Differential Diagnosis for Renal Mass with Elevated Kappa Free Light Chains
Single Most Likely Diagnosis
- Multiple Myeloma with Renal Plasmacytoma: The presence of a renal mass in conjunction with elevated kappa free light chains strongly suggests multiple myeloma with a renal plasmacytoma. Plasmacytomas are discrete, solitary masses of neoplastic plasma cells that can occur in various tissues, including the kidney.
Other Likely Diagnoses
- Renal Cell Carcinoma: Although less likely given the context of elevated kappa free light chains, renal cell carcinoma (RCC) is a common cause of renal masses and should be considered, especially if the mass has characteristics concerning for malignancy.
- Lymphoma Involving the Kidney: Lymphoma can involve the kidney and present as a mass, and the elevated kappa free light chains could be related to a lymphoproliferative disorder.
Do Not Miss Diagnoses
- Renal Abscess or Infection: Although the description does not strongly suggest an infectious process, it's crucial not to miss a renal abscess or severe infection, which could present with a complex mass and would require urgent treatment.
- Metastatic Disease to the Kidney: Metastases to the kidney from other primary cancers can present as renal masses and are important to consider, especially in patients with a known history of cancer.
Rare Diagnoses
- Amyloidosis: While amyloidosis can involve the kidney and cause abnormalities, it is less likely to present as a discrete mass and more commonly causes nephrotic syndrome or renal failure.
- Renal Leiomyoma or Other Benign Tumors: Benign tumors of the kidney, such as leiomyomas, are rare and could present as a renal mass but are less likely given the clinical context of elevated kappa free light chains.