O, do not learn her wrath; she taught it thee;
The milk thou suck'dst from her did turn to marble;
Even at thy teat thou hadst thy tyranny.
Yet every mother breeds not sons alike:
Do thou entreat her show a woman pity. (2.3.7)
There are a couple of things to note in this passage, in which Lavinia begs Demetrius and Chiron not to rape her. First, when Lavinia says "even at [Tamora's] teat thou hadst thy tyranny," she's voicing a 16th century idea that mothers could pass on their traits and characteristics to their children through their breast milk. Second, when Lavinia begs Chiron to ask Tamora to "show a woman's pity," she associates compassion with femininity and violence with masculinity. When Tamora refuses to be merciful, the play suggests that she's somehow unnatural because she's behaving like a man.
Something similar happens in Shakespeare's Macbeth, where Lady Macbeth associates cruelty with masculinity in her famous "unsex me" speech.