Giant ovarian teratoma: an important differential diagnosis of pelvic masses in children

1. Universidade Federal do Triângulo Mineiro (UFTM), Uberaba, MG, Brazil. 2. Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (HCFMRP-USP), Ribeirão Preto, SP, Brazil. Mailing address: Dra. Aline de Araújo Naves. Universidade Federal do Triângulo Mineiro. Avenida Getúlio Guaritá, 130, Nossa Senhora da Abadia. Uberaba, MG, Brazil, 38025-440. E-mail: rdi.alinenaves@gmail.com. A indicates that the tumor is limited to the nasal cavity; stage B indicates that it involves only the nasal cavity and paranasal sinuses; and stage C indicates that it extends beyond the stage B limits. The staging system proposed by Dulguerov employs the tumor-node-metastasis classifi cation. Bone destruction and calcifi cation within the lesion can be characterized by CT. An MRI scan provides more accurate information on the extent of the tumor, especially in terms of intracranial and orbital involvement. On MRI, the majority of olfactory neuroblastomas present a signal that is (in relation to that of muscle tissue) hypointense in T1-weighted sequences and hyperintense in T2-weighted sequences, as well as showing intense enhancement in contrast-enhanced sequences. MRI is also superior to CT in the evaluation of recurrence after craniofacial resection, because of its greater ability to differentiate fi brous scar tissue from residual or recurring neoplasia. Cysts in the intracranial margin of the tumor have been reported in cases of olfactory neuroblastoma. Another relevant aspect is a dumbbell-like morphology, the tumor mass being divided between the anterior cranial fossa and the nasal cavity, the cribriform plate forming the “waist”. The main differential diagnoses of olfactory neuroblastoma include: squamous cell carcinoma, typically in the maxillary antrum, with bone erosion; sinonasal adenocarcinoma, with heterogeneous enhancement, which has been associated with occupational exposure to wood dust; undifferentiated sinonasal carcinoma, which affects older patients; and dural-based invasive meningioma, with poorly defi ned borders and areas of necrosis.

A indicates that the tumor is limited to the nasal cavity; stage B indicates that it involves only the nasal cavity and paranasal sinuses; and stage C indicates that it extends beyond the stage B limits. The staging system proposed by Dulguerov employs the tumor-node-metastasis classifi cation (3,4) .
Bone destruction and calcifi cation within the lesion can be characterized by CT (5) . An MRI scan provides more accurate information on the extent of the tumor, especially in terms of intracranial and orbital involvement. On MRI, the majority of olfactory neuroblastomas present a signal that is (in relation to that of muscle tissue) hypointense in T1-weighted sequences and hyperintense in T2-weighted sequences, as well as showing intense enhancement in contrast-enhanced sequences (6,7) . MRI is also superior to CT in the evaluation of recurrence after craniofacial resection, because of its greater ability to differentiate fi brous scar tissue from residual or recurring neoplasia (6) . Cysts in the intracranial margin of the tumor have been reported in cases of olfactory neuroblastoma. Another relevant aspect is a dumbbell-like morphology, the tumor mass being divided between the anterior cranial fossa and the nasal cavity, the cribriform plate forming the "waist" (5) .
The main differential diagnoses of olfactory neuroblastoma include: squamous cell carcinoma, typically in the maxillary antrum, with bone erosion; sinonasal adenocarcinoma, with heterogeneous enhancement, which has been associated with occupational exposure to wood dust; undifferentiated sinonasal carcinoma, which affects older patients; and dural-based invasive meningioma, with poorly defi ned borders and areas of necrosis (8) . × 20.8 cm, exerting a signifi cant mass effect, displacing the small intestine, aorta, and inferior vena cava, as well as causing slight compression of the pancreas, kidneys, and ureters, with no apparent signs of infi ltration ( Figure 2). Intraoperatively, the mass was seen to be adhered to the left fallopian tube and to the greater omentum ( Figure 1). The tumor was excised without complications, and the patient was discharged fi ve days later. A follow-up abdominal ultrasound revealed no changes.
The occurrence of an abdominal mass in a child should always be evaluated by a pediatrician. The main differential diagnoses are organomegaly and fecal impaction. When abdominal palpation produces nonspecifi c fi ndings, further investigation, employing imaging methods, is required (1) . Ovarian teratoma is the most prevalent germ cell neoplasm, accounting for approximately 32% of all ovarian neoplasms, and can be divided into mature or immature teratoma depending on its cellular differentiation (1) . The cellular components of this lesion are pronounced and varied, potentially encompassing respiratory epithelium, skin, cartilage, mucosa, and neural epithelium (2)(3)(4)(5) . It is a benign neoplasm, presenting on physical examination as a palpable pelvic mass, typically 5-10 cm in diameter, and occurs bilaterally in 10-15% of cases (1) . In 10% of cases, it is considered an emergency, presenting the typical profile of acute abdomen, due to torsion of the vascular pedicle that occurs secondary to its growth (6) . The clinical diagnoses of abdominal masses are diverse and imprecise, requiring complementary diagnostic imaging (7) .
Abdominal X-ray is nonspecific for ovarian teratoma and can occasionally show calcifications in the area surrounding the lesion. Ultrasound and CT are the main imaging methods for the detection of this disease, the rapid detection of which demands recognition of the typical imaging patterns, particularly in cases of emergency (acute onset). Although CT also has high specificity and sensitivity, particularly for the detection of cystic teratoma, it is not routinely employed, because it involves the use of ionizing radiation. The combination of various imaging methods is an essential part of the surgical planning (8) . The histological study is also of importance, determining the macroscopic and microscopic aspect of the lesion, as well as the prognosis. Surgical treatment-excision of the lesion-is the gold standard (8) .

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