Pregnant woman, 32 years old, 10 weeks of gestation, G5P3A1, at the Emergency Service due to sudden and intense abdominal pain, without other complaints or comorbidities. At the exam: regular general condition, tachycardic, eupneic, afebrile, feeling pain at deep palpation in the left iliac region, with painful decompression. Pelvic examination: pain at palpation of the left annex. Previous obstetric ultrasonography (US): normal gestation of 8 weeks and presence of fetal heartbeats. Pelvic US performed (presented images).

Question:
Considering the images and the clinical history described, what is the most likely diagnosis?

UFRJ (2009) - Lígia, 22 years old, at the emergency care unit of Maré presenting sudden and increasing pelvic pain and fever of 37,5°C. Last menstruation 25 days ago and sexual inactivity since 2 months ago. Recent abdominal ultrasonography shows adnexal tumor of 12 cm of diameter, cystic and low perfusion at the Doppler velocimetry. 

Question:
The most likely diagnosis is: