Seed and Soil: Cancer Metastasis Simulator

Cancer type ("seed")

Circulation

CTC release rate 2.0 / s

CTCs released

Metastases formed

Arrivals vs. successful metastasis

Organ	Arrived	Took root

"Arrived" counts every circulating tumor cell that reached that organ. "Took root" counts only the ones whose local microenvironment ("soil") matched this cancer's needs ("seed") and grew into a metastasis.

How it works

Every circulating tumor cell (CTC) released from the primary tumor is carried by simulated blood flow to one of five candidate organs, chosen only by each organ's share of blood flow — identical odds no matter which cancer type is selected. That is why the "Arrived" column looks similar across cancer types.

What differs is what happens on arrival. Each cancer type carries its own seed compatibility profile — a per-organ probability that the local tissue microenvironment ("soil": vessel structure, growth factors, immune activity, chemokine signals) suits that particular cell type. A cell that lands in a compatible organ takes root and a nodule grows; a cell landing in an incompatible organ — even one that receives plenty of arrivals — simply fades away.

Bone-seeking (breast, prostate) — bone marrow's compatibility is high regardless of blood-flow share, so metastases cluster there even though the lungs and liver receive more circulating cells.
Liver-seeking (colorectal) — the portal circulation makes liver soil especially receptive, so most successful metastases appear there first.
Brain/adrenal-seeking (lung) — a compatibility profile skewed toward brain and adrenal tissue despite those organs seeing a smaller share of total arrivals.

This is the seed-and-soil hypothesis: metastatic organ preference is set by microenvironment compatibility, not by which organ simply receives the most circulating cells.

Circulating tumor cell Successful metastasis Failed to take root

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