Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin

Microsecretory adenocarcinoma of the hard palate: a case report and literature review

Microsecretory adenocarcinoma (MSA) is a new type of salivary gland neoplasm identified in the 2022 World Health Organization Classification of Head and Neck Tumour (Skalova et al., Head Neck Pathol 16:40-53, 2022) and is characterized by a unique set of histomorphologic and immunohistochemical features and a recurrent MEF2C::SS18 fusion. MSA was initially misdiagnosed as another salivary gland tumour due to its similar morphology; until recently, only fewer than 50 cases were reported. We present a case of MSA of the hard palate with diverse architectural growth patterns, bland cytological features, abundant basophilic intraluminal secretions and fibromyxoid stroma. The tumour cells were positive for the SOX10, S100, and p63 protein and negative for the p40 protein according to immunohistochemistry. SS18 gene rearrangement was demonstrated via break-apart fluorescence in situ hybridization. We also provided a comprehensive literature review and integrated the clinicopathological features, immunophenotype, and molecular alterations of the disease. A comprehensive understanding of MSA enables us to accurately distinguish and categorize MSA from other salivary gland tumours with analogous morphologies.

Clinicopathological Features of 26 Intraoral Polymorphous Adenocarcinomas from a Single Brazilian Institution

PURPOSE

This study describes a large, well-documented case series of salivary gland polymorphous adenocarcinomas (PAC) from a single Brazilian center.

METHODS

Demographic data, clinical presentation, histopathological and immunohistochemical features from 26 cases of PAC were analyzed and discussed in detail.

RESULTS

Most patients were females (n = 21), with a ratio of 1:4.2 (male: female) with a mean age of 58.8 years (ranging from 36 to 84 years). The most common clinical presentation was a fibrocollagenous, firm nodular lesion, with a mean size of 2.46 cm (ranging from 0.5 to 3 cm). Most lesions occurred on the palate (n = 16), followed by buccal mucosa (n = 3), upper lip (n = 3), buccal vestibule (n = 2) and alveolar ridge (n = 1). Histologically, various growth patterns were observed, including tubular, solid, cribriform, papillary, and cystic. Additionally, glomeruloid slit-like structures, mucous, and clear cells were noted. Surface papillary epithelial hyperplasia was observed in a few cases. Nine cases exhibited myxoid and collagenous areas, while two cases showed fusiform areas and another case demonstrated squamous differentiation. Clear cell predominance was noted in two cases, and peri- and intraneural invasion was seen in eight cases. Immunohistochemical analysis revealed positivity for S-100, p63 and CK7, and negativity for p40 in all cases. The Ki-67 proliferation index was markedly low in most cases, with a mean of 2.5%.

CONCLUSION

We have provided a broad, detailed description of the clinical and microscopic features of PAC in a large, Brazilian cohort. These findings, in a resource-limited area, may be quite useful for establishing a proper diagnosis.

Mucin-rich salivary gland tumors

Salivary gland neoplasms characterized by abundant mucin production are rare but have long been recognized. Due to their scarcity, precise classification has long eluded these mucin-rich tumors. Recent molecular discoveries, however, have shed considerable light on the genetic underpinnings of mucin-rich salivary gland neoplasms. This manuscript will review the most up-to-date information on this fascinating group of salivary gland neoplasms.

Genetic Rearrangements in Different Salivary Gland Tumors: A Systematic Review

Salivary gland tumors (SGT) encompass a wide range of neoplasms, each with its own unique histological type and clinical presentation. This review hones in on prevalent subtypes of SGTs, including adenoid cystic carcinoma (ACC), salivary duct carcinoma (SDC), and polymorphous adenocarcinoma (PAC). The articles, identified through specific keywords, were meticulously screened in databases like PubMed, Scopus, Google Scholar, and Web of Science from 2018 to 2023. Eight articles delved into genetic modifications among the selected SGT types. A fusion protein known as MYB-NF1B is typically associated with ACC, promoting cell proliferation while inhibiting apoptosis. The presence of MYB modifications in ACCs is a beacon of hope, as it is linked to a more favorable prognosis. In contrast, SDCs often exhibit HER2 expression. The invasive nature of SGTs contributes to their resistance to treatment. In the case of PAC, the role of PRKD1 is particularly noteworthy. PRKD1, integrated with other genes from the PRKD1/2/3 cluster, helps to differentiate PAC from other diseases. Furthermore, the genetic profiles of KTN1-PRKD1) and PPP2R2A:PRKD1 are distinct. The significant genetic variability among SGTs necessitates meticulous examination. This field is in a constant state of evolution, with new discoveries reshaping our understanding. Genetics is a key player in deciphering SGTs and tailoring treatments. This complex neoplasm demands ongoing research to uncover all genetic influences, thereby enhancing diagnostic methodologies, therapeutic strategies, and patient outcomes.

Molecular testing in salivary gland cytopathology: A practical overview in conjunction with the Milan system

Recently, significant advances in the molecular characterization of salivary gland neoplasms have facilitated the classification and diagnosis of specific diagnostic entities. In the highly challenging diagnostic scenario of salivary malignancies, molecular testing is increasingly being adopted in routine practice to refine the cytological diagnosis of salivary lesions. Here, we reviewed the most recent evidence in the field of salivary glands molecular cytopathology.

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.

[Fusion genes in salivary gland tumors]

Salivary gland tumors represent a diagnostic challenge for pathologists due to their rarity, their very wide histopathological and immuno-phenotypic spectrum, and the recent identification of new entities. This article presents the main molecular characteristics of these tumors in order to allow any pathologist to perceive the diagnostic tracks of these ENT tumors and to better guide the molecular approach to establish the diagnosis and guide therapy.

Detection of salivary gland and sinonasal fusions by a next-generation sequencing based, ligation-dependent, multiplex RT-PCR assay

AIMS

The discovery of tumour type-specific gene fusion oncogenes in benign and malignant salivary gland and sinonasal (SGSN) tumours has significantly increased our knowledge about their molecular pathology and classification.

