Extrarenal Retroperitoneal Angiomyolipoma Mimicking Metastatic Melanoma: CT and FDG PET Correlation

68Ga-FAPI-04 PET/MRI in a Case of Tuberous Sclerosis Complex With Extrarenal Retroperitoneal Angiomyolipoma

ABSTRACT

Extrarenal retroperitoneal angiomyolipomas are rare benign tumors that may mimic other benign or malignant retroperitoneal tumors. We describe 68Ga-FAPI-04 PET/MRI findings in a case of tuberous sclerosis complex with an extrarenal retroperitoneal angiomyolipoma and multiple angiomyolipomas involving bilateral kidneys. The extrarenal retroperitoneal angiomyolipoma and most of the renal angiomyolipomas were 68Ga-FAPI-04-avid. One left renal angiomyolipoma with extensive hemorrhage and fibrosis had no significant 68Ga-FAPI-04 uptake. Angiomyolipoma should be included in the differential diagnosis of FAPI-avid renal or extrarenal retroperitoneal 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.

Unresectable hepatic PEComa: a rare malignancy treated with stereotactic body radiation therapy (SBRT) followed by complete resection

BACKGROUND

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors occurring in various anatomic regions. Although diagnostic criteria and treatment management are not established, current treatment options consist of surgery and chemotherapy including mTOR inhibitors. Stereotactic body radiation therapy (SBRT) is a non-invasive ablative treatment which has shown excellent control rates for more common types of unresectable liver tumors and metastases. In this report we present a rare case of PEComa of the liver that was treated by stereotactic radiotherapy followed by resection. Staging and evaluation of treatment response was done by FDG-PET/CT. This case highlights the potential of SBRT as a neoadjuvant treatment even for rare liver malignancies. It is the first case of liver PEComa treated by SBRT and resection.

CASE PRESENTATION

A 52-year-old woman presented at an external hospital with abdominal pressure and pain in the right upper abdominal quadrant. A CT scan showed a 700 cm3 liver lesion in segment IV. In repeated biopsy in July 2015 histopathological workup showed a pleomorphic epitheloid tumor with small to medium sized cells expressing vimentin and melan-A while being negative for cytokeratin establishing the diagnosis of PEComa of the liver. To achieve high, ablative doses a stereotactic body radiotherapy (SBRT) technique was chosen consisting of 60Gy (biologically effective dose 105Gy) in 8 fractions of 7.5Gy. Radiotherapy planning was based on MRI resulting in a planning target volume (PTV) of 1944 cm3. Treatment toxicity was limited to a slight elevation of transaminases (grade 1 and 3). A complete resection was performed 21 weeks after radiotherapy confirmed by negative surgical margins. At last follow-up 21 months after therapy, MRI showed neither local nor distant tumor recurrence. The patient was in stable condition (ECOG 1) and without late radiation toxicity.

CONCLUSIONS

This is the first documented case of liver PEComa treated by SBRT and resection. A favorable post-treatment course demonstrates that SBRT is a potential neoadjuvant treatment that is capable of reducing an inoperable rare liver tumor to a resectable lesion.

A Review of the Literature on Extrarenal Retroperitoneal Angiomyolipoma

BACKGROUND

Extrarenal retroperitoneal angiomyolipomas are rare.

AIM

To review the literature.

RESULTS

Angiomyolipomas, previously classified as hamartomas, are now classified as benign tumours. Thirty cases of primary retroperitoneal angiomyolipomas have been reported. Diagnosis of the disease upon is based radiological and pathological findings of triphasic features of (a) fat and (b) blood vessels and myoid tissue. Immunohistochemistry tends to be positive for HMB45, MART1, HHF35, calponin, NKI-C3, and CD117. The lesion is common in women. Treatment options have included the following: (a) radical surgical excision of the lesion with renal sparing surgery or radical nephrectomy in cases where malignant tumours could not be excluded and (b) selective embolization of the lesion alone or prior to surgical excision. One case of retroperitoneal angiomyolipoma was reported in a patient 15 years after undergoing radical nephrectomy for angiomyolipoma of kidney and two cases of distant metastases of angiomyolipoma have been reported following radical resection of the tumour.

CONCLUSIONS

With the report of two cases of metastases ensuing surgical resection of the primary lesions there is need for academic pathologists to debate and review angiomyolipomas to decide whether to reclassify angiomyolipomas as slow-growing malignant tumours or whether the reported cases of metastases were de novo tumours or metastatic lesions.

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.

Forty-three-year-old woman with mediastinal PEComa treated with chemoradiation therapy

The rarity of PEComa tumours has precluded any clinical trials, but surgery remains the most commonly reported treatment modality with just a few reports on treatment plans involving chemoradiation. We describe a patient with a mediastinal PEComa who presented with symptoms concerning for superior vena cava syndrome. She was deemed inoperable and was thus treated exclusively with chemoradiation therapy. The use of chemoradiation in the treatment of PEComa tumours is reviewed.

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.

Retroperitoneal angiomyolipoma: a case report and review of the literature

Retroperitoneal angiomyolipoma is a rare tumour that is difficult to diagnose preoperatively. We present a case of retroperitoneal angiomyolipoma that highlights its diagnostic dilemma. We also performed a literature review and present a review of retroperitoneal angiomyolipoma.