Sister Mary Joseph nodule is an uncommon metastatic intra-abdominal malignancy involving the umbilicus. The present study describes a rare case of desmoplastic small round cell tumor (DSRCT), histological grade 3, high grade, Gilly classification 4, stage IV, in an 18-year-old Thai man presenting with the Sister Mary Joseph nodule, ascites and pleural effusion. The histopathological examination of the umbilical mass revealed the presence of malignant small round cells associated with prominent stromal desmoplasia. Immunohistochemical stains showed positive reactivity to cytokeratin, desmin, neuron-specific enolase, Wilms' tumor 1, CD56, CD99 and SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1 (SMARCB1)/INI1 in the small round cells. Fine needle aspirations of the ascitic fluid and pleural effusion were performed, and immunocytochemistry revealed a metastatic DSRCT. The patient received a VDC/IE regimen of chemotherapy, comprising vincristine, doxorubicin, and cyclophosphamide alternating with ifosfamide and etoposide; however, the patient developed systemic metastasis and succumbed to the disease 6 months later.
Keywords: Sister Mary Joseph nodule; adult; ascitic fluid; desmoplastic small round cell tumor; pleural effusion; umbilical metastasis.