S2580 A Rare Case of Primary Hepatic Sarcoma

Abstract

Introduction: Primary hepatic undifferentiated pleomorphic sarcoma (UPS) is a rare malignant mesenchymal tumor with a nonspecific clinical and radiologic demonstration. Immuno-histological testing rules out hepatic, GIST, hematological, neural and epithelial origin. Stains for mesenchymal origin are usually the only positive ones and it does not demonstrate any evidence of specific mesenchymal cell differentiation. Case Description/Methods: Our patient is a 56 year old Hispanic male with no significant past medical history who presented to the gastroenterology clinic for an abnormal abdominal ultrasound. A computed tomography scan of the abdomen and pelvis exhibited numerous hepatic masses involving right and left hepatic lobe, with several lesions distorting the capsule (largest lesion in the right hepatic lobe is measuring 11.5 x 9.2 cm with bulging of the liver capsule and compressing the inferior vena cava). EGD and Colonoscopy revealed a 1cm nodule with biopsies showing vimentin positive spindle cell neoplasm. A CT guided core needle biopsy of the liver mass also showed a spindle cell neoplasm without recognizable hepatic tissue and IHC was positive for smooth muscle actin. A wide battery of IHC stains failed to establish a more specific histogenesis, and also revealed that spindle neoplastic cells are focal and patchy positive for h-caldesmin (approximately 10-15% of neoplastic cells), and negative for desmin. Given these results, the diagnosis of undifferentiated pleomorphic sarcoma (UPS) of the liver was made. Discussion: UPS, previously known as malignant fibrous histiocytoma (MFH), is the third most common soft tissue sarcoma and accounts for about 0.08 – 1 per 100,000 cases [2]. To date, there have been fewer than 200 cases reported of primary hepatic UPS in medical literature. Liver biopsy is essential in diagnosing UPS. Abdominal imaging studies such as CT and U/S are only able to reveal a mass and are nonspecific for UPS. Primary hepatic UPS is ordinarily a diagnosis of exclusion and made by multiple immuno-histological testing that rules out hepatic, GIST, hematological, neural and epithelial origin. Stains for mesenchymal origin are usually the only positive stain that do not demonstrate any evidence of specific mesenchymal cell differentiation. It is imperative to consider UPS in the differential diagnosis of large liver lesions without evidence of differentiation. Early identification of this rare tumor can prevent the possibility of distant metastasis and improve survival amongst patients.Figure 1.: Immunohistochemistry of the duodenal nodules showed uncharacterized Vimentin positive spindle cell neoplasm.