Exploring Imaging Characteristics in �Extramammary Metastases in Breast�: a multimodality approach

Ga Eun Park, Bong Joo Kang, Sung Hun Kim, Han Song Mun

The Catholic University of Korea, Seoul St. Mary's Hospital, Republic of Korea

Literature reviews

Prevalance

• Extramammary metastasis to the breast is rare, reported rate ranges from 0.1% to 5.0%.
• This rare occurrence of metastases to the breast is believed to be due to large areas of fibrosis and relatively decreased vascularity. No clear predisposing factors have been identified. However, it is suggested that estrogen may cause an increase in vascularity and stroma within the breast, which could play a role as a predisposing factor in the development of metastasis.
• The most common sources are lymphomas/leukemias and melanomas, lung cancer, and ovarian cancer. Less common sources include are gastrointestinal, neuroendocrine, renal, thyroid, and head and neck tumors and sarcomas.
• In children and adolescents, rhabdomyosarcoma is one of the common tumors.

Clinical perspective

• Approximately 50% of these metastases are located in the upper outer quadrant of the breast and are superficially located in subcutaneous tissue or immediately adjacent to the breast parenchyma, attributed to the abundance of vascularity, lymphatic drainage, and glandular tissue in these areas.
• Breast metastasis may be the first manifestation of malignant disease.
• Metastasis to the breast is typically indicates advanced metastatic disease and often carries a poor prognosis, with more than 80% dying within one year.
• Breast tissue confirmation is performed to verify the origin of lesion, given the rarity of metastases to the breast compared to the prevalence of primary breast cancer.

Route of dissemination

• Lesions typically present as diffuse findings in the breast, such as edema, trabecular thickening, skin thickening, and breast parenchymal involvement with or without lymph node enlargement. These may be misinterpreted as inflammatory breast cancer.
• These metastases originate typically from gastrointestinal and gynecological cancers

Hematogenous dissemination

• Lesions usually present as single or multiple, round to oval, circumscribed masses or occasionally as microlobulated hypoechoic masses.
• For this reason, they are indistinguishable from well-defined breast malignancies or even benign lesions, such as fibroadenomas.
• The involvement of axillary lymph nodes is also less common.

Lymphatic dissemination

Imaging characteristics

Mammography

• These lesions usually present as high density, round, and circumscribed masses that resemble benign lesions. Microlobulated or indistinct margins may be present in some cases, making them look like primary breast cancer.
• Unlike primary carcinomas, breast metastases generally do not have spiculated margins and architectural distortion, due to the absence of desmoplastic reaction. Although calcifications are not frequently present, they occur more commonly in patients with ovarian cancer due to the presence of psammomatous bodies.

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Ultrasound

• Most metastatic lesions present as round or oval masses with circumscribed, indistinct or microlobulated margins. Although most lesions are hypoechoic, the echotexture may be heterogeneous, presenting anechoic or hyperechoic areas, frequently associated with posterior enhancement.
• Color Doppler imaging may reveal increased vascularity within the lesion, although this finding is not specific to metastases but may be useful mainly in differential diagnosis with benign lesions.

Imaging characteristics

MRI

• Most metastatic lesions show intermediate signal intensity on T2-weighted sequences and low signal intensity on T1-weighted sequences, with the exception of melanoma metastases, which may show high signal intensity on T1-weighted images.
• After administration of paramagnetic contrast, intense, fast, and homogeneous enhancement is usually observed.

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CT and PET/CT

• In patients with known malignant neoplasms, metastatic breast lesions are often identified incidentally in routine examinations performed for systemic staging or post-therapeutic follow-up.
• These lesions usually present as round or oval circumscribed masses with contrast enhancement in CT. In PET/CT, any lesion with increased metabolism relative to normal breast parenchyma should be considered suspect for malignancy.

Case discussion

Case discussion

• A total of 47 extramammary metastases were confirmed by breast biopsy in our institution
• From January 2011 to June 2024
• 46 female, 1 male
• mean age 50.1 ± 17.4 years (range 13~ 84)

Case discussion

• Breast metastasis was the first manifestation in 15% (7/47) of patients
• The average interval between the diagnosis of primary malignancy and breast metastasis was 2.5 years
• Among the patients, 86% (18/21) expired. �(This excluding 13 patients who were lost to follow-up and 12 patients diagnosed within the past year)

Case discussion

• Categorization based on imaging features

Representative cases

Solitary mass, circumscribed

A 58-year-old woman with a palpable mass in the right breast

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(A) Ultrasound revealed an oval, circumscribed, hypoechoic mass at the superficial layer of the right upper inner breast, corresponding to the palpable site. (B) This lesion exhibited high signal intensity on the precontrast T1-weight image and (C) demonstrated strong early enhancement on the postcontrast images. (D) Another enhancing mass was incidentally detected in the right back region. �Excision of masses confirmed them as melanoma.

Solitary mass, circumscribed

A 75-year-old women with an incidental breast mass detected on PET-CT for known bladder cancer

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(A,B) PET-CT scans showed an irregular solid mass with intense FDG uptake involving the bladder (C,D) Additionally, an ovoid solid mass with intense FDP uptake, comparable to that of the bladder mass, was detected in the left upper central breast periphery. (E) Ultrasound revealed an oval, circumscribed, hypoechoic, benign looking mass with (F) increased vascularity in the Doppler imaging.

