Inflammatory myofibroblastic tumor of the mesentery
Has been complaining of abdominal pain that is sometimes relieved by evacuation. Night sweats. The parents noticed abdominal fullness.
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In the right upper abdomen, there is an encapsulated multicystic, septated mass measuring 7 x 5 x 6.2 cm (LL x AP x CC). The mass is bounded posteriorly by the right kidney and laterally by the gallbladder and shares an interface with the IVC. It exerts a mild mass effect, displacing the head and uncinate process of the pancreas and several bowel loops.
The CT abdomen was done after an abdominal ultrasound done at a clinic (not available) demonstrated a subhepatic heterogeneous lesion with cystic and solid components.
The mass was biopsied.
Abdominal/mesenteric mass, incisional biopsy:
Spindle cell tumor with ETV6-NTRK3 fusion gene.
Spindle cell tumor associated with the ETV6-NTRK3 fusion gene.
The tumoral ovoid/spindled cells are admixed with marked mixed inflammatory cell infiltrate. There is also a pseudocystic area consisting of organizing hematoma. ETV6-NTRK3 fusion gene has been reported in multiple pediatric mesenchymal tumors including infantile fibrosarcoma, cellular mesoblastic nephroma and ALK-negative inflammatory myofibroblastic tumor (IMT) / ETV6-NTRK3 fusion tumor, IMT-like features. It has also been reported in some epithelial and hematolymphoid malignancies. In the present case, the histomorphological findings together with the patient's age and tumor location are consistent with the ETV6-NTRK3 fusion tumor. IMT-like morphology (favor ALK-negative inflammatory myofibroblastic tumor).