Adenoid Cystic Carcinoma, Clinical Presentation, Current Treatment and Approaches Towards Novel Therapies.

Adenoid cystic carcinoma (AdCC) is a rare cancer originating from secretory glands with unknown aetiology. It is one of the most dominant malignant salivary tumours (MST). However, it can arise in other areas of the head and neck region and in secretory glands outside this area. It occurs at all ages, but is more frequent between 50-70 years of age and more common in females than in males. The symptoms of AdCC are generally unspecific and the clinical diagnosis of AdCC maybe challenging, partially due to its heterogenous histopathology and indolent growth. Moreover, there is a lack of good prognostic markers, and due to its rarity, it is difficult to predict which therapeutic methods are the most optimal for each patient, especially since very late recurrences occur. This review presents some major characteristics of AdCC and some current treatments for this disease.

[Diagnosis and treatment of subglottic mass（report of 5 cases）].

Subglottic masses is very rare. The clinical data of five cases of subglottic mass in our hospital from 2017 to 2022 were summarized, and their clinical manifestations, auxiliary examination findings, treatment plan and pathological features were analyzed. Among the 5 patients, 1 case was subglottic pleomorphic adenoma, 1 case was subglottic granuloma, 1 case was subglottic breast cancer metastasis, 1 case was subglottic primary adenoid cystic carcinoma, and 1 case was immunoglobulin G4-related disease. No recurrence was observed in the patients so far. Subglottic mass is easy to be missed. Therefore, when the lesion is suspected in this area, the examination of ear, nose and throat should be carried out systematically to detect the lesion early and improve the prognosis.

Solid basal adenoid cystic carcinoma of the breast: A case report and literature review.

RATIONALE: Adenoid cystic carcinoma (AdCC) is a rare malignancy of the breast with a low Ki-67 index and good prognosis. Owing to the rarity of breast AdCC, the misdiagnosis rate is as high as 50%, and there is no consensus or recognized guidelines for the treatment of this disease. Therefore, it is necessary to conduct a detailed clinical and pathological analysis in combination with a literature review to improve our understanding, diagnosis, and treatment of the disease. METHODS: A 68-year-old woman sought medical attention due to a recently increasing mass in the breast. The left breast mass was 1.3 cm × 1 cm in size. We analyzed the morphology, immunohistochemistry, and molecular characteristics of the tumor removed by surgery, and reviewed relevant literature. DIAGNOSES: Solid basal AdCC of the breast. INTERVENTIONS: We performed biopsy, immunohistochemistry and molecular testing on surgical resection specimens. OUTCOMES: Combining morphological and immunohistochemical features, it is consistent with solid basal AdCC of the breast, and Fish detected MYB gene break. LESSONS: Due to the high misdiagnosis rate of AdCC, accurate histopathological diagnosis is particularly important. At present, breast conserving surgery and local tumor resection are mainly used for the treatment of breast AdCC, and postoperative adjuvant radiotherapy is feasible.

[Correlation of MYB/NFIB gene fusion with the grade and prognosis of head and neck adenoid cystic carcinoma and the concordance of two detection methods].

