Hi,
these chocolate cysts or endometriomas (as they are sometimes called ) are often associated with endometriosis , as Tasha said they are filled with old blood . If your friend has painful periods and pain at other times too, it maybe that she has endometriosis I had it and was doubled over in pain at times . They can be removed and sometimes they go away on their own . 95 % of cysts are benign .
Best wishes Angie
A chocolate cyst is a cyst that is filled with old blood. When opened, it is the color of chocolate, hence the name. Treatment is removal. This can be done laproscopically so there will be minimal recovery time. The pain can be caused by the cyst resting on a nerve. Although 99% of cysts are benign, she is wise in getting treatment.
~Tascha