and Aysegul A. Sahin2
Division of Pathology, Singapore General Hospital, Singapore, Singapore
The University of Texas, M. D. Anderson Cancer Center, Houston, TX, USA
KeywordsHaemangiomaPerilobularAngiosarcomaPseudoangiomatous stromal hyperplasia
A variety of vascular proliferations, both benign and malignant, can occur in the breast. Overall, they represent only a minority of tumours originating in the breast. Benign vascular lesions other than incidental perilobular haemangiomas are extremely rare in the breast. Malignant vascular lesions (angiosarcomas) are also rare, constituting less than 1 % of all breast neoplasms; they may be primary, or they may be secondary tumours occurring after radiation treatment. Also seen in association with radiation therapy are “atypical vascular lesions” affecting the skin of the breast. The relationship between atypical vascular lesions and radiation-associated angiosarcoma is still being debated and remains to be clarified. This chapter reviews the common vascular lesions in the breast, focusing on their diagnostic features and potential interpretive pitfalls.
Benign Vascular Lesions
Haemangiomas are benign vascular proliferations that can arise in breast parenchyma. Most of these lesions, called perilobular haemangiomas, are smaller than 0.5 cm and are identified incidentally on microscopic evaluation. Perilobular haemangiomas are not confined histologically to a perilobular distribution; they can occur in intralobular or extralobular stroma and may not have any relationship with ducts or lobular units. When a benign vascular proliferation is large enough to form a clinically palpable mass or is detectable by imaging (usually larger than 0.5 cm), it is diagnosed as haemangioma.
Clinical and Epidemiological Features
Haemangiomas occur in both female and male breasts and have been reported in a wide age range (infants to 85 years old). Haemangiomas may also occur as part of rare genetic syndromes, including Kasabach–Merritt and Poland syndromes. Rare congenital cases have been reported. Some lesions resolve spontaneously.
Most haemangiomas are incidental findings on biopsies performed for other reasons. Larger lesions may present as palpable masses or may be detected on imaging as superficial, well-demarcated, circumscribed, lobulated masses with an average size of 0.5–2 cm. Phleboliths or calcified venous thromboses may be present. They are commonly hyperechoic on ultrasound examination.
In general, haemangiomas are lobulated, well-circumscribed, soft, or spongy lesions with a dark red, brown, or haemorrhagic appearance.
Just like haemangiomas arising anywhere else in the body, haemangiomas arising in the breast can be of a capillary, cavernous, or venous type (Figs. 8.1, 8.2, 8.3, 8.4, and 8.5). The histologic subclassification has no biologic or clinical significance (Table 8.1).
Haemangioma. Microscopic features. (a, b) Proliferation of small capillaries in breast parenchyma. The vascular proliferation is supported by fibrous stroma. (c) Endothelial nuclei are flat and inconspicuous. No cytologic atypia is evident
Haemangioma. Microscopic features. (a–d) Proliferation of both small and large dilated vascular channels containing red blood cells
Perilobular haemangioma. Microscopic features. (a) An aggregate of histologically benign capillaries in the periductal stroma. (b) Higher magnification of the same case shows that the lesion consists of thin-walled vessels that contain red blood cells
Perilobular haemangioma. Microscopic features. (a, b) A collection of small vessels in periductal and perilobular stroma. (c) Vascular channels extend into intralobular stroma. Vascular channels are lined by small, flat endothelial cells
Breast haemangioma. (a) Circumscribed collection of congested vessels of varying sizes is seen within the breast, with benign breast lobules in the adjacent breast parenchyma. (b) The blood vessels are intensely congested with red blood cells. The border shows a smooth circumscription. (c) High magnification shows flattened endothelial cells with no atypia. Thin, fibrous stroma is seen among the congested vessels
Haemangiomas of the breast: key histologic features
Large, dilated vascular spaces separated by fibrous septa
Compact proliferation of small vessels
Feeding vessel often present at the periphery of the lesion
Irregularly dilated vascular spaces with variable muscular walls
Mixture of large, dilated vessels and dense areas of small capillaries
Cavernous haemangiomas, the most common histologic type, consist of a mesh of dilated vessels congested with red cells. The vascular channels usually do not anastomose and are lined by flat endothelial cells with inconspicuous nuclei.
