Low Cancer Occurrence Rate following Prophylactic Nipple-Sparing Mastectomy.

BACKGROUND: Nipple-sparing mastectomy (NSM) has become widely available for breast cancer prophylaxis. There are limited data on its long-term oncologic safety. The objective of this study was to determine the incidence of breast cancer in patients who underwent prophylactic NSM. METHODS: All patients undergoing prophylactic NSM at a single institution from 2006 through 2019 were retrospectively reviewed. Patient demographic factors, genetic predispositions, mastectomy specimen pathology, and oncologic occurrences at follow-up were recorded. Descriptive statistics were performed where necessary to classify demographic factors and oncologic characteristics. RESULTS: A total of 871 prophylactic NSMs were performed on 641 patients, with median follow-up of 82.0 months (standard error 1.24). A total of 94.4% of patients ( n = 605) underwent bilateral NSMs, although only the prophylactic mastectomy was considered. The majority of mastectomy specimens (69.6%) had no identifiable pathology. A total of 38 specimens (4.4%) had cancer identified in mastectomy specimens, with ductal carcinoma in situ being the most common (92.1%; n = 35). Multifocal or multicentric disease was observed in seven cases (18.4%) and lymphovascular invasion was identified in two (5.3%). One patient (0.16%), who was a BRCA2 variant carrier, was found to have breast cancer 6.5 years after prophylactic mastectomy. CONCLUSIONS: Overall primary oncologic occurrence rates are very low in high-risk patients undergoing prophylactic NSM. In addition to reducing the risk of oncologic occurrence, prophylactic surgery itself may be therapeutic in a small proportion of patients. Continued surveillance for these patients remains important to assess at longer follow-up intervals. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, IV.

Results of Magnetic Resonance Imaging (MRI) Screening in Patients at High Risk for Breast Cancer.

BACKGROUND: Screening MRI as an adjunct to mammography is recommended by the ACS for patients with a lifetime risk for breast cancer > 20%. While the benefits are clear, MRI screening is associated with an increase in false-positive results. The purpose of this study was to analyze our institutional database of high-risk patients and assess the uptake of screening MRI examinations and the results of those screenings. METHODS: Our institutional review board-approved High-Risk Breast Cancer Database was queried for patients enrolled from January 2017 to January 2023 who were at high risk for breast cancer in a comparative analysis between those who were screened versus not screened with MRIs. Variables of interest included risk factor, background, MRI screening uptake, and frequency and results of image-guided breast biopsies. RESULTS: A total of 254 of 1106 high-risk patients (23%) had MRI screening. Forty-six of 852 (5.3%) patients in the non-MRI-screened cohort and nine of 254 (3.5%) patients in the MRI-screened cohort were diagnosed with a malignant lesion after image-guided biopsy (p = 0.6). There was no significant difference between MRI and non-MRI guided biopsies in detecting breast cancer. All malignant lesions were T1 or in situ disease. The 254 patients in the MRI-screened group underwent 185 biopsies. Fifty-seven percent of MRI-guided biopsies yielded benign results. CONCLUSIONS: Although the addition of MRI screening in our high-risk cohort did not produce a significant number of additional cancer diagnoses, patients monitored in our high-risk cohort who developed breast cancer were diagnosed at very early stages of disease, underscoring the benefit of participation in the program.

No Cancer Occurrences in 10-year Follow-up after Prophylactic Nipple-sparing Mastectomy.