METHODS AND RESULTS

We developed a new targeted multiplexed next-generation sequencing (NGS)-based method that utilizes ligation dependent reverse-transcriptase polymerase chain reaction (LD-RT-PCR) to detect oncogenic fusion transcripts involving 116 genes, leading to 96 gene fusions known to be recurrently rearranged in these tumours. In all, 180 SGSN tumours (formalin-fixed, paraffin-embedded samples, 141 specimens and 39 core needle biopsies) from the REFCORpath (French network for rare head and neck cancers) with previously identified fusion genes by fluorescent in situ hybridisation (FISH), RT-PCR, or molecular immunohistochemistry were selected to test its specificity and sensitivity and validate its diagnostic use. Tested tumours encompassed 14 major tumours types, including secretory carcinoma, mucoepidermoid carcinoma, adenoid cystic carcinoma, salivary gland intraductal carcinoma, clear cell carcinoma, pleomorphic adenoma, adamantinoma-like Ewing Sarcoma, EWSR1::COLCA2 sinonasal sarcoma, DEK::AFF2 sinonasal carcinoma, and biphenotypic sinonasal sarcoma. In-frame fusion transcripts were detected in 97.8% of cases (176/180). Gene fusion assay results correlated with conventional techniques (immunohistochemistry [IHC], FISH, and RT-PCR) in 176/180 tumours (97.8%).

CONCLUSION

This targeted multiplexed NGS-based LD-RT-PCR method is a robust, highly sensitive method for the detection of recurrent gene fusions from routine clinical SGSN tumours. It can be easily customized to cover new fusions. These results are promising for implementing an integrated NGS system to rapidly detect genetic aberrations, facilitating accurate, genomics-based diagnoses, and accelerate time to precision therapies in SGSN tumours.

Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners

Polymorphous adenocarcinoma (PAC) is a common, usually low-grade salivary gland carcinoma. While conventional PACs are most associated with PRKD1 p.E710D hotspot mutations, the cribriform subtype is often associated with gene fusions in PRKD1, PRKD2, or PRKD3. These fusions have been primarily identified by fluorescence in situ hybridization (FISH) analysis, with a minority evaluated by next-generation sequencing (NGS). Many of the reported fusions were detected by break-apart FISH probes and therefore have unknown partners or were negative by FISH altogether. In this study, we aimed to further characterize the fusions associated with PAC with NGS. Fifty-four PACs (exclusively cribriform and mixed/intermediate types to enrich the study for fusion-positive cases) were identified and subjected to NGS. Fifty-one cases were successfully sequenced, 28 of which demonstrated gene fusions involving PRKD1, PRKD2, or PRKD3. There were 10 cases with the PRKD1 p.E710D mutation. We identified a diverse group of fusion partners, including 13 novel partners, 3 of which were recurrent. The most common partners for the PRKD genes were ARID1A and ARID1B. The wide variety of involved genes is unlike in other salivary gland malignancies and warrants a broader strategy of sequencing for molecular confirmation for particularly challenging cases, as our NGS study shows.

A novel STRN3::PRKD1 fusion in a cribriform adenocarcinoma of salivary gland with high-grade transformation

Cribriform adenocarcinoma of salivary gland (CASG) is a rare form of salivary gland neoplasm that mostly arises from minor salivary glands. We report a case of CASG with high-grade transformation harboring a novel STRN3::PRKD1 fusion. A 59-year-old male presented with a palatal mass. Morphologically, the tumor consisted of two components: solid high-grade and glandular low-grade areas. The solid high-grade area comprised solid nests of high-grade carcinoma with central necrosis arranged in lobules delineated with prominent stromal septa. The glandular low-grade area comprised of cribriform and microcystic architecture in a hyalinized and hypocellular stroma. Immunophenotypically, the tumor was positive for S100 but negative for p40 and actin. However, due to the high-grade component, tissue was sent for salivary gland NGS fusion panel analysis to confirm the diagnosis. The current case illustrates high-grade transformation in CASG. Furthermore, identification of a STRN3::PRKD1 fusion expands the genetic spectrum of CASG.

Clinicopathologic Study of Sialadenoma Papilliferum of the Minor Salivary Glands: A Series of 8 New Cases With BRAF V600E Mutation-specific Immunohistochemical Analysis

Introduction. Sialadenoma papilliferum (SP) is a rare benign neoplasm that usually arises in the minor salivary glands. Recently, it was demonstrated that SP shares similar molecular genetic alterations (BRAF V600E or HRAS mutations) with its morphologic analog, syringocystadenoma papilliferum. Methods. We sought to perform clinicopathologic and immunophenotypic (BRAF V600E and SOX10) analyses on 8 new cases of SP. Results. The cases were from 4 males and 4 females, with ages ranging from 28 to 81 years (average: 64 years). The common locations were the hard palate (n = 3) and buccal mucosa (n = 3). Histopathologically, 7 cases were classic and 1 case was oncocytic. BRAF V600E immunohistochemistry (IHC) was positive in all classic SP, involving both the exophytic and endophytic components, but negative in the oncocytic SP. SOX10 was positive in the endophytic ductal cells of the evaluated classic SP but was negative in the oncocytic SP. Conclusions. We report 8 new cases of this rare salivary gland neoplasm, using BRAF V600E and SOX10 IHC to further support the following points: (1) the functional role of BRAF V600E mutation, RAS/mitogen-activated protein kinase signaling pathway in the pathogenesis of classic SP of salivary glands by IHC; (2) the analogous relationship between SP, syringocystadenoma papilliferum, and papillary seromucinous adenocarcinoma with sinonasal papilloma-like surface component (PSASP-like surface); (3) endophytic ductal component in classic SP arises from the intercalated ducts and not the excretory ducts; and (4) oncocytic SP is distinct from classic SP.

Salivary Duct Carcinoma with Rhabdoid Features of the Parotid Gland with No E-Cadherin Expression: A Report with Anti-HER2 Therapy and Review of the Literature

Salivary duct carcinoma with rhabdoid features (SDC-RF) is a rare form of salivary gland neoplasm that was recently described. We report a case of SDC-RF of the parotid gland with loss of E-cadherin and decreased β-catenin expression in a 73-year-old male who presented with right facial/neck swelling and intermittent pain. Morphologically, the tumor presented with a discohesive infiltrate of isolated and cords of pleomorphic round cells containing moderate amount of eosinophilic to fine-vacuolated cytoplasm and hyperchromatic nuclei infiltrating through fibroadipose tissue and salivary parenchyma. Immunophenotypically, the tumor was positive for Cytokeratins Oscar and 7, GATA3, GCDFP, HER2, and an androgen receptor but negative for CK20, S100, p40, Melan A, CDX2, TTF1, ER, SATB2, DOG1, synaptophysin, and chromogranin. Due to its diffuse infiltrating pattern, involvement of the parapharyngeal space, supraclavicular fat pad, dermis, and skin without a defined surgical target, the tumor was deemed unresectable. Anti-HER2 therapy (Herceptin and Pertuzumab) was utilized. At the last follow-up, the patient is alive, with complete locoregional control and brain metastases. An electronic search was performed in the following registries for papers published up to June 2023: PubMed, Embase, and Web of Science. For the database searches, the keywords searched were "salivary gland", "salivary duct carcinoma", and "salivary duct carcinoma with rhabdoid features". Our review of the literature identified 30 cases of SDC-RF that reveal there is a predilection for males (83%), parotid gland (72%), and patients older than the 6th decade of life (83%). Immunophenotypically, all SDC-RF cases except one were positive for AR and GCDFP (97%), 81% were positive for HER2, and loss or decreased expression of E-cadherin in 93% of cases. In conclusion, we described a rare case of SDF-RF of the parotid gland with no E-cadherin expression, decreased β-catenin expression, and its immunophenotypic profile.

