S5230 Endosonographic (EUS) Fine Needle Biopsy of a Paraesophageal PET Positive Lesion

Introduction: Differential diagnosis of positron emission tomography (PET)-positive paraesophageal lesions includes a variety of malignant etiologies. Both gastrointestinal stromal tumors (GIST), that have malignant potential, and Schwannomas that very rarely do can be PET-positive. Fine needle aspiration biopsies (FNAB) historically have had variable success in obtaining accurate pathologic diagnosis in GIST and Schwannomas. Case Description: A 55-year-old White woman with a past history of migraines, depression, and schizophrenia underwent diagnostic imaging after a 3-month history of left ear fullness, intermittent dizziness, and a change in her usual migraine headache pattern. Contrast enhanced computed tomography of head and neck revealed a 3 cm solid soft tissue mass along the left posterior thoracic inlet near but not involving the esophagus. Family history was remarkable for lung cancer, ovarian cancer, and non-Hodgkin’s lymphoma. Genetic testing had previously revealed heterozygosity for MSHE del exons 4-8. Social history was negative for tobacco, alcohol, or illicit drug use but positive for marijuana use 1-2 times per month. A normal physical exam with a body mass index 29.4 was noted followed by a fluorine-18 fluorodeoxyglucose PET scan revealed a well circumscribed ovoid mass in the left thoracic inlet with central low attenuation but high attenuation around the periphery measuring 3.2 cm and moderately intense fludeoxyglucose uptake at a max standardized uptake value of 4.5. Relatively diminished uptake was seen centrally suggesting cystic change or necrosis. Curvilinear endoscopic ultrasound (EUS) exam revealed a well circumscribed ovoid heterogeneously hypoechoic lesion with some focal anechoic cystic appearance centrally and a marginal halo in the left paraesophageal region. EUS-directed core biopsy was performed with a 22-gauge Franseen needle. A benign spindle cell Schwannoma was confirmed with special stains positive for S100, SOX-10, and CD56 but negative for Pankeratin, Calretinin, CD34, Desmin, DOG1, and CD117. Discussion: The differential diagnosis of PET-positive paraesophageal lesions includes metastatic malignancies, lymphoma, GIST, and Schwannomas. Imaging features are not reliable for confirming the etiology of such lesions. On EUS, both GIST and Schwannomas are typically heterogeneously hypoechoic often with focal cystic changes but a marginal halo is more typical of a Schwannoma. EUS-FNB core biopsies of extraesophageal PET-positive lesions can be confirmatory of etiology.