Sarcoidosis: This is a systemic granulomatous disease that often presents with mediastinal lymphadenopathy and can cause chest tightness due to pulmonary involvement. It is a common cause of hilar lymphadenopathy and can lead to symptoms like chest discomfort.

Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with mediastinal lymphadenopathy and may cause chest tightness or discomfort due to the mass effect of the lymph nodes.
Tuberculosis (TB): TB can cause mediastinal lymphadenopathy, especially in the context of pulmonary TB, and may lead to chest symptoms including tightness.
Histoplasmosis: This fungal infection can cause mediastinal lymphadenopathy, particularly in endemic areas, and may result in chest tightness or discomfort.

Lymphoma (again, due to its potential for rapid progression): Despite being listed under other likely diagnoses, lymphoma's potential for aggressive behavior and the importance of early diagnosis warrant its inclusion here as well.
Pulmonary Embolism: Although it primarily presents with acute onset dyspnea, chest pain, and possibly syncope, in some cases, it might cause chest tightness. Mediastinal lymphadenopathy is not a typical finding but could be seen in cases of chronic pulmonary embolism or in the context of other diseases like cancer.
Aortic Dissection: This is a medical emergency that can present with sudden chest pain, which might be described as tightness, and can be associated with mediastinal widening on imaging, which could be mistaken for lymphadenopathy.

Castleman Disease: A rare disorder that involves an overgrowth of cells in the body's lymph nodes, which can cause mediastinal lymphadenopathy and potentially lead to chest tightness.
Kimura Disease: A rare, chronic inflammatory disorder that can cause lymphadenopathy, including in the mediastinum, and might lead to chest symptoms.
Mediastinal Germ Cell Tumors: These are rare tumors that can present with mediastinal masses and lymphadenopathy, potentially causing chest tightness or discomfort.