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Table 1 Clinicopathological comparison of our two cases of TPR-NTRK1 and LAMA-NTRK1 fusion-positive sarcomas and 6 cases of our infantile fibrosarcoma

From: Clinicopathological findings of pediatric NTRK fusion mesenchymal tumors

  TPR-NTRK1 fusion-positive pediatric sarcoma LMNA-NTRK1 fusion-positive pediatric sarcoma ETV6-NTRK3 fusion-positive
Inflammatory myofibroblastic tumor
ETV6-NTRK3 fusion-positive pediatric sarcoma
Age/Gender 12 y/ male 3 y/ male 6 mo/female Median age: 2.6 months (range: 1.6 ~ 5.6 months), M: F = 5:1
Site Dura, parieto-occipital Forehead dermis and subcutaneous tissue Left lower lobe of lung Tongue, buttock, shoulder, foot, abdominal cavity, and sacro-coccygeal area
Size 6.0 × 5.0 × 3.0 cm 4.0 × 3.5 × 3.0 cm 5.6 × 3.5 × 3.0 cm Range: 1.4–4.5 cm in biggest diameter
Histology Mixed oval to spindle cells Spindle cells intermixed with prominent lymphoplasma cells Spindle myofibroblastic cells with prominent lymphoplasma cells Mostly spindle cells, with no prominent inflammatory cell infiltration
Histological grade High-grade Low-grade Low-grade High-grade (cellular)
Nuclear pleomorphism Relatively uniform cells without pleomorphism Uniform cells without pleomorphism Uniform cells without pleomorphism Uniform cells without pleomorphism
Tumor necrosis Absent Absent Abent Absent
Mitotic rate 25/10 HPFs 0/10 HPFs 1/ 10 HPFs 10/10HPFs ~ 40/10 HPFs
Ki67 labeling index 36.0% 18.2% 37% 15 ~ 60%
Immuno-positive markers Trk/CD34/Nestin/vimentin/p53 Trk/ S100/CD34/Nestin/vimentin/ Trk/SMA/vimentin Trk/Nestin/vimentin,
S100 (3/6 cases)/CD10(4/5 cases)
Trk positive pattern Nucleus Nuclear membrane Cytoplasmic Cytoplasm and nucleus
Genetic abnormalities other than NTRK1 fusion NTRK1 amplification (copy number: 11), H3F3A amplification (copy number: 12) absent absent Absent
Final diagnosis Undifferentiated sarcoma Infantile fibrosarcoma, low grade Inflammatory myofibroblastic tumor Infantile fibrosarcoma, cellular
Treatment Surgery+ vincristine, doxorubicin, cyclophosphamide (6 cycles)/ifosramide, carboplatin, etoposide (6 cycles), alternative, total 12 cycles Surgery only Surgery only Surgery + vincristine, actinomycin D, cyclophosphamide (X11 or 26 cycles)
Outcomes and follow-up NED (1.4 years) NED (0.8 years) NED (0.3 years) 5 patients: NED (for average 11.7 years, range: 6.0–17.4 years)
1 patient: Follow-up loss
Known mesenchymal tumors with this type of fusion Lipofibromatosis, adult uterine undifferentiated sarcoma Infantile fibrosarcoma, lipofibromatosis-like neural tumor, Undifferentiated sarcoma, Cellular mesoblastic nephroma Infantile fibrosarcoma Infantile fibrosarcoma, inflammatory myofibroblastic sarcoma
  1. NED No evidence of disease