Detection of skeletal muscle metastasis: torso FDG PET-CT versus contrast-enhanced chest or abdomen CT

Ultrasound and CT findings of subcutaneous metastases in trunk and pelvis: a comprehensive analysis

OBJECTIVE

This study aimed to describe the ultrasound, CT findings, and clinical manifestations of pathologically confirmed metastases involving the subcutaneous fat layer of the trunk and pelvis.

MATERIALS AND METHODS

We included 30 patients with subcutaneous metastases in the trunk and pelvis, verified by ultrasound-guided biopsy. We comprehensively reviewed ultrasound findings of all 30 patients and contrast-enhanced CT findings of 25 patients obtained before biopsy. Medical records were reviewed, including primary malignancy type, presence of coexisting distant metastasis, and detection method leading to biopsy referral.

RESULTS

Most subcutaneous metastases were heterogeneously hypoechoic (86.7%) with well-defined margins (80.0%), lobulated (46.7%) or round-to-oval (40.0%) shape, and vascularity (96.7%). Metastases frequently exhibited no contact (53.3%) or focal contact with deep peripheral fascia, resulting in acute contact angle formation (30.0%). Common CT manifestations included central low attenuation with peripheral rim-like enhancement (60.0%) or well-circumscribed lesion with heterogeneous enhancement (32.0%). Lung cancer (46.7%) was the prevalent primary malignancy. CT was the predominant detection method (56.7%). Coexisting subcutaneous metastases were present in 50.0% of cases, and distant metastases (less subcutaneous metastases) were observed in 90.0% of patients.

CONCLUSION

This study describes typical imaging findings of subcutaneous metastases involving the trunk and pelvis. CT may play a crucial role in their early detection, and our results may assist radiologists in their diagnosis.

Skeletal muscle metastases of the trunk and pelvis: focus on ultrasound, CT findings, and clinical manifestations

Objective:

To describe the ultrasound, CT findings, and clinical manifestations of pathologically confirmed skeletal muscle metastases involving trunk and pelvis.

Methods:

71 patients with 71 skeletal muscle metastases of the trunk and pelvis, pathologically proven by ultrasound-guided biopsy, were included in the study, and ultrasound findings were reviewed. CT findings were reviewed for 60 patients who underwent post-contrast CT obtained prior to biopsy, which included skeletal muscle metastases. Medical records, including the type of primary malignancy, presence of coexisting distant metastasis, and method of detection that led to referral for biopsy, were reviewed.

Results:

Most skeletal muscle metastases were hypoechoic (98.6%) with well-defined margins (85.9%), round-to-oval (47.9%), or lobulated (42.2%) with intralesional vascularity (64.8%). Typical CT findings included abscess-like lesions with rim enhancement (53.3%) or round-to-oval lesions with homogeneous enhancement (40.0%). The most common primary malignancy was lung cancer (49.3%), followed by gastrointestinal cancer (7.0%). Distant metastases other than muscle metastases were found in 84.5% of patients, and coexisting skeletal muscle metastases were found in 47.9%. CT was the most common detection method for metastases (57.8%), being more common than positron emission tomography-CT (22.5%).

Conclusion:

The current study describes the typical imaging findings of skeletal muscle metastases of the trunk and pelvis in patients with advanced cancer. CT may play an important role in the early detection of skeletal muscle metastases, and our results may aid radiologists in their diagnosis.

Advances in knowledge:

1. Skeletal muscle metastases of the trunk and pelvis demonstrate typical imaging findings on ultrasound and CT. 2. CT may aid in the early detection of skeletal muscle metastases, which are among the rarest, and our results may aid radiologists in their diagnosis.

Detection of muscle metastases on 18F-fluorodeoxyglucose positron emission tomography/computed tomography scan in 13 cases

Muscular metastases (MMs) form an infrequent entity, and their physiopathology is still not well-defined. In this study, we estimated the incidence of MMs that were detected by ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography and also specified their metabolic characteristics. This study includes 13 patients with MMs from a remotely located primary tumor. The results of this study showed an incidence of MMs at about 1%, with the most frequently involved muscles being iliopsoas and paraspinal. Lung cancer seems to be the most common tumor that causes MMs. Furthermore, these MMs vary in size and physiological uptake; they seem to be out of the ordinary and easily detected. They are often associated with other extra muscular locations and frequently involve the trunk muscles. Their detection in the course of the evolution of a specific neoplasia testifies to their aggressiveness and portends an unfavorable prognosis. The data in our series confirm that in the literature regarding the underlying primary tumors and anatomical sites involved by MMs.

Imaging features and prognostic value of 18F-FDG PET/CT detection of soft-tissue metastasis from lung cancer: a retrospective study

BACKGROUND

Soft-tissue metastasis (STM) is a relatively rare, but not exceptional, manifestation of lung cancer. The purpose of this study was to evaluate the imaging features of STM from lung cancer using fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT), and assess the impact of STM detected at baseline PET/CT on patient survival.

