A Rare Case of Infantile Fibrosarcoma (IFS) Resistance to Treatment Misdiagnosed with Plexiform Neurofibroma

Fibrosarcoma (FS) is a rare, highly aggressive tumor that results from pathological changes in spindle-shaped fibroblasts that divide at an extremely rapid rate. Typically, it manifests as a painless mass usually in the upper and lower extremities, with varying symptoms based on its location and size. Diagnosis of spindle-shaped FS tumor is nearly often one of exceptions due to it is rarity and variability. As a consequence, misdiagnosis of similar tumor types is prevalent and often leading to an inappropriate therapeutic approach resulting in an overall poor prognosis when the correct diagnosis is known. We report a unique case of a 6-year-old boy who presented with a growing mass in his left arm that was initially diagnosed and treated as a plexiform neurofibroma; however, upon further examination, it was discovered to be an infantile fibrosarcoma (IFS) that had spread to the nearby lung, and showing poor response to chemotherapy or radiotherapy. By presenting the case, we aim to draw clinician’s attention to the prevalence of IFS in pediatrics as well as its diagnosis and treatment, given that misdiagnosis is particularly common in underdeveloped countries that lack the resources and expertise to conduct appropriate investigations.