A case report of giant paratesticular myxoid liposarcoma.

Liposarcomas are an uncommon occurrence in the paratesticular region that makes about 20 % of all sarcomas. The clinical appearance is an inguinal lump, which can resemble a hydrocele or hernia. There would be no conventional treatment accessible because it is such a rare disease. We report the case of a 68-year-old man with paratesticular myxoid liposarcoma. Ultrasound and CT-scan came back in favor of a paratesticular tumor. A high inguinal orchidectomy has been done and the diagnostic of myxoid liposarcoma was first evoked by histology and confirmed by molecular biology. At 12 months follow up the patient remains tumor free.

Enormous myxoid/round cell liposarcoma: A case report.

Myxoid/round cell liposarcomas (MRCLPS) are a rare soft tissue sarcoma. We report the largest sarcoma in our institutional history. We discuss the patient's surgical management and treatment of the tumor and challenges given its dimensions. Several complications arose following primary resection that were managed by a multidisciplinary team. Although MRCLPS can vary in size, large MRCLPS must be treated cautiously given the potential for complications. Additionally, multidisciplinary treatment of MRCLPS is essential in diagnosing and treating these complex cases.

Significance of radiation therapy in the myxoid round-cell liposarcoma treatment regimen.

BACKGROUND AND PURPOSE: Because myxoid liposarcomas are more radiosensitive than other soft tissue sarcomas, there have been several reports of 50 Gy preoperative radiation therapy combined with surgery, but the wound complication rate is reportedly high. We have performed preoperative irradiation at a reduced dose of 40 Gy and definitive radiation therapy for unresectable cases. This study aimed to report the tumor reduction rate and oncological results with a reduced dose of preoperative irradiation and the outcome of definitive irradiation for unresectable cases. MATERIALS AND METHODS: Forty-one patients with myxoid liposarcoma treated in our institution between 2002 and 2021 were included. We examined the tumor volume shrinkage rate with preoperative radiation, compared complications and oncological outcomes between preoperative radiation and surgery-only cases, and investigated the prognosis and tumor shrinkage of definitive radiation cases. RESULTS: The total dose irradiated was 40 Gy except in two cases. The mean tumor volume reduction rate was 52.0%. A decreased dose of preoperative radiation did not worsen clinical outcomes with fewer complications. The total dose of definitive radiation was approximately 60 Gy. The mean tumor volume reduction rate was 55.0%. The tumor shrinkage maintenance rate was 100% in a median follow-up period of 50.5 months. CONCLUSION: Preoperative radiation therapy for myxoid liposarcoma near vital organs is a good approach because even with a reduced dose of 40 Gy, significant tumor reduction and excellent results were achieved. Definitive radiation therapy is the recommended treatment for older patients with serious comorbidities or inoperable patients.

Giant Paratesticular Myxoid Liposarcoma: A Case Report of a Rare Entity.

Paratesticular myxoid liposarcoma is an exceedingly rare malignancy originating from the spermatic cord or paratesticular tissues. We report a unique case of a 75-year-old male patient who presented with a painless scrotal swelling that had been growing for four years. Imaging investigations, including ultrasonography (USG) and contrast-enhanced computerized tomography (CECT), revealed characteristics consistent with paratesticular myxoid liposarcoma. The orchidectomy specimen confirmed a grade 2 right paratesticular myxoid liposarcoma. Despite its rarity, clinicians must consider this tumor in the differential diagnosis of painless scrotal swellings. Accurate diagnosis and comprehensive management, encompassing surgical resection with wide margins and potential adjuvant therapies, are pivotal. This case underlines the importance of collaborative research and long-term follow-up in understanding and managing paratesticular myxoid liposarcomas.

Deciphering the role of FUS::DDIT3 expression and tumor microenvironment in myxoid liposarcoma development.

BACKGROUND: Myxoid liposarcoma (MLS) displays a distinctive tumor microenvironment and is characterized by the FUS::DDIT3 fusion oncogene, however, the precise functional contributions of these two elements remain enigmatic in tumor development. METHODS: To study the cell-free microenvironment in MLS, we developed an experimental model system based on decellularized patient-derived xenograft tumors. We characterized the cell-free scaffold using mass spectrometry. Subsequently, scaffolds were repopulated using sarcoma cells with or without FUS::DDIT3 expression that were analyzed with histology and RNA sequencing. RESULTS: Characterization of cell-free MLS scaffolds revealed intact structure and a large variation of protein types remaining after decellularization. We demonstrated an optimal culture time of 3 weeks and showed that FUS::DDIT3 expression decreased cell proliferation and scaffold invasiveness. The cell-free MLS microenvironment and FUS::DDIT3 expression both induced biological processes related to cell-to-cell and cell-to-extracellular matrix interactions, as well as chromatin remodeling, immune response, and metabolism. Data indicated that FUS::DDIT3 expression more than the microenvironment determined the pre-adipocytic phenotype that is typical for MLS. CONCLUSIONS: Our experimental approach opens new means to study the tumor microenvironment in detail and our findings suggest that FUS::DDIT3-expressing tumor cells can create their own extracellular niche.

