Challenges in surgical pathology of adrenocortical tumours

Adrenocortical carcinomas are rare tumours that can be diagnostically challenging. Numerous multiparametric scoring systems and diagnostic algorithms have been proposed to differentiate adrenocortical adenoma from adrenocortical carcinoma. Adrenocortical neoplasms must also be differentiated from other primary adrenal tumours, such as phaeochromocytoma and unusual primary adrenal tumours, as well as metastases to the adrenal gland. Myxoid, oncocytic and sarcomatoid variants of adrenocortical tumours must be recognized so that they are not confused with other tumours. The diagnostic criteria for oncocytic adrenocortical carcinoma are different from those for conventional adrenocortical carcinomas. Adrenocortical neoplasms in children are particularly challenging to diagnose, as histological features of malignancy in adrenocortical neoplasms in adults may not be associated with aggressive disease in the tumours of children. Recent histological and immunohistochemical studies and more comprehensive and integrated genomic characterizations continue to advance our understanding of the tumorigenesis of these aggressive neoplasms, and may provide additional diagnostic and prognostic utility and guide the development of therapeutic targets.

Non-invasive visualization of tumor infiltrating lymphocytes in patients with metastatic melanoma undergoing immune checkpoint inhibitor therapy: a pilot study

Early in the course of immunotherapy there is frequently a transient enlargement of tumor masses (pseudo-progression) due to tumor infiltration by TILs. Current clinical imaging modalities are not able to distinguished pseudo-progression from true tumor progression. Thus, patients often remain on treatment 4-8 weeks longer to confirm disease progression. Nuclear medicine offers the possibility to image immune cells and potentially discriminate pseudo-progression and progression.

We conducted a pilot study in patients with metastatic melanoma receiving ipilimumab (IPI) or pembrolizumab (PEMBRO) to assess safety and feasibility of SPECT/CT imaging with ^99mTc- interleukin-2 (^99mTc-HYNIC-IL2) to detect TILs and distinguish between true progression from pseudo- progression. Scans were performed prior to and after 12w treatment. After labelling,^99mTc-HYNIC-IL2 was purified and diluted in 10 mL of 5% glucose with 0.1% human serum albumin.

Of the 5 patients (2 treated with IPI and 3 with PEMBRO) enrolled, two failed to complete the second scan as they discontinued IPI due grade 3 colitis (1 patient) or patient refusal after developing multiple toxicities attributed to IPI (1 patient). Following the first scan, one patient reported to have a grade 1 pruritus with grade 1 pain. No other toxicities attributed to the radiopharmaceutical infusion were reported. Metastatic lesions could be visualized by ^99mTc-IL2 imaging and there was positive correlation between size and ^99mTc-HYNIC-IL2 uptake, both before and after 12 weeks of therapy.

The results of this pilot study demonstrate the safety and feasibility of ^99mTc-IL2 imaging and has led to a number of hypotheses to be tested in future studies.

Interstage Outcomes in Infants With Single Ventricle Heart Disease Comparing Home Monitoring Technology to Three-Ring Binder Documentation: A Randomized Crossover Study

BACKGROUND

Interstage outcomes for infants with single ventricle remain suboptimal. We have previously described a tablet PC-based platform Cardiac High Acuity Monitoring Program (CHAMP) for remote monitoring which provides immediate access to data, videos, and instant alerts to our single ventricle care team.

METHODS

This study compares traditional three-ring binder monitoring (Binder) to CHAMP using a randomized crossover design to evaluate mortality, resource utilization, and caregiver experience. At discharge, all single ventricle infants were monitored using Binder and randomized to receive CHAMP at either one or two months postdischarge. One month after randomization, caregivers could choose either Binder or CHAMP for the remainder of the interstage period. Caregivers experience was recorded using surveys.

RESULTS

Enrollment included 31 single ventricle infants from May 2014 to June 2015. There was no interstage mortality over 4,911 total interstage days (median: 144/patient). Of 73 readmissions, 45 were unplanned. Of the initial 23 unplanned readmissions, 13 were found to have been based on data obtained exclusively through CHAMP (as instant alerts or based on data review) rather than caregiver concerns. Due to concerns regarding patient safety, additional enrollment was stopped. The CHAMP use was associated with significantly fewer unplanned intensive care unit days/100 interstage days, shorter delays in care, lower resource utilization at readmissions, and lower incidence of interstage growth failure and was preferred by a majority of caregivers.

