Breast

Contributed by Melinda J. Lerwill, M.D.

Contributed by Mark R. Wick, M.D.

Contributed by Melinda Lerwill, M.D. and Mark R. Wick, M.D.

• Morphologic heterogeneity is typically present within individual tumors
• Irregular anastomosing vascular channels dissect through the stroma
• Infiltrative growth through normal structures (e.g., terminal duct lobular units)
• Poorly differentiated tumors often show solid growth of spindle or epithelioid cells with limited vasoformative features
• Necrosis and blood lakes can be seen in poorly differentiated tumors
• Endothelial cell atypia can range from minimal to marked
• Endothelial tufting and papillary formations are common
• Mitotic activity increases in proportion to grade
• Grading is based on a combination of histologic features (Table 1) (Am J Surg Pathol 1981;5:629)
  • Low grade features are more common as a dominant finding in primary angiosarcomas
  • Majority of postradiation angiosarcomas are high grade (Ann Surg Oncol 2013;20:1267, Ann Surg Oncol 2020;27:1002)
  • All histologic grades of angiosarcoma may contain low grade areas, especially at the periphery of the tumor

Table 1. Histologic characteristics of different grades of mammary angiosarcoma

Histologic features	Low grade	Intermediate grade	High grade
Endothelial cell atypia	Minimal	Moderate	Marked
Endothelial tufting	Minimal	Present	Prominent
Papillary formations	Absent	Focally present	Present
Solid and spindle cell foci	Absent	Absent or minimal	Present
Mitotic figures	Absent or rare	Present	Numerous and present in structurally low grade areas
Blood lakes (pools of extravasated erythrocytes)	Absent	Absent	Present
Necrosis	Absent	Absent	Present

Contributed by Melinda Lerwill, M.D.

Contributed by Sofia Lérias, M.D.

• CD31, ERG: strong and diffuse
• CD34, D2-40, Factor VIII, FLI1: variable, often strong and diffuse
• Cytokeratins and EMA: focal expression in epithelioid variants
• MYC: strong and diffuse nuclear positivity in postradiation angiosarcoma (Hum Pathol 2014;45:709)

Which of the following is true regarding postradiation angiosarcoma of the breast?

1. Greater than 90% are low grade
2. Incidence of 10% among patients receiving breast irradiation for breast cancer treatment
3. Most often arises in the breast parenchyma and then secondarily involves the skin
4. Patients have a median age of 40 years
5. Shows strong positivity for MYC by immunohistochemistry

E. Shows strong positivity for MYC by immunohistochemistry. Greater than 90% of postradiation angiosarcomas of the breast show high level amplification of MYC and corresponding strong overexpression of MYC by immunohistochemistry. Postradiation angiosarcoma develops in 0.03 - 0.14% of patients after radiation therapy for the treatment of breast cancer. Reflective of that cohort, the mean age is 70 years. Most postradiation angiosarcomas arise in the skin (from which they may secondarily involve the breast parenchyma) and the majority are of high histologic grade.

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Reference: Angiosarcoma

A 27 year old woman with no significant prior medical history presents with an 8 cm poorly defined left breast mass. A representative histological image is shown above. What is the most likely diagnosis?

1. Atypical vascular lesion of the skin
2. Capillary hemangioma
3. Low grade angiosarcoma
4. Pseudoangiomatous stromal hyperplasia
5. Spindle cell carcinoma with acantholytic pattern

C. Low grade angiosarcoma. The illustrated lesion is a primary, low grade angiosarcoma of the breast parenchyma. It demonstrates irregularly shaped, anastomosing vascular channels that dissect through the fat and collagen and around normal glandular structures. This pattern of destructive invasion distinguishes it from benign vascular proliferations.

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Reference: Angiosarcoma