Widespread metastases from sarcomatoid renal cell carcinoma detected by 18F-FDG positron emission tomography/computed tomography

68 Ga-FAPI-04 PET/CT in a Small Sarcomatoid Renal Cell Carcinoma With Widespread Metastases

ABSTRACT

Sarcomatoid renal cell carcinoma is an uncommon high-grade malignancy with poor prognosis. We describe 68 Ga-FAPI-04 PET/CT findings in a patient with a small (1.8 cm in the maximum diameter) sarcomatoid clear cell renal cell carcinoma with widespread metastatic disease. Both the primary renal tumor and its metastases in bones, lymph nodes, adrenals, and liver showed increased 68 Ga-FAPI-04 uptake. The primary renal tumor showed hypovascularity on contrast-enhanced CT, mimicking papillary renal cell carcinoma. This case indicates FAPI PET/CT may be useful for detecting and staging of this unusual malignancy.

Skeletal Muscle Metastasis From Renal Cell Carcinoma: A Case Series and Literature Review

Objectives

Skeletal muscle metastasis (SMM) from renal cell carcinoma (RCC) has been rarely reported. This case series was performed to increase the clinicians' understanding of its clinical features and treatments.

Methods

We evaluated the clinical presentations, diagnoses, and treatments of 2 patients with SMM from RCC in our hospital and 39 cases reported in the literature.

Results

Among the 41 patients, 4 (9.76%) were women and 37 (90.24%) were all men. The average age was 60.5 ± 12.6 years old (range from 7 to 81). The size of tumors varied from 1 to 28 cm, and the metastatic sites of 6 (14.63%) cases were in the heads, 20 (48.78%) in the limbs, 9 (21.95%) in the trunks, 3 (7.32%) in the buttock, and the other 3 (7.32%) were multiple sites. The mean of intervals between the RCC and the discovery of the first SMM was 73.61 months. More than half of the patients (25, 60.98%) were diagnosed by MRI and 25 (60.98%) patients performed a biopsy of the mass to establish the diagnosis. Finally, 30 (73.17%) cases performed mass excision. Then the adjuvant therapy was performed in 18 patients including immunotherapy, radiotherapy, chemotherapy, and targeted therapy. The median follow-up after SMM was 9 months (P25, P75: 5, 23), in which the longest survival time of patients with SMM of RCC was 8 years while the shortest was only 3 months.

Conclusion

The characteristic clinical feature of SMM from RCC is asymptomatic masses or swelling with a long history which can be preoperative suspiciously diagnosed by MRI. The rapid biopsy of suspected lesions, determination of other metastasis sites, resection of metastasis, and systematic treatment are the recommended treatments of it.

Sarcomatoid renal cell carcinoma: biology, natural history and management

Sarcomatoid dedifferentiation is an uncommon feature that can occur in most histological subtypes of renal cell carcinomas (RCCs) and carries a decidedly poor prognosis. Historically, conventional treatments for sarcomatoid RCCs (sRCCs) have shown little efficacy, and median survival is commonly 6–13 months. Despite being first described in 1968, the mechanisms driving sarcomatoid dedifferentiation remain poorly understood, and information and treatment options available to physicians and patients are limited. When diagnosed at an early stage, surgical intervention remains the treatment of choice. However, preoperative identification through routine imaging or biopsy is unreliable and most patients present with advanced disease and systemic symptoms. For these patients, the role of cytoreductive nephrectomy is disputed. The expansion of immunotherapies approved for RCCs has generated a search for biomarkers that might be indicative of treatment response in sRCCs, although a proven effective systemic agent remains elusive. PDL1 expression is increased in sarcomatoid dedifferentiated renal tumours, which suggests that patients with sRCCs could benefit from PD1 and/or PDL1 immune checkpoint blockade therapy. Treatment outcomes for sarcomatoid tumours have remained relatively consistent compared with other RCCs, but further investigation of the tumour–immune cell microenvironment might yield insights into further therapeutic possibilities.

In this Review, Blum et al. summarize the current knowledge on sarcomatoid renal cell carcinoma, a diagnosis characterized by the presence of sarcomatoid dedifferentiation and a poor prognosis. They discuss the origin, presentation, molecular biology and treatment of this disease.

Sarcomatoid dedifferentiation is not considered to be a unique histological subtype of renal cell carcinomas (RCCs); rather, it can be present within any subtype of RCCs.

Sarcomatoid dedifferentiation appears in ~4% of all RCCs, but is present in ~20% of all metastatic RCCs. According to WHO guidelines, any RCC with sarcomatoid dedifferentiation is a WHO–International Society of Urological Pathology grade 4 lesion.

Sarcomatoid dedifferentiation is often heterogeneously present within RCCs, making routine imaging and biopsy unreliable for preoperative detection. Surgical resection for localized disease is the standard of care, with subsequent close monitoring of patients following surgery.

