The expression "malignancy" is now reserved for such pathologic new formations that will often return after removal and form metastases, if not entirely removed. As the first depends upon incomplete removal, mostly depending on dissemination of tumorgerms in the various forms of the primary growth, the latter property only is the true feature of malignant tumors.
To clear up the nature of this property is a task of the highest scientific and practical importance, and it seems always convenient to review our notions on these points, even though they are not wholly conclusive. At least, such an examination of facts will show the way for further investigation and secure the practitioner and pathologic investigator from mistakes, by removing misunderstandings.
Separating the infectious tumors from the organoid growths, in the second part of my "General Pathology" (1889) I think I have placed the question somewhat clearer. The organoid tumors spread by
KLEBS E. SOME REMARKS ON MALIGNANT GROWTHS.. JAMA. 1897;XXVIII(13):575–579. doi:10.1001/jama.1897.02440130001001