Breast MRI in clinically and mammographically occult breast cancer presenting with an axillary metastasis: A systematic review

Abstract

Background

Axillary metastatic lymphadenopathy with no primary tumour identified in the breast on physical examination, mammography or ultrasound is referred to as occult breast cancer. The goal of this systematic review is to give an overview of the value and additional considerations of using breast MRI in occult breast cancer.

Methods

The databases of Pubmed, Embase, CINAHL and the Cochrane library were searched for studies addressing the use of breast MRI in occult breast cancer. Cross-referencing was used to find additional articles.

Results

8 retrospective studies were included. Breast MRI can detect an otherwise occult breast cancer in more than two thirds of patients with a high sensitivity but lower specificity. In 80% of patients MRI detected lesions could be localized again by using ultrasound. Furthermore the size and localization of the lesions found on MRI most often correlated closely with findings at pathology. Breast MRI also provided the possibility of breast conserving surgery in one thirds of patients.

Conclusion

Breast MRI can result in additional detection of otherwise occult lesions in occult breast cancer. Because of low specificity of malignant lesion detection by breast MRI, lesions should be histologically confirmed. This can be achieved either by MRI or ultrasound guided biopsy, as long as all MRI detected lesions are histologically checked. Routine application of breast MRI in occult breast cancer may also alter locoregional treatment by offering the possibility of breast conserving surgery in one thirds of patients.

Introduction

The most likely source of metastatic lymphadenopathy in the axilla is the ipsilateral breast.1, 2, 3, 4 In 0.3–1.0% of all women with breast cancer metastatic lymphadenopathy is the first presenting symptom.5, 6, 7 Consequently when no other primary source becomes evident during workup or physical examination, and mammography or ultrasound of the breast shows no abnormalities, this is called occult breast cancer.

With the introduction of more advanced diagnostic techniques in the past century, like mammography and ultrasound of the breast, the incidence of occult breast cancer has decreased.⁸ In recent years other diagnostic modalities, like CT, positron emission tomography (PET) and other types of scintigraphy have also been used to find the primary source, but none of these techniques are applied routinely and evidence for routine use in occult breast cancer is insufficient.9, 10, 11, 12, 13, 14

Nowadays MRI of the breast is frequently applied when other diagnostic modalities fail to find a primary source in the breast. Although the sensitivity of MRI for detection of breast cancer is high, the specificity is much lower.¹⁵ Hence the correlation of detected MRI lesions to findings at pathology and the implications for treatment are important issues. Because of the low incidence of occult breast cancer, published studies usually consist of small numbers of patients which prevents addressing these matters adequately.

The goal of this systematic review is to give an overview of the value and additional considerations of using breast MRI in occult breast cancer. The questions that will be addressed are the following:

• What is the sensitivity and specificity of a breast MRI in case of an occult breast cancer?

• Is MRI guided biopsy preferred over MRI guided sonographic biopsy?

• Are the breast MRI findings correlated to the pathological findings?

• What percentage of patients with occult breast cancer and MRI detected lesions can be treated by breast conserving surgery?