case_images: PMC9233566_01
case_images: (A)
  Diagnostic images of a retroperitoneal mass that encompass the major abdominal vessel and an infrarenal aorta aneurysm.
  (B)
  Angio MRI that demonstrates collateral circulation after infrarenal aortic ligation.
  (C)
  Absence of tumor mass after treatment with larotrectinib.
case_images: 10-1055-s-0042-1748866-i210612cr-1.jpg
case_images: PMC9233566_01_10-1055-s-0042-1748866-i210612cr-1.jpg
case_images: FI210612cr-1
case_images: An MRI and angio-CT were performed with suggestive findings of a retroperitoneal mass encompassing major abdominal vessels and aneurysmatic dilatation of the abdominal aorta ( Fig. 1 ) with measures of 6.4 x 4.8 x 9.4 cm. ETV6-NTRK3 mutated CIF and treatment with specific TRK inhibitor (larotrectinib) was initiated at age of 2 months at a dose of 100 mg/m 2 twice daily for 1 year. Excellent response to the treatment was observed with total regression of the retroperitoneal mass by the third month after onset treatment ( Fig. 1 ).
case_images: PMC9233566_02
case_images: (A)
  Ultrasound of the left lower limb with findings suggestive of possible hematoma of the muscle.
  (B)
  MRI shows soft tissue tumor of the left lower limb.
  (C)
  and
  (D)
  demonstrate the absence of evidence of residual tumor on ultrasound.
  (E)
  Left lower limb pre-treatment.
  (F)
  Left lower limb after treatment, biopsy scar is seen.
case_images: 10-1055-s-0042-1748866-i210612cr-2.jpg
case_images: PMC9233566_02_10-1055-s-0042-1748866-i210612cr-2.jpg
case_images: FI210612cr-2
case_images: MRI was made after an ultrasound with suggestive findings of possible hematoma. MRI revealed a soft tissue mass (5.1 x 5.6 x 6.9 cm) compatible with possible vascular malformation without being able to rule out other possibilities such as rhabdomyosarcoma ( Fig. 2 ), so an open biopsy was made. Periodical US controls were made showing the total remission of the tumor by the second month of treatment ( Fig. 2 ).