Salivary duct carcinoma in situ of the parotid gland

New Entities and Concepts in Salivary Gland Tumor Pathology: The Role of Molecular Alterations

CONTEXT.—

Salivary gland tumors are rare tumor types for which the molecular understanding has resulted in a rapid expansion and shuffling of entities. These changes are reflected in the 5th edition World Health Organization Classification of Head and Neck Tumours (WHO 5th edition), although many nuances still remain.

OBJECTIVE.—

To review how molecular alterations have helped recategorize, justify, and reinstate entities into our lexicon as well as defining interrelationships between categories, new entities, and subtypes. Furthermore, newer theranostic applications to molecular phenotype will be summarized.

DATA SOURCES.—

World Health Organization Classification of Head and Neck Tumours (WHO 3rd through 5th editions), literature review, and personal and institutional experience.

CONCLUSIONS.—

Molecular alterations have helped reclassify, retain, and create new categories by augmenting rather than replacing standard criteria. Key entities that have emerged include sclerosing polycystic adenoma, microsecretory adenocarcinoma, and mucinous adenocarcinoma. Molecular phenotypes solidify the range of morphology in established entities such as mucoepidermoid carcinoma and facilitate connectivity between entities. Molecular characteristics now allow for targeted therapeutic approaches for secretory carcinoma and adenoid cystic carcinoma.

Salivary Duct Carcinoma Arising in a Warthin Tumor of the Parotid Gland: A Rare Case Report with Review of Literature and PD-L1 Expression

Warthin's tumor is the second most common neoplasm of the parotid gland and consists of 2 components, including lymphoid stroma and glandular epithelium. Malignant transformation in this tumor is mostly seen in the lymphoid component; however, the carcinomatous transformation of the epithelial component is extremely rare. Cases of latter reported in the literature include squamous cell carcinoma, adenocarcinoma, mucoepidermoid carcinoma, oncocytic carcinoma, Merkel cell carcinoma, and undifferentiated carcinoma. We describe an extremely rare case of salivary duct carcinoma arising in a Warthin tumor in a 64-year-old male. Patient presented with an enlarging left parotid mass, biopsy of which showed salivary duct carcinoma. He subsequently underwent left parotidectomy along with left level II-IV lymph node dissection. Histology revealed both in situ as well as invasive salivary duct carcinoma arising from Warthin tumor. Immunohistochemistry showed tumor cells positive for CK7, AR, and GATA3, while p63 highlighted the myoepithelial cell layer in the in situ component. Her2 was 2+ by immunohistochemistry. In addition, PD-L1 IHC revealed positive expression with a combined positive score of 20%.

Salivary Gland Intraductal Carcinoma: How Do 183 Reported Cases Fit Into a Developing Classification

Salivary gland intraductal carcinoma (IDC) is a very uncommon group of neoplasms. Many names, variations in diagnostic criteria, and newly observed molecular findings (including NCOA4 :: RET , TRIM27 :: RET , HRAS point mutations, and PIK3CA pathway alterations) have generated further confusion in being able to recognize and categorize this group of tumors. Different histologic appearances and patterns of growth suggest there is more than one tumor category, with intercalated duct, apocrine, oncocytic, and hybrid features seen. Frankly destructive invasion further complicates the category, as the name "intraductal" would suggest an "in situ" neoplasm. Recent evidence on fusion-positive IDC demonstrates the same molecular underpinnings in both the ductal and the myoepithelial cells, which aids in further separating these tumors. This article summarizes the historical group of 183 neoplasms classified under the umbrella of IDC and highlights the unique histologic, immunohistochemistry, and molecular features that may further guide nomenclature standardization and harmonization.

Sclerosing Polycystic Adenoma: Conclusive Clinical and Molecular Evidence of Its Neoplastic Nature

Sclerosing polycystic adenosis, initially considered a non-neoplastic salivary gland lesion and classified as such in the 2017 WHO Classification of Head and Neck Tumors, has been the subject of controversy regarding its possible neoplastic nature. The reporting of recurrent PI3K pathway alteration represents evidence to support these lesions as being neoplastic and more appropriately referred to as sclerosing polycystic adenoma (SPA). Herein, we provide additional evidence that supports the classification of SPA as a true neoplasm. Eight cases of SPA were identified in our database and consultation files. All cases were subjected to PTEN immunohistochemistry (IHC) and next-generation sequencing (NGS). In addition, one patient underwent genetic counseling and germline testing. The cases included 5 men and 3 women with a mean age of 41 years (range 11-78) and all tumors arose in the parotid gland. One patient had multiple recurrences over a period of 2 years. Morphologically the tumors were circumscribed and characterized by an admixture of acini, ducts and cysts embedded in a fibrotic/sclerotic stroma. The cells lining the ducts and cysts showed variable granular, vacuolated, foamy and apocrine cytoplasmic features, as well as acinar cells contained intracytoplasmic brightly eosinophilic granules. The apocrine intraductal proliferations showed mild to moderate atypia in 6 cases. One case showed overt malignant morphology that ranged from intraductal carcinoma to invasive salivary duct carcinoma. Seven cases tested for PTEN IHC showed loss of nuclear expression in the acinar and ductal cells with retained PTEN expression in the myoepithelial cell and stroma. NGS detected PIK3CA or PIK3R1 genetic alterations in 7 cases, including a novel TFG-PIK3CA fusion. Coexisting PTEN mutations were seen in 4 cases, including in a patient with clinical stigmata of Cowden syndrome and confirmed by germline genetic testing. Our findings herein documented including recurrence of tumor, malignant transformation, high prevalence of PI3K pathway oncogenic alterations and the possible heretofore undescribed association with Cowden syndrome add support to classifying SPA as true neoplasms justifying their designation as adenoma, rather than adenosis.

Development of head and neck pathology in Europe

This review gives a brief history of the development of head and neck pathology in Europe from a humble beginning in the 1930s to the explosive activities the last 15 years. During the decades before the introduction of immunohistochemistry in the 1980s, head and neck pathology grew as a subspeciality in many European countries. In the late 1940s, the Institute of Laryngology and Otology with its own pathology laboratory was founded in London, and in 1964 the World Health Organization (WHO) International Reference Centre for the Histological Classification of Salivary Tumours was established at the Bland-Sutton Institute of Pathology, also in London. International collaboration, and very much so in Europe, led to the publication of the first WHO Classification of Salivary Gland Tumours in 1972. In the 1960s, a salivary gland register was organised in Hamburg and in Cologne the microlaryngoscopy was invented enabling microscopic endoscopic examination and rather shortly afterwards a carbon dioxide laser attached to the microscope became established and laryngeal lesions could be treated by laser vaporisation. During the last three decades, the use of immunohistochemistry supplemented with cytogenetic and refined molecular techniques has greatly facilitated the pathological diagnostics of head and neck lesions and has had a huge impact on research. Collaboration between different European centres has drastically increased partly due to establishment of scientific societies such as the Head and Neck Working Group (HNWG) within the European Society of Pathology and the International Head and Neck Scientific Group (IHNSG). A very large number of European pathologists have contributed to the 2nd, 3rd and 4th WHO books, and are involved in the upcoming 5th edition. Accredited educational meetings and courses are nowadays regularly arranged in Europe. Numerous textbooks on head and neck pathology have been written and edited by European pathologists. The increased collaboration has created larger series of tumours for research and new entities, mainly defined by their genetic abnormalities, are continuously emerging from Europe, particularly regarding salivary gland neoplasms and "undifferentiated" sinonasal tumours. These findings have led to a better and more precise classification and open the possibilities for new treatment strategies.

