Global Dermatology Research Article ISSN: 2056-7863 Glob Dermatol, 2016 doi: 10.15761/GOD.1000S1003 Volume 3(4): 331-337 and afects a younger population of women in their 20s – 40s [10-12]. Tough rare, with a cumulative incidence of 0.9 per 1000 cases during 15 years, women treated with radiation therapy have a more than 1000-fold increased relative risk of developing cutaneous AS compared with the general population. [7,13]. Billings et al. [6] found a median interval to diagnosis of 59 months, roughly half the time interval seen in other types of secondary AS, with some cases occurring within as few as 3 years. Boice [14] proposed that a tumor induced by radiation therapy will not occur until the age associated with the occurrence of the tumor type in a patient who did not receive radiation, thus the relative short latency may be related to the older age of this group of patients. Te prognosis of radiation-associated AS of the breast is generally poor with unpredictable clinical behavior, and there is a high rate of local and distant recurrence [13]. Te 5-year-survival rate is approximately 50% [15]. AS of the breast presents clinically as erythematous plaques or nodules, with multifocality or difuse involvement of the breast not uncommon [13]. Histologically, AS can show heterogenous features, with well-diferentiated areas mixed with or directly adjacent to Introduction Te development of cutaneous mammary vascular lesions following irradiation as breast cancer therapy has been well-documented. Accurately distinguishing between atypical vascular lesions (AVL) and angiosarcoma (AS) is of great clinical consequence, as their treatment and prognosis difer greatly. Exact classifcation based on histology alone on a small biopsy sample has the potential to be quite challenging, as areas of AS may be histopathologically indistinguishable from AVL. Tis was best illustrated in a study by Mattoch et al. [1] in which approximately 50% of cases diagnosed as AVL were reclassifed as AS upon examination of an excisional specimen. As treatment paradigms have continued to shif from radical mastectomy with lymph node dissection to breast-conserving surgery with adjuvant radiation therapy, dermatopathologists are likely to encounter biopsies of vascular lesions occurring in this setting with increasing frequency. Tis article reviews and compares the clinical and histologic features of AVL and radiation-associated AS, with special emphasis on advances made in the understanding of the genetic basis of these lesions as well as the utility of ancillary testing to aid in this challenging diferential diagnosis. Angiosarcoma Secondary angiosarcoma is a potentially aggressive malignancy that is most commonly seen in patients treated for breast carcinoma. Development of AS subsequent to radical mastectomy and axillary lymph node dissection was frst described in 1949 by Stewart and Treves [2], and is generally accepted to be due to surgically-induced chronic lymphedema. Breast-conserving surgery with adjuvant radiation has since been successful in regards to quality of life, cosmetic outcome, and long-term survival [3-5]. As a result, lymphedema-associated AS is now rare in breast cancer patients, and there appears to be an increasing incidence in post-radiation AS in this patient population [6-9]. Primary angiosarcoma of the breast is rare and arises without a recognized association factor, usually within the breast parenchyma, Dropping the MYC: A review of post-radiation atypical vascular lesions and angiosarcoma of the breast Jennifer R Kaley 1 , Jerad M Gardner 2 and Sara C Shalin 2 1 Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, AR, USA 2 Departments of Pathology and Dermatology, University of Arkansas for Medical Sciences, Little Rock, AR, USA Abstract Te development of cutaneous mammary vascular lesions following irradiation as breast cancer therapy has been well-documented. Accurately distinguishing between atypical vascular lesions (AVL) and angiosarcoma (AS) is of great clinical consequence, as their treatment and prognosis difer greatly. Exact classifcation based on histology alone on a small biopsy sample has the potential to be quite challenging, as areas of AS may be histopathologically indistinguishable from AVL. Studies have confrmed MYC amplifcation in secondary AS, and found lack of amplifcation in radiation-induced AVL. Furthermore, anti-MYC IHC has been shown to be a sensitive marker in AS, and could serve as a useful diagnostic tool for pathologists. Tis review article describes and compares the clinical and histologic features of AVL and radiation-associated AS, with special emphasis on advances made in the understanding of the genetic basis of these lesions as well as the utility of ancillary testing to aid in this challenging diferential diagnosis. Correspondence to: Jennifer R Kaley, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA, E-mail: jraible@gmail.com Key words: secondary angiosarcoma, atypical vascular lesion, MYC amplifcation, radiation-induced angiosarcoma Special Issue: Updates in Dermatology Bruce R. Smoller, M. D. Chair, Department of Pathology and Laboratory Medicine Professor, Department of Pathology and Laboratory Medicine Professor, Department of Dermatology University of Rochester School of Medicine and Dentistry, USA. E-mail: Bruce_Smoller@urmc.rochester.edu Published: June 20, 2016