Low-grade fibromyxoid sarcoma

Case contributed by Dr Yair Glick

Presentation

Recent right hemiarthroplasty, suspected periprosthetic fracture.

Patient Data

Age: 90 years
Gender: Female

No evidence of fracture. No loosening of femoral stem.

Round soft-tissue lesion, hypodense to muscle, measuring 5.3 x 4.3 x 6.3 cm (LL x AP x CC), ballooning into the vastus intermedius from the anterior femoral cortex at the distal end of the femoral stem, eroding through the entire thickness of the cortex.

Nuclear medicine

Total body 99mTc-MDP triphasic bone scintigraphy with pelvic SPECT:

  • high-intensity horizontal uptake focus in the sacrum, compatible with fracture - osteoporotic insufficiency fracture? trauma?
  • moderately increased uptake adjacent to the right hip prosthesis under the trochanter, with elevated early phase perfusion - clinical correlation required for ruling out infection
  • increased irregular uptake in the shoulders and along the spine, degenerative arthritic changes in the knees
ultrasound

Mass measuring 7.3 x 4.5 x 4.9 cm with mixed echotexture in the front of the right hip, mostly hypoechoic with echogenic areas. The mass abuts the femoral bone.

Under local anesthesia with 7 ml of lidocaine 1%, four aspirations from the mass substance with 14G-18G needles. Transparent, whitish gelatinous substance received. Part of the material was placed on 8 slides for cytologic evaluation and part was transferred into a sterile stoppered syringe. In addition, two core biopsies were taken from the echogenic material with a Magnum device using a 14G needle. Two good-quality cores of the gelatinous/tissue material were obtained.

2.5 months after biopsy

mri

Intramedullary fixation in the proximal femoral diaphysis.

At the middle third of the thigh, deep inside the vastus intermedius, there is a lesion displaying a low signal on T1WI and a high signal on T2WI, that undergoes mild heterogeneous contrast enhancement. The lesion measures 4.8 x 4.7 x 8.1 cm (ml x ap x cc). It violates the cortex and reaches the tip of the intramedullary stem. The lesion's characteristics favor a soft-tissue sarcoma.

The neurovascular structures appear normal.

Case Discussion

Incidentally discovered soft-tissue lesion in the right thigh, eroding the femoral cortex. The lesion did not show increased uptake on bone scan. Ultrasound-guided biopsy and cytology obtained.

Pathology:

Soft tissue: (Right thigh Trucut) Cores of tumor composed of benign spindle cells without atypia and mitotic figures in a myxoid stroma.

Immunostains: Vimentin positive. Desmin negative. S100 negative. Smooth muscle actin negative. CD34 negative.

Findings probably of low-grade fibromyxoid sarcoma. For definite diagnosis, the entire lesion is needed for evaluation.

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