Mohs Micrographic Surgery Cases Research Articles

Factors associated with residual tumor at time of Mohs micrographic surgery for basal cell and squamous cell carcinomas

BackgroundResidual tumor is not always clinically apparent following biopsy of cutaneous carcinomas, which may prompt patients to question the need for definitive treatment. ObjectiveWe investigated the percentage of cases in which residual tumor was histologically present at the time of Mohs micrographic surgery (MMS) for basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) and investigated factors associated with residual tumor. MethodsWe examined 483 MMS cases performed for biopsy-proven BCC (n=287) and SCC (n=196) between October 2022 and April 2023. Single-stage MMS specimens were step-sectioned en face to exhaust the block. Univariate and multivariable logistic regression models were created. ResultsResidual tumor was identified in 83.3% of BCC and 66.8% of SCC at time of MMS (p=0.01). In patients clinically appearing tumor-free following biopsy, residual histologic tumor was identified in 68.2% of BCC and 41.5% of SCC. Residual tumor was significantly more likely in men (p=0.04), high-risk sites (p=0.002), smaller biopsy sizes (p=0.0003), and larger pre-operative sizes (p<0.0001). LimitationsSingle center, retrospective cohort ConclusionThe majority of patients with BCC and SCC have residual histologic tumor at the time of MMS, oftentimes even when tumor is not clinically apparent. Multiple factors impact the presence/absence of residual tumor.

Clinical Versus Histologic Margins for Cutaneous Squamous Cell Carcinoma: Comparing Outcomes for High-Risk Tumors Treated With Mohs Micrographic Surgery.

High-risk cutaneous squamous cell carcinoma (cSCC) is associated with poor clinical outcomes. Traditionally, preoperative clinical tumor size ≥2 cm, based on Brigham and Women's Hospital (BWH) staging criteria, is high risk. To compare outcomes of cSCC treated with Mohs micrographic surgery (MMS) with a preoperative size ≥2 cm (clinically ≥2 cm) versus cSCC with preoperative size <2 cm and postoperative defect size ≥2 cm (histologically ≥2 cm). Prospective data were collected from January 1, 2014, to December 31, 2020, on MMS cases for cSCC with a preoperative and/or postoperative size ≥2 cm. Clinical outcomes were followed until March 15, 2023. Data were analyzed using multivariate regression. Three hundred thirty cases of MMS for cSCC were included. Cutaneous squamous cell carcinoma clinically ≥2 cm occurred more frequently in elderly patients; cSCC histologically ≥2 cm were more commonly located in the H region, required wider surgical margins, and more MMS stages to achieve clearance. There were no significant differences in rates of recurrence and metastasis between the groups. These data suggest that postoperative (histologic) MMS defect size may allow for better risk stratification of high-risk cSCC and improved staging of cSCC.

Assessing outcomes of topical 5-fluorouracil as primary and adjuvant therapy for squamous cell carcinoma in-situ.

Cutaneous squamous cell carcinoma in-situ (SCCis) is an intraepithelial tumor with a good prognosis. Standard treatment includes both surgical and non-surgical interventions. We determined the clearance rate for SCCis and residual SCCis identified on frozen section during Mohs micrographic surgery (MMS) after treatment with topical fluorouracil 5% cream (5-FU). All MMS cases were initiated for biopsy-proven invasive squamous cell carcinoma (SCC). A retrospective chart review was conducted from January 2017-February 2024 at Columbia University Irving Medical Center (CUIMC) to identify patients with SCCis who were treated with topical 5-FU as primary therapy or adjuvant therapy(AT) for residual SCCis post-MMS for invasive SCC. 41 patients were included (80% males, 70.1 ± 11.8 years). The average follow-up time for the primary therapy group was 25.4 ± 12.8 months, and for the post-MMS AT group 22.5 ± 11.1 months. In the group treated with topical 5-FU as primary therapy (n = 28), 27 patients (96.43%, 95% confidence interval: 81.65-99.91%) achieved complete clearance. One patient had recurrence at 8 months post-treatment. Of the patients in the post-MMS adjuvant treatment group (n = 13), 12 (92.3% clearance, 95% confidence interval 63.97-99.81%) achieved complete clearance. One patient had recurrence at 8 months post-treatment. This study found that topical 5-FU cream is effective as both primary therapy for SCCis and as adjuvant therapy for residual SCCis following MMS of invasive SCC.

