Primary malignant rhabdoid tumor of greater omentum in 10-year-old girl
A 10-year-old girl visited the Emergency Department for abdominal pain. The pain had developed 7 days prior after getting hit with a ball. There were no associated symptoms such as nausea, vomiting, or diarrhea. On physical examination, the patient complained of tenderness in the lower abdomen. Laboratory findings showed that hemoglobin was 10.8 g/dL and C-reactive protein was 8.06 mg/dL. Other results were not remarkable. Ultrasonography showed a multiseptated large hematoma. A computed tomography scan was undertaken and showed a lobulating hemorrhagic tumor (9 cm × 6 cm × 6.5 cm) with hemoperitoneum in the lower abdomen and pelvis (). Initially, the mass was suspected as a hematoma resulting from bleeding of the lymphangioma or hemangioma in the mesentery. After 3 days of antibiotics treatment, her pain was relieved. For follow-up, we examined the mass by ultrasonography. It revealed a necrotic solid tumor enhancing with peripheral vessels and a small amount of hemoperitoneum. We assumed that the mass was a malignant tumor of the mesentery or retroperitoneum, and performed a laparoscopic exploration. There was a huge omental solid mass that was freely movable and free of adhesions to any other intra-abdominal organs. The mass was removed completely including remnant omentum via laparotomy. Several seeding nodules were found on the small bowel mesentery and Pouch of Douglas and were removed for pathologic confirmation.\nGrossly resected multinodular solid masses showed irregular and infiltrative borders and the cut surface was tan gray and fleshy. There was multifocal hemorrhages and necrosis (). Microscopically nested round to polygonal tumor cells revealed infiltrative borders () and each tumor cell showed eccentric nuclei, prominent nucleoli, as well as a characteristic eosinophilic inclusion or globules in the abundant cytoplasm (). These findings were consistent to that of "rhabdoid" cells. Immunohistochemically neoplastic cells expressed cytokeratin (), vimentin (), and epithelial membrane antigen. However, tumor cells showed negative reaction for desmin, smooth muscle actin and myosin. Importantly neoplastic cells revealed the absence of nuclear expression of INI 1 (), which was recently discovered as a one of the most important histologic markers of malignant rhabdoid tumors [].\nPostoperatively, she recovered uneventfully and resumed her oral diet on the 3rd postoperative day. An fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography was undertaken and revealed no evidence of primary malignancy including kidney and central nervous system. At postoperative day 7, the patient began chemotherapy consisting of VDC/IE (VCR, Doxorubicin, Cyclophosphamide/Ifosfamide, Etoposide) regimen. Despite 4 cycles of chemotherapy of VDC/IE regimen, the mass in the Pouch of Douglas, where previously there had been documented seedings, was now apparent and showed peritoneal carcinomatosis through magnetic resonance imaging. She had been treated with intensive chemotherapy yet died after 9 months due to disease progression.