Multimodality imaging of breast hematomas and their mimickers

Abstract

While breast hematomas are common, their imaging features are often underrecognized or mistaken for other conditions.

Diagnosis of acute hematomas is generally easy when associated with a recent history of breast trauma, surgery, or percutaneous biopsy. However, minor trauma might not always be remembered, and breast hematoma might have longlasting imaging manifestations when associated with fat necrosis. Also, because of the increasing use of breast MRI and FDG-PET/CT, breast hematomas are increasingly detected as incidentalomas and may mimic malignancies.

Conversely, breast hematomas may also be associated with authentic malignant processes.

In this pictorial review, we present the natural history of breast hematomas, their various imaging features, as well as their differential diagnoses, highlighting the situations requiring histopathological correlation.

Introduction

Breast hematomas are relatively common and do not always require imaging checkup. At the acute stage, clinical features are often pathognomonic. At the subacute or chronic phase or in the absence of any remembered traumatic factor, the diagnosis may be challenging, and hematomas can be mistaken as malignant tumors, and vice-versa. Moreover, authentic hematomas may be associated with malignant breast tumors.

In this pictorial review, we present the natural history of breast hematomas, their various imaging features as well as their differential diagnoses.

Etiologies of breast hematoma

Breast hematoma consists of extravascular collection of blood, usually secondary to trauma or iatrogenic cause.

Blunt trauma, such as in falls, sport accidents, or seat belt injury in motor vehicle accidents, are responsible for a significant proportion of non-iatrogenic breast hematomas. ^1–4 However, in about half of all the cases, no specific injury is remembered. Such hematomas may be caused by minor trauma in patients with antithrombotic therapy or bleeding disorders. ^5,6

Breast hematomas are common in the post-operative setting, after mastectomy, implant placement or breast reconstruction – especially with microvascular procedures. Large hematomas may account for higher risk of implant infection or flap complications and are associated with re-intervention. ^7–10

Breast hematomas may also be caused by percutaneous procedure like breast core-needle biopsy, the risk increasing with needle diameter and in patients with antithrombotic therapy. ^11,12

In some rare cases, breast bleeding may be caused by hypervascular or rapidly-growing breast tumors such as high-grade epithelial tumors or sarcomas (especially angiosarcomas). ^13,14

Bland blood products may also be found in the cystic component of some tumors such as encapsulated papillary carcinomas. ¹⁵

Pathological changes induced by breast hematomas

Resorption of breast hematoma is a continuous process that takes from a few days to several weeks to complete, with the serum being rapidly reabsorbed into surrounding capillaries, followed by the degradation of red cells and the release of heme. Heme is cleared by an enzyme called heme oxygenase-1(16), ¹⁶ allowing removal of ferrous ions, which are then chelated by ferritin, and may accumulate in the form of hemosiderin in specialized macrophages known as siderophages (Figure 1). This process explains the classical evolution of bruise color (blue/black, brown, green, yellow) in the first 2 weeks.

Figure 1.

Cytologic analysis of hematoma (A) showing giant cells (with multiple nuclei) and hemosiderin deposition (brownish). Microscopic appearance of hematoma (B) showing dense fibrosis around foci of giant cells and hemosiderin deposition.

In addition to the resorption of blood products, adipose tissue healing involves complex processes of regeneration and scavenging of dead adipocytes. Adipocyte regeneration is maximum in the first 4 weeks after injury, with preadipocytes emerging between crown-like structures (dead adipocytes surrounded by macrophages). ¹⁷ In areas where all adipocytes died, numerous inflammatory cells are seen surrounding oil drops released by adipocytes. Lipids accumulate in foamy macrophages (or foam cells) but in case of significant wound, inflammatory processes may persist well after 12 weeks, while extracellular lipids coalesce into oil cysts. Dense fibrosis may develop progressively around oil cysts, sometimes with dystrophic, eggshell calcifications.

