Skeletal muscle metastases: primary tumours, prevalence, and radiological features. Eur Radiol. 2010;20:649-658. [PMID: 19707767 DOI: 10.1007/s00330-009-1577-1]

Imaging spectrum of atraumatic muscle disorders: a radiologist's guide

Atraumatic muscle disorders comprise a very wide range of skeletal muscle diseases, including metabolic, inflammatory, autoimmune, infectious, ischemic, and neoplastic involvement of the muscles. Therefore, one must take clinical and laboratory data into consideration to elucidate the differential diagnoses, as well as the distribution of the muscle compromise along the body-whether isolated or distributed along the body in a symmetric or asymmetrical fashion. Assessment of muscular disorders often requires imaging investigation before image-guided biopsy or more invasive procedures; therefore, radiologists should understand the advantages and limitations of imaging methods for proper lesion evaluation and be aware of the imaging features of such disorders, thus contributing to proper decision-making and good patient outcomes. In this review, we propose a systematic approach for the assessment of muscle disorders based on their main imaging presentation, dividing them into patterns that can be easily recognized.

Mechanisms Underlying the Rarity of Skeletal Muscle Cancers

Skeletal muscle (SKM), despite comprising ~40% of body mass, rarely manifests cancer. This review explores the mechanisms that help to explain this rarity, including unique SKM architecture and function, which prohibits the development of new cancer as well as negates potential metastasis to SKM. SKM also presents a unique immune environment that may magnify the anti-tumorigenic effect. Moreover, the SKM microenvironment manifests characteristics such as decreased extracellular matrix stiffness and altered lactic acid, pH, and oxygen levels that may interfere with tumor development. SKM also secretes anti-tumorigenic myokines and other molecules. Collectively, these mechanisms help account for the rarity of SKM cancer.

Off the wall: incidental paraspinal and pelvic muscle pathology on abdominopelvic imaging

As the use of cross-sectional abdominal and pelvic imaging has increased exponentially in the past several decades, incidental musculoskeletal findings have become commonplace. These are often unrelated to the indication for the examination and are frequently referred to as the "radiologist's blind spot" on these studies. The differential diagnosis for abnormalities of the paraspinal and pelvic musculature is, in many cases, quite different from the anterior abdominal wall muscles. Furthermore, due to their relatively deep location, pathology involving the former muscle groups is more likely to be clinically occult, often presenting only incidentally when the patient undergoes cross-sectional imaging. Effective treatment of diseases of these muscles is dependent on adherence to a diverse set of diagnostic and treatment algorithms. The purpose of this review article is to familiarize the radiologist with the unique pathology of these often-overlooked muscles of the abdomen and pelvis.

Clinical features of patients with carcinoma soft tissue metastases as surgical indications: a retrospective cohort study

BACKGROUND

Soft-tissue metastasis of carcinoma is rare. In the present study, we investigated the surgical indications and clinical features of patients with soft tissue metastases of carcinoma.

METHODS

In this retrospective cohort study, we enrolled 26 patients with soft tissue carcinoma metastasis referred to our department for treatment. Sex, age, location, size, depth, pain due to the tumor, primary origin, serum C-reactive protein (CRP) level, MRI examinations, diagnosis by a previous physician, carcinoma markers from blood, history of carcinoma, other metastases, performance status (PS), and surgical procedures were documented. Associations between variables and surgery were statistically analyzed.

RESULTS

The primary cancer origin was found to be the lung (n = 10), kidney (n = 7), esophagus (n = 2), stomach (n = 1), breast (n = 1), liver (n = 1), ureter (n = 1), anus (n = 1), and unknown (n = 2). The mean CRP level of all patients was 2.3 mg/dL. Seven tumors (26.9%) were originally suspected to be soft tissue metastases of carcinoma, while 19 tumors (73.1%) were considered soft tissue sarcomas or inflammatory lesions by the previous treating physician. Twenty patients (76.9%) had other metastases. The PS of the 12 patients (46.2%) was zero. Eleven patients (42.3%) underwent surgery for soft tissue metastases. Diagnosis of soft tissue metastasis by a previous physician and good PS (p < 0.05) were significantly associated with surgery.

CONCLUSION

Overall, the present results show that surgical indications for soft tissue metastasis of carcinoma include diagnosis by the referring physician or good PS of the patients.

Lessons in clinical reasoning - pitfalls, myths, and pearls: shoulder pain as the first and only manifestation of lung cancer

OBJECTIVES

Lung cancer is the leading cause of cancer-related death and poses significant challenges in diagnosis and management. Although muscle metastases are exceedingly rare and typically not the initial clinical manifestation of neoplastic processes, their recognition is crucial for optimal patient care.

CASE PRESENTATION

We present a case report in which we identify the unique scenario of a 60-year-old man with shoulder pain and a deltoid muscle mass, initially suggestive of an undifferentiated pleomorphic sarcoma. However, further investigations, including radiological findings and muscle biopsy, revealed an unexpected primary lung adenocarcinoma. We performed a systematic literature search to identify the incidence of SMM and reflect on how to improve and build on better diagnosis for entities as atypical as this. This atypical presentation highlights the importance of recognizing and addressing cognitive biases in clinical decision-making, as acknowledging the possibility of uncommon presentations is vital. By embracing a comprehensive approach that combines imaging studies with histopathological confirmation, healthcare providers can ensure accurate prognoses and appropriate management strategies, ultimately improving patient outcomes.

CONCLUSIONS

This case serves as a reminder of the need to remain vigilant, open-minded, and aware of cognitive biases when confronted with uncommon clinical presentations, emphasizing the significance of early recognition and prompt evaluation in achieving optimal patient care.