Prophylactic nipple-sparing mastectomies (NSM) have become increasingly common, although there is little long-term data on its efficacy in prevention of breast cancer. The objective of this study was to assess the incidence of breast cancer in a cohort of patients undergoing prophylactic NSM with a median follow-up of 10 years. Methods: Patients receiving prophylactic NSM at a single institution from 2006 to 2019 were included in a retrospective nature. Patient demographics, genetic mutations, operative details, and specimen pathology were recorded, and all postoperative patient visits and documentation were screened for cancer occurrence. Descriptive statics were performed where appropriate. Results: Two hundred eighty-four prophylactic NSMs were performed on 228 patients with a median follow-up of 120.5 ± 15.7 months. Roughly, a third of patients had a known genetic mutation, with 21% BRCA1 and 12% BRCA2. The majority (73%) of prophylactic specimens had no abnormal pathology. The most commonly observed pathologies were atypical lobular hyperplasia (10%) and ductal carcinoma in situ (7%). Cancer was identified in 10% of specimens, with only one case of lymphovascular invasion. Thus far, there have been no incidences of locoregional breast cancer occurrence in this cohort. Conclusions: The long-term breast cancer occurrence rate in this cohort of prophylactic NSM patients at the time of this study is negligible. Despite this, continued surveillance of these patients is necessary until lifetime risk of occurrence following NSM has been established.

Changes in Breast Cancer Presentation during COVID-19: Experience in an Urban Academic Center.

The COVID-19 pandemic strained healthcare systems worldwide, delaying breast cancer screening and surgery. In 2019, approximately 80% of breast cancers in the U.S. were diagnosed on screening examinations, with 76.4% of eligible Medicare patients undergoing screening at least every two years. Since the start of the pandemic, many women have been reluctant to seek elective screening mammography, even with the lifting of pandemic-related restrictions in access to routine healthcare. We describe the effect of the COVID-19 pandemic on breast cancer presentation at a tertiary academic medical center greatly impacted by the pandemic.

Long-Term Cancer Recurrence Rates following Nipple-Sparing Mastectomy: A 10-Year Follow-Up Study.

BACKGROUND: Despite the increased use of nipple-sparing mastectomies, there are limited data examining long-term cancer recurrence rates in these patients. The objective of this study was to analyze breast cancer recurrence in patients who underwent therapeutic nipple-sparing mastectomy with a median of 10 years of follow-up. METHODS: All patients undergoing nipple-sparing mastectomy at a single institution were retrospectively reviewed temporally to obtain a median of 10 years of follow-up. Patient demographic factors, mastectomy specimen pathologic findings, and oncologic outcomes were analyzed. Univariate analysis was performed to identify independent risk factors for locoregional recurrence. RESULTS: One hundred twenty-six therapeutic nipple-sparing mastectomies were performed on 120 patients. The most frequently observed tumor histology included invasive ductal carcinoma (48.4 percent) and ductal carcinoma in situ (38.1 percent). Mean tumor size was 1.62 cm. Multifocal or multicentric disease and lymphovascular invasion were present in 31.0 percent and 10.3 percent of nipple-sparing mastectomy specimens, respectively. Sentinel lymph node biopsy was performed in 84.9 percent of nipple-sparing mastectomies, and 17.8 percent were positive. The rate of positive frozen subareolar biopsy was 7.3 percent ( n = 82) and that of permanent subareolar pathology was 9.5 percent ( n = 126). The most frequently observed pathologic tumor stages were stage I (44.6 percent) and stage 0 (33.9 percent). The incidence of recurrent disease was 3.17 percent per mastectomy and 3.33 percent per patient. On univariate analysis, no demographic, operative, or tumor-specific variables were independent risk factors for locoregional recurrence. CONCLUSIONS: Overall recurrence rates are low in patients undergoing nipple-sparing mastectomy at a median follow-up of 10-years. Close surveillance should remain a goal for patients and their providers to promptly identify potential recurrence. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Associations between TERT Promoter Mutations and Survival in Superficial Spreading and Nodular Melanomas in a Large Prospective Patient Cohort.