These late, scarring process, explains persisting radiological images, regrouped in the radio-histological entity called fat necrosis, which is frequently seen after injury of fatty breasts, ^18,19 long after the resolution of skin bruises.

Acute/subacute hematomas (<1 month)

In the acute phase, the diagnosis of breast hematoma is usually straightforward, based on anamnesis (recent trauma, surgical or percutaneous procedure) and clinical features: skin bruise, sometimes associated with acute painful breast lump.

Breast hematomas may have no associated image on mammograms, or present as subtle, ill-defined opacities or focal asymmetric density (Figure 2). The mammographic image usually decreases in density over time and completely resolve over the course of a few weeks or months (Figure 3).

Figure 2.

67-year-old female with a recently appeared left breast lump, with a slight yellowish skin ecchymosis. She remembers a trauma a few weeks ago. Mammography, oblique incidence (A) shows a subtle, partially radiolucent, opacity of the inferior region of the left breast (arrows). Ultrasound (B) shows an ill-defined hyperechoic area, with slight acoustic shadowing, typical of an hematoma. Follow-up at 4 months showed a complete disappearance of the anomaly.

Figure 3.

72-year-old female with hard lump in the right breast, which appeared several months after a fall on the breast. Initial mammogram (A) shows an irregular deep retroareolar mass (arrow). Initial MRI (D: T2 with fat suppression and E: T1 with fat suppression and gadolinium) shows a suspicious hypervascular irregular mass. Pathological examination of samples obtained under stereotactic guidance demonstrated multiple hemorrhagic foci in a large area of fat necrosis with no malignancy. Follow-up mammograms at 6 (B) and 12 months (C) showed progressive disappearance of the anomaly.

In case of larger hematoma, mammography may show well-defined dense mass, possibly with air-fluid level (e.g., in post-operative period or if the hematoma is ruptured through the skin) (Figure 4).

Figure 4.

75-year-old female treated with rivaroxaban for pulmonary embolism, presenting with an expanding hematoma of the left breast, opened to the skin, after a fall 2 weeks before. Mammography, cranio-caudal incidence (A) shows a dense, oval, well-circumscribed mass with gas inside. Ultrasound (B) shows an oval pseudosolid mass with peripheral increased vascularity on Doppler (C). Percutaneous evacuation of this clotted hematoma was performed, cytological analysis showed blood elements, with no abnormal cells. Follow-up at 2 months showed decrease in size of the hematoma, with persistence of peripheral hypervascularity. Pathological analysis of its vascularized component showed an organizing hematoma with neovascularization and papillary endothelial benign hyperplasia, with no malignancy. The lesion then spontaneously gradually disappeared over a 1-year period.

On contrast-enhanced mammography, acute hematomas – that are often seen after percutaneous biopsy – usually do not enhance. ²⁰

On ultrasound, smaller acute breast hematoma may not be detectable or can present as faint areas of increased echogenicity in fat tissue, associated with small cystic lesions. ¹⁹ Larger acute hematomas, like post-procedural hematoma, may present as a cystic lesion with avascular thin septations (fibrin) (Figure 5), fluid-debris levels or pseudosolid content (clot) (Figure 6). ^19,21

Figure 5.

67-year-old female with left breast lesion visible on ultrasound as an irregular attenuating mass with (arrows on B :grayscale ultrasound image) with increased stiffness on elastography (A). Core-needle biopsy of the nodule demonstrated triple negative invasive ductal carcinoma. Ten days after the biopsy, the patient was seen by another radiologist for the placement of a tissue marker before neoadjuvant chemotherapy. Grayscale ultrasound image (C) showed a an irregular cystic image with subtle thin septations (arrowheads), surrounded by hyperechoic fat tissue : it is a post-biopsy subcutaneous hematoma, which was mistaken for the malignant lesion, with a marker erroneously placed inside (D). Pretherapeutic T1w MR images (E) and enhanced T1w images (F)demonstrates the disappearance of the hematoma, the misplacement of the marker (arrowhead) and the neighboring breast cancer (arrow).

