Intra-abdominal desmoplastic small round cell tumor

BACKGROUND The desmoplastic small round cell tumour is a rare and aggressive intra-abdominal neoplasia, with only 200 cases reported, and a higher incidence in men and predilection for the second decade of life. Histologically characterized by the presence of small nests of undifferentiated tumour cells, wrapped in fibrous desmoplastic stroma. CLINICAL CASE A 24 year old male started with abdominal pain of 4 weeks onset in the right upper quadrant, colic type, sporadic, self-limiting and accompanied by early satiety, decreased appetite, and involuntary weight loss of 10 kg in 3 months. At the time of admission the abdomen was globular, with decreased peristalsis, soft, depressible. Computed tomography of the abdomen showed multiple enlarged lymph nodes in the abdominal-pelvic cavity. A laparotomy was performed, with a subsequent omentum resection due to the presence of multiple tumours, which microscopically were characterised by groups of small, round, blue cells, separated by a desmoplastic stroma. The immunohistochemistry was positive for desmin (> 75%), epithelial membrane antigen (> 75%), CD99 (> 50%), and S100 (25%), concluding with an abdominal tumour of small, round, blue cells as a diagnosis. Chemotherapy treatment was initiated based on IMAP plus GM-CSF. CONCLUSIONS The desmoplastic small round cell tumour is a rare neoplasia, with diagnostic complexity and a lethal course. Its clinical presentation is unspecific. Histologically, it is classified as an aggressive soft tissue sarcoma that shares similar characteristics with the family of the small and blue cells tumours.