Kaiser score: breast MRI classification flowchart

What´s behind it?

The Kaiser Score is an algorithm to differentiate benignebenign and malignant enhancing lesions in breast MRI. It applies standard breast MRI descriptors also found in the MRI BI-RADS lexicon.

The Kaiser Score has a high accuracy and low interobserinterobserver variability in mass and non-mass lesions. This is backed up by a high level of evidence.

How can it be applied in clinical practice?

The Kaiser Score is designed as an intuitive flowchart and can be used as a clinical decision rule. In the first step, five diagnostic criteria must be investigated.

Diagnostic criteria

Diagnostic criteria were introduced by Professor Werner Kaiser in the early 90ies and later included in the BI-RADS MRI lexicon. They aim to characterize any enhancing lesion.

1. Spiculation

• Classical spiculations, even subtle ones as well as dendritic branching patterns.
• NOT consistent with a root sign is a tongue-like aspect with rather convex lateral aspects such as can be seen in fibroadenoma and fibroadenomatoid hyperplasia

Note: In case of doubt do not diagnose spiculation and go for non-circumsribed-circumscribed margins

2. Enhancement curves

Note: Always investigate the most suspicoussuspicious part of the lesion. So, if a lesion generally shows Plateau, but a small compartment demonstrates Washout, the final diagnosis will be Washout.

• Washout: type III, suspicious
• Plateau: type II, somewhat suspicious
• Persistent: type I, rather benign

3. Margins

• circumscribed (benign)
• non-circumscribed (suspicious).

Note: Most non-mass enhancements will be non-circumscribed by definition

4. Internal enhancement patterns

• suspicious (rim-like/centripetal and heterogeneous)
• typical benign (homogeneous and centrifugal/central enhancement)

5. EdemaOedema

• Increased water content as visualised by T2WI/STIR sequences around the lesion
• this finding is highly suspicious and typically associated with lymphovascular invasion and lymph node metastases

Calculating the score

Recently a web app was published, to further simplify the practical application of the Kaiser score. Just click through it. In the end, you will get the Kaiser Score corresopondingcorresponding to an increasingincreased risk of malignancy. It ranges from 1 (minimum) to 11 (maximum).

The Kaiser Score can be translated into diagnostic decisions and subsequent clinical recommendations. Note: Always consider the clinical situation and other imaging findings.

As a rule of thumb, scores above 4 should be biopsied.

Where do I get more information?

A pictorial essay was recently published to provide an in depth-depth review of the Kaiser Score. It has been published as open access and can be found here.