Breast ultrasound scans – surgeons’ expectations

Abstract

Recent years have witnessed a dynamic development of mammary gland imaging techniques, particularly ultrasonography and magnetic resonance imaging. A challenge related to these studies is the increase in the precision of the anatomical assessment of breast, particularly for early detection of subclinical lesions, performance of ultrasound-guided biopsy procedures, and accurate preoperative location of pathological lesions so as to optimize the surgical treatment. Ultrasound imaging is a primary and baseline diagnostic procedure the patient with suspected pathological lesions within breast is referred to by the surgeon. Lesions visualized in ultrasound scans are classified according to the BI-RADS US assessment categories. The successive categories (2 through 6) encompass individual pathological lesions, estimating the risk of malignancy and provide guidelines for further diagnostic and therapeutic management. This article described the important aspects of ultrasonographic imaging of focal lesions within the breasts as significant from the standpoint of surgical treatment of patients falling within BI-RADS US categories 3, 4, 5, and 6. Attention is drawn to the importance of ultrasound scans in the assessment of axillary fossa lymph nodes before the decision regarding the surgical treatment.

Introduction

Mammary gland disorders were first described by an ancient surgeon, Imhotep, in a papyrus dated to the 17^th century BC. The breast cancer was described as “swollen breast tumor”. The author described 45 cases of this type, with a final conclusion of “no cure” presented along with the last case in the series.

For more than 3000 years, breast cancer was a mysterious, abashing and incurable disease detected at a very advanced stage. Initially, the surgical treatment of breast cancer was very mutilating. It consisted in extensive procedures of dissecting the mammary gland along with pectoral muscles and axillary, supraclavicular, and often also mediastinal lymph nodes⁽¹⁾. Currently, Halsted's radical mastectomy is performed only in cases of infiltration of pectoral muscles and the range of surgical treatment is decided on the basis of TNM disease staging.

Ultrasonography (US) is one of the basic methods used in detection of focal lesions, including breast cancer staging. First examinations employing ultrasonographic techniques were performed in A-mode using instrument probes immersed in water in the 1950s. In the 1960s, Holmes, Wright, and Meyerdirk developed an ultrasound scanner facilitating two-dimensional B-mode imaging with the use of gel as a contact substance between the probe and the examined structures. The first ultrasound scanner was marketed in 1963. Seven years later, mammography was considered a breast cancer screening test⁽²⁾.

Recent years have witnessed a continuous, dynamic growth in breast and breast pathologies imaging methods [ultrasonography, ultrasonography and sonoelastography, mammography (MMG), magnetic resonance imaging (MRI), including contrast-enhanced imaging and positron emission tomography (PET)].

Thanks to the wide accessibility of MMG and US screening, breast cancer is increasingly often detected and successfully treated at earlier stages. A challenge related to the diagnostic imaging of breasts is the increase in the precision of the anatomical assessment of the gland for early detection of subclinical lesions, performance of ultrasound-guided biopsy procedures with subsequent preoperative location of lesions to optimize the surgical treatment.

Ultrasound imaging is a primary and baseline diagnostic procedure the patient with suspected pathological lesions within breast is referred to by the surgeon. The scan should be performed in compliance with the standards set forth by the Polish Ultrasound Society⁽³⁾. The results of ultrasound scans are subsequently correlated with the results of other imaging tests and, above all, with the clinical evaluation.

Ultrasonographic assessment of focal lesions within the breasts and the lymph nodes within the axillary fossa

Following visualization of pathological lesions in a ultrasound scan, the lesions should be assigned a category according to the BI-RADS US classification.

According to the classification,

• category BI-RADS US 2 includes focal lesions presenting with features of lesions that are unambiguously benign, requiring no further examinations or biopsy verification; follow-up ultrasound scan is recommended in 12 months.

In this category, surgical consultation may be required by clinically enlarging inflammatory lesions, including complex cysts, abscesses or damages to breast implants (Fig. 1).

• category BI-RADS US 3 includes lesions of a probably benign, with probability of malignancy amounting to <2%.

Fig. 1.

A, B. Damaged saline chamber in a patient with a dual-chamber implant

Lesions classified into this category include fibroadenomas (the most common solid lesions within the breasts), thickwalled cysts, dilated milk ducts with thick contents or small cyst aggregates.

