Synchronous Pure Epithelioid Angiomyolipoma of the Kidney and Retroperitoneal Schwannoma in the Same Patient on 18F-FDG PET/CT Imaging

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.

Lipid-Poor Renal Angiomyolipoma Mimicking Renal Cell Carcinoma on 68Ga-FAPI-04 PET/CT

ABSTRACT

FAPI PET/CT findings of renal tumors have been rarely reported. We describe 68Ga-FAPI-04 PET/CT findings in 1 case with lipid-poor renal angiomyolipoma and 1 case with high-grade clear cell renal cell carcinoma. Both tumors showed intense 68Ga-FAPI-04 uptake. These 2 cases indicate that lipid-poor renal angiomyolipoma should be included in the differential diagnosis of FAPI-avid renal tumors.

FDG PET/CT in a Case With Cellular Schwannoma of the Kidney

ABSTRACT

Schwannoma of the kidney is exceedingly rare. We describe contrast-enhanced CT and FDG PET/CT findings in a case with renal cellular schwannoma. Contrast-enhanced CT showed the enhancing tumor was located in the anterior middle portion of the left kidney, encasing the renal vessels and compressing the renal pelvis. The tumor showed inhomogeneous FDG uptake with SUVmax of 8.6 mimicking renal cell carcinoma. This case indicates renal schwannoma should be included in the differential diagnosis of FDG-avid renal lesions.

18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Response Assessment of Perivascular Epithelioid Cell Tumor of the Pelvic Cavity to Irinotecan and Temozolomide

Perivascular epithelioid cell tumors (PEComas) are a rare variety of mesenchymal tumors composed of distinctive cells that show a focal association with blood vessel walls and usually express melanocytic and smooth muscle markers. We present a case of 38-year-old male, diagnosed with PEComa of the pelvic cavity who underwent serial ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography scans for the assessment of response to the chemotherapeutic combination of irinotecan and temozolomide.

The role of (18)F-FDG PET/CT imaging in patient with malignant PEComa treated with mTOR inhibitor

Malignant perivascular epithelioid cell tumor (malignant PEComa) is a rare disease for which the diagnostic criteria and treatment options have not been established. Since PEComa is associated with upregulation of mammalian target of rapamycin (mTOR) pathway which controls Glut-1 (glucose transporter) function, increased ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake may indicate the over activation of mTOR pathway and may guide selectively inhibiting mTOR pathway treatment. We report a malignant PEComa patient who presented for ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) restaging. The tumor had shown significant avidity on PET/CT as well as an evident response to sirolimus (rapamycin, Rapamune™) that supports the utility of mTOR inhibitors as an effective treatment for malignant PEComa. Therefore, ¹⁸F-FDG PET/CT is helpful in restaging and guiding treatment for malignant PEComa with mTOR inhibitors.

Malignant renal epithelioid angiomyolipoma with liver metastasis after resection: a case report with multimodality imaging and review of the literature

Renal epithelioid angiomyolipoma (EAML) is a perivascular epithelioid cell tumor. Although the overwhelming majority of renal EAMLs are benign, cases of aggressive behavior and malignancy have been reported. Here, we report the case of a 62-year-old woman with a 12.5-cm renal EAML, who underwent resection and developed a 10.5-cm hepatic EAML 15 months after the surgery. Although multicentric disease is a possibility, the temporal course is consistent with metastasis from the poorly differentiated primary tumor. This is the only report with multimodality imaging to detail new metastatic disease during surveillance after intended curative resection of an EAML.

Molecular imaging of urogenital diseases

There is an expanding and exciting repertoire of PET imaging radiotracers for urogenital diseases, particularly in prostate cancer, renal cell cancer, and renal function. Prostate cancer is the most commonly diagnosed cancer in men. With growing therapeutic options for the treatment of metastatic and advanced prostate cancer, improved functional imaging of prostate cancer beyond the limitations of conventional CT and bone scan is becoming increasingly important for both clinical management and drug development. PET radiotracers, apart from ¹⁸F-FDG, for prostate cancer are ¹⁸F-sodium fluoride, ¹¹C-choline, and ¹⁸F-fluorocholine, and (¹¹C-acetate. Other emerging and promising PET radiotracers include a synthetic l-leucine amino acid analogue (anti-¹⁸F-fluorocyclobutane-1-carboxylic acid), dihydrotestosterone analogue (¹⁸F-fluoro-5α-dihydrotestosterone), and prostate-specific membrane antigen-based PET radiotracers (eg, N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-4-¹⁸F-fluorobenzyl-l-cysteine, ⁸⁹Zr-DFO-J591, and ⁶⁸Ga [HBED-CC]). Larger prospective and comparison trials of these PET radiotracers are needed to establish the role of PET/CT in prostate cancer. Although renal cell cancer imaging with FDG-PET/CT is available, it can be limited, especially for detection of the primary tumor. Improved renal cell cancer detection with carbonic anhydrase IX (CAIX)-based antibody (¹²⁴I-girentuximab) and radioimmunotherapy targeting with ¹⁷⁷Lu-cG250 appear promising. Evaluation of renal injury by imaging renal perfusion and function with novel PET radiotracers include p-¹⁸F-fluorohippurate, hippurate m-cyano-p-¹⁸F-fluorohippurate, and rubidium-82 chloride (typically used for myocardial perfusion imaging). Renal receptor imaging of the renal renin-angiotensin system with a variety of selective PET radioligands is also becoming available for clinical translation.