Shear wave elastography and grey scale assessment of palpable probably benign masses: is biopsy always required?

OBJECTIVE: to establish if palpable breast masses with benign greyscale ultrasound (US) features that are soft on Shear Wave Elastography (SWE) (mean stiffness ‹ 50 kPa ) have a low enough likelihood of malignancy to negate the need for biopsy or follow up .

METHODS: The study group comprised 694 lesions in 682 women (age range 17-95, mean age 56 y) presenting consecutively to our institution with palpable lesions corresponding to discrete masses at US. All underwent US, SWE and needle core biopsy. Static greyscale images were retrospectively assigned BI-RADS scores by two readers blinded to the SWE and pathology findings, but aware of the patient's age. A mean stiffness of 50kPa was used as the SWE cut off for calling a lesion soft or stiff. Histological findings were used to establish ground truth.

RESULTS: No cancers had benign characteristics on both modalities. Four hundred and sixty six of the 467 (99.8%) cancers were classified BIRADS 4a or above. The one malignant lesion classified as BI-RADS 3 was stiff on SWE. Four hundred and forty six of the 467 (96%) malignancies were stiff on SWE. No cancers in women under 40 years had benign SWE features. Seventy-four (32%) of the 227 benign lesions were BI-RADS 3 and soft on SWE, so biopsy could potentially have been avoided in this group.

CONCLUSIONS: Lesions which appears benign on greyscale US and SWE do not require percutaneous biopsy or short term follow up, particularly in women under 40 years. Advances in knowledge: None of the cancers had benign characteristics on both grey scale US and SWE and 32% of benign lesions were BI-RADS 3 and soft on SWE,; lesions that are benign on both US and SWE may not require percutaneous biopsy or short term follow up.