A rare case of high-grade intraductal carcinoma of the upper lip: immunohistochemical and genetic analyses

Although intraductal carcinoma (IDC) of the salivary glands was previously called low-grade cribriform cystadenocarcinoma, it was newly categorized in the 4th version of the World Health Organization classification. We report a case of IDC of the upper lip and examined it immunohistochemically and genetically. The patient was a 48-year-old Japanese female, who noticed a tiny nodule on her left upper lip. Histologically, the tumor cells, which had eosinophilic cytoplasm, exhibited papillary and solid growth patterns, and regions of suspected microinvasion or intraductal spread were also seen at the periphery of the tumor. Small necrotic foci were noted. Immunohistochemically, the tumor cells were diffusely positive for the androgen receptor, CK19, CK5/6, EGFR, and SOX10, whereas they were focally positive for GCDFP-15, S-100 protein, and mammaglobin. The tumor nests were surrounded by alpha-smooth muscle actin-p63-/calponin-/CK14-positive myoepithelial cells. The Ki-67 labeling index was 51.2%. Genetic analysis showed no evidence of the TRIM27-RET or NCOA4-RET fusion gene. We finally diagnosed the tumor as a high-grade mixed intercalated duct/apocrine-type IDC of the upper lip. IDC of the minor salivary glands is exceedingly rare. We discuss diagnostic problems associated with minor salivary gland lesions, and the "basal-like" phenotype of this case.

Salivary Duct Carcinoma With Rhabdoid Features-No or Aberrant Expression of E-cadherin and Genetic Changes in CDH1: Immunohistochemical and Genetic Analyses of 17 Cases

Salivary duct carcinoma is a relatively uncommon malignancy of the salivary glands; however, it frequently occurs as a carcinomatous component of carcinoma ex pleomorphic adenoma. We previously reported salivary duct carcinoma with rhabdoid features (SDCRF) as an extremely rare subtype of salivary duct carcinoma, and that it occurred as a salivary counterpart of pleomorphic lobular carcinoma of the breast (PLCB). We collected new cases of SDCRF for this study, in which we examined a total of 17 cases immunohistochemically and genetically. As it is known that PLCB exhibits loss of or aberrant E-cadherin expression and carries nonsense/missense mutations in or deletion of the CDH1 gene, we examined the CDH1 gene status of our SDCRF cases. All of the examined SDCRF cases involved the diffuse proliferation of large ovoid cells with eosinophilic cytoplasm and eccentric nuclei, which displayed reduced cell-cell adhesion. Most cases were positive for pan-cytokeratin, androgen receptor, gross cystic disease fluid protein-15, SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1, and WI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily A member 4, whereas they were negative for vimentin. No and decreased/cytoplasmic E-cadherin expression was observed in 11 and 4 of 17 cases, respectively, whereas no and decreased/cytoplasmic β-catenin expression were observed in 10 and 5 of 17 cases, respectively. Among the 11 cases that could be genetically analyzed, a nonsense mutation (1 case), missense mutations (6 cases), and insertions (1 case) were detected in the CDH1 gene. In conclusion, we propose that SDCRF is the salivary counterpart of PLCB due to its morphology and immunophenotype, and the genetic status of CDH1.

The Myoepithelial Cells of Salivary Intercalated Duct-type Intraductal Carcinoma Are Neoplastic: A Study Using Combined Whole-slide Imaging, Immunofluorescence, and RET Fluorescence In Situ Hybridization

Intraductal carcinoma (IDC) is a salivary gland tumor currently believed to be analogous to breast ductal carcinoma in situ, consisting of a complex neoplastic epithelial proliferation surrounded by a continuous layer of myoepithelial cells presumed to be native and non-neoplastic. Recent molecular insights have shown that there are at least 3 different types of IDC: (1) intercalated duct-like, with frequent NCOA4-RET fusions; (2) apocrine, with multiple mutations similar to salivary duct carcinoma; and (3) mixed intercalated duct-like and apocrine with frequent RET fusions, especially TRIM27-RET. Recent observations (eg, IDC occurring in lymph nodes) have challenged the notion that the myoepithelial cells of IDC are non-neoplastic. Five IDCs with known RET fusions by RNA sequencing were retrieved from the authors' archives, including 4 intercalated duct-like IDCs with NCOA4-RET, and 1 mixed intercalated duct-like/apocrine IDC with TRIM27-RET. A panel of immunohistochemistry antibodies (S100 protein, p63 or p40, mammaglobin, smooth muscle actin, calponin, androgen receptor) was tested. To precisely localize RET split-positive cells, each case was subjected to sequential retrieval of whole-slide imaging data of hematoxylin and eosin (HE) staining, immunofluorescence staining for calponin, and fluorescence in situ hybridization (FISH) for RET. Because NCOA4-RET is an inversion difficult to visualize on conventional RET FISH, a novel 3-color FISH technique was utilized to demonstrate it clearly. In all 5 cases, the proliferative ducts were completely surrounded by a layer of myoepithelial cells that were positive for p63 or p40, smooth muscle actin, and calponin. Using combined HE, calponin immunofluorescence, and RET FISH imaging, the positive signals were unmistakably identified in both calponin-negative ductal cells and peripheral, calponin-positive myoepithelial cells in all 5 cases. Utilizing combined HE, calponin immunofluorescence, and RET FISH imaging, we demonstrated that IDCs with RET fusions harbored this alteration in both the ductal and myoepithelial cells. This is compelling evidence that the myoepithelial cells of IDC are not mere bystanders, but are rather a component of the neoplasm itself, similar to other biphasic salivary gland neoplasms like pleomorphic adenoma and epithelial-myoepithelial carcinoma. This finding raises questions about the appropriate terminology, classification, and staging of IDC.

Oncocytic intraductal carcinoma of salivary glands: a distinct variant with TRIM33-RET fusions and BRAF V600E mutations

AIMS

Salivary gland intraductal carcinoma (IDC) is a complex ductal neoplasm surrounded by a layer of myoepithelial cells. Recent insights have shown that there are three different types: intercalated duct-like, with frequent NCOA4-RET fusions; apocrine, with salivary duct carcinoma-like mutations; and mixed intercalated duct-like/apocrine, with RET fusions, including TRIM27-RET. In addition, an oncocytic IDC has been described, but it remains unclear whether it represents a fourth variant or simply oncocytic metaplasia of another IDC type. Our aim was to more completely characterize oncocytic IDC.

