Diplopia as the first symptom of an aggressive metastatic rectal stromal tumor

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms, and metastatic disease is present at diagnosis in about 50%. Most common metastatic sites are the liver, the lungs, and the peritoneum. Bony metastases are uncommon and of unknown prognosis.

A 57-year-old man presented with diplopia due to a clival metastastic lesion from an asymptomatic rectal stromal tumor. This patient also had liver and vertebral metastases. Treatment with imatinib, a tyrosine kinase inhibitor, led to a partial response of the primary tumor and hepatic metastasis, but the patient developed aggressive bone metastases that proved refractory to 3 different tyrosine kinase inhibitors.

Different drug distribution or different mutation patterns of key prognostic receptors (e.g. cKIT receptor) in bone and soft tissues may explain the unusually aggressive pattern of these bony metastases of a GIST. Pharmacodynamic and molecular investigations are warranted to check these hypotheses.