Primary rectal adenocarcinoma with musculoskeletal metastasis as the only metastasis site: A case report with a short literature review

Rectal carcinoma with metastasis to skeletal muscle is a rare occurrence. Since 1970, only 30 cases of skeletal muscle metastasis originating from colorectal adenocarcinomas have been documented, underscoring its exceptionally low incidence. Here, we present the case of a middle-aged man who was diagnosed with rectal adenocarcinoma 3 months ago. During examination, a subcutaneous mass was discovered in the left proximal buttock. Histological analysis of a biopsy confirmed that this mass was a metastatic lesion originating from the primary rectal adenocarcinoma.

A Rare Case of Abdominal Wall Skeletal Muscle Metastasis From Adenocarcinoma of the Pancreatic Head

Pancreatic cancer can be aggressive and commonly metastasizes to various organs. Most commonly, pancreatic cancer metastasizes to the lung, liver, bones, and peritoneum, but very rarely does it spread to the abdominal wall or skeletal muscle. In this case, we discuss a patient who initially presented with weight loss and jaundice from a pancreatic head adenocarcinoma that later metastasized to the rectus abdominis muscle. A 63-year-old female presented with jaundice and weight loss. CT imaging revealed a 2.8 cm pancreatic head mass with pancreatic and biliary ductal dilation. Carbohydrate antigen 19-9 (CA 19-9) level was also found to be elevated to 1810 U/mL. An endoscopic ultrasound-guided biopsy was later performed and confirmed pancreatic adenocarcinoma. The patient underwent a Whipple pancreatoduodenectomy following initial treatment with neoadjuvant FOLFIRINOX chemotherapy. Following the Whipple procedure, she received adjuvant chemotherapy and subsequent imaging revealed no recurrence and decreased CA 19-9 level to 46 U/mL. Eight months afterward, the patient presented once again with lower abdominal pain. Repeat CA 19-9 level was found to have increased to 1503 U/mL. Repeat positron emission tomography scan imaging was performed and showed a 4.7 cm left rectus abdominis muscle mass. The mass was later biopsied, and pathology revealed recurrent, metastatic pancreatic adenocarcinoma. The patient was restarted on chemotherapy with paclitaxel and gemcitabine leading to a reduction in tumor size and CA 19-9 levels of 135 U/mL. However, surgical resection was later pursued due to increased tumor size only four months later. At this time, limited literature is available reporting the occurrence of pancreatic cancer metastasizing to the abdominal wall. Upon literature review, only five cases have been reported to date, and only two of the cases involved the skeletal muscle. Our rare case is the first-time documentation of rectus abdominis metastasis from pancreatic adenocarcinoma arising from the pancreatic head.

Ossifying skeletal muscle metastasis as an initial manifestation of colorectal adenocarcinoma

Skeletal muscle metastases from colorectal cancer (CRC) are very rare. They have usually been described in patients with known CRC and as a well-defined mass. In this case report, we present a unique case of diffuse and ossifying skeletal muscle metastasis as the first manifestation of CRC. A 36-year-old man presented with progressive left thigh swelling and left hip pain of 6 months duration. He denied any gastrointestinal complaints. CT and MRI of the thigh showed diffuse muscular swelling, signal abnormalities with linear calcifications involving the muscles of the posterior and medial compartments of the left thigh and both gluteal regions. Histology confirmed the metastatic nature of a colorectal adenocarcinoma. The patient was treated with chemotherapy and showed a good evolution after 6 months of follow-up.

Imaging features and biopsy yield of soft tissue metastatic lesions: 10-year single tertiary center experience

OBJECTIVE

To evaluate imaging features of soft tissue metastases, technical factors associated with diagnostic yield of image-guided biopsy, and clinical impact of biopsy results on patient outcomes.

MATERIALS AND METHODS

A total of 1605 image-guided soft tissue biopsies were retrospectively identified from December 2010 to December 2020. Included lesions were histologically proven musculoskeletal soft tissue metastases. Lesions were excluded if intraabdominal, intrathoracic, retroperitoneal, associated with osseous lesions or surgical scar implants or arising from skin or lymph nodes. Image guidance modality, needle size, number of cores, and lesion location, size, and depth from skin were recorded. Patient demographics, malignancy history, biopsy-driven changes in management, and survival rate after biopsy were collected.

RESULTS

Forty-six patients met the inclusion criteria with a biopsy diagnostic yield of 44/46 (95.7%). Metastases were most commonly located truncal (82.6%, p < 0.001) and intramuscular (78.3%, p < 0.001). A total of 37/46 (80.4%) biopsies were US-guided. And 9/46 (19.6%) were CT-guided. There was no significant difference in the number of cores or mean needle gauge between diagnostic and nondiagnostic biopsies. At time of review, 23 (50%) patients were deceased, with a mean survival of 13.5 months after biopsy. The majority (71.7%) of patients had a known primary malignancy at time of biopsy, most commonly lung (24.2%) and breast (24.2%). Overall survival showed no association with anatomic location (p > 0.83) or tissue type (p > 0.34). The most common biopsy-driven outcome was initiation of chemotherapy, immunotherapy, and/or radiotherapy (52.2%).

CONCLUSION

Image-guided biopsy for soft tissue metastases has high diagnostic yield and commonly influences clinical management. Metastases were most commonly intramuscular in the trunk and are associated with poor prognosis.