Objective: To explore the correlation between MYB/NFIB gene fusion and clinicopathological features such as tumor grade and prognosis of head and neck adenoid cystic carcinoma (ACC), and to assess the concordant rate of fluorescent in situ hybridization (FISH) with MYB and NFIB immunohistochemistry. Methods: FISH detection of MYB/NFIB gene fusion was performed on 48 head and neck ACC cases and 15 non-ACC salivary gland tumors at National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China during April 2014 and January 2020. ACC cases were divided into grade Ⅰ-Ⅱ, grade Ⅲ and high-grade transformation, according to pathological grading criteria. Prognosis, FISH results and other clinicopathological characteristics were analyzed. MYB and NFIB immunohistochemistry was performed on the 48 ACC and 15 non-ACC cases. The diagnostic accuracy of FISH and immunohistochemistry was compared. Results: FISH detected MYB/NFIB gene fusion in 41.7% (20/48) of the ACC. Its positive rate was inversely correlated with higher pathological grades (P=0.036). The higher histological grade was linked to worse progression-free survival (P=0.024), whereas there was no correlation between the status of gene fusion detected by FISH and progression-free survival (P=0.536). FISH didnot detect MYB/NFIB gene fusion in 15 non-ACC salivary gland tumors The specificity of diagnosing ACC is 100% for both FISH detection of gene fusion and immunohistochemical detection of MYB expression. However, the sensitivity for both methods was only about 41.7%, respectively. By combining FISH and MYB immunohistochemistry, the sensitivity for diagnosing ACC was increased to 66.7%. Conclusions: MYB/NFIB gene fusion has a lower detection rate in grade Ⅲ ACC and high-grade transformation ACC. Meanwhile gene fusion status is not correlated with prognosis. The sensitivity for diagnosing ACC can be improved by combining FISH and MYB immunohistochemistry.

Rare but clinically important salivary gland-type tumor of the lung: A review.

Salivary gland-type tumor (SGT) of the lung, which arises from the bronchial glands of the tracheobronchial tree, was first recognized in the 1950s. SGT represents less than 1% of all lung tumors and is generally reported to have a good prognosis. Mucoepidermoid carcinoma (MEC) and adenoid cystic carcinoma (ACC) are the two most common subtypes, comprising more than 90% of all SGTs. The reported 5-year survival rate of patients with SGT is 63.4%. Because this type of tumor develops in major bronchi, patients with SGT commonly present with symptoms of bronchial obstruction, including dyspnea, shortness of breath, wheezing, and coughing; thus, the tumor is usually identified at an early stage. Most patients are treated by lobectomy and pneumonectomy, but bronchoplasty or tracheoplasty is often needed to preserve respiratory function. Lymphadenectomy in the surgical resection of SGT is recommended, given that clinical benefit from lymphadenectomy has been reported in patients with MEC. For advanced tumors, appropriate therapy should be considered according to the subtype because of the varying clinicopathologic features. MEC, but not ACC, is less likely to be treated with radiation therapy because of its low response rate. Although previous researchers have learned much from studying SGT over the years, the diagnosis and treatment of SGT remains a complex and challenging problem for thoracic surgeons. In this article, we review the diagnosis, prognosis, and treatment (surgery, chemotherapy, and radiotherapy) of SGT, mainly focusing on MEC and ACC. We also summarize reports of adjuvant and definitive radiation therapy for ACC in the literature.

Diagnosis of Adenoid Cystic Carcinoma with Striking Tubular Hypereosinophilia by MYB and EWSR1 Breakapart Fluorescence In Situ Hybridization.

BACKGROUND: Adenoid cystic carcinoma (AdCC), associated with MYB/MYBL1 gene rearrangements, shows epithelial and basaloid myoepithelial cells arranged in tubular, cribriform and solid patterns. Variations from this classic morphology make diagnosis challenging, necessitating molecular testing. AdCC with striking tubular hypereosinophilia (AdCC-STE) is one such recently described histological subtype. METHODS: A 52-year-old female presented with a floor of mouth swelling for two months, diagnosed elsewhere as polymorphous adenocarcinoma (PAC). A biopsy was obtained. With a diagnosis of oncocytic neoplasm, wide excision of the tumor was undertaken. Histological examination, fluorescence in situ hybridization (FISH) and ultrastructural examination were performed. Archival cases of PAC and epithelial myoepithelial carcinoma (EMC) were reviewed, and MYB immunostaining and FISH were performed to identify potential AdCC-STE cases. RESULTS: The excised tumor from the index patient showed bilayered tubules, micropapillae and cribriform pattern. Luminal cells with hypereosinophilic to clear cytoplasm were surrounded by flattened abluminal cells. Focally, basophilic matrix was seen within sharply demarcated pseudocystic spaces. FISH revealed MYB and EWSR1 gene rearrangements, confirmatory of AdCC-STE. Electron microscopy showed features consistent with AdCC; however, mitochondria were not prominent. Among 14 archival PACs, two showed MYB immunopositivity; one showed MYB rearrangement but was classical AdCC. Among 35 EMC, one case showed MYB immunoreactivity and eosinophilia of luminal cells but lacked MYB/MYBL1 rearrangement. CONCLUSION: Awareness of unusual histological subtypes of AdCC, such as AdCC-STE, is imperative, as it may be misdiagnosed as PAC and EMC, among others. Presence of basophilic matrix and squamoid morules in a biphasic tumor even with hypereosinophilic rather than basaloid myoepithelial appearance should raise suspicion for AdCC-STE, and prompt molecular testing for confirmation. With wider accessibility, lower cost and significantly shorter turn-around-time when compared to RNA sequencing, FISH can be employed for confirmation of diagnosis, especially in low- and middle-income countries.