Clinical impact of whole-body MRI in staging and surveillance of patients with myxoid liposarcoma: a 14-year single-centre retrospective study.

OBJECTIVE: To assess the clinical impact of regular whole-body magnetic resonance imaging (WBMRI) surveillance in myxoid liposarcoma patients. METHODS: This was a retrospective cohort study of myxoid liposarcoma patients who underwent at least one WBMRI at our institution between October 2006 and December 2020. The effect of WBMRI on clinical management, namely treatment modification or additional diagnostic investigations was studied. A standardised WBMRI surveillance protocol was instituted in 2015. We compared patient outcomes for the metastatic patients who had and had not received regular WBMRI surveillance and performed survival analysis for both subgroups. RESULTS: Of the 56 patients (60.7% male, median age: 48.1 years) who underwent 345 WBMRI, 17 (30.3%) had metastases, and 168 WBMRI were performed in this group. The median imaging follow-up for the entire cohort was 35 months; the metastatic group had a median follow-up of 42 months. WBMRI changed the clinical management in 13 (76.5%) metastatic patients, with 33 instances of treatment modification. Thirty-five lesions were labelled 'indeterminate,' 16 (45.7%) had additional investigations/interventions, and 4 (11.4%) were confirmed to be metastatic. Twenty-one metastatic lesions were missed initially on WBMRI and confirmed on subsequent WBMRI, of which 5 (23.8%) were clinically significant. The 5-year survival since the detection of metastasis was better in the regular surveillance subgroup (85.7% vs. 45%), but this was not statistically significant (p = 0.068). Five patients (8.9%) developed their first metastasis more than 5 years after diagnosing the primary lesion. CONCLUSION: Regular WBMRI surveillance of myxoid liposarcoma patients considerably impacts clinical management by frequently influencing treatment decisions. CLINICAL RELEVANCE STATEMENT: WBMRI has been recently recommended as an imaging option for the staging and surveillance of myxoid liposarcoma patients. Our study highlights the impact of regular WBMRI surveillance on the clinical management of these patients and how it affects their survival.

Mandibular Myxoid Liposarcoma: a Case Study.

Liposarcomas are described as soft tissue sarcomas derived from adipose tissue. The finding of this tumor in the mandibular region is exceedingly rare. As of now, it has been described mainly in case reports and small series. A multidisciplinary approach is required to offer optimal treatment and may involve surgery, radiation and systemic therapies. Surgical repair of these defects represents a major challenge in oral and maxillofacial reconstructive surgery. We present the case of a 54-year-old man referred to our center with a progressively increasing mass in the anterior portion of the mandible. Biopsy revealed a well-differentiated myxoid liposarcoma. Resection of the tumor was performed with an additional primary reconstruction.

Nuclear morphological atypia in biopsy accurately reflects the prognosis of myxoid liposarcoma.

Currently, it is difficult to predict the prognosis of myxoid liposarcoma (MLS) in biopsy specimens. In this study, we determined whether nuclear morphology may be used to predict the prognosis of MLS in primary biopsy specimens. Two pathologists evaluated nuclear morphology using the modified WHO/ISUP and Fuhrman grades. Survival analyses were performed by grouping nuclear high- and low-grades. We examined 53 MLS cases, which included 29 (54.7%) male and 24 (45.3%) female patients with a median age of 46 years (interquartile range, 37 - 60). In total, 7 (13.2%) and 16 (30.2%) cases were assigned to the high nuclear grade group based on the modified WHO/ISUP and Fuhrman gradings, respectively. Survival analyses revealed a significantly worse disease-free survival in the high-grade group (hazard ratio (HR), 7.51; 95% confidence interval (CI), 2.67-21.1, p < 0.001 by the modified WHO/ISUP grading; HR, 4.45; 95% CI, 1.63-12.1, p = 0.001 by the modified Fuhrman grading). Moreover, the modified WHO/ISUP grade showed a significantly worse overall survival in the high-grade group (HR, 4.39; 95% CI, 1.04-18.6, p = 0.028), and the modified Fuhrman grade exhibited a similar, but not significant, trend. Our results indicate that nuclear morphology grading is a good predictor of patient prognosis at the time of biopsy in MLS. Even when cell density is sparse, treatment strategies should be carefully considered when individual tumor cells exhibit atypical nuclei.