FLI1 and FRA1 transcription factors drive the transcriptional regulatory networks characterizing muscle invasive bladder cancer

Bladder cancer is mostly present in the form of urothelium carcinoma, causing over 150,000 deaths each year. Its histopathological classification as muscle invasive (MIBC) and non-muscle invasive (NMIBC) is the most prominent aspect, affecting the prognosis and progression of this disease. In this study, we defined the active regulatory landscape of MIBC and NMIBC cell lines using H3K27ac ChIP-seq and used an integrative approach to combine our findings with existing data. Our analysis revealed FRA1 and FLI1 as two critical transcription factors differentially regulating MIBC regulatory landscape. We show that FRA1 and FLI1 regulate the genes involved in epithelial cell migration and cell junction organization. Knock-down of FRA1 and FLI1 in MIBC revealed the downregulation of several EMT-related genes such as MAP4K4 and FLOT1. Further, ChIP-SICAP performed for FRA1 and FLI1 enabled us to infer chromatin binding partners of these transcription factors and link this information with their target genes. Finally, we show that knock-down of FRA1 and FLI1 result in significant reduction of invasion capacity of MIBC cells towards muscle microenvironment using IC-CHIP assays. Our results collectively highlight the role of these transcription factors in selection and design of targeted options for treatment of MIBC.

Squamous cell lung carcinoma with gastrointestinal metastasis: a case report and review of literature

Squamous cell lung carcinoma (LUSC) originates from squamous cells and has a high rate of metastasis and recurrence. The lack of effective genetic targets and specific therapies has resulted in a poor prognosis for patients with LUSC. Gastrointestinal metastasis of LUSC is a rare occurrence in clinical practice. Patients with gastrointestinal metastasis usually have worse overall survival and the process of diagnosis is more complicated than those with metastasis elsewhere. What's more, there are no helpful guidelines for treating patients with a clinically confirmed diagnosis of gastrointestinal metastasis, which means the treatment method is limited. Here, we review the clinical features, diagnosis, and treatment of LUSC patients with gastrointestinal metastasis and report a rare case of LUSC accompanied by gastrointestinal metastasis. The patient was admitted to the hospital with coughing and hemoptysis. A tumor was found in his lung, and lesions were initially controlled with standard treatment. The patient's tumor re-occurred again shortly for which treatment was lacking. Without effective treatment methods, the disease was difficult to control. Our learnings from the case demonstrate that LUSC metastasizes to secondary lymphoid organs of the gastrointestinal tract, usually with a poor prognosis.

Breast Cancer Metastatic Dormancy and Relapse: An Enigma of Microenvironment(s)

Multiple factors act in concert to define the fate of disseminated tumor cells (DTC) to enter dormancy or develop overt metastases. Here, we review these factors in the context of three stages of the metastatic cascade that impact DTCs. First, cells can be programmed within the primary tumor microenvironment to promote or inhibit dissemination, and the primary tumor can condition a premetastatic niche. Then, cancer cells from the primary tumor spread through hematogenous and lymphatic routes, and the primary tumor sends cues systematically to regulate the fate of DTCs. Finally, DTCs home to their metastatic site, where they are influenced by various organ-specific aspects of the new microenvironment. We discuss these factors in the context of breast cancer, where about one-third of patients develop metastatic relapse. Finally, we discuss how the standard-of-care options for breast cancer might affect the fate of DTCs.

Unexpected Detection of Skeletal Muscle Renal Cell Carcinoma Metastasis With 99m Tc-EDDA/HYNIC-Tyr3-Octreotide (Tektrotyd) Scan

ABSTRACT

Somatostatin receptor scintigraphy with 99m Tc-Tektrotyd is widely used for the investigation of neuroendocrine tumors. Overexpression of somatostatin receptors has been shown in different tumor types including lymphomas, breast carcinoma, and renal cell carcinoma (RCC). Isolated case reports have shown that RCC metastases can be identified using somatostatin receptor imaging such as Octreoscan scintigraphy and 68 Ga-DOTATATE PET/CT. We report the case of a 70-year-old man with a history of surgically removed RCC who referred to 99m Tc-Tektrotyd scintigraphy for the evaluation of a pancreatic tail lesion. The scan revealed intense tracer uptake in a left splenius cervicis muscle lesion that on biopsy was consistent with metastatic RCC.

Muscular metastasis of superficial esophageal squamous cell carcinoma: a rare case of recurrence after endoscopic submucosal dissection with additional chemoradiotherapy

Esophageal cancer after endoscopic treatment may recur depending on the risk. We present a case of a rare T1b esophageal cancer after endoscopic treatment plus chemoradiotherapy (CRT) that recurred with metastasis of the dorsal muscles. A 70-year-old man was referred for treatment of early-stage esophageal carcinoma. Endoscopic submucosal dissection (ESD) was performed and histopathology showed a poorly differentiated squamous cell carcinoma with invasion to the submucosal layer (sm2) with INFc-type invasion and positive venous invasion. After subsequent CRT, the patient was monitored every 6 months, using computed tomography (CT) and endoscopy. Fifteen months after the treatment, contrast CT revealed a spherical mass with 9 cm ring enhancement within the right erector spinae, that had squamous cell carcinoma confirmed by CT-guided biopsy. Radiation and systemic chemotherapy were initiated for the metastasis of the esophageal carcinoma. However, he died of respiratory failure due to rapid pleural effusion 26 months after ESD. Pathological autopsy showed diffuse squamous cell carcinoma invasion of the cystic wall, forming a lumbar mass, and absence of cancer cell remnants or recurrences in the esophagus. This case report emphasizes the need for systemic observation of superficial esophageal cancer after treatment with a high risk of recurrence.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.