Nasal tip rotation flap for reconstruction of surgical defects on the distal nose.

The nose is a common site for the development of skin cancers. Mohs micrographic surgery (MMS) is a highly curative treatment for skin cancer of the nose. Reconstruction of MMS defects on the nose, especially on the distal aspect, can be challenging given the proximity of multiple subunits and limited adjacent tissue reservoirs. Our goal was to describe our experience using a nasal tip rotation flap (NTRF) for MMS defects on the distal nose. A retrospective review of all MMS cases at multiple institutions between June 2018 and June 2022 was undertaken. Cases that used an NTRF to repair the MMS defect(s) were selected, and data were collected on patient demographics, tumor type, anatomical location of the tumor, preoperative and postoperative size, number of stages needed to clear the tumor, repair dimensions, and any postoperative complications. A total of 66 cases that utilized an NTRF for reconstruction were included. The mean preoperative tumor size was 0.8 cm (range: 0.3-1.6 cm), and the mean defect size was 1.2 cm (range: 0.7-1.9 cm). The defects were most commonly on the nasal tip. There were no significant complications observed. The nasal tip rotation flap is a reliable reconstruction option for MMS defects of the distal nose. This flap can be used for defects that involve the nasal tip, soft triangle, and/or portions of the ala, including the alar rim.

MMS hotspots: a cross-sectional comparison of U.S. counties with and without Mohs micrographic surgery

Healthcare access greatly impacts skin cancer diagnosis and mortality rates. Recognition of current disparities in Mohs micrographic surgery (MMS) access can assist future policy and clinical decisions to correct them. For the years 2014–2018, the CPT codes for MMS (17,311 and 17,313) were counted on a per county level across the United States per the Medicare Centers for Medicare & Medicaid Services (CMS) Medicare Prescriber Database. Any county with 0 MMS CPT codes recorded were classified as “without MMS cases.” MMS “hotspots” were identified as counties that possessed a high average number of MMS cases compared to the national average, while also being surrounded by counties that possessed a low average number of MMS cases compared to the national average. Three thousand eighty-four counties in the United States were analyzed; 785 (25%) counties were designated as “with MMS cases” and 2301 (75%) “without MMS cases.” There were no significant differences in age, ethnicity distribution, or cost per enrollee between the two designations. 74% of counties with MMS cases were considered urban, while only 25% of those without cases were urban (p < 0.01). The median household income was markedly higher in counties with MMS cases ($71,428 vs. $58,913, p < 0.01). With respect to education, more individuals in counties with MMS cases possessed their General Education Development (GED) (89% vs. 86%, p < 0.01) or a college degree (30% vs. 19%, p < 0.01). Forty-nine counties were considered MMS “hotspots.” The density of MMS procedures varies greatly based on geography, maintaining the urban–rural disparity matched by the distribution of MMS surgeons. Additionally, there remains a wide income and educational gap between counties with and without MMS. Identifying MMS hotspots may facilitate further investigation into potential surgical access disparities.

Postoperative Bleeding Complications Associated With Novel Oral Anticoagulants in Mohs Micrographic Surgery.

Novel oral anticoagulants (NOACs) are commonly prescribed, recently developed anticoagulants, but limited data exist on NOAC-related bleeding complications in Mohs micrographic surgery (MMS). To assess the risk of postoperative bleeding in patients taking NOACs compared with patients taking no antithrombotic medications. A 5-year retrospective chart review of all MMS cases performed by a single surgeon was conducted. Patient and surgery characteristics, anticoagulant use, and bleeding complications were recorded. Two thousand one hundred eighty-one MMS cases in 1,545 patients were included. There were 696/2,181 cases in which patients were taking at least 1 antithrombotic medication, with 149 on NOAC monotherapy and 15 on NOAC and aspirin combination therapy. Bleeding complications occurred in 22/2,181 cases. Patients on NOAC monotherapy did not have an increased risk of bleeding complications compared with patients on no antithrombotic medications (odds ratio [OR]:1.70, 95% confidence interval [CI]: 0.36-7.97, p = .50). In contrast, patients on NOAC and aspirin combination therapy exhibited an increased bleeding risk (OR: 20.5, 95% CI: 3.99-105.7, p < .001). Novel oral anticoagulant use alone during MMS was not associated with an increased postoperative bleeding risk, supporting the safety of continuing NOAC therapy during MMS. However, NOAC and aspirin combination therapy was associated with a high postoperative bleeding risk. Nonetheless, these bleeding events did not lead to adverse long-term outcomes.