The Novel Application of Robotic-Assisted Bronchoscopy Combined with Photodynamic Therapy for Adenoid Cystic Carcinoma of the Trachea.

Robotic platforms have been widely used in the various fields of clinical diagnosis and therapy of diseases in the past decade. Robotic-assisted bronchoscopy (RAB) demonstrates its advantages of visibility, flexibility, and stability in comparison to conventional bronchoscopic techniques. Improving diagnostic yield and navigation yield for peripheral pulmonary lesions has been defined; however, RAB platform of treatment was not reported. In this article, we report a case of a 52-year-old woman who was diagnosed with the tracheal adenoid cystic carcinoma and recurred in the second postoperative year, leading to the involvement of the entire tracheal wall and lumen obstruction. Since the lesion was inoperable, we combined RAB and photodynamic therapy (PDT) for the patient. The potential advantages of using RAB for PDT delivery include precise light irradiation of target lesions and stable intra-operative control over the long term. This is a novel application of RAB combined with PDT for airway diseases. The case report may provide a new insight into the diagnosis and treatment of pulmonary diseases. In addition to improving the diagnostic rates, the RAB platform may also play an important role in the treatment of airway and lung disease in the future.

[Misdiagnosis of adenoid cystic carcinoma of oropharynx: a case report].

Adenoid cystic carcinoma usually occurs in the salivary glands of the head and neck. It is a malignant tumor with a high degree of malignancy, resistance to radiotherapy and chemotherapy and poor prognosis. The clinical course of adenoid cystic carcinoma is slow and easy to be misdiagnosed. The main diagnosis and treatment means are individualized and precise treatment under the multi-disciplinary consultation mode, that is, surgical treatment and radiotherapy and chemotherapy. Adenoid cystic carcinoma is prone to relapse and hematologic metastasis, and the traditional radiotherapy and chemotherapy based therapies have not achieved satisfactory efficacy in the past three decades. How to detect, diagnose and treat early is an urgent task faced by clinicians.

A cytodiagnosis of adenoid cystic carcinoma of the tracheobronchial tree through a systematic clinical case comparison and analysis.

BACKGROUND: Primary adenoid cystic carcinoma (AdCC) of the tracheobronchial tree is very rare with a high risk for recurrence and metastasis. The diagnosis of AdCC by histologic and immunohistochemical means has been well studied clinically. However, the identification of AdCC by cytologic features remains elusive due to the atypical features the cancer presents. This study aimed to describe the cytologic features of AdCC by using bronchial brushing, which could aid in distinguishing AdCC from other pulmonary carcinomas. METHODS: The cytopathological features of bronchial brushing smears collected from seven cases were histologically diagnosed as AdCC. The defined cytologic features, which could potentially be diagnostic, were systemically analyzed. RESULTS: Four out of the seven cytologic cases were inconcordance with the histologic diagnosis and cytologically classified as positive for malignant cells, small cell carcinoma, or atypical cells. Three cases showed a characteristic adenoid structure and magenta stroma forming globule, which was distinguished from the four cases. Cytologically, the above mentioned three cases were uniform with relatively small bland nuclei and little cytoplasm. In this study, only one case showed atypical polygonal medium-sized cells with conspicuous nucleoli. CONCLUSIONS: Unlike fine-needle aspiration cytology, magenta stroma globules might offer an alternate clue for cytodiagnosis of AdCC clinically. Bronchial brushings cytology was more present in bland uniform cells with high nuclear to cytoplasmic ratios and background mucoid substance. More cases should be collected and confirmed using histopathology with careful film reading to reduce the rate of misdiagnosis.

