The risk of facial nerve palsy after benign parotidectomy. A quality project.

BACKGROUND: Facial nerve palsy is a potential complication of parotidectomy for benign salivary gland tumours, necessitating a comprehensive understanding of its incidence and associated risk factors for improved patient counselling and preoperative planning. AIM/OBJECTIVES: This single-centre retrospective study aimed to assess the rate of facial nerve palsy following benign parotidectomy at a University Teaching Hospital. MATERIAL AND METHODS: Over a 3-year period, 160 patients undergoing parotid surgery for benign tumours were included. Data, encompassing sex, age, operation technique, tumour pathology, facial nerve function, and follow-up duration, were collected from medical records. Exclusion criteria comprised patients with prior parotid gland surgery or preoperative facial nerve palsy. RESULTS: The study revealed a 3.75% incidence of facial nerve palsy with no total paralysis post-parotidectomy for benign disease. Pleomorphic adenoma (50.6%) and Warthin's tumour (44.4%) were the predominant tumour types. No significant differences were noted between groups with and without postoperative facial palsy based on obtained covariates. CONCLUSION AND SIGNIFICANCE: Our findings endorse partial superficial parotidectomy and extracapsular dissection as low-risk treatments for benign parotid tumours. However, prospective studies are warranted to elucidate recovery rates and long-term consequences of facial nerve palsy, contributing to refined surgical approaches and patient care in parotid surgery.

Missed cancer in the Danish head and neck cancer fast-track program: results from a tertiary cancer center.

BACKGROUND: The Danish head and neck cancer fast-track program is a national standardized pathway aiming to reduce waiting time and improve survival for patients suspected of cancer in the head and neck (HNC). Until now, the frequency of missed cancer in the fast-track program has not been addressed. A missed cancer leads to treatment delay and may cause disease progression and worsening of prognosis. The study objective was to estimate the frequency of patients with missed cancers in the Danish HNC fast-track program and to evaluate the accuracy of the program. MATERIALS AND METHODS: Patients who were rejected from the HNC fast-track program because cancer was not found between 1 July 2012 and 31 December 2018 at Odense University Hospital, Denmark were included and followed for three years. Patients were categorized into groups depending on the diagnostic evaluation. Group 1 included patients evaluated with standard clinical work-up without imaging and biopsy. Group 2 included patients evaluated with imaging and/or biopsy in addition to the standard clinical work-up. The local cancer database and electronic patient records were reviewed to determine if a missed cancer had occurred within the follow-up period. RESULTS: A total of 8345 HNC fast-track courses were initiated during the study period. 1499 were patients suspected of recurrent cancer and were excluded leaving 6846 patients to be assessed for eligibility. Of these, 3752 patients were rejected because cancer was not found. Ten patients were subsequently diagnosed with cancer within the follow-up period resulting in an overall frequency of 0.15%. For group 1 and 2, the frequency was 0.04% and 0.10%, respectively. The sensitivity of the fast-track program was 99.67% and the negative predictive value was 99.73%. CONCLUSION: The frequency of missed cancer in a tertiary HNC center following the Danish fast track program is low.

A rare case of bilateral renal metastases arising from minor salivary gland adenoid cystic carcinoma.

A 67-year-old female patient was diagnosed with bilateral renal metastases from adenoid cystic carcinoma (AdCC) of salivary gland origin five years after the primary diagnosis of minor salivary gland AdCC. Bilateral renal core needle biopsies were performed to distinguish primary renal cell carcinoma (RCC) from metastases and to guide treatment strategy. Few similar cases have been reported; none had bilateral metastases at the time of discovery or biopsy-verified AdCC metastases prior to the treatment decision. RCC was a tentative diagnosis and renal metastases of AdCC have previously been mistaken for RCC.

Epidemiology, outcomes, and prognostic factors in submandibular gland carcinomas: a national DAHANCA study.

