What is the diagnosis for a 63-year-old male with left shoulder pain for 6-12 months, a history of hypertension (High Blood Pressure) for more than 5 years, and symptoms including radiating pain to the epigastric area, stiffening, dyspnea, and insomnia, who is taking Aspirin (acetylsalicylic acid) and has a past medical history of a stroke of unknown type (infarct vs hemorrhage) 4 years ago?

Adhesive Capsulitis (Frozen Shoulder): Given the chronic nature of the left shoulder pain (6 to 12 months) and the description of stiffening of the area, adhesive capsulitis is a plausible diagnosis. This condition is common in individuals with a history of stroke and diabetes, although this patient is non-diabetic. The absence of systemic symptoms such as profuse sweating, cold clammy extremities, and palpitations also points towards a musculoskeletal rather than a cardiovascular cause.

Referred Pain from Gastrointestinal Issues: The radiating pain to the epigastric area could suggest gastrointestinal issues such as peptic ulcer disease or gastroesophageal reflux disease (GERD), which can refer pain to the shoulder region.
Musculoskeletal Strain or Injury: Chronic strain or an unresolved injury to the muscles or tendons around the shoulder could cause prolonged pain and stiffness.
Cardiovascular Disease: Although less likely given the absence of typical cardiac symptoms, the patient's history of hypertension and stroke, along with the complaint of dyspnea, necessitates consideration of cardiovascular diseases such as coronary artery disease or cardiac ischemia.

Myocardial Infarction (MI) or Cardiac Ischemia: Despite the atypical presentation (lack of chest pain, profuse sweating, or palpitations), MI or cardiac ischemia must be considered, especially in a patient with a history of stroke and hypertension. The radiating pain to the epigastric area and dyspnea could be indicative of a cardiac event.
Pulmonary Embolism (PE): Although less common, PE can present with shoulder pain and dyspnea, making it a critical diagnosis not to miss, especially in patients with risk factors for thromboembolic events.
Diabetic Shoulder (Diabetic Amyotrophy): Although the patient is non-diabetic, the possibility of undiagnosed diabetes or another metabolic disorder causing shoulder pain and stiffness should be considered.

Pancoast Tumor: A rare type of lung cancer that can cause shoulder pain due to invasion of the brachial plexus. Given the patient's lack of smoking history, this is less likely but remains a consideration in the differential diagnosis of shoulder pain.
Thoracic Aortic Aneurysm or Dissection: These are rare but life-threatening conditions that can cause chest or back pain radiating to the shoulder. The patient's history of hypertension increases the risk, but the absence of typical symptoms makes this a less likely diagnosis.