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 appearance of a new 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 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.