Which of the following cancers is most likely to spread through the lymphatics?

Seminoma is a testicular cancer that is known for its propensity to spread through the lymphatic system. It primarily invades the retroperitoneal lymph nodes, particularly in the initial stages of metastasis. This characteristic makes seminoma distinct compared to other types of cancers within the provided options, which may have different metastatic patterns.

Choriocarcinoma, while it can spread through blood and lymphatics, often prefers hematogenous routes for metastasis, especially to the lungs. Medulloblastoma, a type of brain cancer, typically spreads through cerebrospinal fluid rather than through lymphatic channels. Osteogenic sarcoma, the most common type of bone cancer, primarily metastasizes hematogenously as well, usually to the lungs, rather than through lymphatics.

Therefore, the likelihood of seminoma spreading through lymphatics aligns with its clinical behavior and is what distinguishes it as the correct choice in this scenario.