we conclude that there are three types of fibrous tumors of the pleura : ( a ) a localized , histologically benign , keratin-negative spindle cell tumor that might be termed `` '' fibroma , '' '' ( b ) a diffuse , histologically malignant , keratin-positive neoplasm that might appropriately be termed a `` '' sarcomatoid mesothelioma , '' '' and ( c ) a histologically malignant , keratin-negative , spindle cell tumor with the potential to spread under the pleura that might appropriately be termed a `` '' sarcoma . '' ''
C0006826
y maligna
C1261473
a `` '' sa