Abstract
BACKGROUND: Solitary fibrous tumors encompass a heterogeneous group of spindle cell neoplasms, ranging from biologically low-risk lesions to, in rare instances, highly aggressive tumors with malignant potential. Dedifferentiation in solitary fibrous tumors is uncommon and typically occurs in the retroperitoneum, with extrapleural involvement being among the least frequently reported. CASE PRESENTATION: A 13-year-old male presented with a rapidly enlarging mass in the lower jaw of 20 days duration, involving the submandibular triangle and floor of the mouth. DIAGNOSIS: Histopathological examination of the excisional biopsy revealed spindle-shaped cells arranged in compact fascicles with a haphazard distribution, and areas of hyalinization. Immunohistochemical analysis demonstrated positivity for CD34, STAT6, MyoD1, α-SMA, Bcl-2, and CD99, confirming the diagnosis of extrapleural dedifferentiated solitary fibrous tumor (DSFT). MANAGEMENT: The lesion was surgically excised but recurred, likely due to disease progression. Re-excision was planned, but the child died 10 days before surgery.