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.

Unusual finding of bronchopulmonary carcinoma through a pterygoid muscle metastasis. About a case

Bronchopulmonary cancer muscle metastases are uncommon, especially when they are visible. They can impact any muscle in the body, but the psoas, diaphragmatic, and paravertebral muscles have a clear advantage. We present a case of lateral pterygoid muscle metastasis of squamous cell carcinoma of the lung in a 70-year-old habitual smoker (40 packs per year) presents headaches more marked on the right and progressively worsening. A complementary brain MRI revealed a well-limited oval formation with irregular contours in hypo signal T1 hyper signal T2 heterogeneous, with area of central necrosis of the right pterygoid muscle, which was revealed to be a secondary location of bronchopulmonary malignancy after further examination (CT scan of the cervico-thoraco-abdomino-pelvic region, TEP scan, and biopsy). Moreover, muscle metastases are rarely revealing of primary cancer.

Psoas muscle metastatic disease mimicking a psoas abscess on imaging

Here, we report a case of malignant psoas syndrome presented to us during the second peak of the COVID-19 pandemic. Our patient had a medical history of hypertension, recently diagnosed with left iliac deep vein thrombosis and previous breast and endometrial cancers. She presented with exquisite pain and a fixed flexion deformity of the left hip. A rim-enhancing lesion was seen within the left psoas muscle and was initially deemed to be a psoas abscess. This failed to respond to medical management and attempts at drainage. Subsequent further imaging revealed the mass was of a malignant nature; histology revealing a probable carcinomatous origin. Following diagnosis, palliative input was obtained and, unfortunately, our patient passed away in a hospice shortly after discharge. We discuss the aetiology, radiological findings and potential treatments of this condition and learning points to prompt clinicians to consider this diagnosis in those with a personal history of cancer.

Liposomal β-Sitosterol Suppresses Metastasis of CT26/luc Colon Carcinoma via Inhibition of MMP-9 and Evoke of Immune System

β-sitosterol (SITO) has been reported with anticancer effects; however, with poor bioavailability. The current study aimed to investigate whether liposomal encapsulated β-sitosterol (LS) has a better inhibition effect on tumor metastasis than β-sitosterol in a CT26/luc lung metastasis mouse model and the possible underlying mechanism. LS was liposomal-encapsulated SITO and was delivered to mice by oral gavage. The cell viability was determined by the MTT assay, and invasiveness of the tumor cells and related protein expression were evaluated with the invasion assay and Western blotting. For therapeutic efficacy evaluation, male BALB/c mice were treated with PBS, SITO, and LS once a day for 7 days prior to intravenous injections of CT26/luc cells; treatments were continued twice a week post-cell inoculation throughout the entire experiment. Tumor growth inhibition was monitored by bioluminescent imaging (BLI). IL-12, IL-18, and IFN-γ in the intestinal epithelium were determined by ELISA. The results show that LS treatment had a better invasion inhibition with lower cytotoxicity than SITO when the same dose was utilized. Notably, mice treated with LS significantly exhibited fewer metastases to the lungs and other tissues/organs compared with the Control and SITO groups. Additionally, the IL-12, IL-18, and IFN-γ levels were significantly increased in the LS-treated mice compared with the Control and SITO groups. The underlying mechanism may be through the inhibition of MMP-9 and elicitation of the antitumoral Th1 immune response, such as increasing CD4⁺ and CD8⁺ T cells, IL-12, IL-18, and IFN-γ.

Isolated pathologies of Tensor Fasciae Latae: Retrospective cohort analysis from a tertiary referral centre

INTRODUCTION

Tensor Fasciae Latae (TFL) and the iliotibial band (ITB) act as a single functional unit in maintaining pelvic stability whilst standing, walking, or running in human beings. The Tensor Fasciae Latae (TFL) muscle acts across the hip and the knee joint. Consequently, though its pathologies traditionally present with lateral hip pain, identifying the precise clinical diagnosis can be a challenge.

PATIENTS AND METHODS

A retrospective search for the keyword 'Tensor Fasciae Latae'/iliotibial band (ITB) was performed of our Radiology Information System (RIS) and Picture Archiving and Communication System (PACS), Computerised Radiology Information System (CRIS) at our tertiary orthopaedic referral centre of a for orthopaedic oncology over a period of 13 years (2007-2020). Data was collected from RIS, oncology database and local histopathology laboratory records. Patient demographics, clinical characteristics, complementary imaging and clinical management outcome were documented.

RESULTS

We identified 35 patients with a mean age of 66 years (range 19-94 years). There were 18 female and 17 male patients. Lateral hip lump and pain were the most frequent clinical finding/presentation features. A variety of pathologies such as benign and malignant tumours, including vascular and tumour mimic lesions involving the TFL muscle were identified. Atrophy and pseudohypertrophy of TFL was the commonest pathology found; accounting for two thirds of the cases.

CONCLUSION

Tensor Fasciae Latae (TFL) can be afflicted with a broad spectrum of pathologies. Radiological imaging especially cross-sectional imaging modality is crucial in guiding appropriate patient management of TFL conditions. Our analysis suggests isolated TFL lesion are more likely to be benign conditions, presenting commonly as hip pain and swelling.

Exploring an Unfathomed Entiry: A Pooled Analysis of Solitory Skeletal Muscle Metastasis from Head and Neck Squamous Cell Carcinoma

BACKGROUND

Skeletal muscle is relatively uncommon site for metastasis in head and neck primary. This study was conducted to report our experience of three such cases and analyze the previously reported cases to assess the overall outcomes and formulate a treatment plan for these patients.

