Differential Diagnosis for Unilateral Swollen Nodule on Side of Neck

Single Most Likely Diagnosis

• Lymphadenitis: This is an inflammation of the lymph nodes, often due to a bacterial or viral infection. It's a common cause of a unilateral swollen nodule on the side of the neck, especially in the context of an upper respiratory tract infection.

Other Likely Diagnoses

• Branchial Cleft Cyst: A congenital anomaly that can present as a swollen nodule along the side of the neck, often becoming more apparent during infections.
• Thyroglossal Duct Cyst: Although typically midline, it can occasionally present off-center and cause a swollen nodule, especially if infected.
• Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with lymphadenopathy, which might be perceived as a swollen nodule on the side of the neck.
• Metastatic Cancer: Cancers from the head and neck region can metastasize to the lymph nodes, causing them to become enlarged and form a nodule.

Do Not Miss Diagnoses

• Tuberculosis (TB) Lymphadenitis: Although less common in some regions, TB can cause significant morbidity if not diagnosed and treated promptly. It often presents with systemic symptoms in addition to lymphadenopathy.
• Cat-Scratch Disease: Caused by Bartonella henselae, this infection can lead to significant lymphadenopathy, typically following a cat scratch or bite.
• Malignant Tumors: Including but not limited to lymphomas, sarcomas, and carcinomas that could metastasize to the neck, emphasizing the importance of a thorough diagnostic workup.

Rare Diagnoses

• Kimura Disease: A rare, chronic inflammatory disorder that can cause lymphadenopathy and eosinophilia, more commonly seen in Asian males.
• Kikuchi-Fujimoto Disease: A rare, self-limiting condition that causes lymphadenitis, often accompanied by fever and night sweats.
• Castleman Disease: A rare disorder that involves an overgrowth of cells in the lymphatic system, which can cause lymphadenopathy among other symptoms.

Each of these diagnoses has a different set of implications for treatment and prognosis, highlighting the importance of a thorough diagnostic evaluation to determine the underlying cause of a unilateral swollen nodule on the side of the neck.