PURPOSE: The aim of this study is to present incidence, histological subtypes, survival rates, and prognostic factors based on a national cohort of patients with salivary gland carcinoma. METHODS: All Danish patients with submandibular gland carcinoma diagnosed from 1990 to 2015 (n = 206) were included and analyzed following histological re-evaluation. Data were collected by the Danish Head and Neck Cancer Group (DAHANCA). Overall, disease-specific and recurrence-free survival were evaluated. Prognostic factors were analyzed with multivariate Cox Hazard Regression. RESULTS: The study population consisted of 109 (53%) men and 97 (47%) women, median age 62 years (range 11-102). Adenoid cystic carcinoma was the most frequent subtype (50%). Tumour classification T1/T2 (75%) and N0 (78%) was most frequent. The mean crude incidence was 0.17/100,000/year. Most patients (n = 194, 94%) were treated with primary surgery, and 130 (67%) received postoperative radiotherapy. The 5- and 10-year survival rates were for overall survival 64% and 41%, disease-specific survival 74% and 61%, and recurrence-free survival 70% and 56%, respectively. Survival rates were higher for adenoid cystic carcinoma compared to other subtypes, but the difference was not significant in multivariate analysis. Recurrence occurred in 69 patients, and 37 (53.6%) of them had recurrence in a distant site. Advanced T-classification and regional lymph-node metastases had significant negative impact on survival rates. CONCLUSION: The incidence of submandibular gland carcinoma in Denmark was 0.17/100,000/year and stable during the time period. The most frequent subtype was adenoid cystic carcinoma. Half of the recurrences presented in a distant site, and multivariate analysis confirmed that advanced stage was independent negative prognostic factor for recurrence and survival.

Malignancy rates of salivary gland tumors in Greenlandic Inuit comparable to non-endemic populations; epidemiological mapping of salivary gland tumors 1990-2019.

BACKGROUND: Salivary gland tumors are assumed to be predominantly malignant in the Greenlandic Inuit population, but there is limited literature on the subject. We conducted a retrospective cohort study using national registers to describe the histological tumor types, location, incidence, and survival of benign and malignant salivary gland tumors. METHODS: We analyzed data on all Greenlandic Inuit with an epithelial-derived salivary gland tumor from 1990 to 2019. We extracted data from the Central Personal Registry and crossmatched it with the Danish Pathology Data Bank. All specimens were reviewed by a specialized pathologist. We noted patient and histological characteristics, calculated crude and age-adjusted incidence rates, overall survival, and excess mortality. RESULTS: Our study found that 76% of salivary gland tumors in the Greenlandic Inuit population were benign, with pleomorphic adenoma being the most common. Malignant tumors accounted for 24% of cases, with lymphoepithelial carcinoma being the most common type. The most common place of origin for malignant tumors was the parotid gland (71%) and the submandibular gland (15%). The median age of onset for malignant tumors was 47 years. Age-adjusted incidence rates of malignant tumors for men and women were 3.00 and 4.12 per 100,000 person-years, respectively. CONCLUSION: Our findings suggest that the proportion of malignant salivary gland tumors in the Greenlandic Inuit population is similar to other nonendemic populations. Our incidence rates are higher than previously reported, likely due to differences in methodology and definitions of the Inuit population. This study provides valuable insights into the epidemiology of salivary gland tumors in the Greenlandic Inuit population and may have implications for other Inuit populations as well.

Surgical treatment of the neck in patients with salivary gland carcinoma.

BACKGROUND: Elective neck dissection (END) in patients with salivary gland carcinoma is controversial and there are no universally accepted guidelines. METHODS: Patients were identified from the Danish Head and Neck Cancer Group. Between 2006 and 2015, 259 patients with primary salivary gland carcinoma were treated with END. Variables potentially associated with regional metastases were analyzed using logistic regression. Neck recurrence-free survival was calculated using the Kaplan-Meier method. RESULTS: Occult metastases were found in 36 of the patients treated with END (14%) and were particularly frequent among patients with T3/T4 tumors and high-grade histology tumors. In multivariate analyses, high-grade histology and vascular invasion were associated with occult metastases. CONCLUSION: We recommend END of levels II and III for patients with high-grade or unknown histological grade tumors, and for T3/T4 tumors. Levels I, II, and III should be included in END in patients with submandibular, sublingual, or minor salivary gland carcinomas.