METHODS

Out of 4543 patients with lung cancer who underwent ¹⁸F-FDG PET/CT in our hospital between January 2013 and September 2018, 85 were diagnosed with STM (78 at baseline PET/CT and 7 at restaging PET/CT) and included in the imaging study. We conducted a comparative survival analysis between patients with stage 4 lung cancer with and without STM at baseline PET/CT (n = 78 in each group) and performed univariate and multivariate analyses to investigate the factors affecting the prognosis of lung cancer.

RESULTS

A total of 219 lesions were identified by ¹⁸F-FDG PET/CT: 215 were detected by PET and 139 by CT. Muscle STM were primarily found in the hip and upper limb muscle, whereas subcutaneous STM were mainly distributed in the chest, abdomen, and back. In 68 patients, STM were found incidentally during routine ¹⁸F-FDG PET/CT staging. Isolated STM were detected in 6 patients, whose tumor staging and treatment were affected by PET/CT findings. There were no significant differences in the 1-, 3-, and 5-year survival rates between patients with and without STM at baseline PET/CT. Brain and adrenal metastases, but not STM, were associated with poor prognosis of stage 4 lung cancer.

CONCLUSIONS

We described the PET/CT imaging characteristics of STM from lung cancer, and confirmed that PET/CT can detect unsuspected STM to change the staging and treatment of some patients. Our analysis indicates that STM is not a useful prognostic indicator for patients with advanced lung cancer, while brain and adrenal metastases portend a poor prognosis.

CT imaging features of skeletal muscle metastasis: A rare tumour group with different patterns

INTRODUCTION

Skeletal muscle metastasis (SMM) are rare and can have different patterns on computed tomography (CT). Our aim was to estimate the frequency of the different patterns, primary tumours and localizations of SMM in a large single-centre sample.

METHODS

A retrospective search in the database of our radiological institution was performed for patients with SMM. The primary tumour, affected muscles and CT patterns were estimated.

RESULTS

Overall, 104 SMM were diagnosed in 82 patients. In 11 patients (13.4%), SMM were the isolated manifestation of metastatic disease in clinical work up. Regarding primary tumours, gastrointestinal tumours (24.4%), lung cancer (20.4%) and malignant melanoma (13.4%) were identified most frequently. Other malignancies were rare. Most commonly, the trunk musculature was affected (41.3% of the cases). SMM type 1 were identified in 37 cases (35.6%), type 2 in 64 cases (61.5%), type 3 in 2 cases (1.9%) and type 4 in one case (1%).

CONCLUSIONS

The present study shows typical imaging appearances of SMM based on a large patient sample in a single centre. SMM has a rare occurrence with several different patterns, which can impose diagnostic difficulties and varies possible differential diagnoses.

The role of radiological and hybrid imaging for muscle metastases: a systematic review

AIM OF THE STUDY

Skeletal muscle metastases (SMM) are a rare entity, mainly detected at autopsy. Nevertheless, radiological and nuclear medicine imaging can contribute to the diagnosis with a significant impact on the treatment and prognosis of neoplastic patients. This study aimed to systematically review the features of SMM at imaging considering the primary tumors and the sites of occurrence.

MATERIALS AND METHODS

We conducted a systematic search of three electronic database (i.e., PubMed, Science Direct, and Web of Science) up to May 2019, without any language or time interval restriction. Two reviewers performed the search and selection process, data extraction, and synthesis. We resolved disagreements by consensus and/or involving a third reviewer. The included studies have been classified according to the Oxford Centre for Evidence Based Medicine (CEBM) grading system.

RESULTS

Out of 8598 and 1077 articles respectively for radiological and hybrid imaging, 29 papers were included. According to CEBM, twelve were level 4. Computed tomography (CT) is mainly applied and, despite the existence of CT and magnetic resonance-based classifications, these are rarely used. Positron emission tomography/CT allowed the detection of small and subtle lesion also in the extremities. Muscles of the trunk were mostly affected and mainly respiratory tumors are associated with this type of metastatic spread.

CONCLUSION

Radiological and hybrid imaging allow a precise characterization of SMM. However, a more systematic approach, including also the application of available classification systems, may increase the diagnostic accuracy for this rare type of metastases.

KEY POINTS

• Skeletal muscle metastases have heterogeneous characteristics at imaging but mostly abscess-like features and high metabolic activity are described. • Skeletal muscle metastases mainly affect the muscles of the trunk. • Pulmonary, urological, and gastrointestinal cancers are the most frequent cause of skeletal muscle metastases.