Differences in sentinel lymph node biopsy utilization in eligible melanoma patients treated with Mohs micrographic surgery or wide local excision: A population-based logistic regression model and survival analysis

Primary melanoma management relies on tumor extirpation and staging sentinel lymph node biopsy (SLNB) in eligible patients. This study compares SLNB utilization in patients undergoing wide local excision (WLE) or Mohs micrographic surgery (MMS). American Joint Committee on Cancer seventh edition≥patients with T1b melanoma undergoing WLE or MMS in the Surveillance, Epidemiology, and End Results program were included. Propensity score matching was performed to compare patients who underwent MMS or WLE. Kaplan-Meier analysis and Fine-Gray cumulative incidence functions were used for overall and melanoma-specific survival. Eight hundred twenty-five MMS cases and 38,760 WLE cases were identified. SLNB was performed in 32.61% of MMS patients and 61.77% of WLE patients with positive rates of 12.5% and 14.82%, respectively. Multiple logistic regression of factors associated with SLNB utilization revealed that WLE, male gender, younger age, extremity location, and nodular and rare melanoma subtypes were significantly associated with increased odds of receiving SLNB whereas head and neck location and lentigo maligna melanoma subtype were significantly less likely to receive SLNB. Potential selection bias from a retrospective data set. Patients receiving WLE for≥T1b melanoma are more likely to receive a SLNB than patients undergoing MMS.

Damage to the Temporal Branch of the Facial Nerve From Mohs Micrographic Surgery.

The temporal branch of the facial nerve is at risk of damage during Mohs micrographic surgery (MMS). This complication leads to motor deficit in the ipsilateral upper face with resultant functional and cosmetic impairment. To identify patient, tumor, and surgical risk factors associated with temporal nerve damage. A single-institution, retrospective review of MMS cases involving anatomic sites within the temporal nerve danger zone was performed. Risk factors were compared between cases with and without nerve damage. Of 616 cases within the danger zone, 28 (4.5%) had postoperative nerve dysfunction. Variables significantly associated with dysfunction included patient immunosuppression, tumor size, aggressive tumor histology, recurrent tumors, high degree of subclinical spread, and greater average number of Mohs stages. Preoperative tumor size and postoperative defect size of ≥3 cm resulted in a ×37 and ×40 increased odds of nerve damage, respectively. Sex, age, and basal versus squamous cell carcinoma were not significantly associated with temporal nerve damage. No patients with a postoperative defect size measuring <2 cm had nerve damage. The overall risk of damage to the temporal nerve during MMS is low, but there are certain risk factors that warrant increased counseling about this potential complication.

Second-Intention Healing in Mohs Micrographic Surgery: A Single-Center Academic Experience.

To describe the trends in second-intention healing (SIH) use at a single Mohs micrographic surgery (MMS) dermatology clinic and assess outcomes and patient satisfaction. The authors conducted a single-center, retrospective study of patients who underwent MMS from November 2012 through November 2018. Data obtained for each patient included sex, age, tumor characteristics, number of MMS stages, final defect size, and postoperative complications. Patient satisfaction of SIH was retrospectively assessed by telephone survey. Providers used SIH in 22% of all MMS cases (n = 159/718). It was most commonly used for defects located on the nose, ear, temple, and periocular region. The average defect size and number of MMS stages for tumor clearance were 1.3 cm and 1.5 stages, respectively. Overall, low rates of postoperative complications were observed, and 95% of patients reported optimal or acceptable levels of satisfaction. This study supports the idea that SIH is a safe, effective alternative for wound management and may have broader practice indications than those traditionally proposed.

Consistency in Distribution of Facial Skin Cancers Treated With Mohs Micrographic Surgery.

