Brief Summary: In a transvaginal tru-cut biopsy, guided by ultrasound, a needle is inserted through the vaginal wall into a pelvic lesion and a few pieces of tissue are obtained for examination. This clinical trial is organized to evaluate the safety and efficacy of transvaginal tru-cut biopsy in a large group of patients with tumors in the small pelvis.

Detailed Description: Ovarian cancer is known to be the 4th most lethal tumour in women and has the highest mortality rate of all gynaecological malignancies. In most women, the disease is not diagnosed until advanced stage \[1\]. Moreover, the pelvis and ovaries in particular, are also a common place for secondary metastases. In 4% of ovarian masses, metastasis can be found from a tumour with another primary origin \[2\]. In primary ovarian cancer, patients may benefit from either primary debulking surgery or neoadjuvant therapy, depending on tumour staging and patients' comorbidities \[5\]. In recurrent disease treatment may include surgery, radiotherapy or systemic therapy, depending on primary tumour histology, extent of recurrence, previous treatment and disease-free interval \[6-8\]. In pelvic masses with ultrasound features suggesting metastatic disease, management will be guided by the origin of the primary tumour \[9,10\]. Therefore, histological diagnosis is important to select the optimal treatment strategy. Tissue sampling by diagnostic laparoscopy or explorative laparotomy requires general anaesthesia and hospital admission, leading to higher costs and to potential surgical morbidity. Moreover, diagnostic laparoscopy is associated with a risk of port-site metastasis, ranging from 0.3-0.4% in endometrial and cervical cancer \[11\] and even 17-49% in advanced ovarian cancer \[12,13\]. Minimally invasive procedures for diagnosis include fine-needle aspiration and tru-cut biopsy. At fine-needle aspiration the quantity and integrity of the tissue is limited, enabling cytological evaluation only \[14\]. Tru-cut biopsy results in a higher specificity compared to fine needle biopsy and it enables histological examination including immunohistochemistry \[15,16\]. A tru-cut biopsy can be performed under the guidance of different imaging modalities including ultrasound, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). However, percutaneous CT-guided biopsies of deep pelvic masses are challenging because vital structures often obstruct the needle pathway \[17\]. Previous studies have investigated the use of ultrasound-guided biopsies for the assessment of abdominal and pelvic masses which showed a high diagnostic adequacy and minimal complication rate \[4,16,18-25\]. This can be done by percutaneous transabdominal approach , a transvaginal or transrectal approach. The main goal of this prospective study is to evaluate the safety and tissue yield of ultrasound guided transvaginal or transrectal tru-cut biopsy in patients with pelvic tumors. Secondly, factors affecting the reliability of the biopsy-results will be analyzed, as well as patients' experience and pain. Finally, a comparison of biopsy results and final histological diagnosis will be performed in those patients undergoing surgical management. 5. Study aims Primary Aim The main goal of our study is 1) to evaluate the safety (defined as absence of procedure-related complications) and 2) tissue yield (defined as sufficient amount of tissue for histological analysis) of ultrasound guided transvaginal or transrectal tru-cut biopsy in patients with pelvic masses. Secondary Aims * Analyzing factors affecting the safety and tissue yield. (The influence of selected variables such as number of biopsies per target lesion, length of the shot (15 vs 22 mm), thickness of needle (16-18 G), target lesion, target lesion size, histotypes etc. on these outcomes will be assessed.) * Assessment of patients' overall experience, assessment of pain and discomfort during the procedure and afterwards. * Comparison of biopsy result with final histological diagnosis: histological type (only in patients finally undergoing surgery) Study design Prospective multicentric observational study