A cell line derived from a clinically benign phyllodes tumor: characterization and implications.

Phyllodes are uncommon tumors of the breast. Improved understanding of their behavior is hampered by the paucity of good laboratory models. We have developed two cell lines, by both xenograft and direct cell culture, derived from a histologically benign phyllodes tumor. Both cell lines have the same characteristics and growth kinetics. They grow as monolayers of spindle-shaped cells, with surface markers consistent with a mesenchymal origin. They do not express either estrogen or progesterone receptors. The cells have a relatively short doubling time of just over 1.5 days, and show a stimulatory effect with the addition of insulin. Karyotype analysis reveals the absence of one X chromosome.