Prognostic scoring models in parotid gland carcinoma.

BACKGROUND: The aim was to identify prognostic factors and test three prognostic scoring models that predicted the risk of recurrence in patients with parotid gland carcinoma. METHODS: All Danish patients with parotid gland carcinoma, treated with curative intent, from 1990 to 2015 (n = 726) were included. Potential prognostic factors were evaluated using Cox regression and competing risk analyses. The concordance of each prognostic model was estimated using Harrel's C index. RESULTS: The study population consisted of 344 men and 382 women, with a median age of 63 years. Age above 60 years, high grade histology, T3/T4 tumor, regional lymph node metastases, and involved surgical margins were all associated with a significant reduction in recurrence-free survival. The prognostic model that agreed best with actual outcomes had a C-index of 0.76. CONCLUSION: Prognostic scoring models may improve individualized follow-up strategies after curatively intended treatment for patients with parotid gland carcinoma.

Incidence and survival of salivary gland cancer in children and young adults in Denmark: A nation-wide study for the period 1990-2015.

OBJECTIVES: The aim of this study was to evaluate incidence and survival of children and young adults with salivary gland cancer (SGC) in Denmark during the period 1990-2015. METHOD: We included all patients aged 0-24 years registered with primary SGC in the Danish Cancer Registry, the Danish Pathology Data Bank, or the DAHANCA database during 1990-2015. Patients were divided in two age-groups: children (0-17 years) and young adults (18-24 years). Incidence rates, overall survival (OS), and recurrence free survival (RFS) was evaluated in relation to age-group, sex, tumor location, tumor histology, and T-, N-, and M-classification. RESULTS: A total of 70 SGC patients between 0 and 24 years (67% female, n = 47) were included. Thirty-six were children at time of diagnosis, and 34 were young adults. The incidence was higher among young adults compared to children (0.29 vs. 0.11 per 100.000) and showed no significant change during the study period. There were no differences in the distribution of sex, tumor location, or tumor histology between children and young adults. The total 5 and 15-year survival rates were 97.1% and 91.7% for OS, and 97.1% and 83.1% for RFS. The survival rates showed no significant differences according to age-groups, sex, tumor location, or tumor histology. Patients diagnosed in stage T4 had significantly worse OS and RFS. CONCLUSION: The incidence of SGC among children and young adults in Denmark was low and stable in the period 1990-2015. The overall survival was very high, demonstrating the excellent prognosis for children and young adults with SGC.

Salivary gland carcinoma in Denmark: a national update and follow-up on incidence, histology, and outcome.

PURPOSE: Salivary gland carcinoma is a rare disease and studies on epidemiology and outcome require data collection over many years. The aim of this study is to present an update of incidence rates, anatomical sites, histological subtypes, and survival rates based on the Danish national cohort of salivary gland carcinoma patients. METHODS: Data from all Danish patients with salivary gland carcinoma diagnosed from 1990 to 2015 (n = 1601) were included and analyzed following histological reevaluation and reclassification. Overall, disease-specific, and recurrence-free survival were evaluated. Prognostic factors were analyzed with multivariate Cox Hazard Regression. RESULTS: The study population consisted of 769 men and 832 women, median age 62 years (range 6-102). The most frequent anatomic site was the parotid gland (51.8%). Adenoid cystic carcinoma was the most common subtype (24.7%). The majority had tumor classification T1/T2 (65.3%). The mean crude incidence was 1.2/100.000/year with an increase of 1.5% per year. There was no increase in age-adjusted incidence. The 5-, 10-, and 20-year survival rates were for overall survival 68, 52, and 35%, for disease-specific survival, 77, 69, and 64%, and for recurrence-free survival, 75, 64, and 51%, respectively. Age, high-grade histological subtype, advanced T-classification, cervical lymph node metastases, vascular invasion, and involved surgical margins had significantly negative impact on survival rates. CONCLUSION: The age-adjusted incidence has been stable for a period of 26 years. Multivariate analysis confirmed that histological grade, advanced stage, involved surgical margins and vascular invasion are independent negative prognostic factors. Survival rates were stationary compared to earlier reports.

