The value of 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography in the detection and characterization of soft tissue metastasis

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.

Prevalence, distribution, and clinical characteristics of hemangiosarcoma-associated skeletal muscle metastases in 61 dogs: A whole body computed tomographic study

BACKGROUND

Skeletal muscle metastases (SMMs) have been described sporadically in canine oncology.

HYPOTHESIS/OBJECTIVES

To determine the prevalence, localization, and clinical signs of SMMs associated with hemangiosarcoma (HSA) in a population of dogs presented for whole body computed tomography (CT).

ANIMALS

Dogs with a histologically confirmed HSA and a tissue core specimen or fine needle aspirate of suspected metastatic lesions were included in the study.

METHODS

Retrospective study. Dogs with a final diagnosis of visceral or muscular HSA that underwent whole body CT scan were enrolled in the study. Final diagnosis of primary tumor and SMMs was reached by histology, cytology, or both. Signalment, clinical signs, localization of the primary lesion, and metastases characteristics were reviewed.

RESULTS

Sixty-one dogs met the inclusion criteria. Skeletal muscle metastases were detected in 15 dogs (24.6%) and all of these dogs had also metastases in ≥1 sites. Presence of SMMs was significantly higher in males but was not significantly related to age, neuter status, breed, localization, and dimensions of the primary tumor. Nine of 15 (60.0%) dogs with SMMs showed lameness or reluctance to move whereas these signs were not recorded in any of the 42 dogs without SMMs (P < .001).

CONCLUSION AND CLINICAL IMPORTANCE

Prevalence of SMMs in our population of dogs with HSA was higher in comparison to previous studies in the human and veterinary medical literature. Whole body CT is recommended for staging of dogs with HSA, because SMMs could be missed by clinical examination and traditional diagnostic imaging modalities.

Tumors Involving Skin, Soft Tissue and Skeletal Muscle: Benign, Primary Malignant or Metastatic?

BACKGROUND

Metastatic cancer with invasion of skin, soft tissue and skeletal muscle is not common. Examples presenting as soft tissue masses could sometimes lead to misdiagnosis with delayed or inappropriate management. The purpose of current study was to investigate clinical characteristics in the involvement of metastatic cancer.

MATERIALS AND METHODS

A total of 1,097 patients complaining of skin or soft tissue masses and/or lesions were retrospectively reviewed from January 2012 to June 2013. Tumors involving skin, soft tissue and skeletal muscle of head and neck, chest wall, abdominal wall, pelvic region, back, upper and lower extremities were included in the study.

RESULTS

Fifty-seven (5.2%) patients were recognized as having malignancies on histopathological examination. The most common involvement of malignancy was basal cell carcinoma, followed by cutaneous squamous cell carcinoma, sarcoma and melanoma. The most common anatomical location in skin and soft tissue malignancies was head and neck (52.6% of the malignancies). Four (0.36%) of the malignant group were identified as metastatic cancer with the primary cancer source from lung, liver and tonsil and the most common site was upper extremities. One of them unexpectedly expired during the operation of metastatic tumor excision at the scalp.

CONCLUSIONS

Discrimination between benign and malignant soft tissue tumors is crucial. Performance of imaging study could assist in the differential diagnosis and the pre-operative risk evaluation of metastatic tumors involving skin, soft tissue and skeletal muscle.

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.

Polysplenia Syndrome With Splenic and Skeletal Muscle Metastases From Thyroid Carcinoma Evaluated by FDG PET/CT: Case Report and Literature Review: A Care-Compliant Article

Polysplenia syndrome (PSS) is a rare congenital abnormality. Metastases to spleen and skeletal muscle from differentiated thyroid cancer (DTC) are also extremely rare. Our case report aims to present an interesting case of PSS associated with splenic metastasis (SM) and skeletal muscle metastasis (SMM) from advanced papillary thyroid carcinoma which was evaluated on fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). An 84-year-old Chinese man was admitted with the history of multiple enlarged masses in bilateral neck, right axillary, and inguinal areas for >2 months. The results of ultrasonography examination were highly suggestive of malignancy. The histological results of the following biopsy were consistent with papillary thyroid carcinoma with involvement of multiple regional lymph nodes. He was referred for an FDG PET/CT imaging to evaluate the situation. FDG PET/CT showed that an intense FDG-avid thyroid mass with widespread regional lymph node involvement and distant metastases in the body. Unexpected sites of metastases were detected in the spleens and skeletal muscles. Most interestingly, FDG PET/CT imaging also described the typical imaging findings of PSS including the 2 right-sided spleens, azygos and hemiazygos continuation of inferior vena cava (IVC), right-sided stomach, middle line liver, a short pancreas, preduodenal portal vein (PPV), and malrotation of gut. Whole body FDG PET/CT imaging can accurately evaluate the situation of DTC by detecting regional lymph node involvement, common and rare sites of distant metastases which are closely related to staging, management, and prognosis of this disease. Whole-body FDG PET/CT is also valuable in demonstrating the typical imaging features of PSS.

Uncommon isolated distant subcutaneous tissue and skeletal muscle metastasis from oesophageal cancer diagnosed by PET/CT (18)F-FDG

Distant soft-tissue metastases (subcutaneous tissues and skeletal muscle) are extremely rare, particularly in oesophageal carcinoma. The case is described of a patient who was treated for oesophageal adenocarcinoma 2.5 years previously. A PET/CT was performed showing metastatic spread due to a solitary focus of increased tracer uptake corresponding to one subcutaneous node in the upper abdomen. An excisional biopsy showed a metastasis from the carcinoma. Restaging PET/CT (18)F-FDG study was performed 2 year later, demonstrating foci of increased uptake within several muscles as isolated distant haematogenous spread of metastases, histopathologically confirmed. As most of soft-tissue metastases are asymptomatic, the physicians should recommend a histopathological study of focal FDG uptake at subcutaneous tissues and/or skeletal muscles, because they may be the first sign of disease spread, so therapeutic management of these patients could be changed.