METHODS

We pooled the data extracted on extensive literature review and analyzed.

RESULTS

A total of 17 patients were analyzed for this study. All the patients had locally advanced primary and 14/17 developed metachronous metastasis. Median duration to development of metastasis was 8.5 months, and 13/17 patients had skeletal muscle as the only site of metastasis. Only 6/13 were treated with aggressive intent, 4 of which who underwent surgical resection had the best survival outcomes.

CONCLUSIONS

Isolated skeletal muscle metastasis in a head and neck primary is relatively rare, and in future, the research work needs to be taken up afresh, on prospective model, with adequate patient sample, to draw a scientifically valid conclusion.

Brachialis muscle metastasis: An unusual, presenting site of metastatic adenocarcinoma of the colon

Skeletal muscle metastasis from gastrointestinal system tumours is extremely rare. We report an unusual presentation of skeletal muscle metastasis in the brachialis muscle as a presenting feature of a previously undiagnosed colonic adenocarcinoma in a 66-year-old male. He presented to us with a painful, flexion deformity of his elbow and suspected to have a biceps brachii rupture. We review the clinico-radiological findings and the relevant literature. This case-report highlights the importance of a thorough clinical evaluation especially in presence of red flag signs, early multi-disciplinary team (MDT) discussion and biopsy to formulate a plan of management.

Skeletal muscle metastasis with bone metaplasia from colon cancer: A case report and review of the literature

BACKGROUND

Colon cancer is a common malignant disease of the gastrointestinal tract and usually occurs at the junction of the rectum and sigmoid colon. Lymphatic and hematogenous metastases occur frequently in colon cancer and the most common metastatic sites include the liver, lung, peritoneum, bone, and lymph nodes. As a manifestation of advanced tumor spread and metastasis, soft tissue metastasis, especially skeletal muscle metastasis with bone metaplasia caused by colon cancer, is rare, accounting for less than 1% of metastases.

CASE SUMMARY

A 43-year-old male patient developed skeletal muscle metastasis with bone metaplasia of the right proximal thigh 5 mo after colon cancer was diagnosed. The patient was admitted to the hospital because of pain caused by a local mass on his right thigh. Positron emission tomography-computed tomography showed many enlarged lymph nodes around the abdominal aorta but no signs of lung or liver metastases. Color ultrasound revealed a mass located in the skeletal muscle and the results of histological biopsy revealed a poorly differentiated adenocarcinoma suspected to be distant metastases from colon cancer. Immunohistochemistry showed small woven bone components that were considered to be ossified.

CONCLUSION

This case reminds us that for patients with advanced colorectal tumors, we should be alert to the possibility of unconventional metastasis.

Multidisciplinary treatment of skeletal muscle metastasis from lung cancer: A case of triceps muscle metastasis of lung squamous cell cancer

A 62-year-old Japanese man presented a hard and painful intramuscular mass in the right upper arm during the chemotherapy for lung squamous cell carcinoma. Initially, this mass containing fluid accumulation was treated by radiotherapy and antibiotics as a muscle metastasis suspected to be complicated with local infection. However, because the swelling and pain of his right arm did not improve, he underwent a surgical debridement of the mass. These local treatments succeeded in relieving the patient's symptoms for a while. However, after temporary remission, the recurrence tumor developed the paralysis of right radial nerve and ulnar nerve in his upper arm. Despite further combined therapy including drainage, additional radiotherapy, and chemotherapy, paralysis made his performance status deteriorated. He was eventually discontinued aggressive treatment due to worsened general condition.

We herein report a case of lung cancer followed unusual course due to muscle metastasis in the triceps muscle. Because the paralysis caused by muscle metastasis can be the factor to deteriorate the performance status of patient, the combined therapy including antibiotics, debridement, radiotherapy and chemotherapy as early as possible should be considered to avoid its risk.

Muscle involvement by widely metastatic squamous cell carcinoma of the lung

Muscle metastases remain rare as a secondary localization for cancers in general and lung cancer in particular. They are discovered incidentally in most cases and in the advanced stages of cancer. We report the case of a 60-year-old man, followed for squamous cell carcinoma, who was found to have muscle metastases during the follow-up of associated muscle pain. This case highlights the existence of these metastases in lung squamous cell carcinoma, rare as it is, and requires particular attention from practitioners in the follow-up of patients to detect these cases as early as possible and improve patient survival. Computed Tomography (CT) remains an excellent exam for the detection of skeletal metastasis.

Challenge of treating skeletal muscle metastasis during the COVID-19 pandemic in a low-resource setting

Background

The authors report on an extremely rare case of skeletal muscle metastasis from primary lung cancer that involved the radial nerve and humerus, which was ‘over-treated’ with wide tumour resection and frozen autograft reconstruction upon misdiagnosis of sarcoma by intraoperative frozen section, amid pressure of expediting hospital care in a low-resource setting during the coronavirus disease (COVID-19) pandemic.

Case presentation

A 61-year-old male living outside Metro Manila presented with painful mass in his left distal arm during the enhanced community quarantine, and requested admission upon testing negative for COVID-19. Imaging studies suggested a diagnosis of soft tissue sarcoma involving the radial nerve and humerus, and intending to prevent nosocomial severe acute respiratory syndrome coronavirus 2infection of patient, treatment was expedited by foregoing biopsy and opting for intraoperative frozen section prior to resection. Frozen section findings suggested malignancy intraoperatively, and surgical team proceeded with wide tumour resection and frozen autograft reconstruction of the humerus using plates and screws. However, permanent sections revealed metastatic carcinoma from primary non-small cell lung cancer, with positron emission tomography (PET) scan confirming lung mass in the right apical lobe.