Figure 6.

93-year-old female with extensive left breast hematoma immediately after a fall. Extensive skin ecchymosis on the left part of the chest was present upon admission. Unenhanced chest CT scan (A) shows high-attenuating hematoma (star), involving the left breast, with surrounding fat stranding and no contrast extravasation nor enhancement (B). Breast ultrasound (C) done after 2 weeks shows a well-defined echogenic collection with diffuse ground-glass echoes, resolving on follow-up.

In the context of acute chest blunt trauma, CT can identify breast hematomas (Figure 6) and may detect post-traumatic vascular lesion such as pseudoaneurysm, that would require angiography and embolization. ²²

Breast MRI is less often indicated in the acute setting. It may show well-defined cystic lesion with spontaneous T1 hyperintensity on fat-suppressed images and fluid-fluid level on T ₂-weighted images (Figure 7).

Figure 7.

55-year-old female, with history of right breast implant reconstruction after breast cancer, presents with right breast pain and skin discoloration (A, arrow). Breast T ₂-weighted (B), unenhanced T ₁-weighted (C) and T ₁-weighted with gadolinium (D) MR images demonstrate retroprosthetic fluid collection with fluid-fluid level, moderate T1 hyperintensity and no enhancement, consistent with spontaneous hematoma. Follow-up studies showed spontaneous decrease in size of the collection.

While typical hematomas may be followed-up on imaging until regression over a few months, the presence of a large, palpable complex cystic mass, or the absence of an obvious causal trauma, usually warrants percutaneous sampling.

Fine-needle aspiration may allow the evacuation of the blood collection and confirm the diagnosis of breast hematoma by cytological analysis. However, if the aspiration fails to evacuate a significant volume of the lesion, or in the presence of a solid component, core-needle biopsy with pathological examination is warranted, to exclude the possibility of a cystic or pseudocystic breast tumor.

Chronic manifestations of breast hematomas

Chronic manifestations of breast hematomas may be misleading because skin bruise is usually absent and causal trauma may not be obvious. Clinical presentation may be a painless breast lump, of medium to firm consistency, more or less circumscribed. Some level of skin dimpling may be found.

Persisting images of breast hematomas on mammography and tomosynthesis is mostly secondary to fat necrosis: isolated radiolucent round mass (possibly with fat-fluid level), architectural distortion or spiculated mass with radiolucent center (Figure 8). Dystrophic calcifications are often present, typically coarse or curvilinear at later stage, but they can appear suspicious at earlier stage. ²³

Figure 8.

Evolution of breast hematoma in two different patients. First patient was involved in a car accident with seatbelt syndrome 1 year earlier and presented with a hard lump in the right breast: caudo-cranial view (A) showed a large, rounded lesion of fat-water mixed density with thick wall. Follow-up mammography after 2 years (B) showed reduction in size, with persistent radiolucent image. Second patient reported a fall on the breast a few years before: two mammograms with 2 years interval (C and D) demonstrate the progressive involution of a dense irregular opacity with increasingly visible coarse calcifications, in favor of post-traumatic fat necrosis.

On ultrasound, oil cysts are typically seen as well-defined, anechoic cystic lesion, with acoustic shadowing especially when wall calcifications are present (Figure 9). However, in some cases, fat necrosis secondary to breast hematomas may have a more worrisome presentation, such as ill-defined spiculated mass with acoustic shadowing (Figure 10) and increased stiffness on elastography, due to extensive fibrosis (Figure 11), without any cystic images, warranting percutaneous sampling.

Figure 9.

