Infantile fibrosarcoma: 2 case reports and literature review

Refractory and metastatic infantile fibrosarcoma harboring LMNA-NTRK1 fusion shows complete and durable response to crizotinib

Infantile fibrosarcoma (IFS) is a rare soft-tissue sarcoma, which classically presents as an aggressive and rapidly enlarging tumor over the distal extremities of children in their first year of life. The presence of ETV6 and NTRK3 gene rearrangement is characteristic of IFS, which can be detected on routine fluorescence in situ hybridization (FISH) testing. Patients with IFS typically respond well to surgical resection and chemotherapy and have an overall survival of ∼90%. In this report, we outline the use of integrative clinical sequencing (ICS) including RNA-seq in a patient with refractory, metastatic IFS to reveal an unusual fusion (LMNA-NTRK1), not detected by routine FISH testing, which was treated with oral crizotinib and resulted in a complete and durable long-term response. This study highlights the utility of ICS in identifying cryptic gene fusions, especially in refractory malignancies, and demonstrates how such information can be used to select targeted therapies in patients with actionable molecular alterations.

Clinical management of infantile fibrosarcoma: a retrospective single-institution review

BACKGROUND

Infantile fibrosarcoma (IFS) is an uncommon soft-tissue sarcoma. Here we review our experience treating this tumor.

PATIENTS AND METHODS

We retrospectively reviewed records of patients with IFS treated at St. Jude Children's Research Hospital between 1980 and 2009.

RESULTS

We identified 15 patients, 8 girls and 7 boys; 13 white and 2 black. Median age at diagnosis was 3 months. Primary sites included the leg (n = 3), chest wall (n = 2), foot (n = 2), and one each in the tongue, occipital region, axilla, parascapular region, arm, forearm, retroperitoneum, and thigh. All patients underwent resection; 11 upfront surgery, and 4 delayed. Complications included loss of the posterior tibial nerve and artery, axillary vein, biceps, pectoralis major, gallbladder, and transverse/sigmoid sinus. Eight received chemotherapy and three radiotherapy. Seven experienced local recurrence and three lung metastasis. Median follow-up was 65 months. At the time of the review, 12 patients were alive and 3 had died. All deaths were in patients older than 1 year at diagnosis with an axial primary site.

CONCLUSIONS

Non-mutilating surgery should be the primary treatment for IFS. Neoadjuvant chemotherapy is indicated when upfront resection is unfeasible. Patients with positive surgical margins should receive adjuvant chemotherapy. Radiotherapy is indicated for axial primary sites where complete resection is impossible.