Mohs micrographic surgery (MMS) has become the standard of treatment for skin malignancies of the head and neck. However, there is a paucity of literature describing facial distributions of MMS. Anatomical location of skin cancer is an important feature to study as it can affect prognosis as well as pathogenesis of skin cancers. This study aims to analyze consistency in head and neck MMS anatomical distributions and compare differences between multiple centers. The study retrospectively reviews 5871 MMS cases performed at a single center in Chevy Chase, Maryland from January 2014 through December 2019. Results show distributions of skin cancers on the face treated with MMS consistently occur at the same anatomical sites year after year with minimal variance. This knowledge of consistency provides a foundation for future studies because it allows for comparison. Comparing and contrasting data across multiple centers can elucidate regional characteristics that may impact the pathogenesis and distribution of facial skin tumors. Many regional or demographical factors may be important in the development of cutaneous malignancies. This information should be considered when assessing risk factors for cancerous skin lesions.J Drugs Dermatol. 2022;21(5):506-509. doi:10.36849/JDD.6143.

Characteristics of Lower Extremity Infection Rates Following Mohs Micrographic Surgery.

Surgical site infection (SSI) is the most common complication for Mohs micrographic surgery (MMS). Lower extremity surgical sites are at an increased risk for developing SSI. This study aimed to evaluate lower extremity SSI rates post-MMS based on closure type and antibiotic usage. A retrospective review was performed of all lower extremity MMS cases from 2011 to 2016 at Vanderbilt University Medical Center. Patient history, surgical details, and follow-up appointments were reviewed. Six hundred twenty MMS lower extremity surgeries were eligible. Review identified an overall lower extremity SSI rate of 7.4%. Infection rates were significantly increased in wound closed by flaps/grafts (p < .001). Although wound size and preoperative antibiotic prophylaxis were initially associated with increased infection rate (p = .03, p = .015), the associations were fully attenuated when adjusting for closure type. More complicated repair techniques (flap/graft) for larger wound sizes contribute to increased SSI risk among lower extremity MMS cases. Providers can use this information to guide antibiotic prophylaxis.

Electrosurgery Use During Post-Mohs Micrographic Surgery Repair and Complication Rates-How Important is a Dry Field?

Electrosurgery is used to achieve hemostasis during surgery. There are no studies exploring the effects of the use or avoidance of electrodessication during Mohs micrographic surgery (MMS) repair. Given the growing concerns for tissue aerosolization, occupational smoke exposure, and spread of infectious diseases, it is important to determine the importance of electrical hemostasis. In this retrospective study, electronic medical records of a single, tertiary, academic dermatology practice were reviewed. All MMS cases that underwent surgical repair from January 1 to December 31, 2019, by 2 dermatologic surgeons (one who used electrodessication during repair and one who did not) were included. Patient demographic data, information regarding the procedures, and complications occurring 90 days after MMS were recorded. One hundred ninety-eight cases of MMS repair used electrodessication, whereas 193 cases did not. There was no significant difference in the demographic makeup, MMS procedure, or 90-day complication rates between the 2 groups. No major adverse events were MMS-related. The use or avoidance of electrodessication during MMS repair was not associated with increased 90-day postoperative complications, suggesting that a greater tolerance of moderate oozing at a surgical site during MMS repair is reasonable to minimize electrosurgical tissue damage and occupational smoke exposure.

Characteristics of Superficial Basal Cell Carcinomas Containing More Aggressive Subtypes on Final Histopathologic Diagnosis.

The prognosis and treatment of basal cell carcinoma (BCC) are largely dependent on tumor subtype, which is typically determined by punch or shave biopsy. Data regarding concordance between BCC subtype on initial biopsy and final histopathology for Mohs micrographic surgery (MMS) or excision with frozen sections (EFS) are limited. To determine the concordance between initial biopsy and final MMS or EFS subtyping of BCC. We aim to investigate the incidence and clinical characteristics of lesions initially diagnosed as superficial BCC (sBCC) that are later found to have a nodular, micronodular, or infiltrative component. We conducted a retrospective review of all MMS or EFS cases performed at a single academic center from August 1, 2015 to August 31, 2017. Inclusion criteria were a biopsy-proven diagnosis of sBCC and presence of residual tumor following stage I of MMS or EFS. Fisher&rsquo;s exact test was used to evaluate significance of clinical characteristics and outcomes associated with the presence of a nodular, micronodular, or infiltrative BCC component. A total of 164 MMS or EFS cases had an initial biopsy showing sBCC. Of these, 117 had residual BCC on stage I, and 43 (37%) were found to have a nodular, micronodular, or infiltrative component. Significant predictors of reclassified BCC subtype included age over 60 years (P=0.006) and location on the head or neck (P=0.043). Reclassified lesions required significantly more stages of MMS to clear (P=0.036). Shave biopsy was used to diagnose 114 (98%) of the included cases. Over one third of shave biopsies that initially diagnosed sBCC failed to detect a nodular, micronodular, or infiltrative component. Management of biopsy-proven sBCC should take into account the possible presence of an undiagnosed deeper tumor component with appropriate margin-assessment treatment modalities when clinically indicated. J Drugs Dermatol. 2021;20(3):283-288. doi:10.36849/JDD.5383.