METHODS AND RESULTS

Six IDCs with oncocytic changes were retrieved from the authors' archives, from three men and three women ranging in age from 45 to 75 years (mean, 63 years). Five arose in the parotid gland, with one in an accessory parotid gland. Four patients with follow-up were free of disease after 1-23 months. Several immunostains (S100, mammaglobin, androgen receptor, and p63/p40) and molecular tools (RNA sequencing, RET fluorescence in-situ hybridisation, BRAF V600E VE1 immunohistochemistry, and Sanger sequencing) were applied. Histologically, the tumours were variably cystic with solid intracystic nodules often difficult to recognise as intraductal. In all, tumour ducts were positive for S100 and mammaglobin, negative for androgen receptor, and completely surrounded by myoepithelial cells positive for p63/p40. Molecular analysis revealed TRIM33-RET in two of six cases, NCOA4-RET in one of six cases, and BRAF V600E in two of six cases. One case had no identifiable alterations.

CONCLUSIONS

Oncocytic IDC shares similarities with intercalated duct-like IDC. Although additional verification is needed, the oncocytic variant appears to be sufficiently unique to be now regarded as the fourth distinct subtype of IDC. Because of its indolent nature, oncocytic IDC should be distinguished from histological mimics.

Intraductal Carcinomas of the Salivary Gland

Intraductal carcinoma of the salivary gland is a rare tumor characterized by intracystic proliferations of papillary, cribriform, and solid architecture of small uniform epithelial cells, reminiscent of ductal carcinoma in situ of the breast. Recent literature has identified 4 distinctive subtypes: the intercalated duct type, apocrine type, mixed/hybrid type, and oncocytic type, all with corresponding immunohistochemical and molecular findings. Although these tumors are typically in situ, as evidenced by a retained myoepithelial layer, they can demonstrate minimal invasion or, rarely, widespread invasive growth. Their overall prognosis is favorable, with few reported cases of recurrences and nodal metastases but no evidence of distant metastases.

Salivary duct carcinoma: Updates in histology, cytology, molecular biology, and treatment

Salivary duct carcinoma (SDC) is an aggressive subtype of primary salivary gland carcinoma, often with an advanced stage at presentation and high rates of metastasis and recurrence. It most commonly arises in the parotid gland of older men and microscopically resembles high-grade breast ductal carcinoma. While 50 years have lapsed since the first report of this entity, recent intensive studies have shed light on its biologic, genetic, and clinical characteristics. The diagnosis of SDC is aided by the immunohistochemical expression of androgen receptor (AR) coupled with its characteristic histomorphology. Fine-needle aspiration typically reveals cytologic features of high-grade carcinoma, and ancillary studies using cell block material can facilitate the specific diagnosis of SDC. In surgical specimens, certain histologic features are important prognostic factors, including nuclear pleomorphism, mitotic counts, vascular invasion, and the morphology at the invasion front. Several clinical studies have shown promising results using targeted therapy for AR and human epidermal growth factor receptor 2 (HER2), and the latest version of the National Comprehensive Cancer Network guidelines recommends the evaluation of AR and HER2 status before treatment. Recent molecular analyses have revealed multiple heterogeneous alterations in well-known oncogenes and tumor suppressor genes, including TP53, HRAS, PIK3CA, PTEN, and BRAF. Clinical trials of drugs targeting these genes may broaden the treatment options for SDC in the near future.

Salivary Intraductal Carcinoma Arising within Intraparotid Lymph Node: A Report of 4 Cases with Identification of a Novel STRN-ALK Fusion

Intraductal carcinoma (IDC) is a rare salivary gland tumor that is considered analogous to ductal carcinoma in-situ of the breast, demonstrating a complex neoplastic epithelial proliferation surrounded by a continuous layer of presumed non-neoplastic myoepithelial cells. It is subcategorized into intercalated duct, apocrine, and hybrid subtypes based on morphologic and immunohistochemical features, with frequent NCOA4-RET and TRIM27-RET fusions, respectively, seen in intercalated duct and hybrid tumors. However, as an expanding clinicopathologic spectrum of IDC has been documented, controversy has emerged as to whether this tumor type is best defined by its intraductal growth pattern or distinctive molecular and immunophenotypic differentiation. Here, we further explore the nature of IDC by evaluating four cases that arose within intraparotid lymph nodes. These intercalated-duct phenotype tumors with diffuse S100 protein expression demonstrated a crowded and complex epithelial proliferation arranged in cystic, cribriform, and micropapillary architecture, surrounded by an intact myoepithelial cell layer, and were completely intranodal. Of two tumors with tissue available for molecular analysis, one demonstrated a NCOA4-RET fusion and one harbored a STRN-ALK fusion that is novel to IDC. Not only does the intranodal presence of IDC present a challenging differential diagnosis, but the complex nature of this proliferation within lymph node tissue raises questions as to whether the myoepithelial component of IDC is actually non-neoplastic in nature. Furthermore, identification of a STRN-ALK fusion expands the genetic spectrum of IDC and adds to evidence of an emerging role for ALK in salivary gland tumors. Further attention to the nature of the myoepithelial cells and documentation of alternate fusion events in IDC may inform continued discussion about its appropriate classification.

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.

Low-grade Apocrine Intraductal Carcinoma: Expanding the Morphologic and Molecular Spectrum of an Enigmatic Salivary Gland Tumor

Intraductal carcinoma (IDC) is the current designation for a salivary gland neoplasm previously referred to as "low-grade salivary duct carcinoma" and "low-grade cribriform cystadenocarcinoma," among others. IDC is conceptually believed to be similar to ductal carcinoma in-situ of the breast. Although IDC is one entity in the current WHO Classification of Head and Neck Tumors, recent studies have suggested that at least three subtypes exist: a low-grade, intercalated duct-like variant with frequent RET rearrangements; a high-grade apocrine variant with complex, salivary duct carcinoma-like genetics; and a mixed variant. We sought to characterize an unusual form of low-grade, purely apocrine IDC. Three cases of apocrine-type IDC with low-grade histology were retrieved from the authors' consultation files. Immunohistochemistry for androgen receptor, GCDFP-15, S100, smooth muscle actin, and p40 was performed. A custom, targeted next generation sequencing (NGS) panel including 1425 cancer-related genes was also done on all cases. All three cases developed in the parotid glands of men, aged 51, 63, and 73 years (mean, 62 years). All cases consisted of large, rounded macrocysts surrounded by smaller nests which were lined by cells with abundant granular eosinophilic cytoplasm and large round nuclei with prominent nucleoli. Pleomorphism was mild, the mitotic rate was low, and necrosis was absent. No cases had any invasive foci or areas of intercalated duct-like morphology. By immunohistochemistry, all cases were diffusely positive for androgen receptor and GCDFP-15, surrounded entirely by an intact layer of small myoepithelial cells positive for S100, smooth muscle actin, and p40. Targeted NGS results were obtained from two cases: both harbored HRAS mutations and copy number losses in TP53, while one case each harbored mutations in PIK3CA, SPEN, and ATM. Fusions were absent in both cases. All three patients were treated by surgery alone, and are currently free of disease (follow up 12-190 months). This study confirms the existence of a low-grade, purely apocrine form of IDC. In its pure form, i.e., without an intercalated duct-type component, low-grade apocrine IDC is genetically similar to high-grade salivary duct carcinoma, with frequent HRAS and PI3K pathway mutations. Despite its molecular similarities to the aggressive salivary duct carcinoma, low-grade apocrine IDC appears to behave in a very indolent manner, supporting is classification as a non-invasive neoplasm, and underscoring the need to distinguish these tumors from each other.

