Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Fat necrosis or a benign fatty lesion: This is the most likely diagnosis given the patient's history of partial nephrectomy and the presence of a similar benign lesion (fat necrosis with mild chronic inflammation and fibrosis) in the paranephric space. The nodule's small size, location in the fat anterior to the psoas muscle, and stability over time also support this diagnosis.
- Other Likely diagnoses
- Post-surgical scar or granuloma: The nodule's appearance one month after partial nephrectomy and its subsequent maturation over time could be consistent with a post-surgical scar or granuloma.
- Benign lymph node or lymph node hyperplasia: Although no lymph nodes were submitted during the initial surgery, it is possible that the nodule represents a benign lymph node or lymph node hyperplasia.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
- Recurrent chromophobe RCC: Although the patient's previous tumor was stage T1A with no sarcomatoid features or necrosis, and the 2023 and 2024 surveillance scans were negative, it is essential to consider the possibility of recurrent RCC, especially given the nodule's location near the surgical bed.
- Metastatic disease: Although the patient's previous cancer was stage T1A, it is crucial to consider the possibility of metastatic disease, especially if the nodule exhibits suspicious features or grows over time.
- Rare diagnoses
- Soft tissue tumor (e.g., lipoma, liposarcoma): Although rare, it is possible that the nodule represents a primary soft tissue tumor, such as a lipoma or liposarcoma.
- Vascular lesion (e.g., hemangioma): The nodule could potentially represent a vascular lesion, such as a hemangioma, although this is less likely given the patient's history and the nodule's appearance.