Malignant and Benign Tracheobronchial Neoplasms: Comprehensive Review with Radiologic, Bronchoscopic, and Pathologic Correlation.

Tracheobronchial neoplasms are much less common than lung parenchymal neoplasms but can be associated with significant morbidity and mortality. They include a broad differential of both malignant and benign entities, extending far beyond more commonly known pathologic conditions such as squamous cell carcinoma and carcinoid tumor. Airway lesions may be incidental findings at imaging or manifest with symptoms related to airway narrowing or mucosal irritation, invasion of adjacent structures, or distant metastatic disease. While there is considerable overlap in clinical manifestation, imaging features, and bronchoscopic appearances, an awareness of potential distinguishing factors may help narrow the differential diagnosis. The authors review the epidemiology, imaging characteristics, typical anatomic distributions, bronchoscopic appearances, and histopathologic findings of a wide range of neoplastic entities involving the tracheobronchial tree. Malignant neoplasms discussed include squamous cell carcinoma, malignant salivary gland tumors (adenoid cystic carcinoma and mucoepidermoid carcinoma), carcinoid tumor, sarcomas, primary tracheobronchial lymphoma, and inflammatory myofibroblastic tumor. Benign neoplasms discussed include hamartoma, chondroma, lipoma, papilloma, amyloidoma, leiomyoma, neurogenic lesions, and benign salivary gland tumors (pleomorphic adenoma and mucous gland adenoma). Familiarity with the range of potential entities and any distinguishing features should prove valuable to thoracic radiologists, pulmonologists, and cardiothoracic surgeons when encountering the myriad of tracheobronchial neoplasms in clinical practice. Attention is paid to any features that may help render a more specific diagnosis before pathologic confirmation. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Subglottotracheal Adenoid Cystic Carcinoma in a 16-Year-Old Female-A Case Report.

Cystic adenoid carcinoma (ACC) is a rare malignant epithelial tumor arising from exocrine glands and accounts for only 1% of head and neck cancers. ACCs are common in the fifth and sixth decades of life, predominantly in women, and characterized by slow progression, local aggression, recurrence, and high metastasis. Subglottotracheal ACC is a rare tumor in the pediatric population, with only a few cases reported in the literature. We present a case of a 16-year-old female who was diagnosed with ACC in the subglottic and tracheal region. The patient presented with respiratory failure but without a history of dysphonia, dyspnea, stridor, or dysphagia. The diagnosis was confirmed by a biopsy, and subsequent imaging studies showed a large tumor involving the subglottic and tracheal region. The therapeutic management of this patient has been challenging due to the rarity of this tumor in the pediatric population and the potential long-term complications associated with tumor recurrence and psychological impact. This case highlights the diagnostic and therapeutic challenges in the management of subglottotracheal ACC in children and the importance of a multidisciplinary approach to optimize patient outcomes.

Pulmonary adenoid cystic carcinoma: molecular characteristics and literature review.

BACKGROUND: Pulmonary adenoid cystic carcinoma (PACC) is an exceptionally rare salivary gland-type malignant neoplasm. Because of its clinical manifestations, imaging features are not different from other types of non-small cell lung cancer, which is a diagnostic challenge for most doctors. CONCLUSIONS: A review of the literature shows that high amounts of immunohistochemical (IHC) markers, such as CK7, CD117, P63, SMA, CK5/6, and S-100 are helpful for PACC diagnosis. Surgical resection is the main treatment of PACC, but treatment options for advanced PACC patients are limited and the research of molecular targeted drugs is ongoing in advanced cases not eligible for surgery. Currently, research on PACC targeted therapy mainly focuses on the exploration of v-myb avian myeloblastosis virus oncogene homolog (MYB) and its downstream target genes. In addition, median tumor mutation burden and PD-1/PD-L1 were lower in PACC, which may indicate poor efficacy of immunotherapy in PACC patients. This review focuses on the pathologic features, molecular characteristics, diagnosis, treatment and prognosis of PACC to establish a comprehensive understanding of PACC.