What do we know about the cytological features of pure intraductal carcinomas of the salivary glands?

OBJECTIVE

Intraductal carcinomas (IDCs) are rare, poorly characterised salivary gland tumours. The cytological features of IDCs are even less known. In this paper, a systematic literature review of pure IDCs (without stromal invasion, not associated with other histotypes) of low-grade (LG-IDCs) and high-grade (HG-IDCs) was performed.

METHODS

The bibliographic research included multiple databases (PubMed, Scopus, Web of Science). Mild-moderate nuclear atypia favoured LG-IDCs, severe atypia favoured HG-IDCs.

RESULTS

Preoperative fine-needle aspiration cytology (FNAC) was performed in 13/94 published cases (14%): 10 parotid; two oral; one submandibular. All the cases were histologically LG-IDCs, except two parotid IDCs. FNAC results included: negative for malignancy (three of 13 cases, 23%); tumour of uncertain malignant potential (seven of 13, 54%); malignancy (three of 13, 23%). The ductal component was identified in two cases; mucoepidermoid carcinoma was suggested in two additional cases. The grade was underestimated on FNAC evaluation in one HG-IDC as focal high-grade features were present on subsequent histological examination. The cases diagnosed as malignant tumours or describing intermediate atypia resulted in LG-IDCs on subsequent histology. Occasional mitoses were described only in one HG-IDC; this feature may have not been considered in the remaining published cases.

CONCLUSIONS

FNAC and clinico-pathological correlation are important aids for clinicians and pathologists. FNAC could assist surgery even if an accurate diagnosis is sometimes impossible. Discrepancy in grading the nuclear atypia between the FNAC material and the resected specimen can occur, sometimes being unavoidable. Further studies are needed to better characterise this rare tumour.

Intraductal carcinomas of the salivary glands: systematic review and classification of 93 published cases

Intraductal carcinomas (IDCs) are rare, not well-characterized salivary gland tumors. A systematic literature review of pure IDCs (without stromal invasion) of low-grade (LG-IDCs) or high-grade (HG-IDCs) was performed: IDCs were classified using the apocrine (AR+/S100-) vs intercalated (S100+/AR-) classification. Eighty-two LG-IDCs and 11 HG-IDCs were identified (84% parotid; 11% oral; 3% submandibular; 1% lacrimal; and 1% unknown). Out of 11 HG-IDCs, 2 HG-IDCs (18%) recurred as HG-IDC or invasive carcinoma. IDCs were classified as follows: intercalated (30%); mixed apocrine and intercalated (27%); apocrine (11%); oncocytic (6%); intercalated with focal oncocytic features (1%); and unclassifiable (25%). Double AR/S100 expressors (4%) or discrepancies between morphology and immunophenotype (9%) were found. Apocrine features and necrosis were more frequent in HG-IDCs (55%; 45%). Pleomorphism favored HG-IDCs (especially when combined with >10 mitoses/10 HPFs and/or Ki67 index >10%), being associated with apocrine areas at least in 3 HG-IDCs (27%). IDCs were typically mammaglobin+/ER-/PR-/DOG1-. No immunomarker clearly distinguished HG-IDCs from LG-IDCs. About 57% IDCs (16 LG-IDCs, 1 HG-IDC) showed RET rearrangements, including NCOA4-RET (eight intercalated and two unclassifiable IDCs) and TRIM27-RET fusions (two mixed IDCs). No ETV6, ALK-1, ROS, NTRK3, MAML2, MAML3, or PLAG1 rearrangements were identified. Complete excision and total sampling should exclude invasive areas.

Molecular Profiling of Salivary Gland Intraductal Carcinoma Revealed a Subset of Tumors Harboring NCOA4-RET and Novel TRIM27-RET Fusions: A Report of 17 cases

Intraductal carcinoma (IC) is the new World Health Organization designation for tumors previously called "low-grade cribriform cystadenocarcinoma" and "low-grade salivary duct carcinoma." The relationship of IC to salivary duct carcinoma is controversial, but they now are considered to be distinct entities. IC is a rare low-grade malignant salivary gland neoplasm with features similar to mammary atypical ductal hyperplasia or ductal carcinoma in situ, that shows diffuse S100 protein and mammaglobin positivity and is only partially defined genetically. (Mammary analogue) secretory carcinoma harboring ETV6-NTRK3, and in rare cases ETV6-RET fusion, shares histomorphologic and immunophenotypical features with IC. Recently, RET rearrangements and NCOA4-RET have been described in IC, suggesting a partial genetic overlap with mammary analogue secretory carcinoma. Here, we genetically characterize the largest cohort of IC to date to further explore this relationship. Seventeen cases of IC were analyzed by next-generation sequencing using the FusionPlex Solid Tumor kit (ArcherDX). Identified fusions were confirmed using fluorescence in situ hybridization break apart and, in some cases, fusion probes, and a reverse transcription polymerase chain reaction designed specifically to the detected breakpoints. All analyzed cases were known to be negative for ETV6 rearrangement by fluorescence in situ hybridization and for ETV6-NTRK3 fusion by reverse transcription polymerase chain reaction. Next-generation sequencing analysis detected a NCOA4-RET fusion transcript joining exon 7 or 8 of NCOA4 gene and exon 12 of RET gene in 6 cases of intercalated duct type IC; and a novel TRIM27-RET fusion transcript between exons 3 and 12 in 2 cases of salivary gland tumors displaying histologic and immunohistochemical features typical of apocrine IC. A total of 47% of IC harbored a fusion involving RET. In conclusion, we have confirmed the presence of NCOA4-RET as the dominant fusion in intercalated duct type IC. A novel finding in our study has been a discovery of a subset of IC patients with apocrine variant IC harboring a novel TRIM27-RET.

Cytopathology approach to rare salivary gland lesions with oncocytic features

Salivary glands located in the head and neck area are known to have different lesions with prominent oncocytic features. Fine needle aspiration is usually the initial approach in the management of these lesions, whether they represent neoplastic or non-neoplastic processes. Owing to the limited material present upon cytopathologic examination, knowledge of variants and subtypes of various oncocytic lesions that can occur in this area is of major importance to provide the most accurate interpretation to the patients and clinicians. In this article, we selected rare lesions of the salivary glands that may exhibit oncocytic changes, and provided a brief discussion of each one of them, with emphasis on challenges in navigating the differential diagnosis that these cases may pose, from the cytopathology standpoint.

