Lymphadenopathy due to infection or inflammation: This is a common cause of inguinal lymph node enlargement, especially in older adults, and can be due to a variety of infectious agents such as bacteria, viruses, or fungi. The size of the node (1.2 inches) suggests a significant inflammatory response.

Metastatic cancer: Given the patient's age, the possibility of metastatic cancer to the inguinal lymph nodes from a primary site such as the skin (e.g., melanoma), prostate, or other pelvic organs should be considered. The size of the lymph node increases the suspicion for malignancy.
Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with lymphadenopathy, and inguinal nodes can be involved. The patient's age and the presence of a significant lymph node enlargement make this a plausible diagnosis.
Benign lymph node hyperplasia: Reactive lymphoid hyperplasia can occur in response to various stimuli, including infections, autoimmune diseases, or other inflammatory conditions. This could be a consideration, especially if the patient has a history of such conditions.

Testicular cancer with metastasis: Although less common, testicular cancer can metastasize to the inguinal lymph nodes. Given the potential for serious outcomes if missed, this diagnosis should be considered, especially in the absence of other obvious causes.
Melanoma with lymph node metastasis: Melanoma can spread to the inguinal lymph nodes, and early detection is crucial for treatment outcomes. A thorough skin examination is necessary to evaluate for any suspicious lesions.
HIV infection: HIV can cause generalized lymphadenopathy, including enlargement of the inguinal lymph nodes. Given the significant implications for management and treatment, HIV should be considered, especially if the patient has risk factors.

Castleman disease: This is a rare disorder that involves an overgrowth of cells in the lymph node. It can present with lymphadenopathy and has different forms, some of which are associated with HIV infection or can evolve into lymphoma.
Kikuchi-Fujimoto disease: A rare, self-limiting condition that causes lymphadenopathy, typically in the cervical region but can involve other nodes, including inguinal nodes. It's more common in young women but can occur in anyone.
Rosai-Dorfman disease: A rare histiocytic disorder that can cause lymphadenopathy, including in the inguinal region. It often presents with massive lymphadenopathy and can be associated with systemic symptoms.