Objectives To aid primary care physicians, emergency medicine physicians, and gynaecologists in the initial investigation of adnexal masses, defined as lumps that appear near the uterus or in or around ovaries, fallopian tubes, or surrounding connective tissue, and to outline recommendations for identifying women who would benefit from a referral to a gynaecologic oncologist for further management. Intended Users Gynaecologists, obstetricians, family physicians, general surgeons, emergency medicine specialists, radiologists, sonographers, nurses, medical learners, residents, and fellows. Target Population Adult women 18 years of age and older presenting for the evaluation of an adnexal mass. Options Women with adnexal masses should be assessed for personal risk factors, history, and physical findings. Initial evaluation should also include imaging and laboratory testing to triage women for management of their care either by a gynaecologic oncologist or as per SOGC guideline no. 404 on the initial investigation and management of benign ovarian masses. Evidence A search of PubMed, Cochrane Wiley, and the Cochrane systematic reviews was conducted in January 2018 for English-language materials involving human subjects published since 2000 using three sets of terms: (i) ovarian cancer, ovarian carcinoma, adnexal disease, ovarian neoplasm, adnexal mass, fallopian tube disease, fallopian tube neoplasm, ovarian cyst, and ovarian tumour; (ii) the above terms in combination with predict neoplasm staging, follow-up, and staging; and (iii) the above two sets of terms in combination with ultrasound, tumour marker, CA 125, CEA, CA19-9, HE4, multivariable-index-assay, risk-of-ovarian-malignancy-algorithm, risk-of-malignancy-index, diagnostic imaging, CT, MRI, and PET. Relevant evidence was selected for inclusion in descending order of quality of evidence as follows: meta-analyses, systematic reviews, guidelines, randomized controlled trials, prospective cohort studies, observational studies, non-systematic reviews, case series, and reports. Additional articles were identified through cross-referencing the identified reviews. The total number of studies identified was 2350, with 59 being included in this review. Validation Methods The content and recommendations were drafted and agreed upon by the authors. The Executive and Board of the Society of Gynecologic Oncology of Canada reviewed the content and submitted comments for consideration. The Board of Directors of the Society of Obstetricians and Gynaecologists of Canada approved the final draft for publication. The quality of evidence was rated using the criteria described in the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology framework (Table A1 of Online Appendix A). See Table A2 of Online Appendix A for the interpretation of strong and weak recommendations. The summary of findings is available upon request. Benefits, Harms, Costs Adnexal masses are common, and guidelines on how to triage them and manage the care of patients presenting with adnexal masses will continue to guide the practice of primary care providers and gynaecologists. Ovarian cancer outcomes are improved when initial surgery is performed by a gynaecologic oncologist, likely as a result of complete surgical staging and optimal cytoreduction. Given these superior outcomes, guidelines to assist in the triage of adnexal masses and the referral and management of the care of patients with an adnexal mass are critical. SUMMARY STATEMENTS (GRADE ratings in parentheses) 1Information from a detailed personal and family history can guide decisions on further testing and evaluation for women with adnexal masses (low). 2The majority of women with ovarian cancer have symptoms in the year prior to their diagnosis, although these symptoms can be vague (low). 3Adnexal masses are best evaluated through subjective pattern recognition by an expert sonographer in order to distinguish benign adnexal masses from malignant adnexal masses (moderate). 4Ultrasound evaluation of adnexal masses with risk prediction models such as the simple rules, developed by the International Ovarian Tumor Analysis group, allows sonographers with varying degrees of expertise to use uniform terminology and accurately classify these masses as "likely malignant," "benign," or "indeterminate" (moderate). 5Laboratory testing can aid in the differential diagnosis of an adnexal mass. Testing for sexually transmitted infection with results showing leukocytosis can help identify tubo-ovarian abscesses, while a positive pregnancy test can lead to diagnosis of possible ectopic pregnancies (low). 6Cancer antigen 125 is a non-specific glycoprotein that can be elevated in benign and malignant gynaecologic conditions and in non-gynaecologic conditions (moderate). 7Only half of all early stage ovarian cancers and 80% of advanced stage ovarian cancers show elevated cancer antigen 125 levels (moderate). 8The sensitivity and specificity of cancer antigen 125 as a tumour marker are higher in women who are postmenopausal because many of the benign clinical conditions that can increase the level of cancer antigen 125 occur in the premenopausal population, while most cases of epithelial ovarian, fallopian tube, and peritoneal cancer occur in the postmenopausal population (moderate). 9Despite having gone through several iterations, the risk of malignancy index, which uses cancer antigen 125 and sonographic features along with the patient's menopausal status, is outperformed by the more recent International Ovarian Tumor Analysis group's logistic regression model 2 and simple rules. The sensitivity and specificity of version 2 of the risk of malignancy index for distinguishing malignant from benign masses are only 75% and 87%, respectively (moderate). RECOMMENDATIONS (GRADE ratings in parentheses) 1Take a detailed history for a woman presenting with an adnexal mass. For a woman with a personal history of infertility, endometriosis, or cancer or a family history of cancer, refer the patient to a gynaecologic oncologist for further evaluation if possible (strong, low). 2Physical examination should include lymph node survey, respiratory examination to rule out pleural effusion or consolidation, breast and axillary examination to rule out breast malignancy, and an abdominal examination to assess for ascites, omental caking, and organomegaly as well as a pelvic examination, including a bimanual and rectovaginal examination, to assess for mass size, contour, mobility, and parametrial, bladder, and rectal abnormality (strong, low). 3If a woman presents with an adnexal mass, request an initial ultrasound using either pattern recognition or the risk prediction model developed by the International Ovarian Tumour Analysis group (strong, moderate). 4Promptly refer to a gynaecologic oncologist any patient who presents with a mass with any of the following sonographic features, suggestive of malignancy: (i) solid component with strong or central colour flow, (ii) ≥4 papillary projections (defined as >3 mm in height), (iii) thick multiple irregular septations, or (iv) ascites and peritoneal nodularity. While awaiting a gynaecologic oncologist consult, where resources permit, pursue further investigations, including tumour marker levels and computed tomography scan of the chest, abdomen, and pelvis, as appropriate (strong, moderate). 5Women with adnexal masses with indeterminate features should be evaluated by ultrasound conducted by an expert sonographer (if available) or by magnetic resonance imaging or be referred to a gynaecologic oncologist (strong, low). 6Do not use cancer antigen 125 testing as a screening tool in asymptomatic women without a pelvic or adnexal mass (strong, moderate). 7The initial ultrasound characterization can be done using either pattern recognition (best in the hands of an expert sonographer) or risk prediction algorithms, such as simple rules, which have been demonstrated to work well for practitioners with varying degrees of expertise. If the lesion is suspicious for malignancy, prompt referral to a gynaecologic oncologist is recommended (strong, moderate). 8In women 9Further tumour marker testing, including carcinoembryonic antigen, cancer antigen 19-9, and cancer antigen 15-3, along with referral to a gynaecologic oncologist are recommended for women presenting with bilateral masses with features of malignancy (strong, moderate).