Figure 1

Tumor formation in the mammary fat pad upon injection of human tumorspheres. A. Light microscopy of a representative tumorsphere isolated from a patient core biopsy following in vitro culture for 10 days. B. Injection of Matrigel alone into the 3rd mammary fat pad of female NUDE mice. C, D. ≤5 × 10³ cells derived from the original patient biopsy were injected into the 3rd mammary fat pad in the form of 'tumorspheres' (with Matrigel) and resulted in formation of small, palpable tumors within 3 months injection with an approximate, sustainable tumor volume of 100 mm³