A 66-year-old man with a brain mass, heavy smoking history, polycythemia, hypercalcemia, and microscopic hematuria has immunostaining positive for EMA and negative for CEA. Which organ is the most likely site of the primary neoplasm?

A 66-year-old man with a brain mass, heavy smoking history, polycythemia, hypercalcemia, and microscopic hematuria has immunostaining positive for EMA and negative for CEA. Which organ is the most likely site of the primary neoplasm?

• A. Lung
• B. Kidney
• C. Brain
• D. Liver

Answer: (B)

Paraneoplastic findings and a bleeding symptom can reveal the organ of origin even when metastases are present. Renal cell carcinoma commonly produces erythropoietin, leading to polycythemia, and can cause hypercalcemia. Hematuria is a classic presenting feature of a renal mass. A brain mass in an older patient with these systemic clues often represents metastasis from a kidney primary rather than a primary brain tumor. Immunostaining helps narrow the origin. EMA positivity supports an epithelial tumor, which is consistent with renal cell carcinoma, while CEA is more typical of colorectal and other GI or some lung adenocarcinomas; its absence argues against those primaries. Put together, the combination of polycythemia, hypercalcemia, hematuria, and the staining pattern points to the kidney as the most likely site of the primary neoplasm.

Paraneoplastic findings and a bleeding symptom can reveal the organ of origin even when metastases are present. Renal cell carcinoma commonly produces erythropoietin, leading to polycythemia, and can cause hypercalcemia. Hematuria is a classic presenting feature of a renal mass. A brain mass in an older patient with these systemic clues often represents metastasis from a kidney primary rather than a primary brain tumor.

Immunostaining helps narrow the origin. EMA positivity supports an epithelial tumor, which is consistent with renal cell carcinoma, while CEA is more typical of colorectal and other GI or some lung adenocarcinomas; its absence argues against those primaries. Put together, the combination of polycythemia, hypercalcemia, hematuria, and the staining pattern points to the kidney as the most likely site of the primary neoplasm.