ACR LI-RADS

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RID: RID39149

Mosaic architecture

Definition:

Observation that appears to consist of nodules or compartments with differing appearances (enhancement, attenuation, intensity). This term can also be applied to lesions with internal enhancing septations. The nodules, compartments, or septations appear randomly distributed within the observation.

Usage:

Mosaic architecture is an ancillary feature favoring malignancy.
- Mosaic architecture specifically favors HCC as opposed to malignancy in general
- Radiologists at their discretion may apply mosaic architecture to upgrade category (up to LR-4) for such masses.

If unsure about feature:

Do not characterize as mosaic architecture

Comments:

Mosaic architecture may manifest as different subtypes.
- Nodule-in-nodule
- Multi-nodule-in-nodule
- Multi-compartment-in-nodule
- Septated solid mass
In patients with cirrhosis or other risk factors for HCC, most masses with mosaic architecture are HCCs. These masses usually can be categorized LR-5 based on major features such as arterial-phase hyperenhancement, diameter ≥ 20mm, “washout”, and “capsule”.
- A mass with mosaic architecture that does not meet major feature criteria for LR-5 (e.g., lacks arterial phase hyperenhancement), cannot be categorized LR-5. For such masses, mosaic architecture is an ancillary feature favoring HCC.

Potential pitfalls and challenges

For masses with mosaic architecture, include the entire mass in the diameter measurement, not just the internal nodule(s) or compartment(s).

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