Fig. 10.1
Fat necrosis. (a) Spot tangential view at the site of a palpable “lump” (as denoted by metallic BB skin marker) shows an irregular fat containing mass with indistinct margins. (b) On targeted ultrasound, an oval, horizontally oriented (parallel) mass is imaged in the subcutaneous fat; it is predominantly hyperechoic with central cystic spaces (arrows).
Abscess/Mastitis
Subareolar abscesses can be distinguished from peripheral abscesses not only by location but by patient predilection, potential etiologies, imaging appearance, and management.
There are two schools of thought regarding the etiology of subareolar abscesses. One supports the predilection seen in smokers: a metaplastic change in ductal epithelium (supposedly related to cigarettes) resulting in luminal obstruction that makes the patient more susceptible to infection. However, these abscesses are also seen in non-smokers. A second hypothesis is that the process starts as a skin infection, such as a folliculitis, that extends into the breast tissue. This can also be challenged, since some patients may have little skin changes, out of proportion to symptoms and extent of the deeper abscess collection [1].
Clinically, patients with abscesses may feel a painful “lump,” overlying which the skin may be erythematous and/or thinned. Depending on the extent of infection, diffuse skin edema, characterized by thickening or peau d’orange change, can be seen, as may purulent drainage.
Subareolar abscesses can be managed with oral antibiotics (more than one course may be required), aspiration, incision and drainage, and/or clinical and ultrasound follow-up. Frustrating to patients and clinicians, even with a good response to initial treatment, they often recur (in 25–40% of patients), requiring (repeat) needle aspiration or incision and drainage acutely, or eventual central duct excision [1, 5]. Recurrent or chronic subareolar abscesses can form fistulous tracts with the skin seen clinically along the areolar margin as draining sinuses. This is known as Zuska disease [6]. Due to repeated bouts of inflammation resulting in fibrosis involving the central ducts, horizontal nipple inversion may eventually occur.
Lactational abscesses can be central or peripheral. These are often managed by the patient’s obstetrician/gynecologist, without imaging, and seem to respond better to antibiotics [5, 7].
Peripheral abscesses not related to lactation are more common in diabetics, perhaps related to compromised immune function. These may not involve the skin directly, but be centered in the parenchyma, and therefore be confused with a mass. First-line management is often ultrasound-guided needle aspiration in addition to oral antibiotics. These are less likely to recur.
Imaging Findings
Subareolar abscess: Increased density, focal asymmetry or mass mammographically, possibly with associated skin and/or trabecular thickening (edema). Edema and patient tenderness may limit compression. Sonographically, an irregular fluid collection/complex cystic and solid mass involving the deep dermal layer; tubular extensions can often be seen “funneling” posteriorly, with increased echogenicity and loss of tissue planes that represents parenchymal edema (Fig. 10.2). There is associated skin thickening if not breakdown and drainage. Echogenic foci may represent air if there is an open wound.
Fig. 10.2
Subareolar abscess and mastitis . (a) Standard CC and MLO views of the left breast in a 47-year-old woman show increased mass-like density in the lower central aspect in the area of a painful, erythematous, palpable “lump” denoted by a metallic BB skin marker. There is also increased skin and trabecular (arrowheads) thickening reflecting edema more diffusely. (b) Spot tangential view better demonstrates the association of the mass with the nipple areolar complex, which is thickened. (c) Irregular, complex fluid collection broadly involving the deep dermal layer (arrows) with posterior acoustic enhancement. (d) Sonography into the upper inner quadrant shows edema: skin thickening, increased interstitial fluid (arrows), loss of tissue planes, and ill-defined hypoechoic areas (mastitis, arrowheads).
Peripheral abscess : A mass or focal asymmetry mammographically, possibly with associated skin (secondarily) and/or trabecular thickening (edema, focal or diffuse). Sonographically, a complex solid and cystic mass, sometimes with mobile internal echoes, and surrounding edema; skin thickening may or may not be apparent. Lactational abscesses also have this appearance; they are more commonly imaged sonographically due to avoidance of radiation while still breastfeeding (Fig. 10.3).