Survival outcomes in melanoma and their association with mutations in the telomerase reverse transcriptase gene TERT promoter remain uncertain. In addition, few studies have examined whether these associations are affected by a nearby common germline polymorphism or vary on the basis of melanoma histopathological subtype. We analyzed 408 primary tumors from a prospective melanoma cohort for somatic TERT-124[C>T] and TERT-146[C>T] mutations, the germline polymorphism rs2853669, and BRAFV600 and NRASQ61 mutations. We tested the associations between these variants and clinicopathologic factors and survival outcomes. TERT-124[C>T] was associated with thicker tumors, ulceration, mitoses (>0/mm2), nodular histotype, and CNS involvement. In a multivariable model controlling for the American Joint Committee on Cancer stage, TERT-124[C>T] was an independent predictor of shorter recurrence-free survival (hazard ratio = 2.58, P = 0.001) and overall survival (hazard ratio = 2.47, P = 0.029). Patients with the germline variant and TERT-124[C>T]-mutant melanomas had significantly shorter recurrence-free survival than those lacking either or both sequence variants (P < 0.04). The impact of the germline variant appeared to be more pronounced in superficial spreading than in nodular melanoma. No associations were found between survival and TERT-146[C>T], BRAF, or NRAS mutations. These findings strongly suggest that TERT-124[C>T] mutation is a biomarker of aggressive primary melanomas, an effect that may be modulated by rs2853669.

Macrophage density is an adverse prognosticator for ipsilateral recurrence in ductal carcinoma in situ.

INTRODUCTION: There is evidence that supports the association of dense tumor infiltrating lymphocyte (TILs) with an increased risk of ipsilateral recurrence in ductal carcinoma in situ (DCIS). However, the association of cellular composition of DCIS immune microenvironment with the histopathologic parameters and outcome is not well understood. METHODS: We queried our institutional database for patients with pure DCIS diagnosed between 2010 and 2019. Immunohistochemical studies for CD8, CD4, CD68, CD163, and FOXP3 were performed and evaluated in the DCIS microenvironment using tissue microarrays. Statistical methods included Fisher's exact test for categorical variables and the two-sample t-test or the Wilcoxon Rank-Sum test for continuous variables. RESULTS: The analytic sample included 67 patients. Median age was 62 years (range = 53 to 66) and median follow up was 6.7 years (range = 5.3 to 7.8). Thirteen patients had ipsilateral recurrence. Of all the clinicopathologic variables, only the DCIS size and TIL density were significantly associated with recurrence (p = 0.023 and 0.006, respectively). After adjusting for age and TIL density, only high CD68 (>50) and high CD68/CD163 ratio (>0.46) correlated with ipsilateral recurrence (p = 0.026 and 0.013, respectively) and shorter time to recurrence [hazard ratio 4.87 (95% CI: 1.24-19, p = 0.023) and 10.32 (95% CI: 1.34-80, p = 0.025), respectively]. CONCLUSIONS: In addition to DCIS size and TIL density, high CD68+ tumor-associated macrophages predict ipsilateral recurrence in DCIS. High CD68+ macrophage density and CD68/CD163 ratio also predict a shorter time to recurrence.

Deep Learning and Pathomics Analyses Reveal Cell Nuclei as Important Features for Mutation Prediction of BRAF-Mutated Melanomas.

Image-based analysis as a method for mutation detection can be advantageous in settings when tumor tissue is limited or unavailable for direct testing. In this study, we utilize two distinct and complementary machine-learning methods of analyzing whole-slide images for predicting mutated BRAF. In the first method, whole-slide images of melanomas from 256 patients were used to train a deep convolutional neural network to develop a fully automated model that first selects for tumor-rich areas (area under the curve = 0.96) and then predicts for mutated BRAF (area under the curve = 0.71). Saliency mapping was performed and revealed that pixels corresponding to nuclei were the most relevant to network learning. In the second method, whole-slide images were analyzed using a pathomics pipeline that first annotates nuclei and then quantifies nuclear features, showing that mutated BRAF nuclei were significantly larger and rounder than BRAF‒wild-type nuclei. Finally, we developed a model that combines clinical information, deep learning, and pathomics that improves the predictive performance for mutated BRAF to an area under the curve of 0.89. Not only does this provide additional insights on how BRAF mutations affect tumor structural characteristics, but machine learning‒based analysis of whole-slide images also has the potential to be integrated into higher-order models for understanding tumor biology.