Skeletal muscle metastasis from squamous cell lung cancer was first found by ultrasound: a case report

Skeletal muscle metastasis (SMM) is rare and very difficult to diagnosis using routine ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), especially in patients without a definitive tumor history. In this report, we describe a 64-year-old man who came to hospital because of pain from a touchable mass at his left thigh. Ultrasonography showed a substantive hypoechoic mass within the left adductor longus muscle with an anechoic area, which was ill-defined and rich in blood supply on color Doppler flow imaging (CDFI). The mass was biopsied under ultrasound guidance. The pathological findings displayed an infiltration of moderately differentiated squamous cell lung cancer (SCLC) and nests of atypical cells. Thoracic plain CT images displayed thickening of the bronchus wall of the right inferior lobe, with obstructive pneumonia and atelectasis at the distal bronchus. The final main diagnosis for this patient was central bronchogenic carcinoma, with intramuscular metastasis of the left adductor longus muscle, and the TNM classification was T2N0M1. Although the incidence of IM originating from SCLC is very rare, patients with an occasional found mass in soft tissue should be examined to exclude SMM, and ultrasound-guided percutaneous biopsy can provide vital information regarding indeterminate soft tissue masses.

F-18 fluorodeoxyglucose positron emission tomography for differential diagnosis and prognosis prediction of vascular tumors

The spectrum of vascular tumors ranges from hemangioma (HEM), to epithelioid hemangioendothelioma (EHE) and to angiosarcoma (AS). To the best of our knowledge, the usefulness of F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for vascular tumors has never been comprehensively studied. The present study investigated the usefulness of FDG-PET for pathologically diagnosed vascular tumors. The present study included 26 patients with vascular tumor (male:female, 17:9; age, 60.9±14.4 years; 7 HEM, 6 EHE and 13 AS) who underwent FDG-PET between January 2007 and May 2014 at the Seoul National University Bundang Hospital (Seongnam, Korea) and Konkuk University Medical Center, (Seoul, Korea). Representative FDG uptake was measured as the maximum standardized uptake value (SUVmax) over the lesion with the highest FDG uptake. Disease progression was clinically defined as the aggravation of known lesions or novel lesion development during follow-up on computed tomography, magnetic resonance imaging, or FDG-PET. FDG-PET revealed multi-organ involvement only in AS (6/13 [46.2%]), whereas HEM and EHE involved a single organ. Tumor SUVmax was significantly greater in AS (6.32±4.84) compared with EHE (3.10±2.68) and HEM (2.33±0.76) (P=0.0284). There was no difference in tumor SUVmax between HEM and EHE (P>0.05). Disease progression was primarily noticed in AS (9/13 [69.2%]). Only 1 patient with EHE (1/6=16.7%) and no patients with HEM (0/7=0%) experienced disease progression. Mortality was reported only in patients with AS (4/13 [30.8%]). Using the cutoff SUVmax of 3.0, the two-year progression-free survival rate of 14 patients with tumor SUVmax <3.0 (75.0%) was significantly higher compared with that of 12 patients with tumor SUVmax ≥3.0 (0%) (P=0.0053). In conclusion, FDG-PET is useful for the differential diagnosis and prognosis prediction of vascular tumors.

Multiple and solitary skeletal muscle metastases on 18F-FDG PET/CT imaging

OBJECTIVE

The aim of this study was to investigate the features and patterns of skeletal muscle metastases (SMM) detected with F-fluorodeoxyglucose (F-FDG) PET/computed tomography (PET/CT).

PARTICIPANTS AND METHODS

Our database was analyzed for patients with pathologically proven malignancy, who underwent F-FDG PET/CT in our institution. The patients with SMM were included in the study group on the basis of the final diagnosis confirmed by follow-up or histopathology. Images were acquired using a PET/CT system Biograph mCT S(64)-4R. CT was performed without contrast enhancement.

RESULTS

The selected group included 31 patients (1.7% of the database, which consisted of 1805 patients). A total of 233 lesions were found. The prevalence of SMM evaluated in specific primary malignancies was the highest in melanoma (6.9%), followed by carcinoma of unknown primary (4.4%), colorectal cancer (4.1%) and lung cancer (2.8%). Three patterns of skeletal muscle metastatic involvement were observed: multiple SMM accompanied by other metastases (64.5%), solitary lesion associated with other metastases (29%) and isolated intramuscular lesions (two cases, 6.5%). Isolated SMM represented recurrence of the malignant disease. In patients with extraskeletal metastases, solitary or multiple SMM did not affect tumor staging.

CONCLUSION

Solitary SMM are less common than multiple on F-FDG PET/CT imaging. SMM are usually associated with other metastases and do not affect tumor staging. The cases of isolated SMM are very rare. Nevertheless, in patients with a diagnosis of malignant disease, a solitary, F-FDG avid intramuscular focus should be suspected to represent metastasis.