Adenoid Cystic Carcinoma (ACC) of the Bartholin's gland misdiagnosed for three times: a case report.

BACKGROUND: Adenoid cystic carcinoma (ACC) in Bartholin's gland is an uncommon malignant tumor. These tumors have a vague clinical feature, so they are diagnosed late and discovered at a high-level stage. Our case presented Three Recurrences and Three times Misdiagnosis of Adenoid Cystic Carcinoma (ACC). CASE PRESENTATION: We report a case of adenoid cystic carcinoma arising in Bartholin's gland of a 64-year-old female patient that appeared after three previous vulvar tumors were excised. The patient underwent bilateral radiotherapy which was performed on the perineum. CONCLUSION: ACC of the vulvar sweat glands is prone to misdiagnosis and delay in both diagnosis and treatment. As seen in our case, it was misdiagnosed three times as Chondroid Syringoma. Further studies need to be conducted to better understand the tumor prognosis, and its optimal treatment options.

Pathological nodal status as a main predictive factor of survival and treatment outcomes of submandibular salivary gland cancers: A 25-year single center experience.

INTRODUCTION: Aim of this study was to explore the survival predictive factors and treatment outcomes in a cohort of SGC patients treated at a single center over a period of 25 years. MATERIALS AND METHODS: Patients who had received primary treatment for SGC were enroled. Outcomes evaluated were: overall survival (OS), disease specific survival (DSS), recurrence free survival (RFS), locoregional recurrence free survival (LRFS) and distant metastasis free survival (DFS). RESULTS: A total of 40 patients with SGC were enroled in the study. The most common tumor was the adenoid cystic carcinoma (60% of cases). Cumulative OS for 5-and 10-year follow up period was 81% and 60%, respectively. Thirteen patients (32.5%) developed distant metastases during follow-up. Nodal status, high-grade histology, tumor stage and adjuvant radiation-therapy (RT) were significant variables on multivariate analysis for survival and treatment outcomes. CONCLUSIONS: Submandibular gland carcinomas represent rare and heterogenous tumor group regarding histological appearance and locoregional and distant metastatic potential. Tumor histological grade, AJCC tumor stage and nodal status were the strongest predictive factors for survival and treatment outcomes. RT improved OS and locoregional treatment outcome, but not DFS. Elective neck dissection (END) could be beneficial for selected cases of SGC. Superselective neck dissection of levels I-IIa may be the level of dissection for END. Distant metastases were the main cause of death and treatment failure. Prognostic factors for poor DMFS were AJCC stage III and IV, high tumor grade and nodal status.

Prognostic Model and Nomogram for Early-Onset Adenoid Cystic Carcinoma of Head and Neck: A Retrospective SEER-Based Analysis.

