Atypical Pelvic Tumors in Children.

Due to the complex anatomy of the pelvis, various tumors may arise in this region. Some of these tumors are well known and have distinctive features that allow them to be identified by magnetic resonance imaging (MRI). These include sacrococcygeal teratoma (SCT), the most prevalent congenital tumor in children, often diagnosed prenatally and most frequently occurring in this anatomical location, and ovarian teratoma, which in its mature form is the most common ovarian neoplasm in children and adolescents. Additionally, rhabdomyosarcoma (RMS), commonly found in the bladder in both genders and in the prostate in males, and Ewing sarcoma (ES), affecting the flat bones of the pelvis, are relatively common tumors. In this study, selected atypical pelvic tumors in children are presented. Most of them are tumors of the reproductive system, such as cervical cancer, small cell neuroendocrine carcinoma of the ovary, ES/primitive neuroectodermal tumor (PNET) of the ovary, diffuse large B-cell lymphoma (DLBCL) of the ovaries and ovarian Sertoli-Leydig cell tumor (SLCT) with RMS due to DICER1 syndrome. Additionally, tumors originating from the nervous system, including neuroblastoma (NBL) and plexiform neurofibroma (pNF), associated and not associated with neurofibromatosis type 1 (NF1), are discussed. Furthermore, Rosai-Dorfman disease involving the pelvic and inguinal lymph nodes is presented. By reviewing the literature and presenting our cases, we tried to find radiological features of individual tumors that would bring the radiologist closer to the correct diagnosis, ensuring the implementation of appropriate treatment. However, the MR images cannot be considered in isolation. Additional patient data, such as the clinical picture, comorbidities/syndromes, and laboratory test results, are necessary.