Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Benign fatty lesion or a small lipoma: 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 could represent a reactive lymph node, especially given its location near the surgical site. However, the lack of significant change in size over three years makes this less likely.
- Small hematoma or seroma: Given the history of recent surgery, a small hematoma or seroma could be considered, although the fact that it has been present for three years without change makes this less likely.
- 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), and the nodule has been stable for three years, it is essential to consider the possibility of a metastatic lymph node, especially given the history of chromophobe RCC. However, the small size and stability of the nodule make this less likely.
- Recurrent RCC: Similarly, while the primary tumor was completely resected, there is always a risk of recurrence, and a new nodule in the vicinity of the surgical site should prompt consideration of this possibility.
- Rare diagnoses
- Soft tissue sarcoma: Although extremely rare, a soft tissue sarcoma could present as a small nodule in the fat. The lack of growth or change over three years makes this unlikely, but it should be considered in the differential diagnosis.
- Other rare benign lesions (e.g., schwannoma, neurofibroma): These lesions are rare and would be unusual in this location, but could be considered in the differential diagnosis if other possibilities are ruled out.