Other benign tumors

Atypical vascular proliferation

Topic Completed: 1 November 2016

Minor changes: 17 February 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Atypical vascular proliferation breast

Monika Roychowdhury, M.D.
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Cite this page: Roychowdhury M. Atypical vascular proliferation. website. Accessed October 25th, 2021.
Definition / general
  • Vascular proliferations that develop after external radiotherapy for breast carcinoma, within field of radiation (Am J Clin Path 1994;102:757)
Essential features
  • Benign atypical vascular proliferations developing after external radiation for breast carcinoma
  • Typically involves skin overlying breast
  • Two types: 1) lymphatic type; 2) vascular type
  • Differentiate from angiosarcoma by well circumscribed nature, lack of multilayering, mitosis and hemorrhage and absence of extension into subcutaneous tissue
  • Vascular type is higher risk for subsequent development of angiosarcoma
  • Complete excision and follow up for recurrence is standard treatment
  • "Atypical vascular lesion" term coined by Fineberg and Rosen in 1994 (Am J Clin Path 1994;102:757)
  • Note: atypical vascular pattern refers to a dermoscopic pattern that helps differentiate benign cutaneous lesions from melanoma
  • Mean age 61 years
  • Develops 1 - 12 years (mean 6 years) after therapy in radiation field
  • Breast exposed to previous radiation, usually in the skin area
Clinical features
Prognostic factors
Case reports
  • Complete excision and careful follow up for recurrence
Clinical images

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Left breast is erythematous with sclerotic tissue changes

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Figs 1 and 4: Papules and nodules in and around the mastectomy scar

Gross description
  • One or more circumscribed papules, bluish purple nodules, small vesicles or erythematous plaques, usually in irradiated field, median 0.5 cm
  • Frequently multiple synchronous lesions with discoloration
Microscopic (histologic) description
  • Relatively well circumscribed, anastomosing growth pattern of irregular slit-like vascular spaces dissecting dermal collagen but not extending into subcutis
  • Lined by single layer of endothelial cells without atypia
  • Often micropapillary tufts
  • Resembles benign lymphangioendothelioma or patch stage Kaposi sarcoma (Am J Surg Pathol 2002;26:328)

    Lymphatic type:
  • Predominantly thin walled, variably anastomosing lymphatics primarily in superficial dermis

    Features of angiosarcoma which are lacking in AVLs:
  • Multilayering of endothelial cells, prominent nucleoli, mitoses, hemorrhage, destruction of adnexa and extension into subcutaneous tissues
Microscopic (histologic) images

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H&E, CD31 and FLI1

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Lesions confined to papillary and reticular dermis

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Dermis showed perivascular lymphocytic infiltrate and collagenization

Positive stains
Negative stains
Molecular / cytogenetics description
Differential diagnosis
  • Angiosarcoma, well differentiated:
    • Atypical endothelial cells, infiltrative margins, usually high grade, larger (median 7.5 cm vs. 0.5 cm for atypical vascular lesions), positive nuclear staining for c-Myc
    • Atypical vascular lesions are well circumscribed, not infiltrative, no multi layering, no mitosis, no hemorrhage
    • However, angiosarcoma may be part of morphologic continuum with atypical vascular lesions (J Am Acad Dermatol 2007;57:126) and may need additional biopsies to distinguish these entities
  • Hobnail hemangioma: smaller, more superficial and more localized
  • Lymphangioendothelioma: has intravascular papillary stromal projections that resemble papillary endothelial hyperplasia
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