In patients with metastatic disease, conventional therapies such as surgery and systemic agents have been ineffective and overall 5-year survival remains at 23.5–33%.

Previous genomic analyses have failed to identify definitive mutational drivers of disease. However, sarcomatoid RCCs (sRCCs) have been shown to have higher PD1 and PDL1 expression than other subtypes of RCCs. Newer combinations of immune checkpoint inhibitor immunotherapies could yield improved responses and outcomes.

Studies investigating sRCCs are limited by patient numbers owing to the low incidence of sRCCs and their advanced stage at presentation. Multi-institutional efforts to establish a consensus on treatment recommendations based on highly powered data are essential.

FDG PET/CT and CT Findings of Renal Cell Carcinoma With Sarcomatoid Differentiation

OBJECTIVE. The purpose of this article is to investigate the value of ¹⁸F-FDG PET/CT and enhanced CT in the diagnosis of renal cell carcinoma (RCC) with sarcomatoid differentiation and the differential diagnosis of clear cell renal cell carcinoma (ccRCC). MATERIALS AND METHODS. Among patients with renal tumors confirmed by pathologic examination from September 2010 to August 2019, 29 patients with RCC with sarcomatoid differentiation and 82 patients with ccRCC who underwent FDG PET/CT, renal contrast-enhanced CT examination, or both, before surgery were studied. Features of the two groups on CT and PET/CT were retrospectively reviewed. RESULTS. The tumor size of RCC with sarcomatoid differentiation was larger than that of ccRCC (p = 0.0086). Cystic necrosis, peritumoral neovascularity, and metastasis were more common in RCC with sarcomatoid differentiation (p = 0.0052, p = 0.0008, p < 0.0001, respectively). The ratio of necrotic area to tumor diameter of RCC with sarcomatoid differentiation was statistically significantly larger than that of ccRCC (p = 0.0032). Three cases of RCC with sarcomatoid differentiation showed a large central necrotic area and dense intratu-moral neovascularity in the surrounding parenchyma, defined as the ring-of-fire sign, which was not found in ccRCC. The maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), and peak standardized uptake value (SUV_peak) of RCC with sarcomatoid differentiation were statistically significantly higher than those for ccRCC (all p < 0.0001), and the SUV_max, SUV_mean, and SUV_peak cutoff values of 5.4, 4.2, and 5.0, respectively, were helpful for discrimination. CONCLUSION. Imaging features including higher SUV_max, SUV_mean, and SUV_peak; a larger ratio of necrotic area to tumor diameter; the presence of peritumoral neovascularity; and metastasis are more commonly associated with RCC with sarcomatoid differentiation than with ccRCC. The ring-of-fire sign and SUV_max, SUV_mean, SUV_peak cutoff values of 5.4, 4.2, 5.0, respectively, may be helpful to indicate RCC with sarcomatoid differentiation.

Extensive Metastatic Sarcomatoid Renal Cell Carcinoma Evaluated by 18F-FDG PET/CT: a Case Report and Review of Literature

Sarcomatoid renal cell carcinoma (sRCC) is a highly aggressive form of dedifferentiated renal cell carcinoma. We report a 62-year-old man who presented with respiratory symptoms and a lung mass on chest computed tomography (CT). The patient underwent positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and was found to have extensive metastatic disease. Based on the history and imaging findings, there were possible primary malignancies, including bronchogenic carcinoma, melanoma, or an aggressive lymphoma. An excisional biopsy surprisingly revealed a high-grade sarcomatoid carcinoma with no evidence of differentiation, and immunohistochemical (IHC) studies showed that the tumor cells were positive for markers of genitourinary origin (PAX-8 and vimentin). The histologic and IHC results, along with multiple FDG-avid exophytic lesions in both kidneys, were considered diagnostic of sRCC. Here we have highlighted the potential role of ¹⁸F-FDG-PET-CT in patients with sRCC, discussed the diagnostic challenges, and presented a brief review.

Skeletal Muscle Metastasis from Renal Cell Carcinoma: 21 cases and review of the literature

OBJECTIVES

This study aimed to raise radiologists' awareness of skeletal muscle metastases (SMM) in renal cell carcinoma (RCC) cases and to clarify their imaging appearance.

METHODS

A retrospective analysis was undertaken of 21 patients between 44-75 years old with 72 SMM treated from January 1990 to May 2009 at the MD Anderson Cancer Center in Houston, Texas, USA. Additionally, 37 patients with 44 SMM from a literature review were analysed.