BACKGROUND: Adenoid cystic carcinoma of head and neck (ACCHN) is an uncommon head and neck cancers, whose predilection age is 40 to 60. Some studies have revealed that early-onset cancers, such as colorectal cancers and esophageal adenocarcinoma, might present some unique clinicopathological features and have different prognosis with late-onset ones. However, little is known about the early-onset ACCHN. This study aimed to develop a prognostic nomogram for overall survival (OS) of patients younger than 40 with ACCHN. METHODS: Cases with ACCHN from 1975 to 2016 were retrieved from SEER-18 program. Demographic, clinical, and survival outcomes data of patients were identified for further analysis. The caret package was used to randomly divide early-onset patients into a training cohort and a validation cohort. A prognostic nomogram was constructed based on the univariate and multivariate Cox analysis. The discriminative ability and calibration power of the nomogram was evaluated by the concordance index (C-index), calibration curve, and receiver operating characteristic (ROC) curve. RESULTS: A total of 5858 cases with ACCHN were selectively retrieved from SEER program in this study. The number of patients younger than 40, which was defined as early-onset ACCHN in this study, was 825. Based on the outcomes of multivariate analysis, tumor size, chemotherapy, surgery, and stage were selected for the construction of nomogram to predict 10-year OS. The C-index was 0.792 (95%CI 0.760-0.823) and 0.776 (95%CI 0.720-0.832) in the training and validation set, respectively. The area under the ROC curve values were 0.875 (95%CI 0.810-0.940) and 0.833(95%CI 0.754-0.912). The calibration plot indicated that this nomogram had proper calibration in both the training and validation cohorts. CONCLUSION: A novel prognostic nomogram for early-onset ACCHN was constructed and validated in this study. This nomogram could be applied for assisting clinicians to more accurately assess the prognosis of young patients, which might facilitate clinical decision-making and subsequent follow-up.

Updated Salivary Gland Immunohistochemistry: A Review.

CONTEXT.­: Salivary gland neoplasms are rare lesions in the head and neck (H&N) pathology realm. There are more than 20 malignant and 15 benign salivary gland neoplasms in the 5th edition of the World Health Organization classification of H&N tumors. These neoplasms consist of heterogeneous groups of uncommon diseases that make diagnosis and treatment challenging for the clinical team. Using an algorithmic immunohistochemical approach-defined tumor origin and type has proven to be effective and advantageous. Immunohistochemistry may be used as sort of a "diagnostic looking glass," not as a positive or negative type tool, but as an indispensable complement to a hematoxylin-eosin morphologic pattern-based approach. Furthermore, the understanding of the novel discoveries of the salivary gland gene fusions and the molecular aspects of these tumors makes the process easier and improve the diagnosis as well as treatment aspects. This review reflects our experience with more recent diagnostic antibodies, which include MYB RNA, Pan-TRK, PLAG1, LEF1, and NR4A3. Each of these is linked with a specific type of neoplasm; for example, gene fusions involving the PLAG1 and HMGA2 oncogenes are specific for benign pleomorphic adenomas, and MYB is associated with adenoid cystic carcinoma. OBJECTIVE.­: To review these more recent antibodies, which highly enhance salivary gland neoplasm diagnosis. DATA SOURCES.­: The study sources involved literature PubMed searches, including multiple review articles, case reports, selected book chapters, and Geisinger Medical Center cases. CONCLUSIONS.­: Salivary gland tumors are a rare, varied group of lesions in H&N pathology. We need to have continuous readings and revisions of the molecular consequences of these fusion oncoproteins and their subsequent targets, which will eventually lead to the identification of novel driver genes in salivary gland neoplasms.

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

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

[Primary salivary gland tumors from a pathology perspective : Morphomolecular peculiarities and diagnostic and therapeutic challenges]. / Primäre Speicheldrüsentumoren aus Sicht der Pathologie : Morphomolekulare Besonderheiten und diagnostisch-therapeutische Herausforderungen.

Similar to tumors of other organs, salivary gland neoplasms were historically viewed as a single neoplastic entity and mostly treated as such. Accordingly, only the clinical tumor stage, and not the histological subtype, was considered to be of significant prognostic impact. However, over the years, several distinct sub-entities have been characterized based on morphological features, such as adenoid cystic carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, and salivary duct carcinoma. Most importantly, the nosology of salivary gland carcinomas has undergone a dynamic "splitting" on the basis of morphological, immunophenotypic, and molecular characteristics, so that 21 independent carcinomas are now listed in the current World Health Organization (WHO) classification. Moreover, it has become evident that splitting of these carcinoma subtypes no longer represents a "pathologist's hobby," but carries significant prognostic and therapeutic relevance for optimized cancer surgery and potentially systemic therapy. The current review summarizes the major features of salivary gland tumors, both benign and malignant, and gives an account of their classification systems and genetic profiles.