RESUMEN
INTRODUCTION AND IMPORTANCE: Congenital Infantile fibrosarcoma is a rare tumor in children and accounts for only 10 % of various malignant tumors in this age group. Manifestations vary according to the site of occurrence. Symptoms of the tumor located in unusual places can be misleading and obscure the actual diagnosis, which in turn may waste precious effort and time until the correct diagnosis is established. Infant malignancies should be considered to reduce the morbidity and mortality associated with this pathology. CASE PRESENTATION: We present the case of a 6-month-old infant, who was admitted to our hospital with a one-month history of high fever and dry cough, with no improvement in symptoms after treatment with antibiotics. Computed tomography showed a heterogeneous mass in the pleural cavity compressing the lung tissue, in addition to bilateral mild pleural effusion. Thoracotomy was indicated and the tumor was completely resected. CLINICAL DISCUSSION: Histopathological and Immunohistochemical approach is crucial because this type of tumor can overlap with many soft tissue sarcomas. After searching in medical literature, no published evidence of a similar case was found, and thus we managed the patient empirically, depending on the usual approach for congenital fibrosarcoma. Complete surgical resection is the golden standard of treatment, followed by chemotherapy depending on pathological findings. CONCLUSION: Clinical awareness is important in any unresponsive pneumonia and malignancies should be taken into consideration.