Complications After Mohs Micrographic Surgery in Patients Aged 85 and Older.

As the US population ages, safe surgical procedures are necessary for treatment of cutaneous neoplasms in very elderly patients. To determine the incidence of complications associated with Mohs micrographic surgery (MMS) in patients aged 85 and older, and the risk factors that predispose to complications. A 9-year retrospective chart review of patients aged 85 and older who underwent MMS at our institution between 07/2007 and 11/2016 was performed. Six types of complications associated with scalpel-based cutaneous surgery were recorded, as well as patient, tumor, and repair characteristics. This study included 949 patients totaling in 1683 MMS cases. There were 30 complications: infection (N = 11), wound dehiscence (N = 6), hematoma (N = 6), hemorrhage (N = 5), flap necrosis (N = 1), and graft necrosis (N = 1), resulting in an overall complication rate of 1.78%. Independent risk factors associated with a statistically higher incidence of complications were anticoagulant use (odds ratio [OR], 2.78; 95% confidence interval [CI], 1.26-6.13; p = .012), extremity location (OR, 2.80; 95% CI, 1.19-6.54; p = .018), greater than 2 MMS stages (OR, 2.43; 95% CI, 1.08-5.46; p = .032), and flap repair (OR, 2.27; 95% CI, 1.05-4.90; p = .036). Mohs micrographic surgery is a safe procedure for treatment of cutaneous neoplasms in the very elderly.

Incidence of Epinephrine Reactions With Local Anesthesia in Mohs Micrographic Surgery

The incidence of reactions to epinephrine-containing local anesthetics in Mohs micrographic surgery (MMS) has not been established. To estimate the incidence of epinephrine-induced reactions from local anesthetics in patients who undergo MMS for the removal of cutaneous malignancies. From 2016 to 2018, 200 MMS patients were recruited from the authors' surgical center. Assessments were obtained throughout the entirety of the Mohs cases during a single visit. This study estimated the incidence of epinephrine reactions in patients who undergo MMS to be 2.0% (95% confidence interval: 0.1%-3.9%). No relationship between epinephrine dose and incidence of adverse effects was found. Patient age was a significant risk factor for the development of an epinephrine reaction. Systemic reactions to epinephrine from local anesthetics are an infrequent adverse event in MMS cases. The data suggest that the absolute dose of local anesthetic with epinephrine does not correlate with the risk of developing an epinephrine reaction. Older age seems to have a protective effect.

Mohs Micrographic Surgery in Patients Younger Than 40 Years.

As the availability of Mohs micrographic surgery (MMS) continues to expand in Australia and incidence of keratinocyte cancer increases in adolescents and young adults, there has been rising interest in the use of MMS in this population. This study aimed to evaluate the characteristics of MMS cases in patients younger than 40 years. A review was performed of all MMS cases in patients younger than 40 years at the time of their surgery from 2012 to 2017 at the Skin and Cancer Foundation Australia, with comparison to a control group, aged older than 40 years. Patient, tumor and management characteristics were analyzed. Four hundred ninety-three cases were eligible. Study and control groups differed significantly regarding gender (p < .001), tumor pathology (p < .001), anatomic site of tumor (p < .001), Mohs surgery stages (p = .039), defect size (p < .001), and repair method (p < .001). Retrospective study at a single institution. Mohs micrographic surgery cases in patients younger than 40 years exhibit unique patient and tumor characteristics influencing choice of repair method.

