CD44ex10 transfectants are more likely to cause systemic metastases in nude mice. Two to four independently derived CD44ex10, CD44ex7-14, CD44ex10-14, CD44H, or vector-only Namalwa transfectants were injected into the tail veins of nude mice. Animals were subsequently followed daily for the onset of hindlimb paralysis, an early indicator of leptomeningeal/CNS infiltration and widely metastatic disease. Animals in which hindlimb paralysis developed were sacrificed and evaluated for additional histologic evidence of disseminated lymphoma. The data represent a summary of two identical experiments in which a cohort of three animals was injected with each of the indicated independently derived Namalwa transfectants (vector-only_{I, II, III, or IV}, CD44ex10_{I, II, or III}, CD44ex7-14_{I or II}, CD44ex10-14_{I or II}, or CD44H_{I or II}). Data are plotted as percentage of injected animals without metastasis over time (50 days). Animals that received CD44ex10 transfectants were significantly less likely to remain free of metastases than animals that were given vector-only transfectants (CD44ex10, 11% v vector-only, 79% metastasis-free, P < .0001). By contrast, animals that received the larger exon 10–containing isoforms or CD44H were as likely to remain free of metastases as vector-only control animals (CD44ex7-14, 83%, CD44ex10-14, 83%, CD44H, 67% vvector-only, 79% metastasis-free, all P values NS). The likelihood of remaining free of metastasis after receiving a given CD44 or vector-only transfectant was determined by averaging the percentages of metastasis-free animals that received each independently derived clone: vector-only, four clones; CD44ex10, three clones; CD44ex7-14, two clones; CD44ex10-14, two clones; CD44H, two clones. Pvalues were calculated using a 2 × 2 Fisher's exact test.