Margin Assessment and Re-excision Rates for Patients Who Have Neoadjuvant Chemotherapy and Breast-Conserving Surgery.

BACKGROUND: Neoadjuvant chemotherapy (NAC) has enabled more patients to be eligible for breast-conservation surgery (BCS). Achieving negative lumpectomy margins, however, is challenging due to changes in tissue composition and potentially scattered residual carcinoma in the tumor bed. Data regarding BCS after NAC have shown variable re-excision rates. MarginProbe (Dilon Technologies, Newport News, VA, USA) has been shown to identify positive resection margins intraoperatively and to reduce the number of re-excisions in primary BCS, but has not been studied in NAC+BCS cases. This study aimed to investigate the clinicopathologic characteristics, margin status, and re-excision rates for NAC+BCS patients with and without the use of MarginProbe. METHODS: The Institutional Breast Cancer Database was queried for patients who received NAC and had BCS from 2010 to 2019. The variables of interest were demographics, tumor characteristics, pathologic complete response (pCR), MarginProbe use, and re-excision rates. RESULTS: The study population consisted of 214 patients who had NAC, 61 (28.5 %) of whom had NAC+BCS. The median age of the patients was 53.5 years. A pCR was achieved for 19 of the patients (31.1 %). Of the remaining 42 patients, 9 (21 %) had close or positive margins that required re-excision. Re-excision was associated with a larger residual tumor size (p = 0.025) and estrogen receptor (ER)-positive disease before NAC (p = 0.041). MarginProbe use was associated with a lower re-excision rate for the patients who had NAC+BCS (6 % vs. 31 %, respectively). CONCLUSION: The patients with a larger residual tumor burden and ER-positive disease had a greater risk for inadequate margins at surgery. MarginProbe use was associated with a lower re-excision rate. Techniques to reduce the need for re-excision will support the use of BCS after NAC.

Optimization of an automated tumor-infiltrating lymphocyte algorithm for improved prognostication in primary melanoma.

Tumor-infiltrating lymphocytes (TIL) have potential prognostic value in melanoma and have been considered for inclusion in the American Joint Committee on Cancer (AJCC) staging criteria. However, interobserver discordance continues to prevent the adoption of TIL into clinical practice. Computational image analysis offers a solution to this obstacle, representing a methodological approach for reproducibly counting TIL. We sought to evaluate the ability of a TIL-quantifying machine learning algorithm to predict survival in primary melanoma. Digitized hematoxylin and eosin (H&E) slides from prospectively enrolled patients in the NYU melanoma database were scored for % TIL using machine learning and manually graded by pathologists using Clark's model. We evaluated the association of % TIL with recurrence-free survival (RFS) and overall survival (OS) using Cox proportional hazards modeling and concordance indices. Discordance between algorithmic and manual TIL quantification was assessed with McNemar's test and visually by an attending dermatopathologist. In total, 453 primary melanoma patients were scored using machine learning. Automated % TIL scoring significantly differentiated survival using an estimated cutoff of 16.6% TIL (log-rank P < 0.001 for RFS; P = 0.002 for OS). % TIL was associated with significantly longer RFS (adjusted HR = 0.92 [0.84-1.00] per 10% increase in % TIL) and OS (adjusted HR = 0.90 [0.83-0.99] per 10% increase in % TIL). In comparison, a subset of the cohort (n = 240) was graded for TIL by melanoma pathologists. However, TIL did not associate with RFS between groups (P > 0.05) when categorized as brisk, nonbrisk, or absent. A standardized and automated % TIL scoring algorithm can improve the prognostic impact of TIL. Incorporation of quantitative TIL scoring into the AJCC staging criteria should be considered.

