Differential Diagnosis for Large Left-Sided Mediastinal and Pleural-Based Mass

Single Most Likely Diagnosis

• Lung Cancer: Given the presence of a large mediastinal and pleural-based mass with a central area of necrosis, along with mediastinal lymphadenopathy and a left upper lobe nodule, lung cancer is the most likely diagnosis. The combination of these findings suggests an advanced stage of the disease, which is consistent with the aggressive nature of lung cancer.

Other Likely Diagnoses

• Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with mediastinal masses and lymphadenopathy. The presence of a pleural-based mass and a lung nodule could also be seen in lymphoma, especially if there is involvement of the lung parenchyma.
• Thymoma: Thymomas are tumors originating from the epithelial cells of the thymus. They can present as anterior mediastinal masses and may be associated with pleural effusions or lung nodules, although the latter is less common.
• Sarcoidosis: While less likely given the necrotic center of the mass, sarcoidosis can cause mediastinal lymphadenopathy and lung nodules. However, it typically presents with a more symmetric pattern of lymphadenopathy and often involves the hilar regions.

Do Not Miss Diagnoses

• Tuberculosis (TB): TB can cause a wide range of pulmonary and mediastinal findings, including masses, lymphadenopathy, and lung nodules. It is crucial not to miss TB due to its infectious nature and the need for specific antimicrobial treatment.
• Histoplasmosis: Similar to TB, histoplasmosis is a fungal infection that can cause mediastinal lymphadenopathy, lung nodules, and masses, especially in endemic areas. It requires specific antifungal treatment.
• Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): GPA is a vasculitis that can affect the lungs and cause nodules, masses, and cavitations, along with renal and systemic symptoms. It is a diagnosis that should not be missed due to its potential for severe morbidity if not treated promptly.

Rare Diagnoses

• Castleman Disease: A rare lymphoproliferative disorder that can present with mediastinal lymphadenopathy and masses, often with systemic symptoms.
• Germ Cell Tumors: These are rare tumors that can occur in the mediastinum, including teratomas, seminomas, and non-seminomatous germ cell tumors.
• Mediastinal Liposarcoma: A rare soft tissue tumor that can present as a mediastinal mass, which may extend into the pleural space.