Renal Masses Detected on FDG PET/CT in Patients With Lymphoma: Imaging Features Differentiating Primary Renal Cell Carcinomas From Renal Lymphomatous Involvement

Imaging features of the renal lymphoma: case report and literature review

Renal affection is common in disseminated non-Hodgkin's lymphoma (NHL) which is known as secondary renal lymphoma (SRL). Primary renal lymphoma (PRL) is an exceedingly uncommon disease, which accounts for less than 1% of all renal masses. Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of NHL in both primary as well as secondary renal lymphomas. PRL is of paramount importance clinically as it is usually managed with neo-adjuvant chemotherapy followed by nephrectomy in contrast to the more frequently seen renal cell carcinoma, which is treated surgically. This outstanding difference in management challenges the longstanding approach that preoperative biopsies are not mandatory prior to nephrectomy for renal masses. Because of its relative rarity, the imaging features of PRL have been described in a few studies, and having an understanding of these typical imaging patterns is crucial for making an accurate diagnosis and differentiation from other renal malignancies. Here, we present a case of a secondary renal lymphoma and discuss its differential imaging features.

Multimodality imaging review of focal renal lesions

Background

Focal lesions of the kidney comprise a spectrum of entities that can be broadly classified as malignant tumors, benign tumors, and non-neoplastic lesions. Malignant tumors include renal cell carcinoma subtypes, urothelial carcinoma, lymphoma, post-transplant lymphoproliferative disease, metastases to the kidney, and rare malignant lesions. Benign tumors include angiomyolipoma (fat-rich and fat-poor) and oncocytoma. Non-neoplastic lesions include infective, inflammatory, and vascular entities. Anatomical variants can also mimic focal masses.

Main body of the abstract

A range of imaging modalities are available to facilitate characterization; ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), magnetic resonance (MR) imaging, and positron emission tomography (PET), each with their own strengths and limitations. Renal lesions are being detected with increasing frequency due to escalating imaging volumes. Accurate diagnosis is central to guiding clinical management and determining prognosis. Certain lesions require intervention, whereas others may be managed conservatively or deemed clinically insignificant. Challenging cases often benefit from a multimodality imaging approach combining the morphology, enhancement and metabolic features.

Short conclusion

Knowledge of the relevant clinical details and key imaging features is crucial for accurate characterization and differentiation of renal lesions.

Infiltrative tumor interface with normal renal parenchyma in locally advanced renal cell carcinoma: Clinical relevance and pathological implications

OBJECTIVES

Locally advanced renal cell carcinoma is considered clinically aggressive, despite heterogeneity in survival outcomes. We investigated the clinical relevance and pathological implications of infiltrative tumor interface with normal renal parenchyma on preoperative imaging in locally advanced renal cell carcinoma.

METHODS

A total of 77 patients with locally advanced renal cell carcinoma (≥pT3a Nany M0) who underwent radical or partial nephrectomy (2008-2018) were analyzed. Preoperative dynamic computed tomography images were reviewed to assess radiological infiltrative features. A radiological infiltrative feature was defined as an ill-defined tumor interface with normal renal parenchyma. The tumor interfaces were analyzed histologically and compared with radiological findings.

RESULTS

The median tumor size was 6.4 cm. Lymphadenopathy was observed in four patients (5.2%). Clear cell renal cell carcinoma was diagnosed in 66 patients (86%) and Fuhrman grade was 3-4 in 38 patients (49%). A total of 30 patients (39%) showed radiological infiltrative features, which were significantly associated with larger tumor size and higher clinical T stage. The specificity and sensitivity of radiological infiltrative features in predicting pathological renal parenchymal infiltration were 90 and 64%, respectively. During a median follow-up period of 3.8 years, 27 patients (35%) developed cancer recurrences, and six patients (7.8%) died of renal cell carcinoma. Multivariable analysis showed that the presence of radiological infiltrative features was an independent risk factor for cancer recurrence. Cancer recurrence and cancer-specific mortality were significantly stratified by the presence or absence of radiological infiltrative features (P < 0.001 and P = 0.02, respectively).

CONCLUSIONS

Locally advanced renal cell carcinoma can show radiological infiltrative features preoperatively, which are significantly associated with unfavorable prognosis. Radiological infiltrative features on preoperative imaging correspond with a high specificity to pathological renal parenchymal infiltration.

