Alveolar soft part sarcoma in a child - a case report.

Background: Alveolar soft part sarcoma (ASPS) is a very rare mesenchymal malignancy of uncertain origin. It mostly affects young people, with about a quarter of cases being diagnosed in children.

Case: An 11-year-old girl had a painless subcutaneous "lump" in the left elbow area. Imaging exams revealed a solid soft-tissue intramuscular mass of suspicious appearance. A surgical excision of lesion was performed. The biopsy consisted of a lobular tumor measuring 35 × 20 × 12 mm. Histology revealed an epithelioid-cell population arranged in organoid pseudoalveolar pattern. It immunohistochemically expressed TFE3 and harbored the ASPSCR1:: TFE3 gene fusion. A diagnosis of ASPS was established. Subsequently, a wide re-excision of the scar was performed without microscopic residual tumor. The patient is currently without evidence of local recurrence or metastasis.

Conclusion: ASPS is considered an aggressive and prognostically unfavorable chemoresistant neoplasm. Children have a better prognosis compared to adults. Early detection of tumor in a localized stage with complete surgical removal remains a mainstay therapeutic option. Due to its tendency to late metastases, a long-term thorough follow-up of the patient is necessary.