"stromal decidualization and secretory glandular changes consistent with progesterone effect."
It means the biopsy cells showed hormonal changes consistent with progesterone hormone phase in the body. NO ABNORMALITY IN CELLS IS MENTIONED. These are normal findings consistent with progesterone hormonal phase in the body.
During normal days, under the influence of progesterone hormone, inner side of the uterus starts perparing naturally for possile conception. and builds up inner lining as described in your biopsy.
But after 28 days if there is no pregnancy, progesterone level goes down and estrogen goes up in the body and this inner built up lining starts shedding off and is called menstrual period or bleeding.
nothing to worry about. Just discuss these changes with your Gyn doctor next week.
It is not considered anything like cancerous.
But acording to the info you have provided, theer is nothing mentioned like cancerous cells. This report should be discussed with your Gyn in context with your clinical scenario.