Salivary Gland-like Tumors of the Breast

CONTEXT

The World Health Organization classification of tumors of the breast recognizes several special type carcinomas and benign lesions with features comparable to those of salivary gland tumors.

OBJECTIVE

To discuss the histologic, immunophenotypic, molecular, and clinical features of salivary gland-like carcinomas of the breast. These breast tumors are often negative for hormone receptors and human epidermal growth factor receptor 2 (HER2), that is, triple-negative, but they generally have a much better prognosis than triple-negative breast carcinomas of no special type. We compare the immunophenotypic, molecular, and clinical features of these breast tumors with their salivary gland counterparts, highlighting similarities and differences. We also discuss benign salivary gland-like breast tumors. Finally, we highlight recent developments in understanding the molecular pathogenesis of these breast tumors and novel ancillary studies that can be used to support their diagnosis.

DATA SOURCES

A literature review was conducted, and papers were selected for further analysis and discussion by the authors of this review based on their novelty, applicability, and impact in the field.

CONCLUSIONS

Breast tumors that exhibit morphologic overlap with salivary gland tumors have been recognized by pathologists for decades, but the similarities and differences in their molecular pathogenesis have not been understood until more recently. These developments have led to novel diagnostic tools and further knowledge of these rare breast lesions.

A novel PPP2R2A::PRKD1 fusion in a cribriform adenocarcinoma of salivary gland

Cribriform adenocarcinoma of salivary gland (CASG) is a rare, salivary gland tumor. In this report, we describe a case of CASG harboring a novel PPP2R2A::PRKD1 fusion. A 58-year-old female presented with an intraoral mass adjacent to the lower left third molar region. Morphological features at histological examination, immunohistochemical staining (p63+, p40-), and tumor location were indicative of CASG. However, due to the potential focal presence of a biphasic component within the tumor, RNA sequencing was performed to confirm the diagnosis. The subsequently found novel PPP2R2A::PRKD1 fusion adds to the rapidly evolving molecular landscape of salivary gland tumors. Additionally, we report that CASG may show some entrapment of pre-existent salivary gland ducts, which may be misinterpreted as tumor cells with myoepithelial differentiation.

Unusual presentation of cribriform adenocarcinoma of salivary glands: A case report

According to the last edition of the World Health Organization classification, cribriform adenocarcinoma of salivary glands (CASGs) was considered a variant of polymorphus adenocarcinoma although many authors proposed CASG as a distinct neoplasm. The aim of this study was to report an unusual presentation of CASG in the buccal mucosa of a 63-year-old male patient that showed signs of encapsulation and no evidence of lymph node metastasis. The lesion was composed of lobules of tumoral cells arranged in solid nests, sheets, papillary, and cribriform or glomeruloid patterns. Most of the peripheral cells show palisaded arrangement with peripheral clefting from the adjacent stroma. Surgical resection of the lesion was done and further neck dissection was recommended.

A Subset of Salivary Intercalated Duct Lesions Harbors Recurrent CTNNB1 and HRAS Mutations: A Molecular Link to Basal Cell Adenoma and Epithelial-Myoepithelial Carcinoma?

BACKGROUND

Intercalated duct lesions (IDLs) are benign salivary gland proliferations that resemble normal intercalated ducts and are subdivided into hyperplastic, adenoma or hybrid types depending on circumscription. While IDLs were historically regarded as non-neoplastic, frequent association with basal cell adenoma (BCA) and epithelial-myoepithelial carcinoma (EMC) has raised the possibility that they are neoplastic precursors.

METHODS

In this study, we performed β-catenin immunohistochemistry and targeted molecular analysis on IDLs to clarify their pathogenesis.

RESULTS

We identified 15 IDLs from the parotid glands of eight men and six women with a median age of 65 years (range 42-85 years). These lesions included nine hyperplastic, three adenoma, and three hybrid types. Nuclear β-catenin localization was present in 7 of 13 lesions tested (54%). Next generation sequencing was successfully completed in 12 IDLs, of which seven (58%) had likely oncogenic mutations. These included three recurrent CTNNB1 mutations in hyperplastic (n = 2) and hybrid (n = 1) lesions and two recurrent HRAS hotspot mutations in adenomas.

CONCLUSION

Despite substantial heterogeneity, these findings confirm that a majority of IDLs are genuinely neoplastic, and some demonstrate molecular overlap with both BCA and EMC, supporting their theorized role as precursors to these tumors. Nevertheless, no oncogenic drivers were present in a significant subset of cases, suggesting that some IDLs may be truly reactive and hyperplastic. As such, IDL appear to represent a diverse morphologic and molecular spectrum that include both neoplastic and hyperplastic lesions. Reconsideration of the boundary between IDL and BCA in the future may be necessary to simplify classification.

Salivary Gland Polymorphous Adenocarcinoma: Clinicopathological Features and Gene Alterations in 36 Japanese Patients

OBJECTIVES

Polymorphous adenocarcinoma (PAC) is a common intraoral minor salivary gland carcinoma in Western countries but is extremely rare in Japan. The current study aimed to characterize the clinicopathological features and status of molecular alterations of PAC-associated genes, such as (e.g., PRKD1/2/3, ARID1A, and DDX3X) in a large cohort of Japanese patients with PAC.

MATERIALS AND METHODS

We examined the cases of 36 Japanese patients with salivary gland PAC and 26 cases involving histopathological mimics. To detect gene splits, fluorescence in situ hybridization was carried out for PAC-associated genes. Additionally, we applied a SNaPshot multiplex assay to identify PRKD1 hotspot mutations.

RESULTS

This study revealed the indolent clinical course of PAC with a high 10-year overall survival rate (92.9%), accompanied by occasional local recurrences and cervical lymph node metastasis (both 23.3%). Twenty cases (55.6%) of PAC (but none of the mimics) exhibited alterations in at least one PAC-associated gene. Rearrangement of PAC-associated genes and PRKD1 E710D were identified in 17 (47.2%) and 4 (11.1%) cases, respectively; one case showed coexisting PRKD3 split and PRKD1 E710D. In the multivariate analysis, high clinical stage (P=0.0005), the presence of prominent nucleoli (P=0.0003), and ARID1A split positivity (P=0.004) were independent risk factors for disease-free survival.

