16 year old girl with abdominal mass.
Very large mildly heterogeneous abdominal mass involving left hemiabdomen (18 X 8 X 24 cm). On FDG PET/CT, the mass has a homogeneous low activity without focal predominant hypermetabolism (SUV max 1.7). The mass is pushing stomach superiorly, liver and small intestines laterally on the right side. Although difficult to assess, the lesion does not seem to arise from liver, stomach, left kidney or spleen.
No other suspicious lesion.
There is some radiotracer stasis in the left urinary tract suggesting mild hydroureter and hydronephrosis probably related to the mass effect.
Absent right kidney (nephrectomy in young age).
Midline abdominal wall hypermetabolism related to recent exploratory laparotomy
Low grade sarcoma
Desmoid-type fibromatosis, also known as deep fibromatosis, aggressive fibromatosis or desmoid tumor (DT), are defined by WHO organization as a ¨clonal fibroblastic proliferations that arise in the deep soft tissues and are characterized by infiltrative growth and a tendency toward local recurrence but an inability to metastasize¨. DT are classified by three main anatomic sites: extraabdominal deep soft tissues, abdominal wall and intraabdominal. The latter is commonly derived from mesentery but can occur in pelvic or retroperitoneal locations.
DT affects a wide range of age, but occur commonly between 10 and 40 years of age. There is a predilection for abdominal wall DT in women during and in the first year following pregnancy. There is an association with familial adenomatous polyposis (FAP). Those patients with FAP have a >800-fold increase risk and commonly present with intraabdominal lesion.
Clinical manifestations depend on anatomic site. Extraabdominal lesions are usually slow growing and cause little or no pain. Progressive lesion may cause decreased joint mobility or neurological problems. Intraabdominal tumors are often asymptomatic mass, but some may have abdominal pain. DT is known to be locally aggressive but stabilization and spontaneous regression can occur.
Optimal treatment for DT is sometimes difficult to choose because of the variable evolution and high rates of recurrence. First-line therapy for circumscribed lesion is surgery. Radiotherapy and systemic therapy are others options.
CT demonstrate usually ill-defined infiltrative mass frequently isodense to skeletal muscle. Areas of higher or lower density can be seen. Imaging DT with MRI is the procedure of choice for accurate evaluation of tumor border and relationship to adjacent structure.
The role of PET/CT FDG is not clearly defined in the management of DT. Report by Kasper et al. demontrated SUVmax range 1.0-8.1 in sixteen patient with DT. He also reported potential role in the evaluation of response of patients under imatinib and as a marker predicting response to cytotoxic therapy.
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