Preliminary analysis of distinct clinical and biologic features of bone metastases in melanoma.

Melanoma disseminates to the skeletal system where it is then difficult to treat. Yet, there remains limited research investigating metastatic bone disease (MBD) in melanoma. Here, we evaluate whether there are distinct clinicopathologic variables at the time of primary melanoma diagnosis that predispose metastases to engraft bone, and we test the hypothesis that patients with MBD have different responses to treatment. Cutaneous melanoma patients enrolled in a prospective database were studied. Individuals with metastatic melanoma and bone metastases (M-Bone) were compared to those with metastatic disease but no M-Bone. Of the 463 (42.7%) patients, 198 with unresectable metastatic melanoma had M-Bone and 98 developed bone metastasis (bone mets) as first site. Progression-free survival and overall survival were significantly worse in patients with M-Bone compared to those without M-Bone (P < 0.001) independent of treatment modalities, and in patients whose melanoma spread to bone first, compared to those who developed first mets elsewhere (P < 0.001). Interestingly, patients with bone mets presented with primary tumors that had more tumor infiltrating lymphocytes (P < 0.001) and less often a nodular histologic subtype compared to patients without M-Bone (P < 0.001). Our data suggest that melanoma bone metastasis is a distinct clinical and biological entity that cannot be explained by generalized metastatic phenotype in all patients. The observed dichotomy between more favorable primary histopathologic characteristics and a grave overall prognosis requires more studies to elucidate the molecular processes by which melanomas infiltrate bone and to build a mechanistic understanding of how melanoma bone metastases yield such detrimental outcomes.

The Devil's in the Details: Discrepancy Between Biopsy Thickness and Final Pathology in Acral Melanoma.

PURPOSE: We hypothesized that initial biopsy may understage acral lentiginous melanoma (ALM) and lead to undertreatment or incomplete staging. Understanding this possibility can potentially aid surgical planning and improve primary tumor staging. METHODS: A retrospective review of primary ALMs treated from 2000 to 2017 in the US Melanoma Consortium database was performed. We reviewed pathology characteristics of initial biopsy, final excision specimens, surgical margins, and sentinel lymph node biopsy (SLNB). RESULTS: We identified 418 primary ALMs (321 plantar, 34 palmar, 63 subungual) with initial biopsy and final pathology results. Median final thickness was 1.8 mm (range 0.0-19.0). There was a discrepancy between initial biopsy and final pathology thickness in 180 (43%) patients with a median difference of 1.6 mm (range 0.1-16.4). Final T category was increased in 132 patients (32%), including 47% of initially in situ, 32% of T1, 39% of T2, and 28% of T3 lesions. T category was more likely to be increased in subungual (46%) and palmar (38%) melanomas than plantar (28%, p = 0.01). Among patients upstaged to T2 or higher, 71% had ≤ 1-cm margins taken. Among the 27 patients upstaged to T1b or higher, 8 (30%) did not have a SLNB performed, resulting in incomplete initial staging. CONCLUSIONS: In this large series of ALMs, final T category was frequently increased on final pathology. A high index of suspicion is necessary for lesions initially in situ or T1 and consideration should be given to performing additional punch biopsies, wider margin excisions, and/or SLNB.

Lentigo maligna melanoma in situ with neurotropism.

Perineural invasion, or neurotropism, is defined by the presence of cancer cells either within the neuronal sheath or found along the nerves. In melanoma, it is most commonly associated with invasive desmoplastic melanoma, a melanoma that is most commonly associated with malignant melanoma in situ, lentigo maligna type. Initially, perineural invasion was included in the reported Breslow thickness; however, recent data suggest that it should not be included. In this report, we describe a case of malignant melanoma in situ, lentigo maligna type, with associated neurotropism in the absence of invasive component.

Metastasectomy for melanoma is associated with improved overall survival in responders to targeted molecular or immunotherapy.