CONCLUSIONS

These findings suggest that CHAMP may offer benefits over Binder (improved interstage outcomes, delays in care, and caregiver experience). These findings should be tested across multiple centers in larger populations.

Immunohistochemistry in Diagnostic Parathyroid Pathology

Pathologists are usually readily able to diagnose parathyroid tissues and diseases, particularly when they have knowledge of the clinical information, laboratory findings, and radiographic imaging studies. However, the identification of parathyroid tissue or lesions can be difficult in small biopsies, ectopic locations, supranumerary glands, and in some oxyphil/oncocytic lesions. Widely available immunohistochemical studies such as chromogranin-A, synaptophysin, keratin, parathyroid hormone, thyroglobulin, and thyroid transcription factor-1 can help in difficult cases. One of the most difficult diagnostic aspects faced by the pathologist in evaluating parathyroid is distinguishing between parathyroid adenoma, particularly atypical adenoma, and parathyroid carcinoma. Many markers have and continue to be evaluated for diagnostic utility, and are even beginning to be studied for prognostic utility. Single immunohistochemical markers such as parafibromin and Ki-67 are among the most studied and most utilized, but many additional markers have and continue to be evaluated such as galectin-3, PGP9.5, Rb, bcl2, p27, hTERT, mdm2, and APC. Although not widely available in many laboratories, a panel of immunohistochemical markers may prove most useful as an adjunct in the evaluation of challenging parathyroid tumors.

Phase II Study of Everolimus in Metastatic Malignant Melanoma (NCCTG-N0377, Alliance)

Lessons Learned.

Everolimus does not have sufficient activity to justify its use as single agent in metastatic melanoma.

Patients treated with 10 mg per day dose were most likely to require dose reductions.

Everolimus appeared to reduce the numbers of regulatory T cells in approximately half of the treated patients; unfortunately, these effects were not correlated with clinical outcomes.

Background.

Everolimus (RAD‐001) is an orally active rapamycin analogue shown in preclinical data to produce cytostatic cell inhibition, which may be potentially beneficial in treating melanoma. We conducted a phase II study to evaluate the efficacy and safety of everolimus in patients with unresectable metastatic melanoma (MM).

Methods.

This study included two cohorts; cohort 1 received 30 mg of everolimus by mouth (PO) weekly, and cohort 2 was dosed with 10 mg of everolimus PO daily. The endpoints of the study were safety, 16‐week progression‐free survival (PFS), overall survival (OS), and measures of immunomodulatory/antiangiogenic properties with therapy. Tumor samples before therapy and at week 8 of treatment were analyzed. Peripheral blood plasma or mononuclear cell isolates collected prior to therapy and at weeks 8 and 16 and at time of tumor progression were analyzed for vascular endothelial growth factor and regulatory T‐cell (Treg) measurements.

Results.

A total of 53 patients were enrolled in cohort 1 (n = 24) and cohort 2 (n = 29). Only 2 patients of the first 20 patients enrolled in cohort 2 had treatment responses (25%; 95% confidence interval, 8.6%–49.1%); this result did not allow full accrual to cohort 2, as the study was terminated for futility. Median OS was 12.2 months for cohort 1 versus 8.1 months in cohort 2; no PFS advantage was seen in either group (2.1 months vs. 1.8 months). Dose‐limiting toxicities included grade 4 myocardial ischemia (3.4%); grade 3 fatigue, mucositis, and hyperglycemia (10.3%); and anorexia and anemia (6.9%). Everolimus significantly reduced the number of Tregs in approximately half of the treated patients; however, these effects were not correlated with clinical outcomes.

Conclusion.

Everolimus does not have sufficient single‐agent activity in MM; however, we have identified evidence of biological activity to provide a potential rationale for future combination studies.

Hobnail Variant of Papillary Thyroid Carcinoma: a Literature Review

Papillary thyroid carcinoma is the most common thyroid malignancy and it is usually associated with a good prognosis. However, recurrence, metastases, and cancer death may occur in 10 to 15% of patients with more aggressive types of papillary thyroid carcinoma, such as tall cell, columnar cell, solid variant, or the more recently described hobnail variant of papillary thyroid carcinoma. Papillary thyroid carcinoma with a prominent hobnail pattern is a moderately differentiated papillary thyroid carcinoma variant with aggressive clinical behavior and significant mortality. The hobnail variant of papillary thyroid carcinoma shows prominent hobnail features, which have also been referred to as micropapillary. The typical hobnail/micropapillary morphological features show loss of cellular polarity/cohesiveness and support an epithelial-mesenchymal transition as a possible mechanism of metastasis. BRAF p.V600E is the most common mutation in papillary thyroid carcinoma, including the hobnail variant; recent and continuing studies are focused on defining other molecular anomalies that may be useful for prognostic stratification and may provide therapeutic targets.

