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Table 2 Radiopathological signification of the main imaging features of colorectal liver metastases treated by systemic therapies

From: Colorectal liver metastases: radiopathological correlation

Imaging feature Histological features Assessment of pathological response to chemotherapy Limitations/pitfalls
Size modification
Size increase Viable tumor
Acinar central necrosis
No response/progression Pseudo-progression with immunomodulating agents
Size decrease Possible remnant viable tumor cell at the periphery
Fibrosis deposition
Infarct-like necrosis
Partial or major histological responsea Poor correlation between size decrease and extent of pathological response
Tumor enhancement
Enhancement on delayed phase Fibrosis deposition The more fibrosis the better the response Impossible to differentiate from pre-existing fibrous stroma on imaging
Importance of comparing pre and post treatment exams
Central enhancement on hepatobiliary phase Fibrosis deposition The more fibrosis the better the response Impossible to differentiate from pre-existing fibrous stroma on imaging
Importance of comparing pre and post treatment exams
Margins
Sharp liver-tumors interface, no enhancement Absence or limited amount of remnant tumor cells Major to complete responseb Only described with CT
Enhancing liver-tumor interfacec Remnant tumor cells Absent or minor responseb The distinction between the two histologic findings is impossible on imaging
Importance of comparing pre and post treatment exams
Dangerous halo (highly proliferating infiltrative tumor cells at the tumor periphery) Peripheral regrowth after initial response
Tumor content
Calcifications Mineralization of necrotic tissue Major response Tumor regrowth is still possible
Central non-enhancing areas, with high ADC value Acinar central necrosis Absent or minor response The distinction between these histologic findings is impossible on imaging
Importance of comparing pre and post treatment exams
Infarct-like necrosis Partial or major histological response
Mucinous subtype
Mucinous regression Variable histological response
  1. aHistological response defined according to the Tumor Response Grade [49], with grade 1 or 2: major response, 3: partial response, and 4 or 5: minor response
  2. bHistological response defined according to Blazer et al. [50], complete response (no residual tumor cells), major response (1% to 49% residual tumor cells), and minor response (≥ 50% residual tumor cells)
  3. cMay show peripheral hypointensity on diffusion-weighted imaging