral Adenosquamous Carcinoma Mimicking a Pyogenic Granuloma: a Challenging Diagnosis

Adenosquamous carcinoma is an aggressive variant of squamous cell carcinoma. This report describes a case of adenosquamous carcinoma with clinical features of a benign lesion and discusses the differential diagnoses, especially regarding histopathological and immunohistochemical analyses. A 45-year-old male was referred to our outpatient clinic complaining about a rapid-growing enlargement in hard palate. Clinical examination revealed an erythematous and pedunculated nodule with lobulated non-ulcerated surface. Excisional biopsy was performed following clinical diagnosis of pyogenic granuloma. Histologically, the specimen consisted of areas characterizing both well-differentiated squamous cell carcinoma and true adenocarcinoma. After a broad list of immunohistochemical markers was evaluated (AE1/AE3, CEA, CK5, CK7, CK8/18, p53, p63 and Ki67), the diagnosis of adenosquamous carcinoma was rendered and the patient referred to complementary surgery. Adenosquamous carcinoma represents a challenge in diagnostic routine due to its rarity, diverse range of clinical presentations and histological features. Furthermore, classical clinical benign features may be present in malignant lesions; hence the submission of every surgical specimen to histological analysis is mandatory to provide the patient the adequate treatment.

Basaloid/blue salivary gland tumors

Basaloid tumors are a common diagnostic problem in salivary gland pathology. However, delineating each of these tumor types is facilitated by an algorithmic approach incorporated by tumor border and cell types. This approach greatly diminishes the challenge of separating polymorphous low-grade adenocarcinoma (PLGA) from adenoid cystic carcinoma (ACC). Despite the overlap in growth pattern, ACC is biphasic while PLGA is not. More relevant challenges, namely differentiation of the biphasic basaloid neoplasms including: epithelial-myoepithelial carcinoma (EMCA), cellular pleomorphic adenoma (PA), basal cell adenoma (BCA), and basal cell adenocarcinoma (BCAC), are resolved by a combination of morphologic, immunophenotypic, and to a limited extent, molecular features. Among the most challenging scenarios is high-grade transformation of any of the aforementioned entities. Here, the diagnosis requires recognition of a conventional component and exclusion of metastatic (or in some cases primary) SCC and even select neuroendocrine carcinomas and sarcomas in some cases.