An 18-year-old Asian male patient with no known medical history was referred to our institution via outpatient clinic due to huge abdominal mass. He had been having upper abdominal discomfort for several weeks, which aggravated over times. As the patient was obese on the first visit (height 166cm, weight 88kg, and body mass index 31.9kg/m2), the mass did not stand out at the sight but was firmly palpable. Abdominal sonography, abdomino-pelvic computed tomography (CT), and positron emission tomography- CT revealed 26cm-long heterogeneously enhanced and lobulated mass with necrotic components (Fig. 1). Whole body bone scan showed no evident metastasis to bones. The mass seemed to originate from omentomesentery, and though the large portion of small bowel were lateralized to the left, there were no obvious signs of organ invasions. On sonography-assisted biopsy, pathology reported spindle cell proliferative lesion in myxoid background and immunohistochemical stains were negative on α-SMA, CD34, MUC-4, S-100, and ALK, and was positive on β-catenin, indicating high possibility of desmoid-type fibromatosis. No genetic analysis was performed for CTNNB1 or adenomatous polyposis coli (APC) gene mutations.
The upfront surgical resection seemed challenging due to its high occupancy in the abdominal cavity, so the patient was first offered being treated with chemotherapy with the regimen of doxorubicin (20mg/m2 infusion for 1 hour in day 1–3) and dacarbazine (300mg/m2 infusion for 1 hour in day 1–3) by pediatric oncologist. Sperm banking was carried out prior to the chemotherapy. After infusing two cycles with 3-week interval, the tumor size had increased into 32cm of diameter in a month from the first visit, causing heavier abdominal discomfort and pain in the patient. Thus, the chemotherapy regimen had changed to etoposide (100mg/m2 infusion for 3 hours in day 1–5), carboplatin (200mg/m2 infusion for 3 hours in day 1–2), and ifosfamide (1,800mg/m2 infusion for 3 hours in day 1–5). However, nonresponsiveness of the tumor and side effects such as neutropenic fever and general weakness of chemotherapy leading to admission via emergency room made it hard to postpone the surgical resection of the tumor. Preparing for the operation, the patient was injected with antibiotics for the neutropenic fever, transfused with platelet concentrations (PCs) for thrombocytopenia, and total parenteral nutrition. Preoperative consults were made with upper gastrointestinal, hepatobiliary, and vascular surgeons for possible cooperation. At the day before the surgery, percutaneous angiographic embolization was performed for the feeding vessel of the tumor, which branched from the superior mesenteric artery. The operation was conducted two months from the first visit.
The surgeon in charge is specialized in colorectal surgery with more than 10 years of clinical experiences in tertiary academic medical center. At the operating field, long midline incision was insufficient for the complete exposure of the mass, leading to crossed incision with additional transverse upper midline incisions (Fig. 2). Tumor dissection was performed by peeling off the adjoined bowel, mesentery, and retroperitoneum. Ileocecectomy was inevitably carried out due to vascular involvement, and vascular team engaged in dissecting superior mesenteric vessel and its angioplasty. The total operation time was 311 minutes, and estimated blood loss was 3000ml while blood transfusions of 10 packed red blood cells, 6 PCs, and 6 fresh frozen plasma were done. After admitting to the surgical intensive care unit postoperatively, the patient was moved to the general surgical ward two days later and was discharged at postoperative day-15 uneventfully after the slow build-up of the diet. The final surgical pathology revealed 38cm-long desmoid type fibrosis and clear resection margin, with the same results of immunohistochemical staining with the initial findings (Fig. 3). The patient has been followed up in the outpatient clinic since for two years, where either CT or magnetic resonance imaging (MRI) scans was achieved with 3-to-6-month intervals. He had been admitted a year after the surgery due to small bowel obstruction for 5 days, but has stayed stable with no recurrence so far.