Capillary haemangiomas consist of densely packed proliferations of capillary-sized small vessels lined by flat endothelial cells. Frequently, a feeder vessel with a muscular wall can be identified.
Venous haemangiomas consist of irregularly dilated vascular channels with vascular walls of varying thickness. A smooth muscle layer can be evident in the vascular walls. Vessels may contain homogeneous pink fluid (presumably lymph) in addition to red blood cells.
“Complex haemangioma” is a term used to describe haemangiomas that have variable patterns, with dilated vascular spaces admixed with dense areas of small capillary proliferation. A complex capillary network with focal anastomoses may be seen.
The diagnosis of haemangioma is often straightforward. As most vascular lesions arising in the breast are malignant, angiosarcoma is the main differential diagnosis. There is a major difference in the growth pattern of these two lesions. Haemangiomas show lobular, well-circumscribed margins, whereas angiosarcomas typically have an infiltrative growth pattern with dissection into the breast parenchyma. Based on this difference, when the edges of the lesion can be assessed on excision, it is easy to establish whether the nature of the vascular lesion is benign or malignant. It may be difficult to establish the diagnosis if only a small biopsy specimen is obtained which does not include the entire tumour edge. In such a situation, it may be necessary to further evaluate the lesion. Additional histologic features that help to differentiate the two lesions include the lack of anastomosing channels and endothelial atypia in haemangiomas and the presence of large blood lakes in angiosarcomas.
Degenerative changes, including infarct and thrombosis, may occur in any type of haemangioma.
Thrombosis with recanalisation or endothelial proliferations, which may have a papillary configuration, can rarely occur. Papillary endothelial proliferation may mimic an angiosarcoma, especially on a small biopsy sample. The lack of cytologic atypia, a non-anastomosing growth pattern, and circumscription of haemangiomas should be helpful in establishing the diagnosis.
Pseudoangiomatous Stromal Hyperplasia
Pseudoangiomatous stromal hyperplasia (PASH) may morphologically mimic haemangioma. In contrast to haemangioma, the cells lining the spaces in PASH are stromal cells (myofibroblasts) and do not express vascular markers. The spaces of PASH are empty; the spaces in haemangiomas typically contain red cells. PASH tends to be a diffuse process, whereas haemangiomas are characteristically lobulated and well circumscribed (Fig. 8.6).
Pseudoangiomatous stromal hyperplasia. (a) Macroscopy shows a diffuse, whitish, rubbery appearance. Several small cysts are seen, representing cystic changes in the breast. (b) Pseudoangiomatous stromal hyperplasia is often an incidental histological finding. (b) Note that the spaces are empty. The lining cells show flattened nuclei of fibroblasts and myofibroblasts
A lymphangioma is also a differential and can be distinguished by the relative absence of red blood cells within the spaces, which instead tend to contain lymphocytes (Fig. 8.7). D2-40 immunostaining decorates the lymphatic endothelium (Fig. 8.8).
Breast lymphangioma. (a) A circumscribed, nodular lesion is seen in the adipose tissue of the breast. The overlying dermis shows oedema. (b) Medium magnification shows empty spaces, which are interconnected among thin fibrous septa. (c) Lymphocytes are seen within the spaces, with some admixed red blood cells
Breast lymphangioma. Immunohistochemistry for D2-40 shows positive staining of the lining lymphatic endothelial cells. The inset shows higher magnification of the lymphatic endothelium
Prognosis and Therapy Considerations
Haemangiomas are benign neoplasms, and simple excision is curative. If the diagnosis is established on a core biopsy, usually an excision is recommended to exclude an angiosarcoma because some angiosarcomas may have areas of overlapping histologic features with haemangiomas. Histologic evaluation of the entire lesion may be necessary to establish the diagnosis. Local recurrence or metastasis of completely excised haemangioma has not been reported. Although some angiosarcomas may have very benign-appearing areas mimicking haemangiomas, transition from haemangioma to angiosarcoma in the breast has not been documented.