Extensive Extranodal Involvement in a case of Non-Hodgkin's Lymphoma with sparing of lymph nodes and lymphatic organs

Non-Hodgkin lymphoma (NHL) is a group of malignant lymphoproliferative disorders arising predominantly in the lymph nodes with various clinical and histological characteristics. At least 25% of NHL originates from tissues other than lymph nodes and sometimes even from sites that do not contain lymphoid tissue. These are referred to as primary extranodal lymphomas (pENLs). pENL is a universal diagnostic challenge to the clinicians and pathologists due to their varied clinical presentations, morphological mimicry, and molecular alterations. The GIT is the most common site of pENL followed by nasopharynx/oropharynx, testis, uterus/ovary, thyroid, and central nervous system. Long bones (tibia), maxillary sinus, skin, and paraspinal soft tissues are the other rare anatomic sites of pENL. We reported a case of a 60-year-old female presented with pain and mass in the pelvis region. ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and fused PET/CT was done, which revealed extensive extranodal involvement of the lung, bilateral kidneys, uterus, ovaries, bones, and muscles with no involvement of lymph nodes or lymphomatous organs. Extensive extranodal involvement with sparing of lymphomatous organ has not been reported earlier.

Quantitative positron emission tomography imaging in the presence of iodinated contrast media using electron density quantifications from dual-energy computed tomography

PURPOSE

As preparation for future positron emission tomography (PET)/dual-energy computed tomography (DECT)T imaging modality and new possible clinical applications, the study aimed to evaluate the utility of clinically available spectral results from a DECT system for improving attenuation corrections of PET acquisitions in the presence of iodinated contrast media. The dependence of the accuracy of PET quantification values, reconstructed with conventional and spectral-based attenuation corrections, was examined as a function of the amount of iodine content and x-ray radiation exposure.

METHODS

Measurements were performed on commercial PET/CT and DECT systems, using a semi-anthropomorphic phantom with seven centrifuge tubes in its bore. Five different configurations of tube contents were scanned by both PET/CT and DECT. With the aim of mimicking clinically observed concentrations, in all phantom configurations the center tube contained a high concentration of radionuclide while the peripheral tubes contained a lower concentration of radionuclide. Iodine content was incrementally increased between phantom configurations by replacing iodine-free tubes with tubes that contained the original radionuclide concentration within a 10 mg/ml iodine dilution. DECT-based attenuation correction maps were generated by scaling electron density spectral results into corresponding 511 keV photon linear attenuation coefficients.

RESULTS

Mean SUV values obtained from the nominal PET reconstruction, using conventional CT images as input for the attenuation correction, demonstrate a monotonic increase of 8.6% when the water and radionuclide mixtures were replaced by iodine, water, and radionuclide (same level of activity) mixture. Mean SUV values obtained from the DECT-based reconstruction, in which the attenuation correction utilizes electron density values as input, demonstrate different, more stable behavior across all iodine insert configurations, with a standard deviation to mean ratio of less than 1%. This observed behavior was independent of the area size used for measurement. A minor radiation dose dependency of the electron density values (below 0.5%) was observed. This resulted in consistent (iodine independent) PET quantification behavior, which persisted even at the lowest radiation dose levels tested in our experiment, that is, 25% of the radiation dose utilized for CT acquisition in the clinical PET/CT protocol.

CONCLUSIONS

Utilization of DECT-generated electron density estimations for attenuation correction benefit PET quantification consistency in the presence of iodine and at nominal and low DECT radiation exposure levels. The ability to correctly account for iodinated contrast media in PET acquisitions will allow the development of new clinical applications that rely on the quantitative capabilities of spectral CT technologies and modern PET systems.

2-[18F]FDG PET/CT parameters associated with WHO/ISUP grade in clear cell renal cell carcinoma

PURPOSE

To explore the potential parameters from preoperative 2-[¹⁸F]FDG PET/CT that might associate with the World Health Organization/the International Society of Urological Pathology (WHO/ISUP) grade in clear cell renal cell carcinoma (ccRCC).

METHODS

One hundred twenty-five patients with newly diagnosed ccRCC who underwent 2-[¹⁸F]FDG PET/CT prior to surgery or biopsy were retrospectively reviewed. The metabolic parameters and imaging features obtained from 2-[¹⁸F]FDG PET/CT examinations were analyzed in combination with clinical characteristics. Univariate and multivariate logistic regression analyses were performed to identify the predictive factors of WHO/ISUP grade.

RESULTS

Metabolic parameters of primary tumor maximum standardized uptake value (SUVmax), tumor-to-liver SUV ratio (TLR), and tumor-to-kidney SUV ratio (TKR) were significantly different between any two of the four different WHO/ISUP grades, except those between the WHO/ISUP grade 3 and grade 4. The optimal cutoff values to predict high WHO/ISUP grade for SUVmax, TLR, and TKR were 4.15, 1.63, and 1.59, respectively. TLR (AUC: 0.841) was superior to TKR (AUC: 0.810) in distinguishing high and low WHO/ISUP grades (P = 0.0042). In univariate analysis, SUVmax, TLR, TKR, primary tumor size, tumor thrombus, distant metastases, and clinical symptoms could discriminate between the high and low WHO/ISUP grades (P < 0.05). In multivariate analysis, TLR (P < 0.001; OR: 1.732; 95%CI: 1.289-2.328) and tumor thrombus (P < 0.001; OR: 6.199; 95%CI: 2.499-15.375) were significant factors for differentiating WHO/ISUP grades.

