Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Benign fatty lesion (e.g., lipoma or fibrolipoma): The fact that the radiologist described the nodule as having "matured" over the past three years suggests a benign process. The location in the fat anterior to the psoas muscle and the small size of the nodule also support this diagnosis.
- Other Likely diagnoses
- Reactive lymph node: Although the nodule is small, it's possible that it represents a reactive lymph node, especially given its location near the surgical bed.
- Post-surgical scar or granuloma: The nodule's presence near the surgical site and its appearance shortly after the partial nephrectomy suggest that it could be related to the surgical procedure.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Metastatic lymph node: Although the primary tumor was small and low-stage (T1A), it's essential to consider the possibility of metastasis, especially given the history of chromophobe RCC.
- Recurrent RCC: The nodule's location near the surgical bed raises the possibility of local recurrence, although the small size and stable appearance over time make this less likely.
- Rare diagnoses
- Soft tissue sarcoma: Although rare, soft tissue sarcomas can occur in the retroperitoneum, and the nodule's location and appearance could be consistent with this diagnosis.
- Other rare benign tumors (e.g., schwannoma, neurofibroma): These tumors can occur in the retroperitoneum and may present as small, incidental nodules.