Radiologically Occult Desmoplastic Small Round Cell Tumor in a 36-Year-Old Man: A Case Report.

Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive mesenchymal malignancy that typically affects adolescents and young adults. We report an unusual case of a 36-year-old man who presented with persistent left flank pain. Initial investigations, including colonoscopy and abdominal computed tomography, were unremarkable. One year later, repeat imaging revealed a large intra-abdominal mass associated with liver metastases. Histopathological examination and immunohistochemical analysis confirmed the diagnosis of DSRCT. This case highlights the diagnostic challenges of DSRCT, particularly when it occurs outside the usual age range and presents with non-specific symptoms. Persistent or unexplained symptoms should prompt repeat and advanced imaging, as well as early tissue diagnosis, to facilitate timely multidisciplinary management.