RESULTS

Among the 21 patients, the majority of SMM were asymptomatic and detected via computed tomography (CT). Mean metastasis size was 18.3 mm and the most common site was the trunk muscles (83.3%). The interval between discovery of the primary tumour and metastasis detection ranged up to 234 months. Peripheral enhancement (47.1%) was the most common post-contrast CT pattern and non-contrasted CT lesions were often isodense. Magnetic resonance imaging (MRI) characteristics were varied. Five lesions with available T1-weighted pre-contrast images were hyperintense to the surrounding muscle. Other organ metastases were present in 20 patients. Of the 44 SMM reported in the literature, the majority were symptomatic. Average metastasis size was 53.4 mm and only 20.5% of SMM were in trunk muscles. The average interval between tumour discovery and metastasis detection was 101 months. Other organ metastases were recorded in 17 out of 29 patients.

CONCLUSION

SMM should always be considered in patients with RCC, even well after primary treatment. SMM from RCC may be invisible on CT without intravenous contrast; contrast-enhanced studies are therefore recommended. SMM are often hyperintense to the surrounding muscle on T1-weighted MRI scans.

A Bizarre, Unexplained, and Progressive External Rotation of the Shoulder as a Presentation of a Metastatic Deposit in the Rotator Cuff

We describe the first reported case of a tumour deposit within the rotator cuff presenting as a bizarre, progressive, and fixed external rotation deformity of the shoulder. It is also the first reported case to our knowledge of an oesophageal primary metastasising to the rotator cuff.

PET/CT imaging of skeletal muscle metastases

BACKGROUND

Skeletal muscle metastases (SMM) are very rare because of complex resistance of the musculature to metastatic invasion. Previously, positron emission tomography (PET) imaging of SMM has been reported only in few reports. A systematic analysis of SMM features in PET/CT has not been performed before.

PURPOSE

To study PET/CT findings of SMM in a larger group of patients with known malignancies and to determine PET/CT patterns of SMM in different primary tumors.

MATERIAL AND METHODS

Between January 2009 and December 2011 581 patients with lung cancer were investigated by PET with 18 F-fluordeoxyglucose (FDG PET) and computed tomography (CT) at the Center of Fusion Imaging, Halle. In five patients SMM were identified. Furthermore, PubMed database was screened for muscle metastases. Only articles containing SUV of SMM were considered in the study. Twenty-one articles with 33 patients could be included in this meta-analysis from the literature.

RESULTS

At our center the prevalence of SMM was 0.9%. Our analysis comprised 38 patients with 67 muscle metastases. All identified SMM presented as intramuscular focal abnormal activity with SUV ranging from 2.4 to 25.9, median SUV 7.8. The median size of the muscle metastases was 2.5 cm (range, 0.6-6.5 cm). There were no significant differences between SUV and size of SMM arising from lung cancer, renal cell carcinoma, and esophageal cancer. Also, there was no correlation between SUV and size of SMM (r = 0.101, P = 0.558) and between SUV of SMM and primary tumors (r = 0.138, P = 0.686). In nine (23.7%) of the 38 patients, the identified SMM were isolated distant metastases or isolated tumor recurrence.

CONCLUSION

SMM manifested on PET/CT as focal hypermetabolic intramuscular areas with different SUV. There were no significant differences between SUV or size of the identified SMM in esophageal cancer, renal cell carcinoma, and lung cancer.

Spectrum of malignant renal and urinary bladder tumors on 18F-FDG PET/CT: a pictorial essay

A wide variety of malignant renal and urinary bladder diseases can be detected on (18)F-FDG PET/CT. Although the PET/CT findings are often nonspecific, the aim of this atlas was to demonstrate that the spectrum of renal and urinary bladder malignancy that can be evaluated with PET/CT is much broader than current medical literature would suggest. PET/CT readers and oncologists should be aware of the variety of urological tumor types that can be detected on PET/CT and some of the patterns of (18)F-FDG uptake that can be observed in these cases.

Intramuscular metastases on FDG PET-CT: a review of the literature

OBJECTIVE

Intramuscular metastases (IM) are both rare and difficult to detect using routine anatomical computed tomography (CT) imaging. However, since the introduction of 18F-fluoro-deoxy-glucose (FDG) PET-CT, the number of detected IM has increased. We review the available literature to illustrate the relevance of these findings for staging and patient management.

METHODS

In a review of the literature, we found one series and 33 case reports of IM shown on FDG PET-CT. No cases were reported before 2005. Furthermore, we present a patient with nonsmall cell lung cancer and a solitary distant metastasis in the left musculus infraspinatus that was not detected on diagnostic CT, but was found on FDG PET-CT.

RESULTS

For a total of 39 recorded cases of IM, we found that FDG PET-CT had a significant impact on patient management in at least 51% of cases. Where reported, lesions were either isodense or hypodense on CT compared with the surrounding muscle tissue. The lesions that were also analyzed with MRI showed heterogeneous intensity. Five out of 39 patients had metastases in the extraocular muscles of one or both orbits.

CONCLUSION

FDG PET-CT appears to be a sensitive tool for detecting IM, with important impact on management in many cases.