A DOUBLE ONCOLOGIC DIAGNOSIS SYNCHRONOUS INVASIVE BREAST CARCINOMA AND GIANT GASTRIC GIST A PROPOS DUN CAS / A CASE REPORT

Background: Gastrointestinal stromal tumors (GISTs) may coexist with other primary malignancies, but synchronous invasive breast carcinoma and gastric GIST remain rarely reported. Case presentation: A 71-year-old postmenopausal woman presented with a palpable left-breast nodule. Mammography and ultrasonography showed a 15 × 10 mm irregular spiculated ACR 5 lesion. Core-needle biopsy demonstrated grade 2 invasive breast carcinoma. Staging thoracoabdominopelvic CT unexpectedly revealed a 107 × 108 mm heterogeneous fundic gastric mass with central necrosis and fistulization into the gastric lumen. Endoscopy showed an ulceroproliferative fundic process. Gastric biopsy disclosed a spindle-cell neoplasm with strong diffuse CD117 expression; DOG1, AE1/AE3, CD45, desmin, and smooth-muscle actin were negative. The findings supported two synchronous primary tumors rather than metastatic breast cancer. The patient was reviewed by a multidisciplinary team and received systemic treatment described in the records as chemotherapy, which remained ongoing at the latest follow-up.