Intramammary lymph nodes: normal and abnormal multimodality imaging features

Abstract

Intramammary lymph nodes (IMLN) are one of the most common benign findings at screening mammography. However, abnormal IMLN features, such as diminished or absent hilum, thickened cortex, not circumscribed margins, increased size or interval change, warrants additional follow-up or pathologic analysis to exclude malignancy. Some benign inflammatory conditions may be associated with imaging-detected suspected abnormal IMLN, such as reactive hyperplasia and silicone-induced lymphadenopathy. In patients with known breast cancer, IMLN are a potential site of locoregional spread, which can change the prognosis and management. In some cases, initial breast carcinomas can also mimic IMLN. Breast radiologists must also be aware of the typical and atypical characteristics of IMLN to suggest further investigation when it is necessary.

Figure 1.

Normal IMLN imaging features. At mammography (A), typical IMLNs (arrow) present as a circumscribed oval mass, with hilar fat, usually at a peripheral location, adjacent to a vein. Ultrasound (B) shows a circumscribed oval mass, with hyperechoic hilum and hypoechoic cortex. MRI demonstrates a circumscribed reniform mass with hilar fat signal in T₁ weighted images (C). The IMLN cortex shows homogeneous enhancement (D) and high signal intensity at T₂ weighted images (E). IMLN, intramammary lymph nodes.

Figure 2.

Patient with previous right breast cancer submitted to nipple-sparing mastectomy presented an atypical IMLN in the upper outer quadrant of the same breast at ultrasound (A) and MRI (B), with round shape, eccentric hilum and thickened heterogeneous cortex. Percutaneous ultrasound-guided fine needle aspiration was negative for malignancy and surgical resection confirmed a reactive inflammatory IMLN. IMLN, intramammary lymph nodes.

Figure 3.

Patient with a typical IMLN in the upper outer quadrant of the right breast at screening mammography (A). After 1 year, the new screening exam (B) showed an increase in the IMLN and a biopsy was suggested. However, after 2 months, when the patient returned to perform the biopsy, the IMLN showed spontaneous regression to normal size (C), suggesting a reactive inflammatory IMLN and the procedure was suspended. IMLN, intramammary lymph nodes.

Figure 4.

Patient submitted to left mastectomy and breast reconstruction with silicone implant that complicated with extracapsular rupture. Mammography (A) showed a circumscribed, dense, oval mass in the upper outer quadrant of the right breast, at typical IMLN location, that showed a “snowstorm” appearance at ultrasound (B), suggesting an enlarged IMLN with intranodal silicone (silicone adenopathy). IMLN, intramammary lymph nodes.

Figure 5.

Mammography (CC view) showing a no special type invasive breast carcinoma in the inner quadrants of the right breast (yellow arrow) associated to an atypical IMLN in the outer quadrants (red arrow), which was confirmed as metastatic. CC, craniocaudal, IMLN, intramammary lymph nodes.

Figure 6.

Pre-operative MRI in a patient with a no special type invasive carcinoma in the right breast (arrow in A) showed an atypical IMLN with round shape and no fat hilum in the lower quadrants of the same breast, located near the chest wall (circle in B). Second-look ultrasound identified the IMLN (circle in C). After pre-operative localization, the suspected IMLN was resected and confirmed as metastatic (D). IMLN, intramammary lymph nodes.

Figure 7.

Patient with a typical IMLN (green arrow) in the upper outer quadrant of the left breast at screening mammography (A). After 1 year, the new screening exam (B) showed stability of the typical IMLN (green arrow), however, there was also a new small circumscribed mass simulating another IMLN in the same location (red arrow). At 6 month follow-up (C) this mass increased and showed irregular shape, being confirmed as a no special type invasive carcinoma. IMLN, intramammary lymph nodes.

Figure 8.

Patient with previous left breast cancer submitted to conservative surgery presented a small circumscribed mass on the left upper outer quadrant at follow-up mammography, mimicking an IMLN (A). Prior exams were not available. At 6 month follow-up, there was an increase in the mass (B), which corresponded to an irregular hypoechoic mass at ultrasound (C) and was confirmed as a recurrent invasive carcinoma after biopsy. IMLN, intramammary lymph nodes.