Imaging and Management of Internal Mammary Lymph Nodes

Area of Science:

• Oncology
• Radiology
• Medical Imaging

Background:

• Internal mammary lymph nodes (IMLNs) receive significant lymphatic drainage from the breast (10%-40%).
• Benign IMLNs typically exhibit a fatty hilum, oval shape, and smooth margins.
• IMLN involvement in breast cancer impacts clinical staging and treatment strategies.

Purpose of the Study:

• To review the imaging characteristics and clinical significance of internal mammary lymph nodes in breast cancer.
• To discuss the role of various imaging modalities in detecting IMLN metastases.
• To outline current guidelines and management approaches for suspicious IMLNs.

Main Methods:

• Review of imaging findings (MRI, PET-CT, US, CT) for IMLNs in patients with and without breast cancer.
• Analysis of morphological criteria for differentiating benign from malignant IMLNs.
• Discussion of diagnostic performance of different imaging techniques.

Main Results:

• Benign IMLNs (up to 10 mm) are common on screening MRI and show specific features like a fatty hilum.
• The incidence of IMLN metastases ranges from 10%-16% across imaging modalities, with MRI and PET-CT showing higher sensitivity.
• Suggested criteria for malignancy include long-axis measurement ≥ 5 mm and abnormal morphology (e.g., loss of fatty hilum, rounded shape).

Conclusions:

• Accurate imaging assessment of IMLNs is vital for correct breast cancer staging and treatment planning.
• MRI and PET-CT are sensitive for detecting IMLN metastases, though FDG avidity can be non-specific.
• Management of suspicious IMLNs typically involves systemic therapy (chemotherapy, radiation) rather than surgery.