NCCTG N0879 (Alliance): A randomized phase 2 cooperative group trial of carboplatin, paclitaxel, and bevacizumab ± everolimus for metastatic melanoma

BACKGROUND

Despite the success of immune checkpoint and targeted therapy, many patients with melanoma ultimately require further treatment. The combination of carboplatin, paclitaxel, and bevacizumab (CPB) has demonstrated promising activity in a single-arm study. In the current study, the authors performed a randomized phase 2 study to confirm efficacy and to determine whether adding everolimus would increase the activity of the combination.

METHODS

Through the North Central Cancer Treatment Group, a total of 149 patients with unresectable AJCC 6th edition stage IV melanoma were randomized from May 2010 to May 2014 to either CPB or CPB with everolimus (CPBE). The primary endpoint was progression-free survival (PFS), with secondary endpoints of overall survival (OS), response rate, and tolerability.

RESULTS

The CPB and CPBE treatment arms were balanced with regard to age (median age: 59 years vs 58 years) and high lactate dehydrogenase (48% vs 51%), but were unbalanced with regard to sex (male sex: 72% vs 55%; P = .03). Overall, there was no difference noted with regard to PFS, with a median PFS of 5.6 months for CPB versus 5.1 months for CPBE (hazard ratio [HR], 1.14; 95% confidence interval [95% CI], 0.81-1.62 [P = .44]), or for OS, with a median OS of 14.5 months for CPB versus 10.8 months for CPBE (HR, 1.16; 95% CI, 0.84-1.84). The confirmed response rate was 13% for CPB and 23% for CPBE (P = .13). Toxicity was higher for CPBE compared with CPB (83% for grade 3 + and 14% for grade 4 + vs 63% for grade 3 + and 11% for grade 4+, respectively) (toxicities were graded using the Cancer Therapy Evaluation Program of the National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0]). Common grade 3 + toxicities were neutropenia, leukopenia, and fatigue, which occurred in both treatment arms with comparable frequency.

CONCLUSIONS

Both experimental arms demonstrated activity, with a PFS of >5 months. However, the addition of everolimus to CPB failed to improve outcomes, with increased toxicity noted. These findings replicate the moderate antitumor activity of CPB, with future development possibly in combination with targeted or immunotherapy. Cancer 2018;124:537-45. © 2017 American Cancer Society.

Primary Renal Paragangliomas and Renal Neoplasia Associated with Pheochromocytoma/Paraganglioma: Analysis of von Hippel-Lindau (VHL), Succinate Dehydrogenase (SDHX) and Transmembrane Protein 127 (TMEM127)

Alterations of von Hippel-Lindau (VHL), succinate dehydrogenase (SDHX), and TMEM127 have been associated with the development of pheochromocytomas (PCs) and paragangliomas (PGLs) and are also associated with the development of renal neoplasms. This study involved 2 primary renal PGL and 12 cases of PC/PGL with associated renal neoplasia with a mean follow up of 74 months. Germline VHL and SDHX mutation status was obtained from the medical record. Immunohistochemistry for SDHB and mutation analysis for TMEM127 was performed, in addition to analysis of The Cancer Genome Atlas datasets for SDHX and TMEM127 mutated renal cell carcinomas (RCCs). The spectrum of renal neoplasia included clear cell and tubulocystic and papillary RCC, as well as a case of multiple papillary adenomas. Three patients had metastatic PC/PGL and three patients had VHL syndrome. Previously unreported TMEM127 alterations were identified in two patients, both without evidence of VHL syndrome or SDH-deficiency, and were classified as variants of uncertain significance. Primary renal PGL and neoplasia was associated with about 2% of 710 cases of PC/PGL. These were diagnosed concurrently or on average 27 months prior to the PC/PGL, and most were low-grade, low-stage clear cell RCCs. Up to half of patients with PC/PGL and renal neoplasia had VHL syndrome, SDH deficiency, or alterations in TMEM127. One (of three) case of metastatic PC/PGL had SDHB mutation and loss of SDHB by immunohistochemistry. The other two cases had retained SDHB expression.

