Differential Diagnosis for a 3mm Nodular Lesion
Single Most Likely Diagnosis
- Suture granuloma: This is a common finding after surgical procedures, including partial nephrectomy. The fact that it has not grown over 3 years and was described as having "matured" supports this diagnosis, as suture granulomas can form around sutures used in surgery and may stabilize in size over time.
Other Likely Diagnoses
- Lipoma: A benign tumor composed of fat tissue, which could explain its location in the fat anterior to the psoas muscle and its stable size over time.
- Hematoma: Although less likely given the time frame and stability of the lesion, a small, organized hematoma from the surgery could present as a nodular lesion.
- Fibrosis: Post-surgical fibrosis could also appear as a nodular lesion, especially in the context of a recent surgical intervention like partial nephrectomy.
Do Not Miss Diagnoses
- Metastasis: Although the stability of the lesion over 3 years makes this less likely, it is crucial not to miss a potential metastatic deposit from a primary malignancy, especially given the recent history of partial nephrectomy, which implies the patient had a kidney tumor.
- Recurrence of primary tumor: Similar to metastasis, recurrence of the primary kidney tumor in the form of a local implant or metastasis to the fat anterior to the psoas muscle is a critical diagnosis not to miss.
Rare Diagnoses
- Desmoid tumor: A rare, benign but locally aggressive tumor that could occur in this location, although it would be unusual for it to remain stable in size for 3 years.
- Soft tissue sarcoma: Extremely rare and unlikely given the small size and stability of the lesion, but it remains a consideration in the differential diagnosis of a nodular lesion in the soft tissues.
- Foreign body reaction: While possible, this would be less common and might be expected to cause more symptoms or changes over time, especially if the reaction was significant enough to form a palpable or visible nodule.