Conclusion

The report concludes that establishment of a definite tumour diagnosis by final histopathological analysis is indispensable, even when planning for emergent surgery in the time of the COVID-19 pandemic.

Distant Intramuscular Metastases of Head and Neck Squamous Cell Carcinoma

OBJECTIVES

Metastasis of head and neck squamous cell carcinoma (HNSCC) usually occurs regionally in the neck lymph nodes, but also more infrequently at distant organs (eg, the lungs, bone, and liver). Intramuscular metastasis (IMM) has rarely been described. Therefore, we aimed to identify this disease characteristic and to evaluate available medical management options.

METHODS

Data of surgically treated HNSCC patients (n = 1150) at the Chi Mei Medical Center, Taiwan (2005-2015), were retrospectively reviewed. Literature searches were also conducted (1985-2015) to analyze the behavior of HNSCC with distant IMMs.

RESULTS

We identified 1 HNSCC patient with histopathologically proven IMMs. Ten similar cases were also identified in the available literature. Two-thirds of lesions arose in patients with laryngeal/hypopharyngeal malignancies, and two-thirds of lesions were located in the lower limbs. Lesions were subjectively painful and usually had rim enhancement with central hypoattenuation in contrast-enhanced computed tomography/magnetic resonance imaging. The mean duration between primary tumor diagnosis and secondary lesion detection was 13.7 months. No patient survived more than 2 years after establishing a diagnosis of HNSCC with IMMs.

CONCLUSIONS

Distant IMMs are extremely rare in HNSCC patients and have a poor clinical outcome. Differentiating this disease from sarcoma via anatomic distribution or diagnostic imaging studies is not straightforward. Biopsies for histopathologic examination are mandatory. Treatment of HNSCC patients with IMMs is mainly palliative for life quality preservation and not lifetime prolongation. Radiotherapy is established as a first-line treatment for symptom control with surgical intervention usually preserved for refractory cases.

Pretreatment serum C-reactive protein is a significant prognostic factor in patients with soft tissue metastases

BACKGROUND

Soft tissue metastasis is rarer than bone metastasis. Patients with soft tissue metastasis generally have a dismal prognosis. The treatment for metastatic lesions is sometimes difficult, because the prognostic factors of patients with soft tissue metastasis remain unelucidated. Therefore, this study aimed to identify these prognostic factors.

METHODS

Thirty-one patients with soft tissue metastasis were included in the study. We evaluated associations of overall survival with clinical parameters and inflammatory markers using Kaplan-Meier curves and Cox proportional hazards models.

RESULTS

Twelve patients received surgery for soft tissue metastasis, while radiation therapy was performed in six cases. The median overall survival after the detection of soft tissue metastasis was 11 months. Univariate analysis revealed that detection of soft tissue metastasis after the multidisciplinary treatment (P = 0.01); solitary metastasis (P = 0.0003); and pretreatment C-reactive protein (CRP) level < 0.4 mg/dL (P < 0.0001), white blood cell count < 8500 × 10³/μL (P = 0.0003), and neutrophil-to-lymphocyte ratio < 5 (P = 0.02) were significant good prognostic factors. Multivariate analysis revealed that a CRP value < 0.4 mg/dL (P = 0.07) and solitary metastasis (P = 0.09) were possible significant predictors of survival. Furthermore, in case of CRP levels <0.4 mg/dL and metastatic tumor resection, patients had a good prognosis; however, when the CRP levels increased to 0.4 mg/dL and above, patients had a poor prognosis, irrespective of tumor resection.

CONCLUSIONS

CRP is potentially useful for determining the indication of radical metastasectomy in soft tissue metastasis.

EML4-ALK positive lung adenocarcinoma with skeletal muscle metastasis in the right calf which was treatable with lorlatinib after resistance to treatment with alectinib

This report concerns a patient with skeletal muscle metastases due to lung adenocarcinoma harbouring an echinoderm microtubule-associated protein-like-4 (EML4)-anaplastic lymphoma kinase (ALK) rearrangement, who was successfully treated with lorlatinib after resistance to alectinib. A right lower lobectomy based on a diagnosis of lung adenocarcinoma was performed on a 77-year-old Japanese woman. After 7 months of surgical resection, a mass in the right calf was observed. A fine-needle aspiration biopsy from the mass was performed and the mass was diagnosed as metastatic adenocarcinoma harbouring EML4-ALK rearrangement. Alectinib was administered for 10 months. Then, administration of lorlatinib, an ALK tyrosine kinase inhibitor classified as third generation, was initiated after resistance to treatment with alectinib. After starting treatment with lorlatinib, the gastrocnemius tumour diminished and has maintained a stable condition. Our case suggests that EML4-ALK positive lung adenocarcinoma is treatable with lorlatinib after resistance to treatment with alectinib.

The Path of Most Resistance: A Rare Instance of Metastatic Pancreatic Adenocarcinoma Identified Within Skeletal Muscle

Soft tissue neoplastic metastases, specifically to the skeletal muscle, are uncommon in comparison to metastases within the abdomen, thorax, or intracranial regions. Specifically, pancreatic adenocarcinoma with skeletal muscle metastasis is a rare clinical phenomenon and is hardly reported. There is a high mortality rate after the diagnosis of metastatic pancreatic adenocarcinoma, attributed to inadequate screening and advanced staging upon incidental discovery. Rarely, metastatic lesions manifest in the skeletal muscle and are hardly documented. Some of the factors that deter skeletal muscle tumor implantation include the deficiency of skeletal muscle mediators and genetic makeup of the primary tumor. Surgical resection of pancreatic adenocarcinoma with adjuvant chemotherapy demonstrates the best prognosis; however, surgical management is usually limited to patients without known metastatic disease. Alternative treatment options such as chemotherapy and radiotherapy are used in the palliative care setting. Here, we present the case of a patient with previously diagnosed and treated pancreatic adenocarcinoma in remission, with biopsy-proven metastases isolated within the skeletal muscle.