Composite Pheochromocytoma/Paraganglioma-Ganglioneuroma: A Clinicopathologic Study of Eight Cases with Analysis of Succinate Dehydrogenase

Ganglioneuromas represent the most well-differentiated spectrum of neoplasia arising from the sympathetic nervous system, while neuroblastomas represent the most poorly differentiated counterpart, and ganglioneuroblastomas represent intermediate stages of differentiation. Small series of cases have documented the co-occurrence of ganglioneuroma with a pheochromocytoma (Pheo)/paraganglioma (PGL) component. We report the clinicopathologic features of eight such cases, diagnosed between 2003 and 2015 with a mean follow-up of 22 months (1-47), which were evaluated for syndrome associations, SDHB expression, and clinical outcome. Mutations of the succinate dehydrogenase (SDH) complex subunits (A, B, C, D, and SDHAF2) have been implicated in predicting metastatic behavior and in identifying possible paraganglioma syndromes. The proliferative index was calculated by manual quantification of Ki-67-positive cells at selected hot-spots using ImageJ (NIH). In our series, composite Pheo/PGL-ganglioneuromas predominantly involved the adrenal gland (Pheo 7, PGL 1). The cases had an equal gender distribution (males 4, females 4), with a mean age at diagnosis of 67 years (range 53 to 86 years), an average size of 5.2 cm (range 2 to 8.2 cm), an average weight of 49.3 g (7.8 to 144.7 g, n = 6), and the majority were functionally active (7 of 8, 88%). The mean Ki67 proliferation rate was 2% (range 0.3 to 3%), and all cases retained SDHB expression (8/8, 100%). No patient (0/8, 0%) developed metastatic disease on follow-up. One patient had a retroperitoneal composite PGL-ganglioneuroma in the setting of neurofibromatosis type 1. No recurrent disease or other associations were identified. In our study, composite Pheo/PGL-ganglioneuromas predominantly affected the adrenal gland in older patients, showed no loss of SDHB, and no disease recurrence was identified.

Endogenous Heat-Shock Protein Induction with or Without Radiofrequency Ablation or Cryoablation in Patients with Stage IV Melanoma

Lessons Learned.

Percutaneous thermal ablation combined with in situ granulocyte‐macrophage colony‐stimulating factor cytokine therapy was technically feasible and well tolerated.

No significant clinical or immunologic responses were seen.

Background.

Melanoma tumor‐derived heat‐shock proteins (HSPs) and HSP‐peptide complexes can elicit protective antitumor responses. The granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) chemokine can also promote uptake and processing by professional antigen presenting cells (APCs). On this basis, we designed a pilot study of percutaneous thermal ablation as a means to induce heat‐shock protein vaccination plus GM‐CSF to determine safety and preliminary antitumor activity of this combination.

Materials and Methods.

This study was designed to assess overall safety of percutaneous ablation combined with GM‐CSF for unresectable, metastatic melanoma including uveal and mucosal types. All patients received heat‐shock therapy (42°C for 30 minutes), then received one of three treatments: (a) intralesional GM‐CSF (500 mcg standard dose); (b) radiofrequency ablation (RFA) + GM‐CSF; or (c) cryoablation plus GM‐CSF. The primary endpoint of the study was the induction of endogenous HSP70 and melanoma‐specific cytotoxic T lymphocytes (CTL).

Results.

Nine patients (three per study arm) were enrolled. No dose‐limiting toxicity was observed as specified per protocol. All patients developed progressive disease and went on to receive alternative therapy. Median overall survival (OS) was 8.2 months (95% confidence interval [CI] 2–17.2). The study was not powered to detect a difference in clinical outcome among treatment groups.

Conclusion.

Percutaneous thermal ablation plus GM‐CSF was well tolerated, technically feasible, and demonstrated an acceptable adverse event profile comparable to conventional RFA and cryoablation. While HSP70 was induced following therapy, the degree of HSP70 elevation was not associated with clinical outcome or induced CTL responses. While percutaneous thermal ablation plus GM‐CSF combinations including checkpoint inhibitors could be considered in future studies, the use of GM‐CSF remains experimental and for use in the context of clinical trials.

