Differential Diagnosis for the 3mm Nodule
- Single most likely diagnosis
- Local recurrence of chromophobe RCC: This is considered the most likely diagnosis given the history of partial nephrectomy for chromophobe RCC and the appearance of a new nodule in the vicinity of the previous surgical site. The fact that the nodule has "matured" and become solid over time, as described by the radiologist, supports this possibility.
- Other Likely diagnoses
- Benign fatty lesion (e.g., lipoma): The location of the nodule in the fat anterior to the psoas muscle could suggest a benign fatty lesion. However, the description of the nodule becoming solid over time makes this less likely.
- Inflammatory or reactive lymph node: Although less common, it's possible that the nodule represents an inflammatory or reactive lymph node, especially given its small size and location.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Metastasis from another primary malignancy: Although the patient has a history of RCC, it's essential to consider the possibility of metastasis from another primary malignancy, given the potential for second primary tumors.
- Lymphoma: Lymphoma can present as a small nodule in the retroperitoneum, and it's crucial to consider this diagnosis to avoid delayed treatment.
- Rare diagnoses
- Soft tissue sarcoma: Although rare, soft tissue sarcomas can occur in the retroperitoneum, and this diagnosis should be considered, especially if the nodule exhibits aggressive features or rapid growth.
- Neurogenic tumor (e.g., schwannoma, neurofibroma): The location of the nodule near the psoas muscle and the fact that it has become solid over time could suggest a neurogenic tumor, although this is a less common possibility.