52-year-old female with an history of breast blunt trauma 6 months before. Screening mammogram (A) shows two adjacent, rounded, well-circonscribed, fat-containing images (arrows), and ultrasound (B) shows anechoic rounded image in a hyperechoic area, typical of an oil cyst. One-year follow-up shows partial decrease in size of one of the cyst, with multiple eggshell calcifications on mammogram (C) explaining attenuation on ultrasound (D).

Figure 10.

46-year-old female with a right breast lump 1 month after a trauma. Cranio-caudal view (A) shows a faint irregular mass (arrows). Ultrasound (B,C) shows an attenuating irregular, partially hyperechoeic mass (star) and hyperechogenicity of the surrounding breast tissue (arrowheads). Given the suspicious appearance on ultrasound (ACR four classification), core-needle biopsy was done, showing intense fibrosis and hemosiderin deposition, in favor of hematoma. The mammographic image is no longer visible at 1 year (D).

Figure 11.

62-year-old with two incidentally found left breast hypermetabolic nodule on PET CT in the upper inner quadrant (A, arrowhead) and lower outer quadrant (B, arrow). Two-dimensional-shear wave elastography with associated 2D images (C and D) demonstrate attenuating hyperechoic areas (arrowheads and arrows) with increased stiffness (areas colored in red). Cranio-caudal view shows ill-defined, partially radiolucent, opacities with some calcifications (arrowheads and arrows). Core-needle biopsies revealed fat necrosis with hemosiderin deposition, in favor of hematoma.

Signs of fat necrosis on MRI should be recognized to avoid misclassification as malignancies. The typical feature of fat necrosis is T1 hyperintensity at the center of the lesion, nulled after fat signal suppression. Depending on the lesion age and the fibrosis vascularization, enhancement may be either completely absent or it may exist an enhancing rim around the central fatty component, which does not usually enhance (Figure 12). ²⁴ Vascularization of fat necrosis may vary with time and short-term follow-up may be helpful in difficult cases.

Figure 12.

70-year-old female treated with oral anticoagulation therapy for atrial fibrillation, presenting with multiple bilateral small, firm breast lumps, without skin anomalies. She cannot remember a single significant trauma, but she has numerous ecchymosis of both arms. Mammography oblique (A) and cranio-caudal views (B) show numerous ill-defined small masses (arrows). Ultrasound 5C) shows small cystic lesions dispersed into hyperechoic areas of fat. T ₁-weighted (D) and fat-suppressed T ₁-weighted MRI (E) shows multiple small, enhanced masses displaying T1 spontaneous hypersignal and peripheral enhancement (arrows), a typical pattern for fat necrosis, secondary to breast hematomas of different ages.

Breast hematomas at every stage may display misleading increased FDG uptake on PET/CT, because of the presence of metabolically active inflammatory cells (Figure 13). Such presentation may accounts for some of PET-detected incidentalomas ^25,26 and should trigger clinical and radiological correlation.

Figure 13.

58-year-old with incidentally found left breast hypermetabolic nodule on PET CT (A, arrow). Breast ultrasound (B) demonstrates a lobulated mass (arrows) with subtle hyperechogenicity of the surrounding fat. Medio-lateral oblique view (C) demonstrates an ill-defined, partially radiolucent, opacity (arrows). Percutaneous biopsy confirmed the diagnosis of subacute hematoma.

Breast tumors presenting as hematomas

Rarely, malignant epithelial tumors may present as breast hematomas. One possible mechanism is the erosion of a large breast vessel by a rapidly growing tumor. In this case, hematoma may be the predominant imaging feature and occult other suspicious features (Figures 14 and 15).

Figure 14.