Intraductal Carcinoma of Salivary Glands Harboring TRIM27-RET Fusion with Mixed Low Grade and Apocrine Types

Intraductal carcinomas (IDCs) of salivary gland are rare neoplasms. Here, we report a case of IDCs harboring TRIM27-RET fusion with mixed low grade and apocrine types. A 79-year-old male presented with slowly-growing left parotid mass for 2.5 years. Histologically, the tumor demonstrated two distinct morphologies; a classic intercalated duct and low grade apocrine component. The intercalated duct component was positive for S100, SOX10 and vimentin, and negative for DOG-1 and HER2. The apocrine component was positive for androgen receptor (AR) and focally positive for HER2. The tumor harbored a TRIM27-RET fusion by FISH, and was negative for ETV6 and PLAG1 rearrangements. This case is unusual in that it displays two true phenotypically distinct components, which has only rarely been reported. This is the first report of intraductal carcinoma with two true phenotypically distinct components composed of low-grade and apocrine types with RET rearrangement and TRIM27-RET fusion.

Clinicopathological Behavior and Treatment-related Outcome of Rare Salivary Duct Carcinoma: The Shaukat Khanum Memorial Cancer Hospital Experience

Background

Salivary gland tumors are rare salivary gland malignancies with resemblance to ductal breast carcinoma. We have described clinicopathological behavior and treatment outcomes of this rare malignancy.

Methods

Salivary duct carcinoma patients treated from 2010 to 2015 were retrospectively analyzed for clinicopathological characteristics and treatment-related outcomes of the disease.

Results

A total of 12 patients with salivary duct carcinoma were included in the study. All were males with mean age of 52.58 ± 13.43. Parotid gland was the most commonly involved major salivary gland while buccal mucosa and anterior tongue were most common oral cavity sub-sites involving minor salivary glands. The disease-free survival was 75% at 10 months and 25% at 20 months. The mean follow-up time was 12 months. There were three local recurrences and one distant metastasis.

Conclusion

Salivary duct carcinoma is a locally aggressive tumor with tendency for local recurrence and distant metastasis. Adverse features such as perineural invasion, extra-capsular spread and advanced nodal disease may worsen prognosis.

Recurrent RET Gene Rearrangements in Intraductal Carcinomas of Salivary Gland

Intraductal carcinoma (IC) is the World Health Organization designation for lesions previously called low-grade cribriform cystadenocarcinoma. The relationship of IC to salivary duct carcinoma (SDC) is controversial, but currently these are considered distinct entities. It is hypothesized that IC and SDC should have different genomic signatures that may be identifiable by next-generation sequencing. A total of 23 ICs were identified: 14 pure IC and 9 invasive carcinomas with an intraductal component. Five invasive carcinomas were subjected to next-generation paired-end RNA sequencing. Data analysis was performed using FusionSeq and Mutation detection algorithms (MuTect and VarScan) for variant callers. Gene fusion candidates were validated by fluorescence in situ hybridization and reverse transcription polymerase chain reaction, and mutations by Sanger sequencing. Among the 9 invasive carcinomas, all except 1 were apocrine SDCs with an intraductal component. The remaining case showed typical intercalated duct type IC with invasive adenocarcinoma. The 14 pure ICs had typical intercalated duct features (2 showed hybrid intercalated/apocrine features). RNA sequencing predicted a NCOA4-RET fusion, confirmed by reverse transcription polymerase chain reaction, in the intercalated duct type IC invasive component. Six additional cases of pure IC showed RET rearrangement by fluorescence in situ hybridization (7/15=47%). No apocrine carcinomas showed RET rearrangement. RNA sequencing and Sanger sequencing identified PIK3CA (p.E545K/p.H1047R) and/or HRAS (p.Q61R) hotspot mutations in 6 of 8 (75%) apocrine carcinomas. In conclusion, 2 distinctive types of intraductal lesions are emerging based on molecular analysis. Classic intercalated type ICs commonly harbor fusions involving RET and rarely show widespread invasion. Apocrine intraductal lesions are typically associated with widespread invasion with no pure examples and show similar PIK3CA and HRAS mutations to SDC.

Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumors of the Salivary Gland

The salivary gland section in the 4th edition of the World Health Organization classification of head and neck tumors features the description and inclusion of several entities, the most significant of which is represented by (mammary analogue) secretory carcinoma. This entity was extracted mainly from acinic cell carcinoma based on recapitulation of breast secretory carcinoma and a shared ETV6-NTRK3 gene fusion. Also new is the subsection of "Other epithelial lesions," for which key entities include sclerosing polycystic adenosis and intercalated duct hyperplasia. Many entities have been compressed into their broader categories given clinical and morphologic similarities, or transitioned to a different grouping as was the case with low-grade cribriform cystadenocarcinoma reclassified as intraductal carcinoma (with the applied qualifier of low-grade). Specific grade has been removed from the names of the salivary gland entities such as polymorphous adenocarcinoma, providing pathologists flexibility in assigning grade and allowing for recognition of a broader spectrum within an entity. Cribriform adenocarcinoma of (minor) salivary gland origin continues to be divisive in terms of whether it should be recognized as a distinct category. This chapter also features new key concepts such as high-grade transformation. The new paradigm of translocations and gene fusions being common in salivary gland tumors is featured heavily in this chapter.

Salivary duct carcinomas can be classified into luminal androgen receptor-positive, HER2 and basal-like phenotypes

AIMS

The aim of this study was to devise a molecular classification for salivary duct carcinomas (SDCs) based on the similarities between SDCs and breast carcinomas and on characteristics of the microarray-based gene expression profiling-defined molecular subtypes of breast cancer.

METHODS AND RESULTS

Forty-two pure salivary duct carcinomas, 35 of which contained an in-situ component as defined by histological review and/or immunohistochemical analysis, were stained with antibodies for oestrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5/6. Based on these markers, tumours were classified into HER2, luminal androgen receptor-positive, basal-like, luminal and indeterminate phenotype. Analysis revealed that 16.7%, 69%, 4.8%, 9.5% and 0% were of HER2, luminal androgen receptor-positive, basal-like, indeterminate and luminal phenotype, respectively. The in-situ and invasive components displayed the same molecular subtype in all but one case.

CONCLUSION

Salivary duct carcinomas can be classified into molecular subgroups approximately equivalent to those in the breast. We also report on the existence of a subgroup of bona fide pure salivary duct carcinomas that have a 'basal-like' phenotype. Understanding the phenotypic complexity of SDCs may help to expedite the identification of novel therapeutic targets for these aggressive tumours.

