Teaching Case

We report a case of a 33-year-old woman, known to have a germline BRCA2 mutation, in whom an enhancing breast nodule was detected on MRI during follow-up.

The small (diameter 5 mm), well-circumscribed nodule lying retroareolar in the posterior third of the right breast was isointense to muscle on the T1-weighted images and showed no diffusion restriction. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with fat suppression exhibited an initial increasing enhancement of the nodule followed by a plateau in the delayed phase (type 2 curve). The nodule was classified as BI-RADS 3 based on its imaging features. Three months later a control MRI was performed but no changes were observed, furthermore the lesion was not apparent on sonography. Due to the uncertainty about the lesion a MRI-guided vacuum-assisted biopsy was taken.

Histopathology showed a benign perilobular haemangioma, characterised by a conglomerate of dilated capillaries growing between the breast acini of a few terminal ductal-lobular units. The normal imaging follow-up, for BRCA2 mutation carriers, was continued.

Perilobular haemangiomas are microscopic vascular lesions of the breast (incidence 1-11%) [1-4]. They are benign and exist predominantly in the capillary form. As they may be small enough to be occult on imaging, they are often incidental findings [3, 4].

Due to their size (microscopically small), perilobular haemangiomas are only occasionally detected by imaging [3]. Mammographically detectable perilobular haemangiomas are oval, round or lobular in shape and well-circumscribed or microlobulated. Sonographically, they can appear as ill-defined hyperechoic or well-defined hypoechoic masses. DCE-MRI typically shows well-defined homogeneously enhancing lesions, demonstrating an intermediate signal on the T1-weighted images and an intermediate to high signal on the T2-weighted images [3].

Perilobular haemangiomas are small, mostly well-circumscribed, lesions consisting of a conglomerate of capillary-sized vessels that are lined by non-atypical endothelial cells. They can occur in the extralobular stroma and, despite their name, in the intralobular stroma [1, 3].

In young patients without a personal history of chronic lymphoedema or breast radiation therapy, as in our case, perilobular haemangiomas need to be differentiated from primary angiosarcomas; size is an important discriminator between them. Angiosarcomas are rarely smaller than 2 cm, whereas perilobular haemangiomas tend to be of microscopic size [1]. Angiosarcomas are cytologically atypical and mitotically active. They display an invasive and complex anastomosing growth pattern [3]. Perilobular haemangiomas on the other hand show no cytologic atypia, complex anastomoses or mitotic activity. They grow around the breast structures without invading them [2, 3]. The main imaging features of angiosarcomas in differentiating them from perilobular haemangiomas are their larger size and more rapid growth [3]. The differential diagnosis of perilobular haemangiomas also includes pseudoangiomatous stromal hyperplasia (PASH). PASH is characterised by pseudovascular spaces that are lined by CD31-negative (myo)fibroblasts instead of CD31-positive endothelial cells [3].

Since there is no evidence that perilobular haemangiomas are precursors of angiosarcoma and (extensive) imaging-guided biopsy is sufficiently reliable to rule out any malignant component; in the absence of radiologic-pathologic discordance, surgical excision of perilobular haemangiomas can be avoided and imaging follow-up of these lesions can be justified [1].