Histopathologic evaluation of response to treatment of human tumors grown in the nude mouse.

The histopathologic changes following chemotherapy treatment of a number of human tumors grown in nude mice were evaluated. On the basis of the histopathologic profile, three response levels were recognized--a mild response, a moderate response and a severe response. Severe response was characterized by arrest of cell division and profound nuclear-cytoplasmic degenerative changes. Regrowth of effectively treated tumors originated in clusters of cells most probably representing resistant tumor cell clones. Histopathologic changes represent a sensitive indicator of the response of nude mouse grown human tumors to anticancer agents. Availability and correct interpretation of the post-treatment histopathologic picture is of importance in selecting the proper combination treatment which would maximize tumor response.