Bresst cancer cells have been stu' diecl hoth in vivo and in vitro bY using the transmission elestron mi' eroscotr)e. Speciflc characteristics Were used with incomPlete certa' inty to identifY various types of cs,ncer cells or i cell lines ( Arnold et a1..1, 9?6;B uphiing and Hacket,19?4; Donrageld and WoYke, 1975;OzeIIo, 19?tr and 19?2 and SPriggs and lutreek1,9 61).M icrovilli were frequently observed in cancer cells. Spring-Mills and Elias (19?5) how' ever, noticed that breast cancerous cells have fewer microvillo than non - caneerous eells. Microvilli Micro-viiii are known to present on the surfaee of some normal cells as the mesothelial lining of serous eavltles (Andrews and Porter, 1973). Ifowever, sired cells in effusions were seen to lose their microvilli (Domagala a.nd V/oyke, lg75). The real signiflcence of microvilli as a rna.ior differenee hetrveen cancer and normal cells has lceen ouestioned