Elective neck dissection in patients with salivary gland carcinoma: A systematic review and meta-analysis.

OBJECTIVE: Elective neck dissection in patients with salivary gland carcinoma and clinically negative lymph nodes is controversial. Reported proportion of occult nodal metastases vary with histological subtype, tumour classification and preoperative diagnostic methods. This is a systematic review and meta-analysis on the role of END in salivary gland carcinoma. METHODS: A search in PubMed, Embase and Cochrane was performed. Original articles in English with data on tumour characteristics, clinical and pathological N-classification, and neck dissection were included. Reporting Items for Systematic Reviews and Meta-analyses were followed. Random effect modelling was performed to pool the data. Meta-analysis of proportions was performed for occult metastases overall, for T3/T4 versus T1/T2 tumours and for tumours with high-grade versus low-grade histology. Heterogeneity across studies was assessed with I-squared statistics. RESULTS: We included 22 articles in the qualitative synthesis and meta-analysis. The pooled proportion of occult metastases was 21%. In patients with T3/T4 tumour, the pooled proportion of occult metastases was 36%, and in patients with high-grade histology, it was 34%. Most studies concluded that END should be performed in patients with advanced T-classification and high-grade histology tumours. Nine studies assessed occult metastases per level. CONCLUSION: The overall occult metastases proportion does not require END in all patients with salivary gland carcinoma. We recommend END in patients with high-grade or unknown histology or T3/T4 tumours. END should involve level II and III, and level I should be included in tumours in the submandibular gland, sublingual gland and minor oral salivary glands.

Reducing Late Dysphagia for Head and Neck Cancer Survivors with Oral Gel: A Feasibility Study.

Dysphagia is a significant late morbidity following treatment with radiotherapy (RT) for head and neck squamous cell carcinomas (HNSCC). The purpose of this feasibility study was to test a gel-based saliva substitute to reduce the subjective assessment of dysphagia while eating food items varying in size and texture. Eligible study subjects treated with curative intended RT and suffering from dysphagia and xerostomia were recruited from the outpatient clinic during a two-month period. Nineteen subjects consented to participation and completed the EORTC QLQ-H&N35 questionnaire and three test meals. A Numeric Rating Scale (NRS) was used for subjective assessment of dysphagia during all test meals. All data on patient, tumor, and treatment characteristics were obtained from the Danish Head and Neck Cancer (DAHANCA) database. NRS data suggested reduction of dysphagia after application of the oral gel. The swallowing dysfunctions, discomfort while swallowing (p = 0.008), stuck food items (p = 0.02), and multiple attempts of clearing the throat (p = 0.05), improved significantly for soft and regular items. Both small- and large-sized food items were tested. EORTC QLQ-H&N35 showed improvement regarding eating problems (p = 0.03) and social eating (p = 0.02). No episodes of food aspiration were recorded during the test meals. Late dysphagia reduces QOL and is an important morbidity following RT. In this feasibility study, the oral gel was able to reduce dysphagia while eating soft and selected regular food items. Eating-related EORTC QLQ-H&N35 items also improved, indicating a beneficial reduction in dysphagia after application of the oral gel.

Upfront PET/CT affects management decisions in patients with recurrent head and neck squamous cell carcinoma.