Myxoid liposarcoma with nuclear pleomorphism: a clinicopathological and molecular study.

Myxoid liposarcoma (MLS) is a common type of liposarcoma. It is characterized by variably lipogenic uniform cells in myxoid stroma with arborizing capillaries and DDIT3 fusion. Nuclear uniformity is the rule, which is maintained even in high-grade round cell examples. In this study, we conducted an in-depth investigation of four MLS tumors that demonstrated nuclear pleomorphism in three patients. These cases accounted for 2.1% of 142 patients with MLS. All patients were male aged 26, 33, and 49 years. Nuclear pleomorphism was observed in both primary and metastatic tumors in one patient, a primary tumor in one patient, and a metastatic tumor in another patient. Pleomorphism was severe in three tumors and moderate in one. Histology resembled that of dedifferentiated liposarcoma with myxoid features, pleomorphic liposarcoma with myxoid features, or myxoid pleomorphic liposarcoma in two tumors, pleomorphic sarcoma with focal cartilaginous and rhabdomyoblastic differentiation in one tumor, and epithelioid pleomorphic liposarcoma in one tumor. All tumors harbored FUS::DDIT3 fusions and immunohistochemically expressed DDIT3. All tumors had TP53 mutations, whereas previous specimens with uniform cytology from the same patients lacked TP53 mutations. One tumor showed RB1 deletion and complete loss of Rb expression, which was unclassifiable using DNA methylation-based methods. The rare occurrence of nuclear pleomorphism is underrecognized in MLS and increases the complexity to the diagnosis of liposarcoma. DDIT3 evaluation can be liberally considered in liposarcoma assessment even in the presence of nuclear pleomorphism.

Is perioperative chemotherapy effective in patients with localized myxoid liposarcoma?

BACKGROUND: This study aimed to compare the local recurrence, distant metastasis and disease-specific survival rates of patients with localized myxoid liposarcoma in the surgery and adjuvant chemotherapy group versus the surgery alone group. METHODS: A total of 456 patients in the Japanese National Bone and Soft Tissue Tumour Registry database who had localized myxoid liposarcoma and underwent surgery and adjuvant chemotherapy or surgery alone between 2001 and 2019 were included in this retrospective study. The study adjusted for background differences between patients who underwent surgery and adjuvant chemotherapy (n = 228) or surgery alone (n = 228) using propensity score matching. RESULTS: Univariate analysis showed no significant difference in local recurrence rate between the two groups (5-year local recurrence-free survival: 98.6% [95% confidence interval: 95.9-99.6] vs. 94.0% [95% confidence interval: 89.7-96.6], P = 0.052). Univariate analysis showed no difference in the incidence of distant metastases between the two groups (5-year distant metastasis-free survival: 80.5% [95% confidence interval: 73.9-85.8] vs. 75.1% [95% confidence interval: 67.7-81.2], P = 0.508). Univariate analysis showed no difference in disease-specific survival between the two groups (5-year disease-specific survival: 92.6% [95% confidence interval: 86.1-96.2] vs. 93.2% [95% confidence interval: 87.6-96.4], P = 0.804). In the high-risk group (n = 203) with high-grade tumours and tumour size ≥10 cm, there were no significant differences in the local recurrence, distant metastasis and disease-specific survival rates between the surgery and adjuvant chemotherapy group and the surgery alone group. CONCLUSION: The effect of adjuvant chemotherapy on localized myxoid liposarcoma appears to be limited.

Case series: cardiac sarcoma.

