Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Benign fatty tissue or a small lymph node: The nodule's stability in size over three years, lack of growth, and definition without enlargement suggest a benign nature. Its location in the fat anterior to the psoas muscle and its small size are consistent with benign fatty tissue or a small, non-pathological lymph node.
- Other Likely diagnoses
- Fibrosis or scar tissue: Given the nodule's appearance post-surgery and its stable nature, it could represent a focus of fibrosis or scar tissue related to the surgical procedure.
- Small hematoma or seroma: Although less likely given the time frame, a small, resolved hematoma or seroma could present as a stable, small nodule.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Metastatic disease: Although the primary tumor was small and of a favorable histology (chromophobe RCC), the possibility of metastatic disease, however small, cannot be entirely excluded. Metastases can sometimes present as small, stable nodules.
- Local recurrence of RCC: Despite the favorable initial tumor characteristics and the absence of adverse features, local recurrence is a consideration, especially given the tumor's breakage during enucleation and the need for deeper margins.
- Rare diagnoses
- Other soft tissue tumors (e.g., lipoma, neurofibroma): While rare, other types of benign soft tissue tumors could present as small, stable nodules in this location.
- Inflammatory pseudotumor: This is a rare condition that could mimic a neoplasm on imaging but is actually an inflammatory process. It is less likely given the stable nature of the nodule but should be considered in the differential diagnosis of a small, unchanging mass.