What Are The Adverse Effects Of Thickening Of Uterus By 1cm?

I 'am 48 years old. I still get me period somewhat on schedule but explained to my gyno that i had two cycles where the period lasted for 10 days. Not heavy bleeding but it was like spotting that didn't stop. He ordered a vaginal sono and found that my uterus is thickening by 1 cm . there was no tumors but he feels i need to get a biopsy.Does thickening always mean cancer or is the fact that there is no tumors a good sign?