Development, Morphology, and Progression of Mammary Tumors During and After Fertile Life in BALB/cfRIII Mice<xref ref-type="fn" rid="fn2">2</xref>

Abstract

A study was done on 368 BALB/cfRIIi mammary tumor-bearing breeding female mice that are of the BALB/c genotype and carry milk-transmitted Rill murine mammary tumor virus (MuMTV) infection initiated by foster-nursing. All tumors were characterized by chronologic, biologic, and morphologic analyses. Mammary tumors occurring during pregnancy-lactation periods were mostly pregnancy-dependent plaques showing organoid tubular structure, sudden growth during late pregnancy, regression after delivery, and slow progression. The frequency of pregnancy-dependent tumors per 100 mice at risk increased steadily from first (1 tumor) to sixth (38 tumors) pregnancy-lactation period. Mammary tumors occurring after fertile life were mostly characterized by an irregular, slow growth and a type B morphology. The frequency of these tumors per 100 mice at risk per 100 days of survival also increased regularly in females undergoing from one (73 tumors) to six (117 tumors) pregnancylactation periods. Data were discussed in the light of the pattern of MuMTV release through BALB/ctAlil milk.-JNCI 1981; 66: 311-319. ABBREVIATION USED: MuMTV=murine mammary tumor virus(es).