PURPOSE: To compare multidisciplinary team conference (MDTC) decisions regarding treatment intent based on either chest X-ray + MRI of the head and neck (CXR/MRI) or 18F-FDG-PET/CT (PET/CT) in patients with recurrent head and neck squamous cell carcinoma (HNSCC). METHODS: Prospective blinded cohort study based on paired data. Consecutive patients with suspected recurrent HNSCC were invited to participate. All included patients underwent CXR/MRI and PET/CT before diagnostic biopsy. An ordinary MDTC using all available imaging data was conducted as per standard practice. After at least three months (to eliminate recall bias in the team), the first project MDTC, based on either CXR/MRI or PET/CT, was conducted, and the tumor board made conclusions regarding treatment. After an additional three months, a second project MDTC was conducted using the complementary imaging strategy. The separate treatment strategies were compared using McNemar's test. RESULTS: A total of 110 patients (90 males and 20 females, median age 66 years, range 40-87) were included. The initial primary tumor originated from the pharynx in 56 (51%) patients, oral cavity in 17 (15%) patients, and larynx in 37 (34%) patients. Based on CXR/MRI, 87 patients (79%) were recommended curative treatment and 23 (21%) palliative treatment. Based on PET/CT, the MDTC decided that 52 (47%) patients were suitable for curative treatment and 58 (53%) for palliative treatment. The absolute difference of 32% was statistically significant (95% CI: 22-42%, p < 0.001). CONCLUSIONS: PET/CT affected MDTC decisions in patients with recurrent HNSCC towards less curative and more palliative treatment.

Risk of Malignancy in FDG-Avid Thyroid Incidentalomas on PET/CT: A Prospective Study.

BACKGROUND: Due to a substantial risk of malignancy, patients with focal FDG-avid thyroid incidentalomas (FFTIs) on PET/CT are in most of Denmark referred to Head and Neck Cancer (HNC) fast track programs. The aim of this study was to determine the risk of malignancy in FFTI managed in a HNC fast track program. METHODS: A prospective cohort study including all patients with FFTI referred to the HNC fast track program, Odense University Hospital between September 1, 2016 and August 31, 2017. Ultrasonography (US) and fine-needle aspiration biopsy (FNAB) were intended to be done in all patients. Nodules with cytology of Bethesda 1, 3, 4, 5, or 6 were planned for surgical removal. RESULTS: A total of 104 patients were included. All patients had US and 101 patients (97%) had FNAB. Forty-two patients had benign cytology classified as Bethesda 2. The remaining 62 patients underwent surgery except from 11 patients, mainly due to comorbidity. The overall risk of malignancy for patients with FFTI referred to our HNC fast track program was calculated to be 24% (23/95) based on patients with unequivocal cytology and/or histology. The only statistically significant US characteristic to predict malignancy was the appearance of irregular margins with a sensitivity of 47% and specificity of 96%. CONCLUSION: The risk of malignancy of FFTIs handled in our HNC fast track program is 24%.

Up-front F18-FDG PET/CT in suspected salivary gland carcinoma.