Mohs micrographic surgery as treatment option for non-basal cell or squamous cell carcinomas in the United States

Background: Skin cancer has the highest incidence of all cancers in the United States. Conventional surgical excision (CSE) and Mohs micrographic surgery (MMS) are among the most common surgical treatment options for skin cancer.Objective: The purpose of this study was to examine utilization patterns of MMS compared to CSE in the United States for non-basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) skin cancers.Methods: Data from the NCI SEER program, collected from 1973 to 2015, were retrospectively analyzed. Cases were separated into MMS and CSE. Patient characteristics were analyzed. Multivariate models were fitted to evaluate significant predictors for MMS.Results: Of the total procedures performed during the years 1988–2015, a total of 12,654 MMS cases and 267,291 CSE were considered for analysis. Females, white, and non-Hispanic patients of increasing age were more likely to undergo MMS compared to CSE. Cases diagnosed in the pacific coast, east, and southwest regions were more likely to be treated with MMS compared to those in the northern plains Additionally, in situ cases and of the face had the highest likelihood of being treated with MMS.Conclusions: Studying demographics and tumor characteristics aid in understanding the utilization patterns of MMS.

Histopathologic upgrading of nonmelanoma skin cancer at the time of Mohs micrographic surgery: A prospective review

Anecdotal experience and data from multiple retrospective studies have suggested that a significant percentage of nonmelanoma skin cancers (NMSCs) display an aggressive histologic subtype that is not diagnosed on initial biopsy. To prospectively determine the proportion of NMSCs upgraded at the time of Mohs micrographic surgery (MMS) and examine the surgical parameters of upgraded lesions. In this prospective, cross-sectional study, all patients undergoing MMS for NMSC at our institution over the course of 1year were screened for inclusion. Frozen sections were reviewed independently by 2 fellowship-trained Mohs surgeons. In total, 265 of 2578 (10.3%) tumors displayed a more aggressive skin cancer histologic subtype on frozen-section analysis at the time of surgery than at the initial biopsy. Upgraded tumors required significantly more stages to reach tumor clearance, had a larger postoperative defect size, and more often required complicated repairs than nonupgraded tumors. Single center study, limited time period, and cross-sectional design. A significant portion of MMS cases were upgraded at the time of surgery to a more aggressive subtype than that seen at the initial biopsy. Upgraded cases were larger and more surgically challenging than nonupgraded ones. This finding has important implications for primary dermatologists' referral practices and Mohs appropriate use criteria guidelines.

Time to recurrence after surgical excision of atypical fibroxanthoma-updated systematic review and meta-analysis.

Atypical fibroxanthoma (AFX) remains a rare cutaneous dermally based fibrohistiocytic tumour with high rates of local recurrence. Mohs micrographic surgery (MMS) and wide local excision (WLE) with margins 1-2 cm are two surgical options. It is unclear whether timing of recurrence following surgical excision of AFX differs according to technique. A systematic review and meta-analysis were performed according to PRISMA guidelines. There was a total of 188 MMS cases and 783 WLE cases. The pooled proportion of MMS cases of recurrence is 6.6% (95% CI 3.6-11.9%), compared with WLE 11.3% (95% CI 7.1-16.5%), which was not significantly different (P = 0.12) Pooled time to recurrence of MMS for AFX to be 14.2 (95% CI 11.6-16.8%) months, compared to 13.3 (95% CI 9.99-16.6%) months (P = 0.86). Our findings suggest that recurrence rates are similar between MMS and WLE techniques and that timing of recurrence is similar regardless of surgical technique employed.

Mohs Micrographic Surgery Dermatopathology Concordance in Canada: A Single-Institution Experience.

Mohs micrographic surgery (MMS) is a surgical modality that achieves high cure rates of nonmelanoma skin cancers but is dependent on accurate histologic examination of surgical margins. Therefore, quality assurance is essential to ongoing assessment of histological margins. To prospectively determine the concordance rate between a Mohs surgeon (MS) and dermatopathologist (DP) with respect to tumour status (ie, present or absent) and tumour type. Secondary end points were to determine the relationship between discordant interpretations and slide quality and to assess the feasibility of using an electronic webform for data collection. Ten percent (10%) of the planned MMS cases between January 2015 and March 2016 were randomly selected by a histotechnologist at the start of each month. The MS and DP were blinded to the chosen cases, and slides were reviewed independently at the beginning of the following month. Data were collected using an online webform. A blinded third party determined if there were discrepancies in interpretation, and any discordant slides were reviewed together and a consensus was reached. A total of 270 slides from 54 total cases were reviewed. The overall tumour status concordance rate was 93.6%. Cohen's κ was 0.86. Tumour type concordance was 98.9%. No discrepancy required a change in patient care. All discrepant slides were from cases that required multiple stages. This is the first study looking at MS-DP concordance in Canada, and our findings support the MS acting as his or her own pathologist.