Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Benign fatty lesion (e.g., lipoma or fibrolipoma): The fact that the nodule has been present since one month after the partial nephrectomy and has "matured" over the past three years, as described by the radiologist, suggests a benign nature. Its small size and stable appearance over time also support this diagnosis.
- Other Likely diagnoses
- Reactive lymph node: Although the nodule is described as being in the fat anterior to the psoas muscle, it's possible that it represents a reactive lymph node, especially given its proximity to the surgical site. However, its stability over time makes this less likely.
- Post-surgical scar or granuloma: The nodule's presence since shortly after surgery could suggest a post-surgical scar or granuloma, which can sometimes appear as small nodules on imaging.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Metastatic disease (e.g., metastatic renal cell carcinoma to a lymph node): Although the primary tumor was small and of a favorable histology (chromophobe RCC), and the nodule has been stable, metastatic disease must always be considered, especially in a patient with a history of cancer. The fact that it was not present before surgery but appeared afterward could raise suspicion, despite its small size and stable nature.
- Rare diagnoses
- Soft tissue sarcoma: This would be an unusual occurrence, especially given the nodule's small size and stable appearance over time. However, sarcomas can occasionally present as small, slow-growing masses.
- Other rare benign tumors (e.g., schwannoma, neurofibroma): These could potentially present as small nodules in the fat anterior to the psoas muscle, but they would be less likely given the clinical context and the description provided.