Co-occurrence of steatocystoma multiplex, eruptive vellus hair cysts, and trichofolliculomas

An association between steatocystoma multiplex (SCM) and eruptive vellus hair cysts (EVHCs) has been recognized. Steatocystoma multiplex and EVHC have similar clinical features but distinctive histologic features. Rare cases of co-occurrence of these conditions have been known to occur on the trunk and the forehead. We report a rare case of the simultaneous occurrence of SCM, EVHC, and trichofolliculomas localized to the forehead.

Non-invasive clinical visualization of tumor infiltrating lymphocytes in patients with metastatic melanoma undergoing immune checkpoint inhibitor therapy: A pilot study

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Background: Unique to modern immune therapy for cancer is that early in the course of treatment, patients frequently exhibit transient tumor enlargement (pseudo-progression, pPROG) due to tumor infiltration by lymphocytes (TIL). Currently, pPROG cannot be reliably distinguished from true tumor progression (PROG). There is a need for biomarker techniques to discriminate pPROG (effect of therapy) and PROG (therapy failure). Nuclear medicine offers radiopharmaceuticals capable of imaging immune cells; images can be fused to evaluate functional and anatomic characteristics of tumors, and potentially discriminate pPROG from PROG. Methods: In our study of metastatic melanoma patients, SPECT/CT imaging with 99mTc-interleukin-2 (99mTc-IL2) was performed to visualize TIL. Images were collected before/after 12 weeks of ipilimumab (IPI) or pembrolizomab (PEMBRO) therapy. The 99mTc-IL2 tracer was synthesized by conjugating succinimidyl-6-hydrazinopyridine-3-carboxylate (HYNIC-NHS) with commercial interleukin-2 (Aldesleukin). HYNIC-IL2 was incubated with tricine, 99mTcO4- (370-740 MBq) and SnCl2. After labelling 99mTc-IL2 was purified by reverse-phase chromatography and diluted in 5% glucose with 0.1% human albumin before injection. Five patients were enrolled in this study. Two patients failed to complete the 12 week 99mTc-IL2 scan due to discontinuation of IPI after: 1) grade 3 colitis and 2) patient refusal for adverse events attributed to IPI. No adverse events attributable to the tracer infusion were reported. Results: Metastatic lesions could be visualized by the tracer. Some lesions decreased in size, while others increased. A positive correlation was found between size and 99mTc-IL2 uptake, before and after therapy, suggesting the potential discrimination of tumor PROG (no 99mTc-IL2 uptake) from pPROG (high 99mTc-IL2 uptake). Immunohistochemical staining for TIL of 99mTc-IL2 positive and negative lesions are illustrated. Conclusions: The results demonstrate feasibility of 99mTc-IL2 imaging as a clinically useful tool capable of discriminating tumor PROG from pPROG. A clinical validation study is in progress. Clinical trial information: NCT01789827.

Sporadic Gastric Well-Differentiated Neuroendocrine Tumors Have a Higher Ki-67 Proliferative Index

Well-differentiated neuroendocrine tumor (WDNET) of the stomach can arise in three distinct clinical settings: (1) in association with autoimmune atrophic gastritis, (2) in association with multiple neuroendocrine neoplasia type I (MEN I) or Zollinger-Ellison syndrome (ZES), or (3) sporadic. The Ki-67 proliferative index (PI) in gastric WDNETs in these three distinct clinical settings has not been evaluated in detail. Forty-five gastric WNETs underwent polypectomy (n = 4), endoscopic mucosal resection (n = 12), and surgical resection (n = 29) between 1994 and 2015 were included. H&E slides from each case were reviewed, and Ki-67 immunostain was performed on one representative tumor block. Ki-67 PI was determined by quantitative Aperio image analysis software in areas of strongest nuclear labeling ("hot spots"), and correlated with underlying clinical and pathological features. Twenty-one patients were male and 24 female with a median age of 57 years (range, 30-80 years). Tumors were classified as type I (n = 17), type II (n = 6), and type III (n = 22) WDNETs. Types II and III showed more advanced TNM stage compared to type I (p = 0.02, overall). WHO grade based on Ki-67 PI was higher in type III WDNETs [grade 1 (G1), n = 3; grade 2 (G2), n = 15; and grade 3 (G3), n = 4] than in type I WDNETs [G1, n = 5; G2, n = 12] and in type II WDNETs [G1, n = 2; G2, n = 4] (p = 0.050, overall). Ki-67 PI was significantly higher in type III WDNETs (mean ± SD = 13.0 ± 13.3 %) than in non-sporadic (type I and II) WDNETs (mean ± SD = 5.3 ± 3.3 %; p = 0.015). There was no difference in Ki-67 PI between type I WDNETs (mean ± SD = 5.2 ± 3.5 %) and type II WDNETs (mean ± SD = 5.6 ± 3.1%; p = 0.817). Higher Ki-67 PI was associated with higher tumor T stage (p = 0.003) and also tended to be associated with lymph node metastasis (p = 0.071). In the Kaplan-Meier survival analysis, type I was associated with a significantly longer disease-free survival (DFS) time compared to type II (p = 0.018) or III (0.010). Also, the WHO G3 group had a significantly shorter DFS time than the WHO G1 (p = 0.020) or G2 (p = 0.007) group. Gastric WDNET is a heterogeneous disease entity encompassing three clinical subtypes-type I, type II, and type III-having their own distinct clinicopathologic characteristics and prognosis. Our results showed that sporadic (type III) WDNET had a significantly higher Ki-67 PI than non-sporadic cases (type I or II); increased PI was associated with higher tumor stage. We also described four type III cases of morphologically WD gastric NET with WHO grade 3 on the basis of Ki-67 PI.

