Differential Diagnosis for the 3 mm Nodule
- Single most likely diagnosis
- Post-surgical change or scar: This diagnosis is likely due to the nodule's appearance after surgery and its evolution over time, becoming more defined and solid in texture. The radiologist's experience and review of prior scans support this diagnosis.
- Other Likely diagnoses
- Benign fat necrosis: Similar to the biopsy result of the 1.5 cm soft tissue mass, the 3 mm nodule could be a result of benign fat necrosis, which can occur after surgery.
- Reactive lymph node or inflammatory change: Although no adenopathy is reported, a small reactive lymph node or inflammatory change in the fat anterior to the psoas muscle could be a possible explanation for the nodule.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Recurrent chromophobe RCC: Despite the low likelihood, given the patient's history of RCC, it is essential to consider the possibility of recurrence, especially since the nodule appeared after surgery and has evolved over time.
- Metastasis from another primary cancer: Although the patient's scans have been clear, and no other primary cancer is mentioned, it is crucial to consider the possibility of metastasis from an unknown or undiagnosed primary cancer.
- Rare diagnoses
- Soft tissue sarcoma: Although rare, a soft tissue sarcoma could present as a small nodule in the fat anterior to the psoas muscle.
- Other rare benign tumors (e.g., lipoma, hemangioma): These tumors are unlikely but could be considered in the differential diagnosis, especially if the nodule's characteristics are atypical for post-surgical changes or other likely diagnoses.