Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Fibrotic or inflammatory nodule: Given that the nodule has been present since one month after partial nephrectomy and has "matured" over three years, it is likely a benign process related to the surgical site, such as a fibrotic or inflammatory reaction.
- Other Likely diagnoses
- Suture granuloma: A small nodule in the fat anterior to the psoas muscle, appearing after surgery, could be a suture granuloma, which is a benign reaction to suture material.
- Hematoma or seroma: Although less likely given the time frame, a small hematoma or seroma could have evolved into a fibrotic nodule over time.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Local recurrence of chromophobe RCC: Although the primary tumor was small (1.3 cm) and of low stage (T1A) with no adverse features, the possibility of local recurrence cannot be entirely excluded, especially given the nodule's location near the surgical site.
- Metastasis: Extremely unlikely given the small size of the primary tumor and the lack of other metastatic sites, but metastasis to the fat or soft tissues, although rare, is a consideration that should not be missed.
- Rare diagnoses
- Soft tissue sarcoma: Very rare, but a new soft tissue mass in the vicinity of a previous surgical site could potentially be a soft tissue sarcoma, which would have significant implications for treatment and prognosis.
- Other rare benign tumors: Such as lipomas, neurofibromas, or other soft tissue tumors, which are less likely but could be considered in the differential diagnosis of a small nodule in the fat anterior to the psoas muscle.