Salivary duct carcinoma with rhabdoid features: a salivary counterpart of pleomorphic lobular carcinoma of the breast

AIM

To analyse the clinicopathological features and immunohistochemical characteristics of nine cases of salivary duct carcinoma (SDC) with rhabdoid features (SDCRF), representing a new, extremely rare type of salivary gland malignancy.

METHODS AND RESULTS

We analysed 2511 cases of salivary gland tumour, clinicopathologically and immunohistochemically. The incidence of SDCRF was 0.4%. Eight patients were male. The age of patients ranged from 36 years to 85 years (mean, 61 years). SDC arose from the parotid glands and submandibular gland in six and three cases, respectively. Seven cases appeared as a carcinoma component of carcinoma ex pleomorphic adenoma cases. Six patients died of disease. Histologically, diffuse proliferations of non-coherent large ovoid or polygonal carcinoma cells with eosinophilic cytoplasm and eccentric nuclei were observed in all cases; such cytological characteristics were defined as 'rhabdoid features'. Immunohistochemically, all cases were positive for cytokeratin, gross cystic disease fluid protein-15, androgen receptor, and SMARCB1, seven cases were positive for HER2, and two cases were positive for epidermal growth factor receptor. However, all cases were negative for vimentin and myoepithelial markers. Eight cases showed no or aberrant expression of E-cadherin and β-catenin. The results suggest that SDCRF is an extremely rare subtype of SDC, and not a sarcomatoid variant of SDC. SDCRF is histologically unique, and is positive for SDC markers but negative for vimentin, unlike rhabdoid-type carcinomas arising from other organs.

CONCLUSIONS

The morphogenesis of SDCRF is related to no or aberrant expression of cell-cell adhesion molecules. Therefore, SDCRF could be a salivary counterpart to pleomorphic lobular breast carcinoma.

Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland

AIMS

Polymorphous low-grade adenocarcinoma (PLGA) is the second most common intra-oral salivary gland malignancy. The vast majority of PLGAs harbour a PRKD1 E710D hot-spot somatic mutation or somatic rearrangements of PRKD1, PRKD2 or PRKD3. Given the kinase domain homology among PRKD1, PRKD2 and PRKD3, we sought to define whether PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements would be driven by somatic mutations affecting the kinase domains of PRKD2 or PRKD3.

METHODS AND RESULTS

DNA was extracted from eight microdissected PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements. Samples were thoroughly centrally reviewed, microdissected and subjected to Sanger sequencing of the kinase domains of the PRKD2 and PRKD3 genes. None of the PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements harboured somatic mutations in the kinase domains of the PRKD2 or PRKD3 genes.

CONCLUSION

PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements are unlikely to harbour somatic mutations in the kinase domains of PRKD2 or PRKD3. Further studies are warranted to define the driver genetic events in this subgroup of PLGAs.

An extremely rare salivary gland tumor: intraductal carcinoma of the buccal mucosa

Intraductal carcinoma of the salivary gland is a rare, indolent neoplasm characterized by intraductal malignant cell proliferation but lacking invasiveness, in contrast to conventional salivary duct carcinoma, a clinically aggressive neoplasm with invasive characteristics. The tumor affects the major salivary glands much more frequently than the minor salivary glands. This report describes an extremely rare intraductal carcinoma arising from the buccal mucosa in a 61-year-old man who presented with a painless mass in the left buccal mucosa, which he had had for 1 month. A biopsy of the tumor indicated it was most likely an adenocarcinoma, but accurate preoperative diagnosis was difficult. The tumor was completely removed, along with sufficient margins. Histological examination revealed that the lesion was composed of proliferating epithelial cells surrounded by an intact myoepithelial layer, with no evidence of invasion. The final diagnosis was intraductal carcinoma of the salivary gland. No recurrence has been observed for over 3 years. In conclusion, the difficulty in preoperatively diagnosing this rare entity suggests that complete surgical excision with sufficient margins remains the best treatment option.

Intratumoral heterogeneity of HER2 protein and amplification of HER2 gene in salivary duct carcinoma

Salivary duct carcinoma (SDC) is an aggressive adenocarcinoma of the salivary glands, and accounts for 1-3% of all malignant salivary gland tumors, resembling morphologically invasive ductal carcinoma (IDC) of the breast. In contrast to IDC of the breast and gastric carcinoma (GC), the study of human epidermal growth factor receptor 2 (HER2) in SDC has not progressed. Therefore, we investigated the relationship between HER2 protein expression and amplification of the HER2 gene, and compared them in terms of intratumoral heterogeneity (ITH) in 13 cases of SDC using immunohistochemistry and dual color in situ hybridization. We found seven cases with protein overexpression (53.8%) and five cases with gene amplification (38.5%) in accordance with ASCO/CAP guidelines. ITH of HER2 protein expression was seen in seven cases (53.8%). Interestingly, the ratio of the HER2 gene showed homogenous distribution with or without the presence of ITH of HER2 protein expression. SDC tends to have more ITH of HER2 protein similarly to GC, in contrast to IDC of the breast. ITH of HER2 protein in SDC has no heterogeneity of the HER2 gene amplification. The mechanism of HER2 protein expression in SDC might proceed through a more complex pathway relative to that of IDC of the breast.

Recent advances in the diagnostic pathology of salivary carcinomas

This review concentrates on the most important developments since the WHO classification of 2005. In particular, the identification of specific translocations is revolutionising the way salivary tumours are considered and will have a major impact on future diagnostic practice. This is true so far in four malignancies: mammary analogue secretory, mucoepidermoid, adenoid cystic and hyalinising clear cell carcinomas. In each, the gene rearrangement is found in 80 % or more of cases. Two 2014 publications have added further possible candidates with molecular abnormalities to the list (cribriform adenocarcinoma of the tongue and minor salivary glands and epithelial-myoepithelial carcinoma), but these findings have yet to be confirmed by other investigators. The advances in molecular pathology have also allowed re-evaluation of the morphology; for example, it is now realised that the histological spectrum of hyalinising clear cell carcinoma includes intracellular mucin in over half of cases, as well as tumours with only scanty clear cells. In a separate development, it is now proposed that salivary duct carcinoma can be subdivided along molecular lines, in ways analogous to breast cancer, suggesting new therapeutic prospects in an otherwise highly aggressive malignancy.