Cohesive cancer invasion of the biophysical barrier of smooth muscle

Smooth muscle is found around organs in the digestive, respiratory, and reproductive tracts. Cancers arising in the bladder, prostate, stomach, colon, and other sites progress from low-risk disease to high-risk, lethal metastatic disease characterized by tumor invasion into, within, and through the biophysical barrier of smooth muscle. We consider here the unique biophysical properties of smooth muscle and how cohesive clusters of tumor use mechanosensing cell-cell and cell-ECM (extracellular matrix) adhesion receptors to move through a structured muscle and withstand the biophysical forces to reach distant sites. Understanding integrated mechanosensing features within tumor cluster and smooth muscle and potential triggers within adjacent adipose tissue, such as the unique damage-associated molecular pattern protein (DAMP), eNAMPT (extracellular nicotinamide phosphoribosyltransferase), or visfatin, offers an opportunity to prevent the first steps of invasion and metastasis through the structured muscle.

When a House Is Not a Home: A Survey of Antimetastatic Niches and Potential Mechanisms of Disseminated Tumor Cell Suppression

Over the last four decades, the cancer biology field has concentrated on cellular and microenvironmental drivers of metastasis. Despite this focus, mortality rates upon diagnosis of metastatic disease remain essentially unchanged. Would a small change in perspective help? Knowing what constitutes an inhospitable, rather than hospitable, microenvironment could provide the inspiration necessary to develop better therapies and preventative strategies. In this review, we canvas the literature for hints about what characteristics four common antimetastatic niches-skeletal muscle, spleen, thyroid, and yellow bone marrow-have in common. We posit that thorough molecular and mechanistic characterization of antimetastatic tissues may inspire reimagined therapies that inhibit metastatic development and/or progression in an enduring manner.

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.

Ovarian adenocarcinoma metastasis mimicking psoas abscess on imaging: a case report

Malignant psoas syndrome (MPS) is very rare with poor prognosis, and usually occurs in patients with advanced and recurrent cancer. Authors report herein the case of a 48-year-old female with history of neoadjuvant chemotherapy has been performed before hysterectomy with bilateral adnexectomy and ovariectomy for ovarian adenocarcinoma. She presented 18 months posttreatment with MPS due to a psoas abscess mimicking metastasis confirmed on computed tomography guided fine needle aspiration cytology.

Skeletal Muscle Metastases from Carcinomas: A Review of the Literature

* Bones are a common site for metastases; however, muscle metastases recently have been more commonly reported, not only as a result of the multidisciplinary approach in the treatment of these patients but also because of more sensitive imaging modalities such as positron emission tomography-computed tomography (PET-CT) that identify these lesions in early stages.* The most common carcinoma is lung carcinoma, with a hematogenous route of spread mainly to the axial region of the body (the psoas muscle, the gluteal muscles, and the paravertebral muscles). * Clinically, skeletal muscle metastases from carcinomas frequently present as painful palpable masses with or without swelling and are commonly found before diagnosis of the primary carcinoma.* Multiple imaging modalities, including radiographs, CT, magnetic resonance imaging (MRI), and PET-CT, have been used for diagnosis and staging, but tissue sampling is needed for a final diagnosis. The most important differential diagnosis of skeletal muscle metastases is with soft-tissue sarcomas.* Treatment is mainly based on chemotherapy and/or radiation; surgery is performed in cases of symptomatic lesions that fail to respond to nonoperative treatment.

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.

Gluteus medius muscle pathologies - A case series & pictorial review

Introduction

Gluteus medius lesions are rare and can present with lateral hip pain. We present a spectrum of pathologies involving the gluteus medius and discuss the imaging features.

Material and methods

A search of our oncology database at tertiary orthopaedic oncology service was performed. The imaging features of these were analysed.

Results

There were nine cases involving the gluteus medius, which included soft tissue sarcomas, lipomas, infection and trauma with an average age of 62 years.

Conclusion

Gluteus medius lesions are rare and one should be aware of these as these can present as lateral hip pain.

Skeletal Muscle Metastasis to Vastus Lateralis from a Urothelial Carcinoma: A Case Report and Review of Its Diagnosis and Management

Bladder cancer is a common genitourinary tract malignancy. Urothelial carcinoma is the most frequent type of bladder cancer and it commonly metastasises to lymph nodes, bone, lung and liver by a haematogenous route. Skeletal metastases are very rare and are usually present in patients with advanced metastatic disease. We present an unusual case of a 71-year-old male with a urothelial carcinoma metastasis to the vastus lateralis muscle 3 months following a cystoprostatectomy for muscle invasive bladder cancer.

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.

The added value of18F-FDG PET/CT in staging non-small cell lung cancer

Background

Non-small cell lung cancer (NSCLC) accounts for about 80% of all lung cancers. The current criteria for its staging are based on the TNM system that determines treatment options and predicts survival rate in patients. The aim of the study was to evaluate the diagnostic accuracy of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography PET/CT in staging of NSCLC patients.

