mammary gland is modification of sweat gland or sebaseous gland

Hi Dear,
I must appreciate your question.
Mammary glands work for secretion of milk which provide nutrion to the new born baby.
And regarding the point that you are asking i must say it is still a dispute what type of gland are they. Sebaceous or sweat glands.
Most probably, they are believed to be modified apocrine sweat glands.