Clear Cell Adenocarcinoma of the Lung Mimicking Clear Cell Renal Cell Carcinoma.

We present an unusual manifestation of a malignancy in a 61-year-old female who presented clinically and cytologically with what appeared to be clear cell renal cell carcinoma, but was found with immunohistochemistry to be clear cell adenocarcinoma of the lung. The patient presented with CT imaging demonstrating a mass in the left kidney, and cytologically, the tumor cells had high nuclear grade and clear cytoplasm. However, immunohistochemically, a positive TTF-1 nuclear stain and CK7+/CK20- profile demonstrated that these cells were of lung primary. The patient did not respond to a round of carboplatin and pemetrexed, and the patient was discharged to a hospice for pain management and palliative care.