OBJECTIVE: To investigate whether a 18F-FDG PET/CT (PET/CT)-based diagnostic strategy adds decisive new information compared to conventional imaging in the evaluation of salivary gland tumours and the detection of cervical lymph node metastases, distant metastases, and synchronous cancer in patients with salivary gland carcinoma. METHODS: The study was a blinded prospective cohort study. Data were collected consecutively through almost 3 years. All patients underwent conventional imaging-magnetic resonance imaging (MRI) and chest X-ray (CXR)-in addition to PET/CT prior to surgery. Final diagnosis was obtained by histopathology. MRI/CXR and PET/CT were interpreted separately by experienced radiologists and nuclear medicine physicians. Interpretation included evaluation of tumour site, cervical lymph node metastases, distant metastases, and synchronous cancer. RESULTS: Ninety-one patients were included in the study. Thirty-three patients had primary salivary gland carcinoma and eight had cervical lymph node metastases. With PET/CT, the sensitivity was 92% and specificity 29% regarding tumour site. With MRI/CXR, the sensitivity and specificity were 90% and 26%, respectively. Regarding cervical lymph node metastases in patients with salivary gland carcinoma, the sensitivity with PET/CT was 100% and with MRI/CXR 50%. PET/CT diagnosed distant metastases in five patients, while MRI/CXR detected these in two patients. Finally, PET/CT diagnosed two synchronous cancers, whereas MRI/CXR did not detect any synchronous cancers. CONCLUSIONS: Compared with MRI/CXR PET/CT did not improve discrimination of benign from malignant salivary gland lesions. However, PET/CT may be advantageous in primary staging and in the detection of distant metastases and synchronous cancers.

Impact of age, comorbidity, and WHO performance status on delay of treatment in patients undergoing fast-track work-up for head and neck cancer.

OBJECTIVES: Fast-track programs for diagnostic work-up and start of cancer treatment are defined by legislation in Denmark. The aim was to examine whether age, comorbidity or WHO performance status influence the time from referral due to suspicion of cancer to start of treatment (waiting time) in the Danish fast-track program. MATERIAL AND METHODS: For this descriptive cohort study, consecutive head and neck cancer (HNC) patients who underwent radiotherapy or surgery from January 2014 to July 2016 at Odense University Hospital (OUH) were identified in the database of the Danish Head and Neck Cancer group (DAHANCA). Age (<70 vs. ≥70 years), comorbidity (none vs. any), and WHO performance status (0-1 vs. 2-4) were correlated to waiting time. RESULTS: In total, 650 HNC-patients were included and of those, 92% were discussed at the multidisciplinary team conference. Patients ≥70 years were less frequently discussed in a multidisciplinary setting compared to younger patients (88% vs. 93%, p < 0.05). The time spent for diagnostic workup and treatment planning (waiting time) was longer for patients having primary radiotherapy than for primary surgery (p < 0.001), and 21% of patients treated with primary radiation exceeded the recommended maximum waiting time, whereas this was the case for only 7% of the patients treated with primary surgery. However, age ≥ 70 years, presence of comorbidity or poor performance status did not significantly influence the waiting time. CONCLUSION: Age ≥ 70 years, comorbidity and poor WHO performance status did not influence the waiting time among patients with head and neck cancer treated at OUH.

MicroRNA dysregulation in adenoid cystic carcinoma of the salivary gland in relation to prognosis and gene fusion status: a cohort study.

Adenoid cystic carcinoma (ACC) is among the most frequent malignancies of the salivary gland, and is notorious for its prolonged clinical course characterized by frequent recurrences often years after initial treatment. No molecular marker has been shown to have independent prognostic value in ACC, including characteristic gene fusions involving MYB, MYBL1, and NFIB. MicroRNA has been shown to be associated with clinical outcome in numerous malignancies, including one study of ACC, warranting further validation of this class of markers in this disease. Here, we investigate the prognostic value of microRNA in two ACC cohorts: a training cohort (n = 64) and a validation cohort (n = 120) with microarray and qPCR. In the training cohort, multivariate analysis of microarray data found high expression of hsa-miR-6835-3p to be associated with reduced recurrence-free survival (RFS) (p = 0.016). Measuring the highest ranking microRNAs identified in survival analysis in the same cohort, qPCR identified high expression of hsa-miR-4676 to be associated with reduced overall survival (OS) and high expression of hsa-mir-1180 to be associated with improved RFS. This was not confirmed in the validation cohort, in which qPCR identified high expression of hsa-mir-21, hsa-mir-181a-2, and hsa-mir-152 to be associated with reduced OS and high expression of hsa-miR-374c to be associated with improved RFS. Interestingly, two distinct subsets of ACC separated in microRNA expression irrespective of gene fusion status, but without significant difference in outcome. Collectively, qPCR identified several microRNAs associated with OS and RFS, and different subsets of ACC separated according to microRNA expression, suggestive of ACC being a heterogeneous group of malignancies in its microRNA profile.