BACKGROUND AND OBJECTIVES: Metastasectomy for melanoma provides durable disease control in carefully selected patients. Similarly, BRAF-targeted and immune checkpoint inhibition has improved median overall survival (OS) in metastatic patients. We hypothesized that there is an increasing role for metastasectomy in melanoma patients responding to these therapies. METHODS: Retrospective analysis of a prospectively maintained database identified 128 patients with stage IV melanoma who received targeted molecular and/or checkpoint inhibitors at an academic institution from 2006 to 2017. Records were reviewed to characterize clinicopathologic characteristics, response to treatment, and intent of surgery for those who underwent metastasectomy. OS was analyzed by the Kaplan-Meier method. RESULTS: Median OS from stage IV diagnosis was 31.3 months. A total of 81 patients received checkpoint inhibitors, 11 received targeted inhibitors, and 36 received both. A total of 73 patients underwent metastasectomy. Indications for surgery included the intent to render disease-free (54%), palliation (34%), and diagnostic confirmation (11%). Responders to systemic therapy who underwent metastasectomy had improved OS compared to responders who did not (84.3 vs. 42.9 months, P = .018). CONCLUSIONS: Metastasectomy for melanoma is associated with improved OS in patients that respond to targeted molecular or immunotherapy. Resection should be strongly considered in this cohort as multimodality treatment results in excellent OS.

TERT, BRAF, and NRAS Mutational Heterogeneity between Paired Primary and Metastatic Melanoma Tumors.

Mutational heterogeneity can contribute to therapeutic resistance in solid cancers. In melanoma, the frequencies of intertumoral and intratumoral heterogeneity are controversial. We examined mutational heterogeneity within individual patients with melanoma using multiplatform analysis of commonly mutated driver and nonpassenger genes. We analyzed paired primary and metastatic tumors from 60 patients and multiple metastatic tumors from 39 patients whose primary tumors were unavailable (n = 271 tumors). We used a combination of multiplex SNaPshot assays, Sanger sequencing, mutation-specific PCR, or droplet digital PCR to determine the presence of BRAFV600, NRASQ61, TERT-124C>T, and TERT-146C>T mutations. Mutations were detected in BRAF (39%), NRAS (21%), and/or TERT (78%). Thirteen patients had TERTmutant discordant tumors; seven of these had a single tumor with both TERT-124C>T and TERT-146C>T mutations present at different allele frequencies. Two patients had both BRAF and NRAS mutations; one had different tumors and the other had a single tumor with both mutations. One patient with a BRAFmutant primary lacked mutant BRAF in at least one of their metastases. Overall, we identified mutational heterogeneity in 18 of 99 patients (18%). These results suggest that some primary melanomas may be composed of subclones with differing mutational profiles. Such heterogeneity may be relevant to treatment responses and survival outcomes.

Pharmacogenetics in Practice: Estimating the Clinical Actionability of Pharmacogenetic Testing in Perioperative and Ambulatory Settings.

Most literature describing pharmacogenetic implementations are within academic medical centers and use single-gene tests. Our objective was to describe the results and lessons learned from a multisite pharmacogenetic pilot that utilized panel-based testing in academic and nonacademic settings. This was a retrospective analysis of 667 patients from a pilot in 4 perioperative and 5 outpatient cardiology clinics. Recommendations related to 12 genes and 65 drugs were classified as actionable or not actionable. They were ascertained from Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines and US Food and Drug Administration (FDA) labeling. Patients displayed a high prevalence of actionable results (88%, 99%) and use of medications (28%, 46%) with FDA or CPIC recommendations, respectively. Sixteen percent of patients had an actionable result for a current medication per CPIC compared with 5% per FDA labeling. A systematic approach by a health system may be beneficial given the quantity and diversity of patients affected.

Melanoma Prognosis: Accuracy of the American Joint Committee on Cancer Staging Manual Eighth Edition.