Background: Cardiac masses encompass a wide differential including primary and secondary malignancies and can present with a variety of symptoms, many of which are non-specific. Early identification and classification are important, particularly for cardiac malignancies such as sarcomas as these are aggressive tumours with exceptionally poor prognoses when metastases are present at diagnosis. Case summary: We report two cases of patients who presented with dyspnoea and were diagnosed with cardiac sarcomas; the former a primary sarcoma (undifferentiated pleomorphic subtype) and the latter a secondary sarcoma (round cell myxoid liposarcoma) that serve as comparisons for presentation and management of different types of this disease. Computed Tomography (CT) and echocardiography imaging findings are demonstrated showing the typical location and morphology of each subtype. Discussion: Cardiac sarcomas are the most common primary cardiac malignancy, of which undifferentiated pleomorphic sarcoma is a common subtype. Undifferentiated pleomorphic sarcomas are aggressive, have a tendency to arise in the left atrium, and can appear similar to benign cardiac masses. Round cell myxoid liposarcomas by contrast are rare causes of secondary cardiac malignancies, metastasizing to the heart from soft tissues. Both diagnoses carry poor prognoses and although rare, are important to recognize as timely intervention with surgery, radiotherapy, and consideration of chemotherapy is key to maximizing survival.

An extremely rare case of recurrent pleomorphic myxoidliposarcoma with response to eribulin chemotherapy - A case report.

Pleomorphic myxoid liposarcoma (PML) is a newly recognized entity with aggressive clinical behavior and a tendency to recur. It has histological features of both myxoid and pleomorphic liposarcoma and lacks the molecular and structural chromosomal abnormalities associated with myxoid and pleomorphic liposarcoma. The data about their response to chemotherapy is quite sparse. We report a case of incidentally detected pleomorphic myxoid liposarcoma of the mediastinum in a 32-year-old gentleman. After resection and adjuvant chemotherapy with doxorubicin and ifosfamide, there was no evidence of residual disease at the end of treatment. During a routine follow-up 5 months later, he was found to have a recurrence of the disease with histological confirmation. He received a trabectedin given its activity in myxoid liposarcoma. However, he had toxicities and progression leading to its discontinuation. Subsequently, eribulin was started as the next line of therapy. After 4 cycles of chemotherapy, response assessment was suggestive of partial response, which is still maintained after 7 cycles of eribulin. This is the first report of this entity responding to a newer chemotherapy regimen.

Solitary Metastasis to the Breast From Thigh Myxoid Liposarcoma.

Metastasis to the breast from non-mammary malignancies are rare and suggestive of advanced disease. Accurate and prompt diagnosis of breast metastasis can provide important prognostic information and guide treatment planning. Interestingly, in contrast to primary breast malignancies, non-mammary metastatic breast lesions often have benign-appearing imaging characteristics. Knowing a patient's clinical history and having prior breast imaging studies for comparison is important for making accurate assessments and appropriate recommendations. Imaging-guided biopsy is often indicated for definitive tissue diagnosis. We report a rare case of solitary metastasis to the breast from thigh myxoid liposarcoma.

Myxoid liposarcoma: MRI features with histological correlation.

BACKGROUND AND AIMS: Myxoid liposarcoma is classified in the group of sarcomas with adipose differentiation, which is the second most common group of sarcomas. However, myxoid liposarcoma is not a homogeneous entity, because the behavior and clinical course of these tumours can vary widely. This study aimed to describe the magnetic resonance imaging (MRI) features of myxoid liposarcomas and to determine whether the MRI features are associated with the histologic grade and can differentiate between low-grade and high-grade tumours and thus help in clinical decision making. MATERIAL AND METHODS: We studied 36 patients with myxoid liposarcomas treated at our centre between 2010 and 2018. We analysed clinical variables (age, sex, and tumour site) and MRI features (size, depth, borders, fatty component, myxoid component, non-fatty/non-myxoid component, apparent diffusion coefficient (ADC), and type of enhancement after the administration of intravenous contrast material). We correlated the MRI features with the histologic grade and the percentage of round cells. RESULTS: In our series, patients with myxoid liposarcomas were mainly young adults (median age, 43 years). There were no differences between sexes; 97.2% were located in the lower limbs, 86.1% were deep, and 77.8% had well-defined borders. Of the 23 myxoid liposarcomas that contained no fat, 16 (69.6%) were high grade (p = 0.01). All the tumors with a myxoid component of less than 25% were high grade (p = 0.01); 83.3% of those with a non-fatty/non-myxoid component greater than 50% were high grade (p = 0.03) and 61.5% had more than 5% round cells (p = 0.01). Diffusion sequences were obtained in 14 of the 36 patients; ADC values were high (median, 2 × 10-3 mm2/s), although there were no significant associations between low-grade and high-grade tumours. Contrast-enhanced images were available for 30 (83.3%) patients; 83.3% of the tumours with heterogeneous enhancement were high grade (p = 0.01). CONCLUSIONS: MRI can be useful for differentiating between high- and low-grade myxoid liposarcomas and can help in clinical decision making.

Comparison of pre-operative and post-operative radiotherapy in patients with localized myxoid liposarcoma.

