A Rare Case of Rectal Gastrointestinal Stromal Tumor Associated with Parapharyngeal Metastasis

Background: Gastrointestinal stromal tumors are the most frequent mesenchymal tumors and represent 1- 3% of all digestive neoplasms. Their incidence is 0.68 per 10,000 people. GISTs originate from the interstitial cells of Cajal, which are known as the gastrointestinal pacemaker, and carry mutations in the KIT gene in 95% of those affected. GISTs occur mainly in the middle-aged and rarely under the age of 40. The main age of presentation is 64 years old. The most common site of metastasis is the liver (65%), and exceptionally the bone (3%). Discussion: Rectal GISTs represent 5 to 15% of all GISTs. They are usually asymptomatic and discovered incidentally. Surgical resection with curative intent is the standard treatment for localized GISTs. Complete excision of the tumor is the most significant factor related to the outcome and can be accomplished in 40- 60% of cases. For borderline or unresectable lesions, neoadjuvant treatment with anti-tyrosine kinase (imatinib) should be considered. Imatinib is considered to be a relatively safe treatment and is generally well-tolerated by patients. Overall, the five-year survival rate is 90% for low-grade GIST, but the prognosis is worse for high-grade tumors (< 20%). Bone metastasis is a rare site of GIST metastases and usually presents itself during disease relapse. We present a rare case of a patient with an oligometastatic with pelvic bone lesion rectal GIST who developed parapharyngeal metastasis infiltrating C3 with airway compromise. Unfortunately, the patient passed away after massive tracheal bleeding. Conclusion: Bone metastasis from GIST is uncommon. The development of dyspnea and hoarseness should prompt the diagnosis of potential life-threatening complications such as parapharyngeal metastasis.