[The so-called "chocolate cyst"--frequently misinterpreted as ovarian endometriosis?].

Limitation of morphological diagnostic and possible misinterpretations are shown in a patient with anamnestic ovarian endometriosis. In cases of "chocolate cysts" it is necessary to differentiate between ovarian endometriosis and functional cysts. Hints for the existence of a functional cyst are an atypical past history or perioperative findings. Biochemical analysis of the cyst fluid may lead to a correct diagnosis.