Envisioning the next WHO head and neck classification

The next WHO classification should abandon "salivary duct carcinoma"; conventional salivary duct carcinoma should be classified as "high-grade salivary duct carcinoma". Low-grade salivary duct carcinoma should replace the current nosology of "low-grade cribriform cystadenocarcinoma". Cystadenocarcinoma should be classified with the descriptor "Not Otherwise Specified" and should be considered an exclusionary diagnostic category. On the other hand, "Not Otherwise Specified" does not fit for hyalinizing clear cell carcinoma (HCCC). The EWSR1-ATF1 fusion is specific for HCCC within the context of salivary neoplasia. We recommend adding "hyalinizing" even though this feature is not present in all cases; the benefit of which is the mental association with a salivary clear cell malignancy. Sinonasal Renal Cell-like Adenocarcinoma (SNRCLA) is a distinct clear cell neoplasm and should be added to the next WHO classification. Future studies will bear out whether SNRCLA is even a low-grade carcinoma, or may be reclassified as "adenoma". Lastly, the next WHO monograph should include the Risk Model in the general introductory statements on oral squamous cell carcinoma, under a subheading of "Histological Prognosticators". The positive predictive value for developing locoregional recurrence in patients with low-stage oral cavity squamous carcinoma (OSCC) and "worst pattern of invasion type-5" (WPOI-5) is 42 %. Low-stage high-risk OSCC with a combination of features other than WPOI-5 is associated with 32 % likelihood for locoregional progression. WPOI-5 also predicts occult metastatic disease (p = 0.0001, Chi squared, 2 DF). Thus the Risk Model can also be used to make decisions regarding staged elective neck dissections.

Cytomorphological findings and histological correlation of low-grade cribriform cystadenocarcinoma of salivary gland in fine-needle aspiration: a case study

Low-grade cribriform cystadenocarcinoma (LGCCC) of the salivary gland is a rare tumor. We report the cytologic features and histologic correlation of a patient with LGCCC. A 57-year-old man had a hardly palpable, nontender mass in the right cheek area followed over nine months. Radiologic analysis revealed a 1.2 cm multiseptated, cystic, solid nodule in an anterior superficial lobe of the right parotid gland. Fine-needle aspiration cytology revealed many irregular overlapping sheets or clusters of ductal epithelial cells forming solid, pseudopapillary, and cribriform architectures. Nuclei of the tumor cells revealed inconspicuous atypia with minimal size variation. On the basis of these findings, we confirmed a diagnosis of ductal epithelial proliferative lesion, favoring neoplasm, with uncertain malignant potential. Tumor excision was performed, revealing a tiny multicystic nodule (0.7 cm). Histopathologically, this tumor showed the characteristic morphology of LGCCC. This is the first report of cytomorphological findings of LGCCC in Korea.

Salivary duct carcinoma of the parotid gland: is adjuvant HER-2-targeted therapy required?

PURPOSE

Salivary duct carcinoma (SDC) of the parotid gland is a highly aggressive and uncommon tumor. Overexpression of human epidermal growth factor receptor 2 (HER-2) is characteristic of SDC. HER-2 overexpression is considered a poor prognostic marker for SDC, and anti-HER-2 therapy has been suggested as a therapeutic option.

MATERIALS AND METHODS

Two patients with SDC were analyzed for HER-2 overexpression and gene amplification using immunohistochemistry and fluorescence in situ hybridization.

RESULTS

In 1 patient, no expression of HER-2 was found. In the other patient, HER-2 was demonstrated. The patient with HER-2 overexpression had a worse prognosis, and trastuzumab proved to be an effective treatment.

CONCLUSIONS

The present results have also suggested that HER-2 overexpression is associated with a poor prognosis. Therefore, HER-2 status should be evaluated at least in the presence of advanced SDC, and targeted therapy should be considered in the adjuvant setting.

Low-grade salivary duct carcinoma or low-grade intraductal carcinoma? Review of the literature

Low-grade salivary duct carcinoma (LG-SDC) is a rare neoplasm characterized by predominant intraductal growth, luminal ductal phenotype, bland microscopic features, and favorable clinical behavior with an appearance reminiscent of florid to atypical ductal hyperplasia to low grade intraductal breast carcinoma. LG-SDC is composed of multiple cysts, cribriform architecture with "Roman Bridges", "pseudocribriform" proliferations with floppy fenestrations or irregular slits, micropapillae with epithelial tufts, fibrovascular cores, and solid areas. Most of the tumor cells are small to medium sized with pale eosinophilic cytoplasm, and round to oval nuclei, which may contain finely dispersed or dark condensed chromatin. Foci of intermediate to high grade atypia, and invasive carcinoma or micro-invasion have been reported in up to 23 % of cases. The neoplastic cells have a ductal phenotype with coexpression of keratins and S100 protein and are surrounded by a layer of myoepithelial cells in non-invasive cases. The main differential diagnosis of LG-SDC includes cystadenoma, cystadenocarcinoma, sclerosing polycystic adenosis, salivary duct carcinoma in situ/high-grade intraductal carcinoma, and papillary-cystic variant of acinic cell carcinoma. There is no published data supporting the continuous classification of LG-SDC as a variant of cystadenocarcinoma. Given that most LG-SDC are non-invasive neoplasms; the terms "cribriform cystadenocarcinoma" and LG-SDC should be replaced by "low-grade intraductal carcinoma" (LG-IDC) of salivary gland or "low-grade intraductal carcinoma with areas of invasive carcinoma" in those cases with evidence of invasive carcinoma.

Carcinoma ex pleomorphic adenoma, with particular emphasis on early lesions

Carcinoma ex pleomorphic adenoma (CXPA) is a broad category of carcinomas of the salivary glands which includes at least 2 clinically relevant categories; one is referred here as early CXPA (ECXPA), the other as widely invasive CXPA. The former includes several histological patterns ranging from non-invasive/in situ/intraductal/intratubular, early invasive/extratubular/intracapsular and extracapsular (up to 6 mm). The latter includes any CXPA with invasion of >6 mm. The clinical behaviour of ECXPA is not aggressive and tends to overlap that of a pleomorphic adenoma (PA) which makes the histological report of carcinoma contradictory. These early malignant changes in PA are known since the 1970s but it has been the use of immunohistochemical and molecular genetic analysis for HER-2 and TP53 gene in the last decade that has clarified the genuine malignant nature of the cells. HER-2 and TP53 gene and protein are involved in the early stages of malignant transformation of PA. Moreover the immunohistochemical over-expression HER-2, p53 protein and Mib-1 proliferation marker may be useful markers to identify malignant areas in PA.

Salivary duct carcinoma: new developments--morphological variants including pure in situ high grade lesions; proposed molecular classification

Salivary duct carcinoma (SDC) is an aggressive primary salivary malignancy which microscopically resembles high-grade ductal carcinoma of the breast, with both in situ and invasive patterns. It is typically found in older men, most often in the parotid. It can arise de novo or as the malignant component of carcinoma ex pleomorphic adenoma. SDC is generally a hematoxylin and eosin stain-based diagnosis, with special stains and immunohistochemistry acting mainly in a confirmatory role. Other than epithelial markers, SDC expresses androgen receptors in most cases, with true HER2 positivity seen in about 15 %. Based on these data and analogous to similar schemes in the breast, it is suggested that SDCs can be classified into three main groups: luminal androgen receptor positive, HER2+ and basal phenotype. This may form the basis for prognostic information and new therapeutic possibilities. In addition to the usual type of SDC, a few less common morphological variants have been reported: papillary, micropapillary, mucin-rich, sarcomatoid and oncocytic, as well as pure in situ cases.