56-year-old female with relapsing right breast hematoma (A). Breast enhanced T ₁-weighted MR images on sagittal (B) and axial (C) views show a large breast mass with T1 hyperintensity (star) associated with enlarged axillary lymph node (arrow). Subtracted enhanced T ₁-weighted MR image (D) demonstrates mural nodular enhancement (arrowhead). Ultrasound (E) shows large cystic mass with fibrinous content, collapsing after percutaneous drainage (F). Cytological examination of the mass only showed red cells and hemosiderin, while biopsy of the abnormal lymph node demonstrated involvement by high grade triple negative breast cancer. The patient was treated with neoadjuvant chemotherapy and mastectomy and lymphadenectomy. Pathology revealed a 5-cm-large necrotic and hemorrhagic area within which was seen a 10-mm residual carcinoma, as well as a residual 6-mm macrometastasis in one axillary lymph node.

Figure 15.

50-year-old female with left breast hematoma, appearing after a fall on the breast. Cranio-caudal view (A) shows a round mass with focally indistinct margins posteriorly. Ultrasound (B) shows a cystic mass displaying posterior mural nodularity with increased Doppler signal (arrowheads). T ₂-weighted (C), unenhanced T ₁-weighted (D) and enhanced T ₁-weighted MR images show a cystic mass with fluid-fluid level and hemorrhagic content, and suspicious enhancing nodules (arrowhead). Hemorrhagic component was evacuated percutaneously (F), cytological examination demonstrated atypical epithelial cells. Core-needle biopsy of the nodular part of the lesion demonstrated high grade invasive ductal cancer.

Cystic tumors such as cystic papillary carcinoma, may contain blood products. These lesions are usually characterized by the presence of solid, vascularized vegetations. ^15,27 (Figure 16)

Figure 16.

80-year-old female with growing bluish mass of the right breast (A). She could not remember a trauma. Cranio-caudal view (B) shows a well-defined dense round mass. On ultrasound (C), the lesion is predominantly cystic with mural nodule and papillary projections. The mass was resected, pathology analysis showed intracystic papillary carcinoma.

Phyllode tumors or breast sarcomas may also present as pseudocystic lesions, ²⁸ usually with complex structure and inner vascularization.

A particular form of sarcoma is radiation-induced angiosarcoma, which tends to present as bluish or violaceous skin lesions and breast hematomas, sometime without any significant palpable mass (Figure 17). This difficult diagnosis requires a high level of clinical suspicion, in the presence of recurring or extending breast ecchymosis, in females with an history of radiation therapy.

Figure 17.

72-year-old females presenting with relapsing left breast hematoma and ecchymosis. Clinical examination shows several confluent violaceous skin nodules with ill-defined margins (A, arrowheads). The patient had a history of left breast cancer treated with wide local excision and radiation therapy 7 years before. Cranio-caudal view (B) shows rounded dense mass (arrow) and diffuse skin thickening. Ultrasound shows skin thickening with increased Doppler signal (C, arrowheads) and a cystic lesion with fibrinous content (D, arrow). Enhanced T ₁-weighted sagittal image (E) shows a round mass with thin peripheral enhancement suggestive of hematoma (arrow) and enhancing skin thickening (arrowheads). Cutaneous biopsy demonstrated angiosarcoma. The patient underwent mastectomy. Gross examination of the surgical sample shows infiltrating violaceous subcutaneous lesion (F, arrowheads). Microscopic examination at low magnification (G) shows infiltrating, anarchic network of vascular channels (arrowheads) lined by spindled cells with atypia, in favor of high-grade radiation-induced angiosarcoma.

Mass-forming breast lesion with hemorrhagic content, outside of a specific context (recent surgery, acute blunt trauma), should always be considered suspicious and warrants percutaneous biopsy. The presence of a solid, vascularized portion in a hemorrhagic lesion should be carefully assessed, because it is strongly associated with malignancy.

Conclusion

Breast hematomas have various imaging presentations, based on their age and the coexistence of fat necrosis. Over time, hemorrhagic content is gradually replaced by fibrosis, which may have worrying imaging presentation. Conversely, fatty content on mammography or MRI is evocative of benign post-traumatic process.

Some authentic malignant processes may present as hematoma or blood-filled collection. The presence of a vascularized solid component should raise suspicion and warrants biopsy.