Magnetic Resonance Imaging Features of Congenital Infantile Fibrosarcoma

Abstract

Background Congenital/infantile fibrosarcoma is a rare soft tissue tumor presented in early age of life. It should be considered in the differential diagnosis of the large soft tissue masses especially in the extremities at the age of infancy. These tumors frequently are misdiagnosed at birth as hemangioma. Histologically, they can resemble their adult counterparts and they are characterized by the chromosomal translocation t(12;15) (p13;q25) resulting in the ETV6-NTRK3 gene fusion. Objective A retrospective review of the MRI features of histopathology-proven congenital/infantile fibrosarcoma provides our own institutional experience and supports the limited radiology literature written about this disease. Material and method The list of our patients is obtained after reviewing our radiology and pathology database in the period between June 1st, 2007 and May 31st, 2017 (10 years) at King Faisal Specialist Hospital & Research Center, Riyadh. Phrases used to search in our MRI examinations database are: congenital infantile fibrosarcoma, infantile fibrosarcoma, juvenile fibrosarcoma, soft tissue sarcoma, malignant soft tissue mass, sarcomatous soft tissue mass, fibrosarcoma, spindle cell sarcoma, myomatous sarcoma. Result In our database and picture archiving and communication system (PACS) during the period of the study, the word (fibrosarcoma) was mentioned in the radiology report of 182 patients. Only four cases were histopathologically proven to be a congenital/infantile fibrosarcoma and had completed their own MR exams - three of them were primary/new cases, males with an age range between 0 days and 5 months (median age: 5 months). The fourth case was a female with a history of 1^st presentation at the age of one month and proved by histopathology examination but there was no available imaging at that time; however, tumor recurrence in the same patient was at the age of 4 years with available MR imaging and pathology sample. Conclusion Congenital infantile fibrosarcoma is a rare entity that has no specific MRI findings. However, it should be always considered as part of the differential diagnosis of congenital soft tissue masses with aggressive behavior.

Keywords: congenital infantile fibrosarcoma; congenital mass; imaging features; pathological features; soft-tissue sarcoma.

Figure 1. In Case 1, lobulated infiltrative soft tissue mass centered within the right upper medial thigh adductor muscles. (A) The tumor appears hypointense in axial T1WI. (B) Shows heterogeneous hyperintense signal in axial T2WI with FS. (C) Pre-gadolinium axial dry gradient image shows intermediate to low signal intensity of the mass. (D) Post-gadolinium axial image shows avid heterogeneous enhancement of the mass and demonstrates the extension of the lesion into the right side perineum.

FS: Fat Suppression

Figure 2. Single right lung nodule suggestive of metastases.

Figure 3. (A) In case 1, low power of the tumor shows cystic spaces and dilated blood vessels. An area of calcification, necrosis and haemorrhage is seen on the left side. (B) High power of the same tumor shows solid sheets of oval mesenchymal cells with moderate atypia and few mitoses.