An analysis of PLAG1 and HMGA2 rearrangements in salivary duct carcinoma and examination of the role of precursor lesions

AIMS

Salivary duct carcinoma (SDC) often arises in pleomorphic adenoma (PA). Putative precursors, including low-grade cribriform cystadenocarcinoma (LGCCC) and ductal carcinoma in-situ (DCIS), are more controversial. Rearrangement of PLAG1 or HMGA2 is seen in 50-70% of PAs, but this has not been investigated in SDC. Using a large collection of SDCs from a single institution, we aimed to study these genes by fluorescence in-situ hybridization (FISH), and to correlate the presence of precursor lesions/intraductal proliferations with gene alterations.

METHODS AND RESULTS

Forty-four SDCs were stained for smooth muscle actin, CK14, and p63, and examined with PLAG1 and HMGA2 FISH. Eight cases were SDC ex-PA; ten had a hyalinized nodule (HN), which is suspicious for PA; six arose in association with LGCCC; and twenty were 'de-novo' SDCs. Ten cases had PLAG1 rearrangement/amplification (22.7%) and eight had HMGA2 (18.2%) rearrangement/amplification. The positive cases were four SDC ex-PAs, eight SDCs with an HN, and five 'de-novo' SDCs. Twenty-three SDC ex-PAs were present in total (52.3%). All six SDC ex-LGCCCs were FISH-negative. Myoepithelial staining surrounded all LGCCCs, and demonstrated DCIS in 17 cases. Eleven DCIS lesions were in SDC ex-PAs or FISH-positive 'de-novo' SDCs. These cases represent 'cancerization' of ducts. Only six FISH-negative 'de-novo' SDCs showed DCIS.

CONCLUSIONS

A large proportion of SDCs arise in PAs (with or without residual evidence of a PA). A small proportion of SDCs arise in LGCCCs. Cases showing DCIS often represent cancerization.

Low-grade cribriform cystadenocarcinoma of salivary glands: report of two cases and review of the literature

Abstract

Low-grade cribriform cystadenocarcinoma (LGCCC) is a recently described rare tumor of salivary gland which exhibits clinically indolent behavior. This tumor predominantly consists of intraductal components and frequently exhibits papillary-cystic or cribriform proliferation pattern. Considering the histological features of LGCCC, it should be distinguished with papillocystic variant of acinic cell carcinoma, conventional salivary duct carcinoma, cystadenocarcinoma, polymorphous low-grade adenocarcinoma, carcinoma ex pleomorphic adenoma and mammary analogue secretory carcinoma. Herein, we presented two cases of LGCCC. One arose in the left parotid region in a 48-year-old male, and the other one arose in the right parotid gland in a 59-year-old female. For both cases, immunohistochemically, the luminal tumor cells showed diffuse expression of CK and S100; p63 and smooth muscle actin displayed a continuous rim of myoepithelial cells around all tumor islets; no myoepithelial cells were admixed with the luminal cells. Both patients were alive with no tumor recurrence or metastasis at follow-up.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2593621568999135

Detection of novel actionable genetic changes in salivary duct carcinoma helps direct patient treatment

PURPOSE

Salivary duct carcinomas (SDC) are a rare and aggressive subtype of salivary gland cancers for which cytotoxic chemotherapy has limited efficacy. We investigated whether genotyping analysis could detect novel tumor-specific mutations that would help direct SDC patient treatment using targeted agents.

EXPERIMENTAL DESIGN

We genotyped 27 SDC archival specimens from patients followed at Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary (Boston, MA) between 2000 and 2011. These included the tumors of 8 patients who were tested prospectively. Targeted mutational analysis of 13 clinically relevant cancer genes was conducted using SNaPshot multiplexed genotyping. FISH was conducted to detect HER2 gene amplification. Patient medical records and tumor histopathologic features were retrospectively reviewed.

RESULTS

Mutually exclusive genetic aberrations were detected in 15 of 27 (56%) tumors, including 2 (7%) mutations in BRAF, 5 (19%) mutations in PIK3CA, and 8 (30%) cases of HER2 gene amplification. To our knowledge, this is the first time that BRAF and PIK3CA mutations have been reported in this tumor type. Prospective clinical testing of 8 patients with SDC identified actionable genetic alterations in 6 tumors and influenced therapeutic decisions for all 6 patients.

CONCLUSION

SNaPshot molecular profiling identified novel genetic changes in SDCs, expanded the therapeutic options for patients with this rare tumor, and is changing SDC management at our institution. These findings highlight the importance of using broad-based genetic profiling to expedite the identification of effective-targeted therapies for patients with rare malignancies.

Invasive salivary duct carcinoma ex pleomorphic adenoma of the parotid gland: a teaching case giving rise to the genuine diagnostic difficulty on an inadequate cytology specimen

A history of a recent rapid increase in long-standing swelling mass was presented in the right parotid gland of an 85-year-old male. The inadequate cytologic specimens contained few small clusters of three-dimensional malignant epithelial cells having hyperchromatic pleomorphic nuclei and prominent nucleoli, adjacent to a cluster of benign monomorphic myoepithelial cells. We first interpreted it merely as an adenocarcinoma, not otherwise specified. A radical parotidectomy was performed, and gross examination revealed an encapsulated and firm tumor lesion, looking grayish-blue to yellowish-white, focally associated with extracapsular invasion. On microscopic examination, the tumor was predominantly composed of a proliferation of highly atypical epithelial cells having abundant eosinophilic cytoplasm, often arranged in a Roman-bridge appearance with foci of comedo necrosis, alternating with extensive infiltration to adjacent stroma in a trabecular or alveolar fashion with severe vessel permeation. Within the background of pleomorphic adenoma, the carcinoma cells sometimes replaced ductal luminal cells while retaining an intact-like myoepithelial layer. Therefore, we finally made a diagnosis of invasive salivary duct carcinoma ex pleomorphic adenoma. We should be aware that owing to its characteristic features, cytopathologists might be able to determine correct diagnosis, based on multiple and adequate samplings.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2126158270695815.

Salivary duct carcinoma: what is already known, and can we improve survival?

Salivary duct carcinoma is an aggressive malignancy with a high mortality rate, which phenotypically resembles high-grade breast ductal carcinoma. The parotid gland is the most common location. Standard treatment is surgery to the primary tumour together with post-operative radiotherapy. Despite this, there is a high rate of local recurrence, cervical nodal involvement and distant metastasis. Chemotherapy is currently considered only for end-stage, disseminated disease; however, current evidence indicates that chemotherapy used with radiotherapy may result in improved disease control and survival.Human epidermal growth factor receptor-2 is a proto-oncogene which is over-expressed in both breast ductal carcinoma and salivary duct carcinoma. Clinical studies of patients with metastatic breast cancer, using trastuzumab, a monoclonal antibody directed against human epidermal growth factor receptor-2, have shown significant efficacy in tumour response, resulting in improved survival. Such advances in immunohistochemistry, and in targeted immunotherapy for breast ductal carcinoma, should be applied to the treatment of salivary duct carcinoma.