BACKGROUND: Myxoid liposarcoma is more radiosensitive than other soft tissue sarcomas, and radiotherapy has been reported to reduce tumour size. This study was performed to compare the rates of local recurrence, survival and wound complications between pre- and post-operative radiotherapy for localized myxoid liposarcoma. METHODS: From the Japanese Nationwide Bone and Soft Tissue Tumor Registry database, 200 patients with localized myxoid liposarcoma who received pre- (range, 30-56 Gy) or post-operative (range, 45-70 Gy) radiotherapy and surgery were included in this retrospective study. Propensity score matching was used to adjust for background differences between patients who received pre- and post-operative radiotherapy. RESULTS: Local recurrence occurred in five (5.0%) and nine (9.0%) patients in the pre- and post-operative radiotherapy groups, respectively (both n = 100). The median follow-up time from diagnosis was 40.5 months (IQR, 26.3-74). Univariate analysis showed a similar risk of local recurrence between the pre- and post-operative radiotherapy groups (5-year local recurrence-free survival 94.9% [95% CI 87.0-98.1] vs. 89.0% [95% CI 79.6-94.3]; P = 0.167). Disease-specific survival was similar between the pre- and post-operative radiotherapy groups (5-year disease-specific survival 88.1% [95% CI 75.5-94.6] vs. 88.4% [95% CI 77.3-94.5]; P = 0.900). The incidence of wound complications was similar between the pre- and post-operative radiotherapy groups (7.0% vs. 12.0%; P = 0.228). CONCLUSIONS: There was no difference in local recurrence, survival or incidence of wound complications between pre- and post-operative radiotherapy for localized myxoid liposarcoma. Therefore, pre-operative radiotherapy for myxoid liposarcoma provides clinical results equivalent to post-operative radiotherapy.

Incidental Diagnosis of Primary Pleural Liposarcoma in a COVID-19-Positive Patient.

A few cases of primary liposarcoma of pleura have been reported worldwide. We report a young gentleman who was admitted with what was initially thought as coronavirus disease 2019 (COVID-19)-related pulmonary symptoms. His chest CT showed a large pleural effusion causing a mediastinal shift and compressing vital structures. He did not respond to conservative drainage intervention and subsequently underwent a left thoracotomy for his worsening clinical picture. He was found to have a large left pleural mass that was incompletely resected. Histopathology examination showed low-grade soft tissue sarcoma with lipogenic differentiation suggestive of myxoid liposarcoma. He was subsequently given adjuvant chemotherapy but succumbed and died because of the progression of the disease.

Histological response to radiotherapy is an early event in myxoid liposarcoma.

Compared to other sarcomas, myxoid liposarcoma (MLS) is exceptionally sensitive to radiation therapy, but the underlying mechanism remains unknown. The objective was to assess the tissue-based changes in MLS during and after neoadjuvant radiotherapy in 26 patients of the DOREMY trial. Morphological assessment was performed on biopsies pre-treatment, after 8 fractions, 16 factions, and after surgical resection and included percentage of viable tumor cells, hyalinization, necrosis, and fatty maturation. Furthermore, immunohistochemistry was performed for apoptosis (cleaved caspase-3), anti-apoptosis (Bcl-2), activity of mTOR signaling (phospho-S6), hypoxia (CAIX), proliferation (Ki67), inflammation (CD45 and CD68), and microvessel density (CD34 Chalkley count). A pronounced reduction in vital tumor cells was observed early with a drop to 32.5% (median) tumor cells (IQR 10-93.8%) after 8 fractions. This decreased further to 10% (IQR 5-30%) after 16 fractions and 7.5% (IQR 5-15%) in the surgical specimen. All but one patient had an excellent response with < 50% remaining tumor cells. Inversely, treatment response was mainly observed as hyalinization and less often as fatty maturation. Additionally, a decrease of inflammatory cells was noticed especially during the first eight fractions. Microvessel density remained stable over time. Immunohistochemical markers for apoptosis, anti-apoptosis, activity of mTOR signaling, proliferation, and hypoxia did not show any marked changes within the remaining tumor cells during and after radiotherapy. As a modest dose of neoadjuvant radiotherapy induces profound tissue changes in MLS, mainly during the first 8 fractions, current findings might suggest that in a carefully selected patient population further deintensification of radiotherapy might be explored.

Myxoid Liposarcoma of the Breast Mimicking Phyllodes Tumor: A Case Report.