BACKGROUND: The American Joint Committee on Cancer (AJCC) maintains that the eighth edition of its Staging Manual (AJCC8) has improved accuracy compared with the seventh (AJCC7). However, there are concerns that implementation may disrupt analysis of active clinical trials for stage III patients. We used an independent cohort of melanoma patients to test the extent to which AJCC8 has improved prognostic accuracy compared with AJCC7. METHODS: We analyzed a cohort of 1315 prospectively enrolled patients. We assessed primary tumor and nodal classification of stage I-III patients using AJCC7 and AJCC8 to assign disease stages at diagnosis. We compared recurrence-free (RFS) and overall survival (OS) using Kaplan-Meier curves and log-rank tests. We then compared concordance indices of discriminatory prognostic ability and area under the curve of 5-year survival to predict RFS and OS. All statistical tests were two-sided. RESULTS: Stage IIC patients continued to have worse outcomes than stage IIIA patients, with a 5-year RFS of 26.5% (95% confidence interval [CI] = 12.8% to 55.1%) vs 56.0% (95% CI = 37.0% to 84.7%) by AJCC8 (P = .002). For stage I, removing mitotic index as a T classification factor decreased its prognostic value, although not statistically significantly (RFS concordance index [C-index] = 0.63, 95% CI = 0.56 to 0.69; to 0.56, 95% CI = 0.49 to 0.63, P = .07; OS C-index = 0.48, 95% CI = 0.38 to 0.58; to 0.48, 95% CI = 0.41 to 0.56, P = .90). For stage II, prognostication remained constant (RFS C-index = 0.65, 95% CI = 0.57 to 0.72; OS C-index = 0.61, 95% CI = 0.50 to 0.72), and for stage III, AJCC8 yielded statistically significantly enhanced prognostication for RFS (C-index = 0.65, 95% CI = 0.60 to 0.70; to 0.70, 95% CI = 0.66 to 0.75, P = .01). CONCLUSIONS: Compared with AJCC7, we demonstrate that AJCC8 enables more accurate prognosis for patients with stage III melanoma. Restaging a large cohort of patients can enhance the analysis of active clinical trials.

Sentinel lymph node positivity in patients undergoing mastectomies for ductal carcinoma in situ (DCIS).

Current guidelines recommend sentinel lymph node biopsy (SLNB) for patients undergoing mastectomy for a preoperative diagnosis of ductal carcinoma in situ (DCIS). We examined the factors associated with sentinel lymph node positivity for patients undergoing mastectomy for a diagnosis of DCIS on preoperative core biopsy (PCB). The Institutional Breast Cancer Database was queried for patients with PCB demonstrating pure DCIS followed by mastectomy and SLNB from 2010 to 2018. Patients were divided according to final pathology (DCIS or invasive cancer). Clinico-pathologic variables were analyzed using Pearson's chi-squared, Wilcoxon Rank-Sum and logistic regression. Of 3145 patients, 168(5%) had pure DCIS on PCB and underwent mastectomy with SLNB. On final mastectomy pathology, 120(71%) patients had DCIS with 0 positive sentinel lymph nodes (PSLNs) and 48(29%) patients had invasive carcinoma with 5(10%) cases of ≥1 PSLNs. Factors positively associated with upstaging to invasive cancer in univariate analysis included age (P = .0289), palpability (P < .0001), extent of disease on imaging (P = .0121), mass on preoperative imaging (P = .0003), multifocality (P = .0231) and multicentricity (P = .0395). In multivariate analysis, palpability (P = .0080), extent of disease on imaging (P = .0074) and mass on preoperative imaging (P = .0245) remained significant (Table 2). In a subset of patients undergoing mastectomy for DCIS with limited disease on preoperative evaluation, SLNB may be omitted as the risk of upstaging is low. However, patients who present with clinical findings of palpability, large extent of disease on imaging and mass on preoperative imaging have a meaningful risk of upstaging to invasive cancer, and SLNB remains important for management.