CONCLUSION

Japanese patients with PAC showed clinicopathological features similar to those reported in Western countries. This study disclosed that PAC-associated genetic alterations were common and specific findings in PACs. The diagnostic role and possible prognostic significance of PAC-associated genetic alterations in PACs were suggested.

Diagnostic Value of Nuclear Receptor Subfamily 4 Group A Member 3 in Salivary Gland Carcinomas

Salivary gland carcinomas are diagnostically challenging lesions in heterogeneous groups. However, recently described genomic alterations may be helpful and have future therapeutic implications. The molecular investigation is becoming useful tool to help diagnosis and provide prognostic information. Diagnosis of acinic cell carcinoma (AcCC) is challenging due to its rarity and similarity with other SGCs or normal acinar cells. Herein, the diagnostic performance of transcription factor nuclear receptor subfamily 4 group A member3 (NR4A3) was analysed immunohistochemically. This study was done on 68 cases of SCCs, including 32 of AcCC, 14 of adenoid cystic carcinoma (AdCC), 8 of mucoepidermoid carcinoma (MEC), 7 of epithelial myoepithelial carcinoma (EMC), 4 of salivary duct carcinoma (SDC), and only one case from each of carcinoma ex pleomorphic adenoma (CXPA), polymorphous adenocarcinoma (PAC) and secretory carcinoma (SC) for detecting NR4A3. All stained samples of AcCC (100%) responded positively to the NR4A3 antibody. However, only one case of AdCC and MEC demonstrated NR4A3 immunostaining in less than 10% of cells. On the other hand, the different types of SGCs, including EMC, SDC, CXPA, PAC, and SC, revealed negative expressions. Therefore, we can conclude that NR4A3 can be used as a potential marker for AcCC rather than other SGCs.

Overarching roles of diacylglycerol signaling in cancer development and antitumor immunity

Diacylglycerol (DAG) is a lipid second messenger that is generated in response to extracellular stimuli and channels intracellular signals that affect mammalian cell proliferation, survival, and motility. DAG exerts a myriad of biological functions through protein kinase C (PKC) and other effectors, such as protein kinase D (PKD) isozymes and small GTPase-regulating proteins (such as RasGRPs). Imbalances in the fine-tuned homeostasis between DAG generation by phospholipase C (PLC) enzymes and termination by DAG kinases (DGKs), as well as dysregulation in the activity or abundance of DAG effectors, have been widely associated with tumor initiation, progression, and metastasis. DAG is also a key orchestrator of T cell function and thus plays a major role in tumor immunosurveillance. In addition, DAG pathways shape the tumor ecosystem by arbitrating the complex, dynamic interaction between cancer cells and the immune landscape, hence representing powerful modifiers of immune checkpoint and adoptive T cell-directed immunotherapy. Exploiting the wide spectrum of DAG signals from an integrated perspective could underscore meaningful advances in targeted cancer therapy.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Salivary Glands

The salivary gland section in the 5th edition of the World Health Organization Classification of Head and Neck Tumours features a description and inclusion of several new entities, including sclerosing polycystic adenoma, keratocystoma, intercalated duct adenoma, and striated duct adenoma among the benign neoplasms; and microsecretory adenocarcinoma and sclerosing microcystic adenocarcinoma as the new malignant entities. The new entry also includes mucinous adenocarcinoma subdivided into papillary, colloid, signet ring, and mixed subtypes with recurrent AKT1 E17K mutations across patterns suggesting that mucin-producing salivary adenocarcinomas represent a histologically diverse single entity that may be related to salivary intraductal papillary mucinous neoplasm (IPMN). Importantly, the number of entities in the salivary chapter has been reduced by omitting tumors or lesions if they do not occur exclusively or predominantly in salivary glands, including hemangioma, lipoma, nodular fasciitis and hematolymphoid tumors. They are now discussed in detail elsewhere in the book. Cribriform adenocarcinoma of salivary gland origin (CASG) now represents a distinctive subtype of polymorphous adenocarcinoma (PAC). PAC is defined as a clinically, histologically and molecularly heterogeneous disease group. Whether CASG is a different diagnostic category or a variant of PAC is still controversial. Poorly differentiated carcinomas and oncocytic carcinomas are discussed in the category "Salivary carcinoma not otherwise specified (NOS) and emerging entities". New defining genomic alterations have been characterized in many salivary gland tumors. In particular, they include gene fusions, which have shown to be tightly tumor-type specific, and thus valuable for use in diagnostically challenging cases. The recurrent molecular alterations were included in the definition of mucoepidermoid carcinoma, adenoid cystic carcinoma, secretory carcinoma, polymorphous adenocarcinoma, hyalinizing clear cell carcinoma, mucinous adenocarcinoma, and microsecretory adenocarcinoma.

Fusion-Positive Salivary Gland Carcinomas

Salivary gland tumors are a rare, heterogeneous group of neoplasms that pose significant diagnostic challenges for the histopathologist. Histopathological diagnosis relies primarily on morphological assessment, with ancillary special stains and immunohistochemistry. In recent years, new defining genomic alterations have been characterized in these tumors. In particular, they include gene fusions which have shown to be tightly tumor-type specific, and thus valuable for use in diagnostically challenging cases. These discoveries also help in refining tumor classification. Furthermore, such genetic alterations may have prognostic as well as potentially therapeutic implications in the era of personalized medicine. This review aims at providing a summary of the most recent updates in this field.

How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review

BACKGROUND

Recently, histologic grade was removed from salivary tumor nomenclature by the WHO to include disease of higher grade. One such entity, cribriform adenocarcinoma (CAC), is an aggressive group of polymorphous adenocarcinoma (PAC), with frequent nodal metastasis and locoregional recurrence. We aim to examine the biologic behavior of this disease as compared with the PAC general cohort inclusive of all subtypes.

METHODS

A systematic review of the literature on polymorphous adenocarcinoma and cribriform adenocarcinoma was completed. A descriptive analysis was performed for the following predictor variables: nodal and distant metastasis, in addition to recurrence. The outcome variables, disease free recurrence, and disease specific survival, where plotted using Kaplan-Meier curves.

RESULTS

PAC and CAC both show median age of diagnosis in the sixth decade of life and a female predominance. CAC occurs most frequently in the tongue and PAC in the palate. The 2 groups show a similar biologic behavior in regards to incidence of distant metastasis (4.1 vs 5.5%), recurrence (12.5 vs 17.8%), and death from disease (3 vs 2.7%). However, there was an increased incidence of nodal metastasis in CAC (53%) as compared with that in PAC of all subtypes (14%).