A biopsy confirmed metastasis of bladder cancer.

Solitary mass, not-circumscribed

A 58-year-old woman with palpable masses in the �left breast and axilla

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A) Mammography showed an irregular, high density mass in left upper breast and an enlarged lymph node in the left axilla, corresponding to palpable lesions. (B) Ultrasound revealed an enlarged lymph node with marked cortical thickening in the left axilla, and (C) an irregular, not circumscribed, hypoechoic mass in the left upper outer breast periphery, mimicking primary breast cancer.

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Biopsy of both sites confirmed metastatic adenocarcinoma with micropapillary feature. She was then diagnosed with primary peritoneal carcinoma during systemic evaluation. The breast was the first manifestration of malignant disease.

Solitary mass, not-circumscribed

A 52-year-old woman with a palpable mass in the right breast

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(A) Ultrasound showed a irregular, not-circumscribed, hypoechoic mass with posterior enhancement at the 9 o’ clock direction of the right breast. This lesion showed (B) intermediate signal intensity on T2-weighted image, (C) homogeneous enhancement in post-contrast T1-weighted image, and (D) a low ADC value, less than 0.6 x 10-3 mm2/s on the ADC map (b value = 800).

A biopsy confirmed granulocytic sarcoma, suggesting involvement of myelogeneous leukemia.

Multiple masses, circumscribed

A 13-year-old girl with newly developed masses in both breasts during treatment response evaluation for known rhabdomyosarcoma

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(A,B) Contrast-enhanced chest CT showed newly developed, variably sized, several ovoid masses with well defined margin and homogeneous enhancement in both breasts. (C,D) These massed showed intense FDG-uptake in PET-CT. (E,F) Ultrasound revealed several oval, circumscribed, hypoechoic masses scattered in both breasts. A biopsy confirmed metastatic rhabdomyosarcoma.

Mutiple masses, not-circumscribed

A 77-year-old woman with palpable masses in the right breast

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(A) Mammography showed three high density masses in the right upper outer breast. (B,C) Ultrasound revealed three irregular not-circumscribed heterogeneous masses located in the superficial layer with diffuse skin thickening. (D) These masses showed heterogeneous enhancement in contrast-enhanced breast MRI.

A biopsy confirmed diffuse large B cell lymphoma.

Mutiple masses, not-circumscribed

A 60-year-old woman undergoing screening mammography

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(A,B) Mammography showed multiple high density masses in both breasts. (C-F) Ultrasound demonstrated multiple variably sized, irregular, not-circumscribed hypoechoic masses, most of which were located just below the premammary fat layer. A biopsy confirmed myeloid sarcoma.

Nonmass lesions

A 39-year-old woman with a palpable mass in the right breast

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(A,B) Mammography revealed global asymmetry in the right breast compared to the left. (C) Ultrasound showed regional hypoechoic nonmass lesions in the right breast. (D) Contrast-enhanced breast MRI demonstrated segmental nonmass enhancement in the right inner breast. Additionally, irregular heterogeneous enhancing masses involving the chest wall were detected (arrowheads).

A breast biopsy confirmed metastatic high-grade serous carcinoma, originating from the ovary.

Nonmass lesions

A 50-year-old woman with breast abnormalities during initial work-up of known non-small cell carcinoma

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(A) Mammography showed diffuse skin and trabecular thickening and increased parenchymal density in the right breast, with axillary lymphadenopathy. �(B) Ultrasound showed heterogeneous nonmass lesions in the right upper inner and central breast with skin thickening. �(C) Contrast-enhanced MIP showed nonmass enhancement in the right upper inner breast with asymmetric nipple-areolar complex enhancement.

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A breast biopsy confirmed metastatic non-small cell carcinoma with predominant lymphatic spread.

Nonmass lesions

A 39-year-old man with a palpable mass in the left chest wall

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(A) Ultrasound showed hypoechoic nonmass lesions at the left retroareolar region, initially interpreted as gynecomastia at the time and decided to follow up. After two months, a follow up ultrasound was performed due to the patient's complaint of persistent discomfort in the area. (B) Ultrasound revealed a significant increase in the volume of the previous nonmass lesions (C) with hypervascularity on Doppler image. (D) The lesions showed intense FDG uptake in PET-CT. A breast biopsy confirmed metastatic rhabomyosarcoma.

Take home message

• Metastases to the breast are rare, with a reported incidence of 0.1-5%.
• Lymphoma/leukemia is the most common, followed by melanoma, lung, ovarian, and GI tract

• Imaging features may vary depending on the primary tumor and route of dissemination
• Hematogenous dissemination usually presents as oval circumscribed solitary or multiple masses, which could be mistaken for primary breast malignancies or benign tumors.
• Lymphatic dissemination usually presents, with diffuse skin and trabecular thickening and parenchymal involvement, which are indistinguishable from inflammatory breast cancer.

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• Despite their rare, radiologists can suspect the diagnosis of extramammary breast metastases based on specific imaging findings, a careful patient history of malignancy, and the timing of imaging.

References

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