Fig. 10.3
Lactational abscess . (a) 41-year-old woman treated empirically with two courses of antibiotics with no decrease in size of a palpable mass and continued decrease in milk production from this side. Targeted ultrasound shows an irregular complex solid (iso-/hyperechoic) and cystic mass and surrounding edema. The internal echoes were mobile in real-time. (b) Ultrasound-guided needle aspiration is done, draining the fluid collection to completion. (c) Follow-up ultrasound 2 weeks later was normal (not shown).
In patients with infectious mastitis, physical exam and imaging findings tend to be diffuse as there may not be a discrete associated fluid collection to suggest an abscess. Focal areas of irregular hypoechoic tissue, or diffusely dilated subdermal lymphatics, may be noted by ultrasound [1]. This clinical picture may overlap that of a locally advanced malignancy more so than with an abscess; therefore, short term follow-up is paramount with biopsy to follow if exam and imaging findings do not resolve with antibiotics. In that vein, direct correlation with clinical signs and symptoms with ultrasound findings are imperative in distinguishing between infectious and malignant processes.
Granulomatous mastitis is a rare noninfectious condition typically seen in women of childbearing age, within several months to years of pregnancy. The etiology is unknown, but some postulate an autoimmune mechanism. It may present with a painful, palpable lump, which may overlap the clinical presentation of an abscess. Mammographic findings may include a mass or parenchymal asymmetry; sonographically, masses or hypoechoic tubular densities may be seen (Fig. 10.4), their irregular shape warranting biopsy, on which perilobular noncaseating granulomas would be reported [1, 8]. If the diagnosis is unequivocally confirmed histologically, treatment consists of corticosteroids (if there is any doubt, a course of antibiotics may be tried first to avoid exacerbating a possible infection). Granulomatous mastitis can be recalcitrant even to long-term steroid treatment—and may still require excision [8].
Fig. 10.4
Granulomatous mastitis . (a) Orthogonal ultrasound images in a 28-year-old woman with a painful “lump” show an irregular hypoechoic tubular-shaped structure (arrows) at the base of the nipple. Histology on core needle biopsy showed a mixed picture of acutely inflamed breast parenchyma with granulomatous features. Even though stains for microorganisms were negative, the patient was started on antibiotics given the acute inflammation reported histologically. (b) After 1 month of no clinical improvement and increase in size of the mass, she was started on a course of corticosteroids for presumed granulomatous mastitis given granulomas also seen on pathology. She eventually underwent surgical excision.
Vascular Lesions
These may present clinically as a superficial “lump,” or be found incidentally mammographically or sonographically as a round or oval mass, sometimes with calcifications (phleboliths), with vascularity confirmed on color Doppler imaging. They can be hypoechoic to hyperechoic on ultrasound [9]. Common benign lesions include hemangiomas (Fig. 10.5) and angiolipomas. Angiosarcomas in the breast may be primary or secondary—the latter most often related to prior radiation therapy—and present with overlying bluish skin discoloration. These may be more irregular in appearance on imaging and hyperechoic or mixed echogenicity on sonography (Fig. 10.6) [1, 9, 10, 11].
Fig. 10.5
Capillary hemangioma . (a) Low-density oval mass with circumscribed margins on spot compression view. (b and c) Irregular, predominantly hyperechoic mass on ultrasound—this appearance prompted biopsy.
Fig. 10.6
Angiosarcoma . Orthogonal sonographic views show an irregular hyperechoic mass with indistinct margins and central decreased echogenicity in the subcutaneous fat. Given this appearance, and its location deep to a bluish discoloration on the skin in a 52-year-old with a history of radiation following lumpectomy for breast cancer, biopsy was done. An equal density irregular mass was imaged on correlative mammogram (not shown).
Pseudoaneurysm of the breast is rare, and of these, most are post-traumatic, namely, complications from percutaneous biopsies resulting from a disruption in the arterial wall. They may present as a palpable, pulsatile mass and demonstrate swirling internal vascular flow (“yin-yang” sign; Fig. 10.7). Pseudoaneurysms may thrombose spontaneously (self-limited) or be treated under ultrasound with sequential manual compression; thrombin or alcohol injection; embolization with coils, Gelfoam, or glue; or surgically [11, 12].
