le ▁designed ▁an ▁exception ally ▁large ▁micro t ome ▁that ▁could ▁cut ▁ ▁square ▁sections , ▁ ▁with ▁which ▁his ▁techn ician ▁prepared ▁whole - organ ▁sections ▁of ▁the ▁breast . ▁Over ▁a ▁ 3 5 - year ▁period ▁he ▁built ▁a ▁huge ▁collection ▁of ▁normal ▁and ▁dise ased ▁breast ▁sections . ▁Using ▁them , ▁he ▁was ▁able ▁to ▁prove ▁that ▁P aget ' s ▁disease ▁of ▁the ▁breast ▁was ▁the ▁result ▁of ▁an ▁underlying ▁breast ▁cancer , ▁and ▁that ▁the ▁calls ▁that ▁are ▁now ▁called ▁car cin oma ▁in ▁situ ▁was ▁not ▁pre - can cer ous ▁or ▁potentially ▁cancer ous , ▁ ▁but ▁were ▁in ▁fact ▁already ▁m align . ▁He ▁also ▁showed ▁that ▁simple ▁hyper pl asia ▁and ▁Pap ill omas ▁were ▁not ▁m align , ▁as ▁was ▁generally ▁thought , ▁but ▁were ▁in ▁fact ▁ben ign . ▁Based ▁on ▁his ▁studies ▁of ▁whole - organ ▁sections , ▁Che at le ▁proposed ▁that ▁ep ith el ial ▁pro l ifer ation ▁leading ▁to ▁cancer ▁had ▁lo b ular ▁rather ▁than ▁du ct al ▁orig ins . ▁ ▁In ▁a ▁ 1 9 2 2 ▁article ▁in ▁the ▁British ▁Medical ▁Journal ▁Che at le ▁said ▁that ▁by ▁the ▁time ▁breast ▁cancer ▁became ▁visible ▁it ▁was ▁often ▁too ▁late ▁to ▁be ▁c ured ▁by ▁surg ery . ▁In ▁ 1 9 2 2 ▁Che at le ▁proposed ▁that ▁infl amed ▁and ▁c yst ic ▁bre asts ▁should ▁be ▁removed ▁surg ically . ▁He ▁co author ed ▁the ▁text book ▁T um ours