Differential Diagnosis for the 3mm Nodular Finding
- Single most likely diagnosis:
- Surgical clip or artifact: Given that the 3mm nodular finding has been present since 1 month after partial nephrectomy and has become more visible due to advancements in CT imaging (thinner slice thickness and higher resolution), it is most likely a benign finding related to the previous surgery, such as a surgical clip or an artifact from the surgical procedure.
- Other Likely diagnoses:
- Fibrotic change or scar tissue: This could be a result of the healing process following the partial nephrectomy, which over time could appear more defined on imaging due to the reasons mentioned (improved imaging techniques).
- Benign cyst or simple renal cyst: Although less likely given the description and location, small benign cysts could be considered, especially if the imaging characteristics are not fully indicative of a solid mass.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
- Metastasis or recurrence of chromophobe RCC: Although the primary tumor was small (T1a, 1.3 cm) and of a type (chromophobe RCC) that generally has a good prognosis, recurrence or metastasis, even years after the initial surgery, is a possibility that must be considered. The fact that the 1.5 cm mass in the perinephric space was biopsied and found to be benign (surgical changes) does not rule out the possibility of malignant changes in other areas.
- Lymph node metastasis: The location described (anterior to the psoas, caudal to the lower pole of the left kidney) could potentially be a lymph node, and although the size is small (3mm), any new or enlarging lymph node in a patient with a history of cancer warrants careful evaluation.
- Rare diagnoses:
- Other benign tumors (e.g., angiomyolipoma, oncocytoma): While these are less likely given the small size and the patient's history, they could be considered in the differential diagnosis, especially if the imaging characteristics are atypical for a simple cyst or scar tissue.
- Inflammatory or infectious processes: Although rare, given the patient's history of surgery, an inflammatory or infectious process could potentially present as a small nodular finding, especially if there has been any recent intervention or complication.