Differential Diagnosis for a 58-year-old Male with Weak Urine Stream and Thigh Mass

Single Most Likely Diagnosis

• Benign Prostatic Hyperplasia (BPH): The patient's complaint of a weak urine stream, which worsens even with straining, is highly suggestive of BPH, a common condition in older men where the prostate gland enlarges, obstructing the flow of urine.

Other Likely Diagnoses

• Prostate Cancer: Similar to BPH, prostate cancer can cause urinary obstruction symptoms. The presence of a mass, although described in the thigh, prompts consideration of metastatic disease, which could explain both the urinary symptoms (if the cancer is advanced and involves the prostate) and the palpable mass.
• Urethral Stricture: This condition, characterized by a narrowing of the urethra, can cause a weak urine stream. It might not directly explain the thigh mass but is a plausible cause for the urinary symptoms.
• Neurogenic Bladder: Conditions affecting the nerves controlling the bladder can lead to urinary retention and a weak stream. This could potentially be related to a neurological issue affecting the lower extremities, possibly explaining the mass if it's related to a neurological condition.

Do Not Miss Diagnoses

• Metastatic Cancer: While the primary concern might be prostate cancer, other cancers (e.g., colorectal, renal) could metastasize to both the prostate area (causing urinary symptoms) and to the thigh (as a soft tissue metastasis), making this a critical diagnosis not to miss.
• Spinal Cord Compression: A mass in the spine (e.g., from metastasis) could compress the spinal cord, leading to neurological symptoms including urinary retention and weakness in the lower extremities. This is a medical emergency.
• Deep Vein Thrombosis (DVT): Although less directly related to the urinary symptoms, a DVT in the thigh could cause swelling and might be perceived as a mass. Given the potential for pulmonary embolism, DVT is a critical diagnosis not to miss.

Rare Diagnoses

• Rhabdomyosarcoma: A rare type of cancer that could present as a mass in the thigh and, if metastasized, potentially cause urinary symptoms through various mechanisms.
• Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with masses and systemic symptoms. While rare, lymphoma could potentially explain both the thigh mass and, if involving the prostate or spinal cord, the urinary symptoms.