Stable Angina: The patient's symptoms of chest pain radiating to the back, accompanied by shortness of breath (SOB), and triggered by exertion (walking) are classic for angina. The fact that the pain improved with Tylenol but lingered suggests a possible cardiac origin. The patient's history of type 2 diabetes mellitus (T2DM) increases her risk for coronary artery disease (CAD).

Acute Coronary Syndrome (ACS): Although the patient's pain improved with Tylenol, the episodes of chest pain, especially one occurring at rest, could suggest unstable angina or a non-ST-elevation myocardial infarction (NSTEMI), both forms of ACS.
Gastroesophageal Reflux Disease (GERD): The chest pain radiating to the back could also be consistent with GERD, especially if the pain is exacerbated by lying down or relieved by antacids, though the exertional component might be less typical.
Musculoskeletal Pain: Given the location and radiation of the pain, musculoskeletal causes such as costochondritis or musculoskeletal strain should be considered, especially if there's a history of recent trauma or overuse.

Myocardial Infarction (MI): It's crucial not to miss an MI, as timely intervention can significantly improve outcomes. The presence of chest pain, especially with radiation to the back and exertional triggers, necessitates careful consideration of MI.
Pulmonary Embolism (PE): Although less likely given the exertional nature of the pain and the absence of other typical symptoms like hemoptysis or risk factors, PE is a diagnosis that could be deadly if missed. The presence of SOB is a red flag.
Aortic Dissection: This is a life-threatening condition that can present with sudden, severe chest pain radiating to the back. Risk factors include hypertension and atherosclerosis, which might be more common in patients with T2DM.

Pericarditis: Inflammation of the pericardium can cause chest pain that may radiate to the back and can be constant or pleuritic. It's less likely given the exertional component but should be considered if other diagnoses are ruled out.
Esophageal Spasm: This condition can cause chest pain that mimics cardiac pain but is usually associated with swallowing difficulties or relieved by nitroglycerin.
Pneumothorax: Although unlikely without trauma or underlying lung disease, pneumothorax can cause sudden chest pain and SOB, necessitating immediate medical attention.