Case Six – June 2017

• 30 year old female presented with a new 1 cm pink, papule overlying the axillary tail of the breast
• She has a history of radiation therapy for breast cancer approximately 8 years ago

• Angioma
• Nevus
• Metastatic breast cancer

Sections show a diffuse proliferation of variably-sized, ectatic and irregularly branching vessels throughout the dermis.

High power examination shows the vascular spaces are lined by a single layer of endothelial cells. Small intraluminal papillary projections and hobnailing of the endothelial cells are seen. No significant cytologic atypia is present.  HHV-8 immunohistochemical stain is negative.

Atypical vascular lesion

• Atypical vascular lesion, AVL, represents a benign postradiation vascular proliferation
• AVL can be classified histologically into two categories: lymphatic and capillary vascular type
• The main histologic differential diagnosis includes angiosarcoma arising in the setting of prior radiation therapy
• AVL are often <1 cm in size, circumscribed, limited to the dermis and contain no significant cytologic atypia or multilayering of endothelial cells
• In contrast, angiosarcomas average 7 cm in size, may extend into the subcutaneous tissue, and show multilayered, atypical tumor cells with prominent nucleoli
• Both AVL and angiosarcomas can be multifocal
• Postradiation angiosarcoma often shows amplification of the MYC oncogene using immunohistochemical or FISH techniques
  • AVL does not show MYC amplification
• The clinical behavior of atypical vascular lesions is not entirely known
  • Approximately 10-20% of patients with AVL will develop multiple lesions
  • A subset of AVL may progress to angiosarcoma
  • This progression may be more frequently associated with the capillary vascular type and in any AVL with nuclear atypia
• Most AVL patients have a favorable clinical course following complete excision

• Atypical vascular lesion, AVL, represents a benign postradiation vascular proliferation which mimics angiosarcoma clinically and histologically
• AVLs are often <1 cm in size, circumscribed, limited to the dermis and contain no significant cytologic atypia or multilayering of endothelial cells
• In contrast, angiosarcomas average 7 cm in size, can extend into the subcutaneous tissue, and show multilayered, atypical tumor cells with prominent nucleoli
• The clinical behavior of atypical vascular lesions is not entirely known, and some believe a subset of AVL may progress to angiosarcoma
• Most AVL patients have a favorable clinical course following complete excision