Lesions classified into this category may be subject to fineneedle aspiration biopsy (FNAB), follow-up examination in 6 months, or sonoelastographic examination. Results of surgical evaluation taking into account the patient's age, family history and preferences are decisive for the choice of therapeutic management.

Fibroadenomas are the most common lesions of this category subjected to microscopic verification. They are characterized by high structural diversity as shown in ultrasound scans, reflecting their complex structure, including histopathological structure. According to Stavros, only 40–50% of fibroadenomas present with features typical of BI-RADS US category 3; presentation of the remaining ones is considered “suspicious”, resulting in their being classified as BI-RADS US category 4 (Fig. 2) and requiring histopathological assessment⁽⁴⁾.

Fig. 2.

Hypoechogenic, oval solid focal lesions with segmentally rough edges; BI-RADS US category 4. Histopathological verification: complex fibroadenomas

Asymptomatic fibroadenomas, do not become enlarged usually remain monitored and do not require surgical treatment. Patients referred to surgical treatment are usually patients with rapidly-growing fibroadenomas or fibroadenomas larger than 4–5 cm in size, causing pain, presenting with features of atypia, or suspected of malignant growth. Patients’ preferences are usually taken into account as well.

The incidence of malignancies in fibroadenomas is very low and accounts for 0.002% to 0.125% of cases. In situ carcinomas: ductal (DCIS) and lobular (LCIS) are diagnosed most commonly. Usually, they consist in small foci of malignant growth within large adenofibromas and the prognosis is better compared to the overall prognosis in breast cancer. In these cases, ultrasound monitoring of lesion size, echogenicity, echostructure, shape and vascular pattern is particularly important⁽⁵⁾.

Due to the large diversity and potentially benign character of lesions falling within this category, the therapeutic decisions, usually conservative in nature, are made mainly on the basis of ultrasound scans. Precise determination of lesion morphology ensures appropriate therapeutic decision, increases emotional comfort of the patient as well as facilitates planning further follow-up without more invasive diagnostics.

• Lesions classified as BI-RADS US category 4 and BI-RADS US category 5 are referred to as suspicious lesions characterized by the probability of malignancy being larger than 2% and requiring microscopic verification. Thick needle biopsy is preferred in case of lesions falling within these categories (Fig. 3 A). In exceptional cases, following negative microscopic verification, vacuum- assisted biopsy (VAB) or surgical biopsy may be considered.

Fig. 3.

A 28-year-old female, using contraceptives, with clinically palpable tender tumor within the supramamillary region in the right breast. Family history of breast or ovarian cancer negative. Ultrasound scan reveals a hypoechogenic, solid lesion with not circumscribed margin, AP dimension >LL dimension. BI-RADS US category 4. Core-needle biopsy. Histopathological verification: hamartomas

In case of benign lesions classified as BI-RADS US category 4, including complex fibroadenoma, hamartoma (Fig. 3) or other benign lesions, no further treatment is required. Determination of cancer cells implies therapeutic management appropriate for the cancer type and stage. In case of an invasive or an in situ carcinoma being diagnosed in these categories, primary treatment involves surgical resection.

There are two basic methods of surgical treatment:

• breast conserving therapy (BCT), consisting in resection of the breast tumor including a healthy margin, placement of radiopaque clips within the tumor bed followed by axillary lymphadenectomy (AL) or sentinel lymph node biopsy (SLNB) and subsequent radiation therapy;

• mastectomy involving resection of the mammary gland including the fascia of the major pectoral muscle and axillary lymph nodes (lymphadenectomy of SLNB, as in the case of cN0).

Radical mastectomy following Halsted's procedure performed only in case of infiltration of pectoral muscles.

Ultrasonographic diagnostics of breast cancer – surgeons’ expectations

Surgeons’ expectations regarding ultrasound scans performed in patients with lesions suspected of malignant growth and patients diagnosed with breast cancer and referred to ultrasound imaging examinations before planned surgery include the precise assessment of the focal lesion with: the size and location, echo pattern, shape, orientation, margin, vascularity, potential calcifications, evaluation of location relative to the surrounding structures such as skin, nipple, pectoral muscles of ribs, surrounding breast tissues and the axillary fossa.

