Cat Scratch Disease: This is a common condition caused by Bartonella henselae, transmitted through cat scratches or bites, leading to axillary lymphadenopathy and sometimes erythema at the site of the scratch.

Breast Cancer: Axillary lymphadenopathy can be a sign of breast cancer, especially if there's a palpable mass or other symptoms like nipple discharge. Erythema might be seen in inflammatory breast cancer.
Infectious Causes (e.g., Staphylococcus aureus, Streptococcus pyogenes): Bacterial infections can cause lymphadenopathy and erythema, particularly if there's an abscess or cellulitis in the axillary region.
Lymphoma: Although less common, lymphoma can present with lymphadenopathy, and erythema might be seen if there's skin involvement.

Breast Abscess: An abscess in the breast tissue can cause axillary lymphadenopathy and significant erythema. It's crucial to diagnose and treat promptly to avoid complications.
Necrotizing Fasciitis: A severe infection that can cause erythema, swelling, and sometimes lymphadenopathy. It's a medical emergency requiring immediate attention.
Inflammatory Breast Cancer: A rare and aggressive form of breast cancer that presents with rapid onset of erythema, edema, and warmth of the breast skin, often without a distinct lump.

Kikuchi-Fujimoto Disease: A rare, self-limiting condition that causes lymphadenopathy, often in the neck but can be axillary, and might be accompanied by systemic symptoms.
Kimura Disease: A chronic inflammatory disorder that can cause lymphadenopathy and eosinophilia, more common in Asian males, and might present with erythema if there's skin involvement.
Silicone Implant-Related Lymphadenopathy: In individuals with silicone breast implants, lymphadenopathy can occur due to a reaction to the silicone, potentially accompanied by erythema if there's an associated infection or inflammation.