CONCLUSIONS

CAC exhibits more aggressive biologic behavior as compared with the PAC cohort. Although CAC is not an officially recognized entity, these tumors likely comprise a significant portion of the cases of PAC with poor outcomes and are deserving of attention and consideration for escalation in oncologic treatment.

Cribriform adenocarcinoma of minor salivary glands presented as a nasopharyngeal tumor: A case report highlighting the significance of cytology

Cribriform adenocarcinoma of minor salivary gland (CAMSG) is a rare malignancy presenting cytologic features resembling papillary thyroid carcinoma, localized in the oral cavity and oropharynx. Although cervical lymph node (LN) metastasis is a frequent manifestation of CMSG, there are few publications evaluating its cytology. The aim of this report was to present a CAMSG in an unusual location in the light of cytologic features, thereby enriching the spectrum of fine-needle aspiration biopsy (FNAB) differential diagnosis. We report a case of a 76-year-old woman presenting an enlarged submandibular LN on physical examination. Computed tomography revealed a submucosal lesion situated predominantly in the nasopharynx. FNAB and subsequently an open biopsy of submandibular LN were conducted. In cytologic smear cribriform, dense clusters of monomorphic round-oval tumor cells with scant cytoplasm were observed. Histologically, the tumor was composed of oval, overlapping cells with bright nuclear chromatin and nuclear grooves forming cribriform, papillary, and solid structures. Immunohistochemistry panel revealed the following: TTF-1 (-), thyroglobulin (-), S100 (+), p63 (+), Gal-3 (+), and CK19 (+) focally. The diagnosis of CAMSG should be considered when dealing with nasopharyngeal mass. Commonly, nodal metastases are observed in this tumor; therefore, appropriate evaluation of cytologic smear is crucial for patient management.

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.

Targeted RNA sequencing in the routine clinical detection of fusion genes in salivary gland tumors

Salivary gland tumors represent a diverse group of neoplasms that occasionally pose a diagnostic challenge for pathologists, particularly with limited sampling. Gene fusions, which may reflect genetic drivers, are increasingly recognized in a subset of these neoplasms, and can be leveraged for diagnostic purposes. We performed a retrospective analysis on a cohort of 80 benign and malignant salivary gland tumors, enriched for subtypes known to harbor recurrent fusion events, to validate the diagnostic use of a targeted RNA sequencing assay to detect fusion transcripts. Testing identified fusion genes in 71% (24/34) of pleomorphic adenoma and carcinoma-ex-pleomorphic adenoma, with 56% of cases showing rearrangement of PLAG1 and 15% HMGA2. In addition to confirming known partners for these genes, novel PLAG1 fusion partners were identified, including DSTN, NTF3, and MEG3; CNOT2 was identified as a novel fusion partner for HMGA2. In adenoid cystic carcinoma, 95% of cases (19/20) were positive for a fusion event. MYB was rearranged in 60% (12/20), MYBL1 in 30% (6/20), and NFIB in 5% (1/20); two tumors exhibited novel fusion products, including NFIB-TBPL1 and MYBL1-VCPIP1. Fusion genes were identified in 64% (9/14) of cases of mucoepidermoid carcinoma; MAML2 was confirmed to partner with either CRTC1 (43%) or CRTC3 (21%). One salivary duct carcinoma was found to harbor a novel RAPGEF6-ACSL6 fusion gene. Finally, as anticipated, gene fusions were not detected in any of the five acinic cell carcinomas included in the cohort. In summary, targeted RNA sequencing represents a diagnostically useful ancillary technique for identifying a variety of existing, and novel, fusion transcripts in the classification of salivary gland neoplasms.

Immunocytochemistry for diagnostic cytopathology-A practical guide

Cytological specimens, which are obtained by minimally invasive methods, are an excellent source of diagnostic material. Sometimes they are the only material available for diagnosis as well as for prognostic/predictive markers. When cytomorphology is not straightforward, ancillary tests may be required for a definitive diagnosis to guide clinical management. Immunocytochemistry (ICC) is the most common and practical ancillary tool used to reach a diagnosis when cytomorphology is equivocal, to differentiate entities with overlapping morphological features, and to determine the cell lineage and the site of origin of a metastatic neoplasm. Numerous immunomarkers are available, and some are expressed in multiple neoplasms. To rule out entities within a differential diagnosis, the use of more than one marker, sometimes panels, is necessary. ICC panels for diagnostic purposes should be customised based on the clinical context and cytomorphology, and the markers should be used judiciously to preserve material for additional tests for targeted therapies in the appropriate setting. This review offers a practical guide for the use of ICC for diagnostic cytopathology, covering the most commonly encountered non-hematolymphoid diagnostic scenarios in various body sites.

SalvGlandDx - a comprehensive salivary gland neoplasm specific next generation sequencing panel to facilitate diagnosis and identify therapeutic targets

Diagnosis of salivary gland neoplasms is often challenging due to their high morphological diversity and overlaps. Several recurrent molecular alterations have been described recently, which can serve as powerful diagnostic tools and potential therapeutic targets (e.g. NTRK or RET fusions). However, current sequential molecular testing can be expensive and time consuming. In order to facilitate the diagnosis of salivary gland neoplasms, we designed an all-in-one RNA-based next generation sequencing panel suitable for the detection of mutations, fusions and gene expression levels (including NR4A3) of 27 genes involved in salivary gland neoplasms. Here we present the validation of the "SalvGlandDx" panel on FFPE histological specimen including fine needle aspiration (FNA) cell block material, against the standard methods currently used at our institution. In a second part we describe selected unique cases in which the SalvGlandDx panel allowed proper diagnosis and new insights into special molecular characteristics of selected salivary gland tumors. We characterize a unique salivary gland adenocarcinoma harboring a ZCCHC7-NTRK2 fusion, a highly uncommon spindle cell and pseudoangiomatoid adenoid-cystic carcinoma with MYBL1-NFIB fusion, and a purely oncocytic mucoepidermoid carcinoma, whereas diagnosis could be made by detection of a CRTC3-MAML2 rearrangement on the cell block specimen of the FNA. Further, a rare case of a SS18-ZBTB7A rearranged low-grade adenocarcinoma previously described as potential spectrum of microsecretory adenocarcinoma, is reported. In addition, features of six cases within the spectrum of polymorphous adenocarcinoma / cribriform adenocarcinoma of salivary gland including PRKD1 p.E710D mutations and novel fusions involving PRKAR2A-PRKD1, SNX9-PRKD1 and ATL2-PRKD3, are described.