Myxoid liposarcoma is an extremely rare malignant breast tumor. We report the case of a 44-year-old woman who had myxoid liposarcoma of the breast with a history of phyllodes tumor and describe the imaging findings on US, mammography, and MRI. Before surgery, the mass was considered to be a recurrent phyllodes tumor. However, using US, we retrospectively identified some differences between myxoid liposarcomas and phyllodes tumors.

Suppression of antitumor cytokine IL­24 by PRG4 and PAI­1 may promote myxoid liposarcoma cell survival.

Suppression of the antitumor cytokine interleukin-24 (IL-24) is critical for the survival of myxoid liposarcoma (MLS) cells. It has been previously demonstrated by the authors that an MLS-specific chimeric oncoprotein, translocated in liposarcoma-CCAAT/enhancer-binding protein homologous protein (TLS-CHOP), supresses IL24 mRNA expression via induction of proteoglycan 4 (PRG4) to sustain MLS cell proliferation. However, IL-24 has also been revealed to be suppressed by the ubiquitin-proteasome system in human ovarian and lung cancer cells. Therefore, the aim of the present study was to elucidate the mechanism of IL-24 suppression in MLS cells. The results revealed that the proteasome inhibitor, MG-132, induced cell death in MLS cells in vitro; this effect was reduced following IL-24 knockdown. This indicated that proteasomal degradation of IL-24 may be an important process for MLS cell survival. In addition, it was also previously revealed by the authors that knockdown of plasminogen activator inhibitor-1 (PAI-1), a TLS-CHOP downstream molecule, suppressed the growth of MLS cells, thus instigating the investigation of the effect of PAI-1 on IL-24 expression in MLS cells. Double knockdown of PAI-1 and IL-24 negated the growth-suppressive effect of PAI-1 single knockdown in MLS cells. Interestingly, PAI-1 single knockdown did not increase the mRNA expression of IL24, but it did increase the protein abundance of IL-24, indicating that PAI-1 suppressed IL-24 expression by promoting its proteasomal degradation. Moreover, treatment of MLS cells with a PAI-1 inhibitor, TM5275, induced IL-24 protein expression and apoptosis. Collectively, the results of the present as well as previous studies indicated that IL-24 expression may be suppressed at the transcriptional level by PRG4 and at the protein level by PAI-1 in MLS cells. Accordingly, PAI-1 may represent an effective therapeutic target for MLS treatment.

Primary renal myxoid liposarcoma with pancreatic invasion on 18F-FDG PET/CT: first case report and literature review.

Background: Myxoid liposarcoma (MLS) is a rare malignant soft tissue sarcoma that predominantly manifests in the deep soft tissues of the extremities, particularly within the musculature of the thigh. Unlike other types of liposarcoma, MLS demonstrates a propensity for metastasis to atypical sites, including the lung parenchyma, soft tissues, retroperitoneum, mediastinum, breast, liver, thymus, lymph nodes, and bones. The definitive diagnosis primarily relies on histology with HE staining. Imaging modalities such as ultrasound, CT, MRI, and 18F-FDG PET/CT scans serve as valuable tools for tumor identification. Case report: A 57-year-old man presented with symptoms of abdominal distention and vomiting 1 month ago. Contrast-enhancement CT revealed a heterogeneous hypodense mass in the upper-middle part of the left kidney, displaying irregular morphology and protrusion towards the exterior of the kidney, with abundant blood supply and had a maximum dimension of approximately 10.7 cm × 9.0 cm. Additionally, a rounded soft tissue density was identified in the pancreatic body. Multiplanar reconstruction demonstrated a connection between the pancreatic lesion and the kidney mass. 18F-FDG PET/CT was conducted for staging, revealing significant growth of the lesion in the upper-middle part of the left kidney, extending beyond the kidney and infiltrating the pancreatic body. The lesion demonstrated remarkably high 18F-FDG uptake (SUVmax = 10.2, MTV = 136.13 cm3, TLG = 484.62). The postoperative pathological examination confirmed the diagnosis of MLS. On the 10th day post-surgery, the patient presented with tumor recurrence and underwent another surgical resection. Unfortunately, during the operation, the patient experienced a sudden cardiac arrest and died. Conclusion: Renal MLS with invasion into the pancreas is very rare in clinical practice. Due to the limited research on the utilization of 18F-FDG PET/CT in this particular context, given the rarity and low incidence of MLS, its role remains largely unexplored. As PET/CT imaging becomes increasingly prevalent, thorough imaging of disease sites becomes indispensable for the development of treatment protocols and the monitoring of treatment response.