Dupuytren's Contracture: This condition is characterized by the formation of nodules and thickened tissue in the palmar fascia, leading to flexion contractures of the fingers. The presence of inflammatory nodules in the metacarpal region of the palms is a common presentation.

Palmar Psoriasis: Psoriasis can manifest as inflammatory plaques or nodules on the palms, among other areas. The metacarpal region can be involved, and the condition often accompanies psoriatic arthritis.
Eczema (Dyshidrotic or Palmoplantar): Eczema can cause inflammatory nodules and vesicles on the palms, including the metacarpal area. It's often associated with intense itching and can be triggered by various factors, including allergies and stress.
Sarcoidosis: Although less common, sarcoidosis can present with skin manifestations, including nodules on the palms. It's a systemic disease that can affect multiple organs, making it a consideration in the differential diagnosis.

Squamous Cell Carcinoma or Other Skin Cancers: While less likely, any nodule on the skin, especially in sun-exposed areas or areas with chronic inflammation, warrants consideration of skin cancer. Early detection is crucial for effective treatment.
Infectious Processes (e.g., Mycobacterial Infections): Certain infections, including those caused by mycobacteria, can present with skin nodules. These conditions can be serious and require specific treatments, making them important not to miss.

Multicentric Reticulohistiocytosis: A rare condition characterized by the development of skin nodules, including on the palms, and potential systemic involvement, including arthritis.
Gouty Tophi: In chronic gout, urate crystals can deposit in the skin, forming nodules called tophi. While more commonly found on the ears, elbows, and feet, they can occasionally appear on the palms.
Rheumatoid Nodules: Associated with rheumatoid arthritis, these nodules can appear on the skin, including the palms, but are more commonly found over bony prominences.