Extraskeletal Osteosarcoma with Extensive Gastrointestinal Tract Involvement

Abstract

Abstract Introduction/Objective Extraskeletal osteosarcoma (ESOS) is a rare aggressive mesenchymal tumor that originates from soft tissues or visceral organs, differentiating it from primary bone osteosarcoma. ESOS represents less than 5% of all osteosarcomas and less than 1% of soft tissue sarcomas. Primary ESOS in the gastrointestinal tract (GIT) is exceedingly uncommon, with a low incidence rate Methods/Case Report A 70 year-old-man with a history of hypertension, Myasthenia Gravis, hypothyroidism (status post total thyroidectomy), and skin cancer presented to the clinic with a chief complaint of abdominal fullness of 4 months duration. Primary work-up revealed anemia (Hemoglobin 7 g/dl) and peripheral blood smear was suggestive of bone marrow infiltration. Evaluation with upper gastrointestinal endoscopy and ultrasound demonstrated regular mucosal folds of the stomach with a solid-cystic lesion between the body of the pancreas and the posterior aspect of the stomach. The patient underwent a fine needle biopsy showing a spindle cell lesion with positive immunohistochemistry (IHC) for Smooth Muscle Actin (SMA), beta-Catenin, CD34, and negative for panCK, DOG-1, and CD117; suggestive of leiomyoma. The patient underwent a total gastrectomy, distal pancreatectomy, and splenectomy. Examination of the specimen confirmed a high-grade malignant spindle cell lesion with numerous associated osteoclast-like multinucleated giant cells, and focal areas consistent with osteoid changes. The IHC was requested and the cells were positive for WT1 and Muscle Specific Actin, SATB2, and Ki-67>90% whereas the cells were negative for SMA, Myo-D1, Myogenin, S100, SOX10, MART1, CD34, CD31, and Calretinin. Also, the genetic analysis for MDM2 was negative. These findings confirmed the diagnosis of ESOS with abdominal visceral involvement (stomach, pancreas, and omentum) Results (if a Case Study enter NA) NA Conclusion ESOS is an extremely rare condition that demands a comprehensive evaluation involving clinical, radiological, histopathological, and immunohistochemical analyses to establish an accurate diagnosis. Distinguishing ESOS from primary bone osteosarcoma is vital due to the different treatment strategies. Additionally, ESOS requires a unique therapeutic approach compared to more prevalent gastrointestinal sarcomas like GIST or leiomyosarcoma. The mainstay of ESOS treatment entails complete surgical resection of the tumor with clear margins, accompanied by adjuvant chemotherapy. Ensuring precise diagnosis is of utmost importance to provide suitable and effective treatment