Methods

A retrospective study was conducted. We reviewed the CT and PET/CT examinations done in our institution on pathologically proven patients of NSCLC, in the period between October 2018 and end of July 2019.

Results

A total of 40 patients were evaluated with the age ranging from 37 to 77 years old, and the mean was 55.63 years (SD ± 10.29). There were 31 male cases and 9 female cases. When we compared contrast enhanced CT (CECT) to PET-CT for staging, PET-CT helped upstage disease in 10 of 40 patients (25%) and downstage in 3 of 40 patients (7.5%).

Conclusion

PET/CT is a useful imaging tool in initial staging of the newly diagnosed patients with NSCLC. It is better thаn СT alone fоr detection of malignant lesions for accurate staging. It can change the strategy of treatment according to its findings.

A case of medial pterygoid muscle metastasis of lung cancer presenting with trismus

A man in his 60s with severe trismus was referred to our hospital. Based on computed tomography (CT), positron emission tomography/computed tomography (PET/CT), and biopsy, his initial diagnosis at another hospital was oropharyngeal cancer with cervical lymph node and distant metastases. After the review of the contrast-enhanced CT and reevaluated PET/CT images, we updated his diagnosis to left primary lung cancer that had metastasized to the cervical lymph nodes, bones, and skeletal muscles including the right medial pterygoid muscle. Since metastasis from primary lung cancer to the contralateral cervical lymph node is relatively rare, cervical lymph node metastases were thought to have originated from the metastatic lesion in the right medial pterygoid muscle. As metastases in the masticator muscles from lung cancer are rare, it is sometimes necessary to differentiate from primary head and neck lesions. Here, we report a rare case of lung cancer with the onset of trismus due to metastasis to the masticator muscle and perineural spread along the mandibular nerve.

Soft-Tissue Metastases From Esophageal Cancer

BACKGROUND

Metastatic carcinoma to skeletal muscle and/or subcutaneous fat is a rare event. Only 27 cases of esophageal cancer to soft tissue have been described in the English-language literature.

PURPOSE

Our goal was to describe the prevalence and clinical characteristics of soft-tissue metastasis among patients with primary esophageal cancer at a single institution.

METHODS

We performed a retrospective review of all patients with primary esophageal cancer. Data points analyzed included histologic subtype, anatomic location, metastasis pattern, treatment, and survival. Kaplan-Meier curves were used to estimate survival time, and log-rank tests were used for comparisons. For all analyses, P < 0.05 was considered significant.

RESULTS

Of 1341 patients with primary esophageal cancer, 25 (1.9%) had metastases to soft tissue. Soft-tissue metastases were diagnosed at a median age of 64 years, a median 9.6 months after esophageal cancer diagnosis. Adenocarcinoma was the predominant histopathological type, and soft-tissue metastasis was most common in the lower extremity. Local intervention was used for 10 symptomatic patients with favorable prognoses. Chemotherapy was the only treatment modality in 18 patients. Median survival time after diagnosis of soft-tissue metastasis was 8.9 months and was longer in patients with metastasis in soft tissue only (24.6 months, P = 0.007) and in those who received local intervention (11.1 months vs those who did not, P = 0.020).

CONCLUSION

We estimate the prevalence of soft-tissue metastasis to be 1.9% among patients with esophageal cancer. Local intervention may be beneficial for patients in otherwise good health with symptomatic soft-tissue lesions.

Diagnostic value of spectral reconstructions in detecting incidental skeletal muscle metastases in CT staging examinations

Background

To investigate if iodine density overlay maps (IDO) and virtual monoenergetic images at 40 keV (VMI_40keV) acquired from spectral detector computed tomography (SDCT) can improve detection of incidental skeletal muscle metastases in whole-body CT staging examinations compared to conventional images.

Methods

In total, 40 consecutive cancer patients who underwent clinically-indicated, contrast-enhanced, oncologic staging SDCT were included at this retrospective study: 16 patients with n = 108 skeletal muscle metastases confirmed by prior or follow-up CT, ¹⁸F-FDG-PET, MRI or histopathology, and a control group of 24 patients without metastases. Four independent readers performed blinded, randomized visual detection of skeletal muscle metastases in conventional images, IDO and VMI_40keV, indicating diagnostic certainty for each lesion on a 5-point Likert scale. Quantitatively, ROI-based measurements of attenuation (HU) in conventional images and VMI_40keV and iodine concentration in IDO were conducted. CNR was calculated and receiver operating characteristics (ROC) analysis of quantitative parameters was performed.

Results

Regarding subjective assessment, IDO (63.2 (58.5–67.8) %) and VMI_40keV (54.4 (49.6–59.2) %) showed an increased sensitivity for skeletal muscle metastases compared to conventional images (39.8 (35.2–44.6) %). Specificity was comparable in VMI_40keV (69.8 (63.2–75.8) %) and conventional images (69.2 (60.6–76.9) %), while in IDO, it was moderately increased to 74.2 (65.3–78.4) %. Quantitative image analysis revealed that CNR of skeletal muscle metastases to circumjacent muscle was more than doubled in VMI_40keV (25.8 ± 11.1) compared to conventional images (10.0 ± 5.3, p ≤ 0.001). Iodine concentration obtained from IDO and HU acquired from VMI_40kev (AUC = 0.98 each) were superior to HU attenuation in conventional images (AUC = 0.94) regarding differentiation between healthy and metastatic muscular tissue (p ≤ 0.05).

Conclusions

IDO and VMI_40keV provided by SDCT improve diagnostic accuracy in the assessment of incidental skeletal muscle metastases compared to conventional CT.