What does cervical region shows echogenic endometrium with 5x5mm size irregular cystic area with mild hypervascularity mean. is it decidual tissue. ?

Doubtful: Decidual tissue is only present when you are pregnant. Assuming you are not pregnant, these findings on you ultrasound could represent a uterine polyp, a fibroid or a cancer in the uterus. You might want to consider having a biopsy of the inside of the uterus or a hysteroscopy. A hysteroscopy is a procedure where you look into the uterus with a small camera. Best wishes!