Renal epithelioid angiomyolipoma: computed tomography manifestation and radiologic-pathologic correlation depending on different epithelioid component percentages

Elevated 18F-FDG accumulation in a malignant epithelioid angiomyolipoma: a case report and review of literature

Epithelioid angiomyolipoma (EAML) is a tumor with malignant potential, as evidenced by its pathological features. Further investigation into its additional characteristics, particularly in imaging, is of great significance for non-invasive detection methods to understand its malignant potential. In this context, we present a case study of a 47-year-old male patient with a right renal EAML. The patient underwent nephrectomy but subsequently developed liver metastasis. Next-generation sequencing confirmed mutations of tuberous sclerosis 2 (TSC2) in both the primary and metastatic lesions. Consequently, the patient received maintenance treatment with the mTOR inhibitor, everolimus. However, treatment was discontinued after six months due to disease progression. Subsequent 18F-FDG PET/CT imaging revealed a large heterogeneous hypermetabolic mass in the liver, along with two other hypermetabolic metastases near the liver capsule. The patient's prognosis was poor, with indicators such as TSC2 mutation, tumor necrosis, high Ki-67 expression, and α-SMA-negative fibroblasts. Despite reoperation, the patient still succumbed to disease progression. The occurrence of malignant metastatic EAML detected using 18F-FDG PET/CT imaging is infrequent. We conducted a comprehensive review of the relevant literature on 18F-FDG PET/CT imaging for EAML. Notably, this article emphasizes that elevated 18F-FDG uptake in EAML may serve as a novel indicator of malignant EAML.

Primary renal malignant epithelioid angiomyolipoma with distant metastasis: a case report and literature review

Epithelioid angiomyolipoma (EAML) is a rare type of mesenchymal angiomyolipoma with potential malignancy in the kidney that can cause lymph node metastases, local recurrence, and distant metastases. Herein, we describe a case of EAML in the right kidney of a 51-year-old man who was admitted to the hospital with a right abdominal mass. Computed tomography revealed a heterogeneously enhanced mass with blurred margins, which was considered a malignant tumor. A radical nephrectomy was then performed. Two years later, the patient developed liver metastases from EAML and was administered sintilimab combined with bevacizumab. The patient survived after 6 months of follow-up. Histologically, the tumors showed clear boundaries and no obvious capsules. The tumor tissue mainly consisted of epithelioid tumor cells, thick-walled blood vessels, and a small amount of adipose tissue. Tumor cells with lipid vacuoles and acinar areas were large, round, polygonal, eosinophilic, or transparent in the cytoplasm. The enlarged and hyperchromatic nuclei were accompanied by distinct nucleoli and pathological mitosis. These histopathological findings resembled those of renal cell carcinoma, and immunohistochemical analysis was performed. The tumor cells were diffusely positive for HMB45, Melan-A, CK20, vimentin antibodies, and TFE3, suggesting that the tumor originated from perivascular epithelioid cells, excluding renal cell carcinoma. The Ki-67 index was 10%. These histopathological features were observed in liver mass puncture tissues. We also summarized 46 cases of EAML with distant metastasis and explored the clinicopathological features of EAML to improve the treatment of the disease. EAML is often ignored in the clinical setting, leading to metastasis and recurrence. Therefore, EAMLs require long-term follow-up, and timely detection of recurrent disease can improve the prognosis.

Differentiating renal epithelioid angiomyolipoma from clear cell carcinoma: using a radiomics model combined with CT imaging characteristics

PURPOSE

This study aims to assess the computed tomography (CT) findings of renal epithelioid angiomyolipoma (EAML) and develop a radiomics-based model for differentiating EAMLs and clear cell renal cell carcinomas (RCCs).

METHOD

This two-center retrospective study included 28 histologically confirmed EAMLs and 56 size-matched clear cell RCCs with preoperative three-phase kidney CTs. We conducted subjective image analysis to determine the CT parameters that can distinguish EAMLs from clear cell RCCs. Training and test sets were divided by chronological order of CT scans, and radiomics model was built using ten selected features among radiomics and CT features. The diagnostic performance of the radiomics model was compared with that of the three radiologists using the area under the receiver-operating characteristic curve (AUC).

RESULTS

The mean size of the EAMLs was 6.2 ± 5.0 cm. On multivariate analysis, a snowman or ice cream cone tumor shape (OR 16.3; 95% CI 1.7-156.9, P = 0.02) and lower tumor-to-cortex (TOC) enhancement ratio in the corticomedullary phase (OR 33.4; 95% CI 5.7-197, P < 0.001) were significant independent factors for identifying EAMLs. The diagnostic performance of the radiomics model (AUC 0.89) was similar to those of genitourinary radiologists (AUC 0.78 and 0.81, P > 0.05) and superior to that of a third-year resident (AUC 0.63, P = 0.04).

CONCLUSIONS

A snowman or ice cream cone shape and lower TOC ratio were more closely associated with EAMLs than with clear cell RCCs. A CT radiomics model was useful for differentiating EAMLs from clear cell RCCs with better diagnostic performance than an inexperienced radiologist.