The size of the tumor is one of the factors taken into consideration in treatment planning. Malignant lesions less than 3 cm in size and absence of secondary lesions in other organs or regions (M0) are an indication for breast conserving therapy (Fig.s 4 and 5)⁽⁶⁾. Contraindications for breast conserving therapy include:

• multifocal carcinoma

• history of radiation therapy delivered to the breast

• extensive microcalcifications reported in MMG summary

• certain collagenoses

• lack of patient's consent

Fig. 4.

Types of the surgical treatment of breast cancer⁽⁶⁾

Fig. 5.

Hypoechogenic lymph node without visible hilum, with indistinct capsular margin. FNAB revealed cancer cells. Patient diagnosed with breast cancer was qualified for axillary lymphadenectomy

Relative contraindications include retromamillar location of the tumor and pregnancy.

Breast conserving therapy is also possible in patients with tumors >3 cm in size, particularly at specialist oncology centers. This pertains to patients with large breasts in whom the cosmetic effect will be maintained and in cases when the tumor size had regressed secondary to systemic treatment as evidenced by imaging studies.

Dissection of axillary lymph nodes is a standard of care in breast cancer. The lymph node status is an important prognostic factor. Precise ultrasound assessment of the lymph nodes within the axillary fossa as well as in the supraclavicular and subclavicular lesions, often combined with FNAB, is essential for the surgeon in order to properly plan the surgical procedure within the fossa.

Currently, patients with no palpable lymph node enlargement in the clinical evaluation of axillary fossa (N0) are qualified for sentinel lymph node biopsy (SLNB). This allows to avoid axillary lymphadenectomy which is known to be associated with numerous adverse effects. However, it should be stressed that in case of a macrometastasis (as detected in histopathological examination) into the sentinel node, patients are usually qualified for another surgical procedure. As demonstrated by numerous publications, sensitivity of ultrasound assessment combined with FNAB verification of lymph nodes presenting with suspicious image in the ultrasound scan allows for more accurate disqualification of patient from the SLNB procedure as compared to clinical examination⁽⁷⁾, thus allowing to avoid a double instead of a single surgical procedure.

Ultrasonographic examinations by Choi et al. showed that the thickness of the lymph node cortical layer of more than 3 mm is a sensitive marker of metastases into the lymph nodes within the axillary fossa⁽⁸⁾. Determination of the number of visible lymph nodes, their size, shape, echogenicity or morphological abnormalities such as the image of the nodular hilum, capsule and outline, is also important. Assessment of vascularity by color Doppler scan and comparison with contralateral axillary fossa lymph nodes is also helpful.

The potential importance of ultrasound scans is supported by the results of a recent study ACOSOG Z0011, suggesting a possibility of abandoning lymphadenectomy in case metastatic involvement of 1–2 sentinel nodes in N0 patients subjected to a breast conserving procedure and adjuvant tangential fields radiotherapy covering the entire breast including the axillary fossa⁽⁶⁾. In addition, ultrasound scan detection of abnormal lymph nodes within the supraclavicular region and cytology-confirmed presence of cancer cells within the FNAB (cN3) disqualifies patients from surgical treatment and is an indication for systemic induction treatment (stage IIIC). In case of finding benign neoplastic tumors (including fibrocystic breast disease) in this category of lesions, the recommended treatment involves tumorectomy without adjuvant treatment.

Besides preoperative assessment and monitoring of changes, ultrasound scans are also basic tools for the monitoring of postoperative lesions such as intraglandular hematomas or mastitis as well as for assessment of complications of subsequent radiotherapy. In addition, ultrasound scans are often primary examinations used in the assessment of palpable lesions, nearly half of which corresponds to variants of normal mammary gland structure.

Summary

Ultrasound scan of mammary glands is often the primary examination in the diagnostics of mammary disorders. It allows for precise estimation of malignancy of the detected focal lesions, monitoring of biopsy procedures and localization of lesions prior to surgical treatment. It is a non-invasive and common imaging procedure. Current worldwid e recommendations include the establishment of centers where surgery, oncology, radiotherapy and diagnostics specialists can make joint decisions regarding the treatment of breast cancer patients. This is obviously the optimum approach, similar as in the case of any other clinical and procedural discipline.

Conflict of interest

None.