A 62-year-old man with prostatic adenocarcinoma develops low back pain. Bone scan shows multiple sclerotic lesions in the lumbar vertebrae. The predilection of prostate cancer to metastasize specifically to bone rather than other organs illustrates which principle?

• A Mechanical trapping of tumor emboli in the first capillary bed encountered
• B Retrograde lymphatic spread through valveless channels
• C Direct extension of tumor through tissue planes
• D Seed and soil hypothesis, where the target organ provides a favorable growth environment ✓

Explanation

The seed and soil hypothesis states that metastasis is not random: tumor cells (the seed) colonize organs whose local milieu (the soil) supports their survival and growth. Prostate cancer homes to bone because the bone microenvironment supplies growth factors that favor its proliferation. Option A describes passive distribution, which cannot explain site-specific patterns such as skeletal tropism of prostate, thyroid, and lung cancers. Batson's vertebral plexus contributes to spinal spread but the broader principle tested here is organ selectivity.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.