Urinary Bladder Paragangliomas: Analysis of Succinate Dehydrogenase and Outcome

Paragangliomas of the urinary bladder can arise sporadically or as a part of hereditary syndromes including those with underlying mutations in the succinate dehydrogenase (SDH) genes, which serve as tumor suppressors. SDH deficiency can be screened for by absence of immunohistochemical detection of SDHB. In this study of 11 cases, clinical follow-up was available for 9/11 cases. The cases were reviewed and graded based on the grading system for adrenal pheochromocytomas and paragangliomas (GAPP) criteria. Immunohistochemistry was performed for Ki67 and SDHB. Proliferative index was calculated by quantification of Ki67-positive cells at hot spots. The medical record was accessed for documentation of germline SDH mutations. Urinary bladder paragangliomas had a female predilection (8/11 cases), and 5/11 cases exhibited metastatic behavior. Patients with metastatic disease tended to be younger (mean age 43 vs 49 years), have larger lesions (5.8 vs 1.5 cm), and presented with catecholamine excess (4/4 vs 2/6 patients with non-metastatic lesions). Patients with metastatic disease had a higher mean Ki67 proliferation rate (4.9 vs 1.3 %) and GAPP score (mean of 5.8 vs 3.8) (p = 0.01). IHC for SDHB expression revealed loss of expression in 2/6 cases of non-metastatic paragangliomas compared to 4/5 patients with metastatic paragangliomas. Interestingly, of these four patients, two had a documented mutation of SDHB, one patient had a SDHC mutation, and another patient had a history of familial disease without mutation analysis being performed. Our study, suggests that SDH loss was suggestive of metastatic behavior in addition to younger age at diagnosis, larger tumor size, and higher Ki67 proliferation rate and catecholamine type.

Results of NCCTG N0275 (Alliance) - a phase II trial evaluating resection followed by adjuvant radiation therapy for patients with desmoplastic melanoma

To examine, in a prospective fashion, the utilization and efficacy of adjuvant radiation therapy (RT) in patients with resected desmoplastic melanoma (DM). Adult patients with resected, margin‐negative, and nonmetastatic DM were eligible for this single‐arm prospective phase II study. Patients were to receive postoperative RT, 30 Gy in five fractions, to the operative bed with 2‐ to 3‐cm margins (depending on the tumor location). Nodal basin RT was not allowed. The primary study endpoint was the 2‐year local recurrence rate (LRR). Secondary endpoints included the incidence of regional and distant metastatic disease, progression‐free survival, overall survival (OS), and treatment‐related toxicity. Twenty patients with a single de novo DM lesion meeting trial eligibility criteria were enrolled and treated. The 2‐year LRR was 10%, with two patients demonstrating a LR within 2 years of completion of protocol therapy. No regional or distant failures occurred. OS at 2 and 5 years was 95 and 77%, respectively. There were no grade 3 or higher acute or late adverse events that were related to the protocol therapy. Adjuvant RT after wide local excision (WLE) for DM is efficacious and well tolerated. It should be considered for DM patients after margin‐negative WLE. Additional study is needed to further refine low‐risk patient populations that can potentially have adjuvant RT omitted as part of the treatment plan.