Radiation Induced Atypical Vascular Lesion in the Breast.

Background And Purpose: Atypical vascular lesion (AVL) became a separate WHO diagnosis in November 2019. Due to a possible risk of developing angiosarcoma, extensive surgery with excision of AVL has been recommended but the benefit from this is questionable. We investigated whether the change in WHO classification has led to an increase in the number of patients diagnosed with AVL, thereby leading to an increase in extensive surgery.

Method: The Danish National Pathology Databank was used to identify patients diagnosed with AVL between June 1, 2010 to June 31, 2020. The rate of AVL diagnosed before and after change in WHO classification was compared.

Results: In total, 13 cases of AVL were identified, 3 cases diagnosed before changes in WHO classification corresponding to 0.025 cases per month, compared to 8 cases, 1.143 cases per month, after the change in WHO classification. This corresponded to a 45-fold increase (95%CI: 10.88-265,31) (P < .0001) in AVL diagnosis. The mean patient age at diagnosis was 67 years. Patients received treatment varying from yearly follow up to extensive surgery. Non developed angiosarcoma in the follow-up period of 22 months.

Conclusion: The changes in WHO classification of AVL has led to a considerable increase in the number of patients diagnosed with the lesion. No standardized treatment exists for this rare condition, but extensive surgery is often recommended to this frail population despite the lack of evidence for prognostic benefit from the procedure. Prospective follow-up studies are needed to determine the optimal treatment strategy.