Genetic rearrangements, hotspot mutations, and microRNA expression in the progression of metastatic adenoid cystic carcinoma of the salivary gland.

Adenoid cystic carcinoma (ACC) is among the most common salivary gland malignancies, and is notorious for its unpredictable clinical course with frequent local recurrences and metastatic spread. However, the molecular mechanisms for metastatic spread are poorly understood. This malignancy is known to frequently harbor gene fusions involving MYB, MYBL1, and NFIB, and to have a low mutational burden. Most studies have focused on primary tumors to understand the biology of ACC, but this has not revealed a genetic cause for metastatic dissemination in the majority of cases. Hence, other molecular mechanisms are likely to be involved. Here, we characterize the genetic and microRNA expressional landscape of primary ACC and corresponding metastatic lesions from 11 patients. FISH demonstrated preservation of MYB aberrations between primary tumors and metastases, and targeted next-generation sequencing identified mutations exclusive for the metastatic lesions in 3/11 cases (27.3%). Global microRNA profiling identified several differentially expressed miRNAs between primary ACC and metastases as compared to normal salivary gland tissue. Interestingly, individual tumor pairs differed in miRNA profile, but there was no general difference between primary ACCs and metastases. Collectively, we show that MYB and NFIB aberrations are consistently preserved in ACC metastatic lesions, and that additional mutations included in the 50-gene hotspot panel used are infrequently acquired by the metastatic lesions. In contrast, tumor pairs differ in microRNA expression and our data suggest that they are heterogeneous according to their microRNA profile. This adds an additional layer to the complex process of ACC metastatic spread.

Adenoid cystic carcinomas of the salivary gland, lacrimal gland, and breast are morphologically and genetically similar but have distinct microRNA expression profiles.

Adenoid cystic carcinoma is among the most frequent malignancies in the salivary and lacrimal glands and has a grave prognosis characterized by frequent local recurrences, distant metastases, and tumor-related mortality. Conversely, adenoid cystic carcinoma of the breast is a rare type of triple-negative (estrogen and progesterone receptor, HER2) and basal-like carcinoma, which in contrast to other triple-negative and basal-like breast carcinomas has a very favorable prognosis. Irrespective of site, adenoid cystic carcinoma is characterized by gene fusions involving MYB, MYBL1, and NFIB, and the reason for the different clinical outcomes is unknown. In order to identify the molecular mechanisms underlying the discrepancy in clinical outcome, we characterized the phenotypic profiles, pattern of gene rearrangements, and global microRNA expression profiles of 64 salivary gland, 9 lacrimal gland, and 11 breast adenoid cystic carcinomas. All breast and lacrimal gland adenoid cystic carcinomas had triple-negative and basal-like phenotypes, while salivary gland tumors were indeterminate in 13% of cases. Aberrations in MYB and/or NFIB were found in the majority of cases in all three locations, whereas MYBL1 involvement was restricted to tumors in the salivary gland. Global microRNA expression profiling separated salivary and lacrimal gland adenoid cystic carcinoma from their respective normal glands but could not distinguish normal breast adenoid cystic carcinoma from normal breast tissue. Hierarchical clustering separated adenoid cystic carcinomas of salivary gland origin from those of the breast and placed lacrimal gland carcinomas in between these. Functional annotation of the microRNAs differentially expressed between salivary gland and breast adenoid cystic carcinoma showed these as regulating genes involved in metabolism, signal transduction, and genes involved in other cancers. In conclusion, microRNA dysregulation is the first class of molecules separating adenoid cystic carcinoma according to the site of origin. This highlights a novel venue for exploring the biology of adenoid cystic carcinoma.