NR4A3 (NOR-1) Immunostaining Shows Better Performance than DOG1 Immunostaining in Acinic Cell Carcinoma of Salivary Gland: a Preliminary Study

Objectives

Acinic cell carcinoma of salivary gland harbours recurrent and specific chromosomal rearrangement [t(4;9)(q13;q31)], resulting in the translocation of secretory calcium-binding phosphoprotein gene cluster at 4q13 to nuclear receptor subfamily 4 group a member 3 at 9q31. This upregulates the transcription factor nuclear receptor subfamily 4 group A member 3, which can be detected by immunohistochemistry. The purpose of this pilot study is to evaluate the performance of nuclear receptor subfamily 4 group A member 3 immunostaining on whole-slide acinic cell carcinoma tissue, in comparison with discovered on GIST-1 immunostaining.

Material and Methods

We retrieved 6 cases of acinic cell carcinoma (AciCC), including 5 conventional low-grade and 1 dedifferentiated high-grade. Immunohistochemistry (IHC) for nuclear receptor subfamily 4 group A member 3 (NR4A3) and discovered on GIST-1 (DOG1) were performed at the University of Pittsburgh Medical Centre in Pittsburgh, Pennsylvania on all retrieved cases.

Results

The result shows that NR4A3 IHC shows better performance than DOG1 IHC: 5 of the 6 (83.3%) AciCC cases (including the dedifferentiated high-grade) demonstrated strong diffuse nuclear staining for NR4A3, also five AciCC cases (including the dedifferentiated high-grade) demonstrated weak to moderate membranous staining with variable distribution for DOG1. Moreover, only 3 (50%) cases showed complete membranous staining with DOG1.

Conclusions

This pilot study showed that nuclear receptor subfamily 4 group A member 3 immunostaining is a sensitive marker for acinic cell carcinoma and of better utility than discovered on GIST-1 immunostaining in making a diagnosis of acinic cell carcinoma.

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.

Polymorphous Adenocarcinoma

Polymorphous adenocarcinoma (PAC) is typically originated from the minor salivary glands and is characterized by cytology uniformity and architectural diversity. PAC commonly harbors PRKD1 E710D mutation. PAC has an excellent prognosis. However, greater than or equal to 10% papillary or greater than or equal to 30% cribriform pattern is an independent adverse prognostic factor. Cribriform adenocarcinoma of salivary gland (CASG) is a controversial entity that is considered within the same histologic spectrum of PAC in current classification schemes; however, it is regarded by some pathologists as a separate entity. CASG shows a propensity to base of tongue location, a lobulated growth pattern, a predominant solid/cribriform architecture, and a high frequency of PRKD1/2/3 fusion.

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.

Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.

A contemporary update on hyalinizing clear cell carcinoma: compilation of all in-house cases at our institution and a literature review spanning 2015-2020

Tumors of the head and neck with clear cell features prompt a broad differential diagnosis. A relatively uncommon, but increasingly recognized, entity is hyalinizing clear cell carcinoma (HCCC). This neoplasm, first described in 1994, consists of clear cells arranged in nests or trabecule with a hyalinized stroma. These are low-grade neoplasms that only infrequently metastasize and rarely recur. They also often harbor a unique EWSR-ATF1 gene rearrangement. As the prognosis is excellent compared with other clear cell neoplasms, the correct diagnosis is key. Here we present all of the cases of HCCC in the past decade from our institution alongside a comprehensive literature review spanning 2015-2020 to further characterize this unusual malignancy.

Expanding the Molecular Spectrum of Secretory Carcinoma of Salivary Glands With a Novel VIM-RET Fusion

BACKGROUND

Secretory carcinoma (SC), originally described as mammary analogue SC, is a predominantly low-grade salivary gland neoplasm characterized by a recurrent t(12;15)(p13;q25) translocation, resulting in ETV6-NTRK3 gene fusion. Recently, alternative ETV6-RET, ETV6-MAML3, and ETV6-MET fusions have been found in a subset of SCs lacking the classic ETV6-NTRK3 fusion transcript, but still harboring ETV6 gene rearrangements.

DESIGN

Forty-nine cases of SC revealing typical histomorphology and immunoprofile were analyzed by next-generation sequencing using the FusionPlex Solid Tumor kit (ArcherDX). All 49 cases of SC were also tested for ETV6, RET, and NTRK3 break by fluorescence in situ hybridization and for the common ETV6-NTRK3 fusions using reverse transcription polymerase chain reaction.

RESULTS

Of the 49 cases studied, 37 (76%) occurred in the parotid gland, 7 (14%) in the submandibular gland, 2 (4%) in the minor salivary glands, and 1 (2%) each in the nasal mucosa, facial skin, and thyroid gland. SCs were diagnosed more frequently in males (27/49 cases; 55%). Patients' age at diagnosis varied from 15 to 80 years, with a mean age of 49.9 years. By molecular analysis, 40 cases (82%) presented the classic ETV6-NTRK3 fusion, whereas 9 cases (18%) revealed an alternate fusion. Of the 9 cases negative for the ETV6-NTRK3 fusion, 8 cases presented with ETV6-RET fusion. In the 1 remaining case in the parotid gland, next-generation sequencing analysis identified a novel VIM-RET fusion transcript. In addition, the analysis indicated that 1 recurrent high-grade case in the submandibular gland was positive for both ETV6-NTRK3 and MYB-SMR3B fusion transcripts.

CONCLUSIONS

A novel finding in our study was the discovery of a VIM-RET fusion in 1 patient with SC of the parotid gland who could possibly benefit from RET-targeted therapy. In addition, 1 recurrent high-grade case was shown to harbor 2 different fusions, namely, ETV6-NTRK3 and MYB-SMR3B. The expanded molecular spectrum provides a novel insight into SC oncogenesis and carries important implications for molecular diagnostics, as this is the first SC-associated translocation with a non-ETV6 5' fusion partner. This finding further expands the definition of SC while carrying implications for selecting the appropriate targeted therapy.

ALK alterations in salivary gland carcinomas

Salivary gland carcinomas represent a heterogeneous group of poorly characterized head and neck tumors. The purpose of this study was to evaluate ALK gene and protein aberrations in a large, well-characterized cohort of these tumors. A total of 182 salivary gland carcinomas were tested for anaplastic lymphoma kinase (ALK) positivity by immunohistochemistry (IHC) using the cut-off of 10% positive cells. ALK positive tumors were subjected to FISH analysis and followed by hybrid capture–based next generation sequencing (NGS). Of the 182 tumors, 8 were ALK positive by IHC. Further analysis using hybrid capture NGS analysis revealed a novel MYO18A (Exon1-40)-ALK (exon 20-29) gene fusion in one case of intraductal carcinoma. Additional genomic analyses resulted in the detection of inactivating mutations in BRAF and TP53, as well as amplifications of ERBB2 and ALK. ALK rearrangements are a rare entity in salivary gland carcinomas. We identified a potentially targetable novel ALK fusion in an intraductal carcinoma of minor salivary glands.

