• One or more nodular or nodule-like observations within a larger nodular or nodular-like observation. 

Usage: 

Comments:

• “Nodule-in-nodule” architecture is a subtype of mosaic architecture; hence, similar comments apply.
• • Diameter measurement: For masses with nodule-in-nodule architecture, include the entire mass in the measurement, not just the internal nodule(s).
  • In patients with cirrhosis or other risk factors for HCC, most masses with nodule-in-nodule 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 nodule-in-nodule 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, nodule-in-nodule architecture is an ancillary feature favoring malignancy