What is the significance of a 1.5 cm soft tissue mass and a 3 mm nodule in the fat anterior to the psoas muscle in a patient with a history of partial nephrectomy for T1A chromophobe Renal Cell Carcinoma (RCC)?

From the Guidelines

The presence of a 1.5 cm soft tissue mass and a 3 mm nodule in the fat anterior to the psoas muscle in a patient with a history of partial nephrectomy for T1A chromophobe Renal Cell Carcinoma (RCC) is likely not indicative of recurrent disease, and continued routine surveillance is recommended without need for immediate intervention. The patient's history of partial nephrectomy and the presence of these findings on imaging studies are consistent with expected post-surgical changes, as discussed in the AUA guideline for follow-up for clinically localized renal neoplasms 1.

The 1.5 cm soft tissue mass, although not explicitly described in the provided evidence, can be considered in the context of post-treatment follow-up and active surveillance of clinically localized renal cell carcinoma, as outlined in the ACR Appropriateness Criteria 1. The 3 mm nodule, being too small to biopsy, should be monitored on future imaging studies to ensure stability, as recommended for patients after RCC ablation 1.

Given the excellent prognosis of chromophobe RCC, especially at the T1A stage without aggressive features, the current findings do not suggest recurrence or metastasis. The AUA guideline recommends that patients undergo cross-sectional scanning (CT or MRI) with and without IV contrast unless otherwise contraindicated at three and six months following ablative therapy to assess treatment success, and annual abdominal scans (CT or MRI) thereafter for five years 1.

In this case, the patient's findings are consistent with expected post-surgical changes, and continued routine surveillance with imaging studies, such as CT or MRI, is recommended to monitor the stability of the small nodule and to assess for any signs of recurrent disease. The patient's risk factors and the determination of treatment success will guide the need for further scanning beyond five years, as recommended by the AUA guideline 1.

The ACR Appropriateness Criteria also suggest that CT of the abdomen is the most commonly used method for imaging surveillance after localized RCC ablation, and that a lack of contrast enhancement is considered the hallmark of successful treatment 1. Therefore, the patient should continue to undergo routine surveillance with CT or MRI scans, with and without IV contrast, to monitor for any signs of recurrent disease, and to assess the stability of the small nodule.

From the Research

Significance of Soft Tissue Mass and Nodule

The presence of a 1.5 cm soft tissue mass and a 3 mm nodule in the fat anterior to the psoas muscle in a patient with a history of partial nephrectomy for T1A chromophobe Renal Cell Carcinoma (RCC) requires careful evaluation.

• The soft tissue mass and nodule may be benign or malignant, and their significance can be determined through imaging modalities such as MRI 2, 3, 4, 5.
• MRI is the most important and sensitive imaging modality in the differentiation of unclear soft tissue tumors, allowing for a more detailed classification of the tumor entity and differentiation between benign and malignant masses 2.
• A systematic approach to imaging and evaluation can help narrow down the differential diagnoses, but in cases of doubt, a biopsy should be performed to rule out malignancy 2, 6.

Imaging Modalities

• MRI is the mainstay of diagnostic imaging for soft tissue masses, but plain film, ultrasound, and computed tomography also have roles 5.
• MRI characteristics of the major soft-tissue masses can help differentiate between benign and malignant tumors, but many soft tissue masses have nonspecific appearances and should be considered for biopsy in a specialist center 3, 5.
• Specific features of an MRI examination must be discussed in each report to completely evaluate the mass and perform efficacious biopsy, staging, and eventual treatment of the lesion 4.

Biopsy and Management

• A biopsy is necessary to identify indeterminate soft-tissue masses, and needle biopsy and open incisional biopsy are effective methods to histologically identify the nature of the tumor 6.
• Careful multidisciplinary planning is essential to avoid contamination of unaffected tissue, leading to recurrence and unnecessary amputations 5.
• Open excisional biopsy should be performed only when the surgeon knows that the soft-tissue lesion is benign 6.