Salivary Gland Tumors: A Retrospective Study of 164 Cases from a Single Private Practice Service in Mexico and Literature Review

Salivary gland tumors (SGT) represent an uncommon heterogeneous group of tumors with complex clinical and pathological characteristics. The prevalence of these lesions varies between studies but has been estimated between 3 and 6% of all tumors in the head and neck region. The present study aimed to evaluate the distribution and demographic findings of salivary gland tumors diagnosed in an oral pathology service in Mexico. A retrospective descriptive cross-sectional study was performed. A total of 164 cases of SGT from a private oral pathology service were diagnosed between 2000 and 2019 in Mexico City. All cases were reviewed histologically, and demographic data and histopathological diagnoses were collected. A total of 110 (67.1%) tumors were benign, and 54 (32.9%) were malignant. The majority of patients were female (n = 100, 61.0%) with an overall female:male ratio of 1.6:1. The minor salivary glands were affected more than the major salivary glands (68.9% vs. 25.6%). The palate (n = 67, 40.9%) was the most commonly affected site, followed by the parotid gland (n = 37, 22.6%), lips (n = 16, 9.8%), and buccal mucosa (n = 14, 8.5%). Pleomorphic adenoma (n = 88; 80.0%) and mucoepidermoid carcinoma (n = 16, 29.6%) were the most frequent benign and malignant tumors, respectively. The general features of SGT from the studied Mexican population shared some similarities and differences compared to previously reported series from various parts of the world.

Frequent activating PIK3CA mutations in sporadic angiolipoma

BACKGROUND

Angiolipoma (AL) is considered as a lipoma variant that is characterized by the combination of mature adipocytes and capillary blood vessels diffusely distributed within the tumor. With the exception of recurrent PRKD2 mutations of uncertain pathogenetic significance, the genetic abnormalities of ALs are unknown, in the absence of any of the specific chromosomal aberrations described in other lipoma variants.

METHODS

Formalin-fixed and paraffin-embedded blocks of 13 conventional ALs and 5 cellular ALs from 17 individuals were retrieved and analyzed for mutations in exons 9 and 20 of PIK3CA by polymerase chain reaction and Sanger sequencing.

RESULTS

Activating PIK3CA mutations were identified in 14 tumors (78%). All PIK3CA-mutated samples carried the same exon 9 mutation, c.1634A>C (p.E545A). No mutation was detected in exon 20 of PIK3CA. No significant difference between PIK3CA-mutated and wild-type samples appeared to exist based on age, gender, and location of the tumor. All 5 cellular ALs carried the p.E545A PIK3CA mutation.

CONCLUSION

The high frequency of the p.E545A PIK3CA mutation in both conventional and cellular ALs suggests that activation of the PI3K/AKT pathway plays a key role in AL pathogenesis and reinforces the concept that cellular AL should be regarded as a variant of AL.

MYB-NFIB Translocation by FISH in Adenoid Cystic Carcinoma of the Head and Neck in Nigerian Patients: A Preliminary Report

Adenoid cystic carcinoma (AdCC) is a relatively rare malignancy of head and neck sites such as the salivary glands, lacrimal gland, sinonasal region, and pharynx and may arise in other exocrine glands. The oncologic event in AdCC is the translocation between MYB proto-oncogene transcription factor (MYB) and nuclear factor I/B (NFIB) resulting in t(6;9)(q22-23;p23-24). We carried out a preliminary evaluation of MYB-NFIB translocation by fluorescence in-situ hybridization on seven archived formalin-fixed paraffin-embedded tissues of AdCC of Nigerian patients and its clinicopathologic features. Only 3 of the 7 cases were successfully hybridized, all featuring MYB-NFIB translocations with a range of 14.7-83.3% of translocated cells in 60 cells examined. The 3 translocation positive cases were located in the maxillary sinus, buccal mucosa and parotid. Their morphologic appearances were cribriform-solid (1) & cribriform (2) and classified as grades III (1) & I (2), respectively. These patients may potentially benefit from MYB-targeted anti-neoplastic therapy.

Histologic Classification and Molecular Signature of Polymorphous Adenocarcinoma (PAC) and Cribriform Adenocarcinoma of Salivary Gland (CASG): An International Interobserver Study

Polymorphous adenocarcinoma (PAC) shows histologic diversity with streaming and targetoid features whereas cribriform adenocarcinoma of salivary gland (CASG) demonstrates predominantly cribriform and solid patterns with glomeruloid structures and optically clear nuclei. Opinions diverge on whether CASG represents a separate entity or a variant of PAC. We aimed to assess the level of agreement among 25 expert Head and Neck pathologists in classifying these tumors. Digital slides of 48 cases were reviewed and classified as: PAC, CASG, tumors with ≥50% of papillary architecture (PAP), and tumors with indeterminate features (IND). The consensus diagnoses were correlated with a previously reported molecular alteration. The consensus diagnoses were PAC in 18/48, CASG in16/48, PAP in 3/48, and IND in 11/48. There was a fair interobserver agreement in classifying the tumors (κ=0.370). The full consensus was achieved in 3 (6%) cases, all of which were classified as PAC. A moderate agreement was reached for PAC (κ=0.504) and PAP (κ=0.561), and a fair agreement was reached for CASG (κ=0.390). IND had only slight diagnostic concordance (κ=0.091). PAC predominantly harbored PRKD1 hotspot mutation, whereas CASG was associated with fusion involving PRKD1, PRKD2, or PRKD3. However, such molecular events were not exclusive as 7% of PAC had fusion and 13% of CASG had mutation. In conclusion, a fair to moderate interobserver agreement can be achieved in classifying PAC and CASG. However, a subset (23%) showed indeterminate features and was difficult to place along the morphologic spectrum of PAC/CASG among expert pathologists. This may explain the controversy in classifying these tumors.

