Lobular breast cancer eligible for SOUND had node rates close to the trials

Design

Retrospective single-centre cohort

Population

639 women with cT1N0 HR+/HER2− pure invasive lobular carcinoma and normal axillary ultrasound

Primary outcome

Pathological axillary nodal metastasis at sentinel node biopsy

Effect

Node-positive 17.7%; pN2–3 2.3%; vs 13.7% (SOUND) and 15.1% (INSEMA)

The SOUND and INSEMA trials showed that sentinel node biopsy can be omitted in selected women with small, clinically node-negative, hormone receptor-positive, HER2-negative breast cancer and a normal axillary ultrasound. Few of their patients had invasive lobular carcinoma, which is harder to see on ultrasound.

This single-centre US series reviewed 639 women with cT1N0 hormone receptor-positive, HER2-negative pure lobular cancer and a normal axillary ultrasound who had upfront surgery with sentinel node biopsy. Nodal metastases were found in 17.7%, and extensive nodal disease (pN2–3) in 2.3%. That compares with node-positive rates of 13.7% and 15.1% in the biopsy arms of SOUND and INSEMA. Lymphovascular invasion was the only independent predictor of nodal disease.

This is a retrospective series, not a trial of omission, so it cannot show that outcomes would be the same without biopsy. It does suggest that lobular histology on its own need not exclude a woman from the omission discussion, while lymphovascular invasion, high grade or premenopausal status weigh against it. It was published on 28 September 2026.

• Lobular histology alone may not exclude a SOUND-eligible postmenopausal woman with a low- to intermediate-grade tumour from discussing sentinel node omission.
• Lymphovascular invasion on core biopsy weighs towards performing sentinel node biopsy.
• Extensive nodal disease was uncommon (2.3%) in this group.
• Discuss omission in the multidisciplinary meeting, including whether nodal status would change adjuvant therapy.

Why it matters

It widens a de-escalation option to a histology many surgeons had excluded by default.

Don't overread it

It compares node rates with the trials; it does not test outcomes after omitting biopsy in lobular cancer.

The statistics, in plain English

A 17.7% node-positive rate means about one in six women had cancer in the axilla despite a normal ultrasound. That is a little higher than in the trials, which found omission non-inferior at node rates in this range; whether that holds for lobular cancer has not been tested. This is one specialist centre, so rates elsewhere could differ.

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