Endometriosis is common and associated with a risk of developing some ovarian cancers, including clear cell carcinoma. A standardized incidence ratio of 8.95 over 17 years2 is reported for development of clear cell carcinoma within endometriomas. The prognosis for many ovarian cancers is poor: in 2012 there were 151 000 deaths from and 238 000 new cases of ovarian cancer globally3. Survival for clear cell carcinoma is particularly poor, especially in advanced stages4.
A 36-year-old nulliparous woman was referred early 2016 with pelvic pain, vaginal discharge and sonographic evidence of a 6cm left ovarian endometrioma. Laparoscopic left ovarian cystectomy and excision of endometriosis was performed in 2017. Intra-operatively there was endometriosis and the cyst drained 'chocolate' fluid. Macroscopically, the cyst lacked thickness or nodularity, however histologic examination revealed an unexpected clear cell adenocarcinoma arising within endometriosis, confined to the ovary (FIGO Stage 1a). One week post-operatively, the patient had a generalized tonic clonic seizure. A grade 3 anaplastic astrocytoma (IDH1 mutated, ATRX loss) in the left frontal lobe was identified on MRI and resected 6 days later, but considered pre-existing and low-grade. Following multidisciplinary discussion, the decision was made to surgically treat the ovarian malignancy before commencing adjuvant chemoradiotherapy for the astrocytoma, as this was potentially curative. The patient underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy. Pre-operative CA-125 was normal (17 units/mL), thus serial tumour markers were not useful for surveillance. Ovarian and colorectal gene panels including TP53 gene identified no mutations.
This was a case of a clinically occult malignancy arising within an endometriotic cyst, in the setting of a concurrent, apparently unrelated brain tumour. To date, an association between these two malignancies has not been identified. The importance of the multi-disciplinary meeting in optimising therapeutic decision-making is highlighted, especially in cases of multiple tumours.
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