Abstract Introduction A mediastinal mass typically raises suspicion for a primary thoracic malignancy, lymphoma, or metastatic disease from lung or breast cancer. Metastatic spread to the mediastinum from pancreatic ductal adenocarcinoma (PDAC) is rare. The frequency of mediastinal lymph node metastases in pancreatobiliary malignancies detected by Endoscopic Ultrasound (EUS) has been reported to range from 5% to 7%. The coexistence of pancreatic cancer with other primary malignancies occurs in approximately 1%-20% of cases, most commonly with gastric, colorectal, thyroid, or genitourinary tumors. The presence of synchronous pancreatic and lung cancers, however, is exceedingly uncommon. Case Description We report a 73-year-old woman who presented with chest pain and melena. CT Chest, abdomen and Pelvis revealed a 3.6 x 3.8 x 2.2 cm mass in the uncinate process of the pancreas with hepatic lesions, bilateral pulmonary nodules, left adrenal nodule, and a large mediastinal mass measuring 7.1 x 6.9 x 7.1 cm abutting the superior vena cava (SVC). Gastric biopsy demonstrated undifferentiated carcinoma involving the mucosa, and liver biopsy showed an epithelioid malignant neoplasm with an immunophenotype most consistent with a pancreaticobiliary origin. Endobronchial Ultrasound (EBUS) of the right paratracheal (4R) mediastinal lymph node demonstrated poorly differentiated carcinoma with immunostains positive for p40 and negative for TTF-1, NUT, SOX-10, SMARCA-4, raising concern for a squamous cell primary. She was initially diagnosed with two separate primaries- Stage IV adenocarcinoma of the pancreas and metastatic squamous cell carcinoma of the lung. However, multidisciplinary tumor board review favored a unifying diagnosis of Stage IV (T4, cN0, pM1) adenocarcinoma of the pancreas with local extension into the stomach and involvement of the liver, mediastinum and lungs. Patient was initiated on chemotherapy with FOLFIRINOX and concurrent radiation to the chest. Discussion Mediastinal metastasis from pancreatic ductal adenocarcinoma is rare but documented. Proposed mechanisms include lymphatic spread via mediastinal nodal stations or transdiaphragmatic/retroperitoneal extension, which may clinically mimic a second thoracic primary. Additionally, there have been case reports of simultaneous lung and pancreatic masses, both lesions with discordant histologic and immunohistochemical profiles. Awareness of these possibilities, along with integrated clinicopathologic, radiologic, and molecular assessment, is crucial to prevent diagnostic misclassification and to guide appropriate management. This abstract is funded by: None
Dutta et al. (Fri,) studied this question.