Infantile Fibrosarcoma-A Clinical and Histologic Mimicker of Vascular Malformations: Case Report and Review of the Literature

Infantile fibrosarcoma is a rare soft tissue tumor that usually presents either at birth or in the 1st year of life. Here we describe a case of a 4-month-old female who presented with a congenital right axillary mass. The initial clinical impression was benign vascular/lymphatic malformation. The core biopsy showed a spindle cell lesion with abundant vasculature represented by small vascular channels. However, immunohistochemical analysis did not support a diagnosis of vascular lesion/tumor. Polymerase chain reaction study for ETS Translocation Variant 6/neurotrophic tyrosine kinase receptor, type 3 fusion transcript was positive, and the diagnosis of infantile fibrosarcoma was established. The patient underwent resection of the axillary mass. Microscopic examination of the resection specimen showed numerous vascular channels. Intermixed there were also cellular areas composed of spindle cells similar to those seen in the biopsy material. Molecular studies were repeated and confirmed the diagnosis of infantile fibrosarcoma. Infantile fibrosarcoma has been previously reported in the literature to clinically masquerade as hemangioma. In addition, this case proves that infantile fibrosarcoma could also mimic vascular malformations on clinical, radiologic, and pathologic exams. In fact, the vascular component of the tumor is very unusual in our patient and represents a histologic feature that has not been described before. The case highlights the diagnostic challenges at clinical, radiologic, and pathologic levels in some cases of infantile fibrosarcoma and raises awareness among clinicians and pathologists related to another peculiar pattern that can be encountered in this disease.