Angiolipoma is a benign neoplasm that may occur in the subcutis or in breast parenchyma. Angiolipomas are considered variants of lipomas. When the angiolipoma develops in the subcutaneous tissue overlying the breast, it presents as a well circumscribed and painful nodule. Angiolipoma arising within the breast parenchyma usually occurs as a small and painless nodule.
Clinical and Epidemiological Features
An angiolipoma manifests as a mass, which is either identified on imaging or palpated on physical examination.
Mammographic and ultrasonographic features are very similar to those of haemangiomas. These lesions also present as superficial small masses, usually less than 2 cm They are often well-demarcated but can sometimes appear ill-defined. They are hyperechoic on ultrasound examination.
Angiolipomas usually appear as well-circumscribed and often encapsulated masses. The cut surface is typically yellow and somewhat lobulated, indistinguishable from a conventional lipoma. As the vascular component increases, angiolipomas may appear more firm and red/brown.
Angiolipoma is characterised by a dispersed proliferation of small-calibre capillary vessels showing prominent intravascular fibrin microthrombi in a lipomatous background (Figs. 8.9 and 8.10). The lipomatous component has a benign appearance, with no nuclear atypia or pleomorphism. The small, round, usually thick-walled blood vessels tend to congregate at the periphery of the lesion. Fibrin thrombi may be the most conspicuous feature in some cases. In cellular angiolipoma, a prominent vascular component is seen withlittle to no admixed lipomatous elements.
Angiolipoma. Excision shows a circumscribed lipovascular lesion with congeries of congested capillaries interspersed with mature adipocytes (Reproduced with permission from Goh et al. ) Inset shows congested capillaries with occasional fibrin thrombi
Angiolipoma. (a) On core biopsy, the circumscribed border of the lesion is not readily appreciated histologically, though there is a clue from the upper end of the tissue core where a relatively distinct interphase of the lesion from the adjacent adipose is seen. (b) Higher magnification of the core biopsy material shows capillaries with fibrin thrombi. Although the subcutaneous location and radiological circumscription may point to the correct diagnosis, a benign conclusion of this lipovascular lesion on core biopsy is often not definitive, and excision may be required to confirm the diagnosis
Angiolipoma is usually a straightforward diagnosis.However, it may be difficult to recognise in some cases especially in small core biopsies. An excision may be required to exclude an angiosarcoma. Lipomatous–predominant angiolipoma may be confused with lipoma and atypical lipomatous tumour (ALT). Although both lipomas and angiolipomas are well circumscribed, often with thin fibrous capsules, lipomas usually have scant vascularity and do not possess fibrin microthrombi. ALTs show variation in nuclear size and shape in adipocytes of the lipomatous component, with occasional lipoblasts. Immunohistochemical stains for MDM2 and CDK4 demonstrate nuclear positivity in most ALTs. Cellular angiolipomas may be misdiagnosed as a haemangioma or angiosarcoma due to its high cellularity and inconspicuous adipose component. In contrast to angiolipoma, haemangiomas comprise vessels of different calibres without displaying any fibrin microthrombi. Angiosarcoma shows an infiltrative growth pattern with dissection into the breast parenchyma and nuclear atypia. Vascular channels in angiolipoma and angiosarcoma are positive for endothelial markers such as factor VIII, CD31, and CD34. Angiosarcoma however, lacks smooth muscle actin-positive pericytes surrounding its vasoformative channels.
Prognosis and Therapy Considerations
Angiolipomas are benign lesions and simple excision is curative.
Atypical Vascular Lesions of the Breast Skin
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