Human Tissue Kallikreins in Polymorphous Adenocarcinoma: A Polymerase Chain Reaction and Immunohistochemical Study

Polymorphous adenocarcinoma (PAC) is the second most common malignant salivary gland tumour of minor salivary glands. Human tissue kallikreins (KLKs) are a family of highly conserved serine proteases expressed by various tissues and organs. The literature demonstrates a link between KLKs and salivary gland neoplasms. The purpose of this study was to determine levels of KLK mRNA in tissue samples of PAC and to determine if KLK expression is limited to tumour cells. Nineteen cases of PAC were reviewed (1987-2013). The diagnosis was confirmed, demographic data was collected, and formalin fixed paraffin-embedded PAC and normal salivary gland tissue samples were obtained. RNA isolation was achieved, followed by conversion to complementary DNA via reverse transcription. Using PCR, the quantitative level of expression of KLKs1-15 was recorded. Samples exhibiting high and low KLK expression were selected for immunohistochemistry staining. Results revealed a statistically significant increase in mean KLK mRNA expression for KLK1, KLK4, KLK10, KLK12 and KLK15 in PAC tissue samples, compared with normal salivary gland tissue (Mann-Whitney U test, p < 0.05). Immunohistochemistry results demonstrated that KLKs were present in tumor cells. Notably, all samples demonstrating relatively higher KLK mRNA expression showed equivalent or increased staining scores relative to the low KLK mRNA expression samples. In conclusion, there appears to be aberrant kallikrein expression in polymorphous adenocarcinoma, suggesting the possibility of a kallikrein cascade influence on tumor development and progression.

A clinicopathologic study of secretory carcinoma of minor salivary gland: a series of 4 cases and diagnostic considerations

OBJECTIVE

Secretory carcinoma (SC) of salivary gland is a recently described low-grade malignant neoplasm of the salivary gland, characterized by rearrangement of the ETV6 gene. SC of salivary gland shares striking morphologic, immunophenotypic, and molecular similarity to SC of breast.

STUDY DESIGN

We report the clinicopathologic features of 4 ETV6-rearranged SCs of minor salivary gland and histopathologic diagnostic considerations.

RESULTS

Two cases were located in the lip, 1 in the soft palate, and 1 in the mandibular vestibule. No patient presented with regional or distant metastases at diagnosis. All cases were positive for S100 protein and mammaglobin, and all cases were negative for p63. All cases were positive for ETV6 rearrangement.

CONCLUSIONS

SC of the minor salivary glands are rare. Because of its shared histopathologic features with other salivary gland tumors, positivity for ETV6 gene rearrangements is recommended before rendering a diagnosis of SC of salivary gland.

Clinicopathological study of intraductal carcinoma of the salivary gland, with emphasis on the apocrine type

Intraductal carcinoma (IC) is a rare salivary gland tumor with low- to intermediate-grade cytological features. It is further classified into intercalated duct type and apocrine type based on its distinct histologic and immunohistochemical expression. Conventional salivary duct carcinoma (SDC) is an aggressive carcinoma with high-grade features and is usually associated with poor prognosis. In this study, immunohistochemistry and mutation analyses (including HRAS/PIK3CA mutations, RET rearrangement, and human epidermal growth factor receptor 2 [HER2] amplification) of 9 ICs (including 3 pure ICs, 6 ICs with invasive carcinoma) and 24 conventional SDCs were performed and the results were compared. Four intercalated duct-type cases were positive for SOX10 and S100 and negative for AR; five apocrine-type cases showed opposite results. All five apocrine-type cases had cysts with relatively circumscribed tumor borders and morphologically mimicking breast low-grade ductal carcinoma in situ or papillary carcinoma. RET fusion is detected in half of the 4 intercalated duct-type IC but not in the apocrine-type or conventional SDC. HER2 amplification was only observed in conventional SDC. The monoclonal antibody (clone RBT-NRAS) against NRAS Q61R is a sensitive and specific marker used for detecting HRAS Q61R mutation in the salivary gland tumors. The apocrine-type IC had different cytological grades, distinct tumor growth patterns, and no evidence of low- to high-grade transition, suggesting that apocrine-type IC should be distinguished from apocrine SDC with an in situ component.

NCOA4-RET and TRIM27-RET Are Characteristic Gene Fusions in Salivary Intraductal Carcinoma, Including Invasive and Metastatic Tumors: Is "Intraductal" Correct?

Intraductal carcinoma (IC) is the new WHO designation for tumors previously encompassed by "low-grade cribriform cystadenocarcinoma" and "low-grade salivary duct carcinoma." The relationship of IC to salivary duct carcinoma (SDC) is controversial, even though they are considered to be distinct entities. IC is a rare low-grade malignant salivary gland neoplasm with histopathological features reminiscent of atypical ductal hyperplasia or ductal carcinoma in situ of the breast, showing diffuse S100 protein and mammaglobin positivity, while it is partially defined genetically. Recently, RET rearrangements including NCOA4-RET and TRIM27-RET have been described in IC. Here, we genetically characterize the largest cohort of IC to date (33 cases) including 8 cases with focal or widespread invasive growth and 1 case with lymph node metastasis. Thirty-three cases of IC were analyzed by next-generation sequencing (NGS) using the FusionPlex Solid Tumor kit (ArcherDX). Identified gene fusions were confirmed using fluorescence in situ hybridization break-apart and fusion probes and an reverse transcription polymerase chain reaction designed specifically for the detected breakpoints. Ten cases of SDC were analyzed for comparison using NGS panels that detect mutations and fusion transcripts. NGS analysis detected an NCOA4-RET fusion transcript in 11 cases of intercalated duct-type IC joining exon 7 or 8 of NCOA4 gene and exon 12 of the RET gene. Eight cases of IC had an invasive growth pattern, including one with widespread invasion and lymph node metastasis. Three invasive ICs harbored an NCOA4-RET fusion transcript, while 1 case was negative, and 2 cases were not analyzable. In addition, a novel TRIM27-RET fusion transcript between exon 3 of TRIM27 and exon 12 of RET was identified in 2 cases of IC with apocrine features, and one of them displayed invasive growth. Two IC cases with invasive growth harbored novel fusions TUT1-ETV5 and KIAA1217-RET, respectively. A total of 42.4% of the cases in this series of IC harbored fusions involving RET. Such fusion transcripts were not detected in any of the 10 SDC cases. We have confirmed NCOA4-RET as a predominant fusion in intercalated duct-type IC, including 3 cases with invasive growth pattern. A novel finding in our series was a case of widely invasive intercalated duct-type IC, with a single lymph node metastasis that revealed an NCOA4-RET fusion transcript. We also demonstrated that a subset of apocrine ICs harbored a TRIM27-RET gene fusion, including one case with invasive growth. In contrast, neither NCOA4-RET nor TRIM27-RET fusions were detected in any tested SDCs. Thus, the distinct molecular findings in IC and SDC support that the tumors are separate malignant salivary tumor entities. The presence of tumor-type-specific NCOA4-RET or TRIM27-RET translocations in a subset of widely invasive carcinomas with intercalated duct-like immunoprofiles suggests that a recharacterization of IC including its redesignation as "intercalated duct carcinoma, invasive or noninvasive" may be appropriate.