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
- Post-surgical scar or granuloma: Given the nodule's proximity to the surgical site and its appearance one month after partial nephrectomy, it is possible that the nodule represents a post-surgical reaction.
- Lymph node: Although the size of the nodule is small, it could potentially represent a lymph node, especially given its location near the kidney.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Metastasis: Although the primary tumor was small and had favorable histology (chromophobe RCC), it is essential to consider the possibility of metastasis, especially given the new appearance of the nodule after surgery.
- Recurrence of RCC: Similarly, recurrence of the primary tumor must be considered, although the location of the nodule in the fat anterior to the psoas muscle makes this less likely.
- Rare diagnoses
- Soft tissue sarcoma: This is a rare possibility, but it must be considered in the differential diagnosis of a new soft tissue mass.
- Other rare benign tumors (e.g., schwannoma, neurofibroma): These tumors are uncommon, but they could potentially present as a small nodule in the fat anterior to the psoas muscle.