Stretchy Astrid women's animal print cardigan sweater 3/4 sleeves button front

This pre-owned women's cardigan has a fun animal print, 9 button front closure, and 3/4 sleeves. The tag that is halfway fallen off has the brand name Astrid but there is no size, contents or care tag. The approximate measurements are: 18" across the back underarm to underarm. 12" underarm to cuff. 22" neck to hem. it is soft and has a nice stretch to it. Size small or medium?