CONCLUSION

Elevated TLR (> 1.63) and presence of tumor thrombus from preoperative 2-[¹⁸F]FDG PET/CT can distinguish high WHO/ISUP grade ccRCC effectively. 2-[¹⁸F]FDG PET/CT may be a feasible method for noninvasive assessment of WHO/ISUP grade.

PET imaging in renal cancer

PURPOSE OF REVIEW

Worldwide, over 400 000 new cases of kidney cancer were diagnosed and over 175 000 deaths anticipated in 2018. It is ranked as the 14th most common cancer in women and 9th most common in men. Imaging is important for initial detection, staging, and monitoring to assist treatment planning, but conventional anatomic imaging is limited. Although functional PET/CT has proven helpful in the diagnosis and management of many cancers, its value in renal cell carcinoma (RCC) is still in evolution.

RECENT FINDINGS

FDG is probably the most useful radiotracer in RCC, although CAIX imaging can be helpful in clear cell RCC. Current research on PET imaging agents in RCC including 89Zr bevacizumab, 89Zr geruntuximab, 18F fluoro-L-thymidine (FLT), prostate-specific membrane antigen (PSMA), 11C choline, 18F sodium fluoride (NaF), and18F fluorodeoxyglucose (FDG) have shown some interesting results for detection and prognosis of the disease.

SUMMARY

Many innovative radiotracers have been tested in RCC, but robust differentiation of primary disease from normal parenchyma remains elusive for almost all of them. The metastatic setting and response to therapy for this cancer are more favorable PET applications. Continued research in promising molecular tracers will hopefully advance both diagnostic and therapeutic strategies to ultimately eradicate RCC.

Primary renal lymphoma: A population-based analysis using the SEER program (1973-2015)

Objective

Primary renal lymphoma (PRL) is defined as a non‐Hodgkin lymphoma (NHL) restricted to kidneys without extensive nodal disease. The literature on epidemiology and outcome in PRL is limited to case reports and small case series.

Methods

We utilized Surveillance, Epidemiology, and End Result database (1984‐2015) to study the demographic, clinical, and pathological characteristics of PRL. We conducted analysis to assess factors associated with overall survival (OS) and cause‐specific survival (CSS).

Results

A total of 599 (0.17% of all NHL) patients were eligible for the study. The age‐adjusted incidence was 0.035/100,000 population and is increasing. The median age was 72 years, and most of the patients were Caucasians and were males. Most of the patients had unilateral tumors, and diffuse large B‐cell lymphoma (DLBCL) was the most common histologic type. The median OS was 112 months, while median CSS was not reached. Age ≥ 60 years was the strongest independent risk factor for worse OS and CSS, while non‐DLBCL histology was associated with better OS and CSS.

Discussion

Primary renal lymphoma is a rare lymphoma with increasing incidence in more recent years. In this study, we describe demographic, clinical, and pathological characteristics of PRL and factors affecting survival among these patients.

Lymphomas with kidney involvement: the French multicenter retrospective LyKID study

The LyKID study is a nationwide survey in France of lymphoma patients with renal involvement based on biopsy and/or imaging, to evaluate its impact on disease outcome and renal function. A total of 87 adult cases of B or T-cell lymphomas were retrospectively analyzed. Interstitial topography was observed in most of the kidney biopsies (54/66; 80%). Kidney failure (glomerular filtration rate <60 mL/min/1.73 m²) was present in 47% of patients and was associated with non-significantly different outcome. After lymphoma treatment, 44% of patients had persistent chronic kidney failure (CKF); kidney failure at diagnosis was the only parameter associated with CKF in multivariate analysis. DLBCL (diffuse large B-cell lymphomas) represented half of the series, with noticeably CNS (central neurological system) relapse in 17% patients, while fewer than one of two patients had received CNS prophylaxis. To our knowledge, the LyKID study represents the largest published non-autopsy lymphoma series with renal involvement.

Radiomics based on 18 F-FDG PET/CT could differentiate breast carcinoma from breast lymphoma using machine-learning approach: A preliminary study

PURPOSE

Our study assessed the ability ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) radiomics to differentiate breast carcinoma from breast lymphoma using machine-learning approach.

METHODS

Sixty-five breast nodules from 44 patients diagnosed as breast carcinoma or breast lymphoma were included. Standardized uptake value (SUV) and radiomic features from CT and PET images were extracted using local image features extraction software. Six discriminative models including PETa (based on clinical, SUV and radiomic features from PET images), PETb (SUV and radiomic features from PET images), PETc (radiomic features only from PET images), CTa (clinical and radiomic features from CT images), CTb (radiomic features only from CT images), and SUV model were generated using least absolute shrinkage and selection operator method and linear discriminant analysis. The areas under the receiver operating characteristic curve (AUCs), accuracy, sensitivity, and specificity were calculated to evaluate the discriminative ability of these models.

RESULTS

PETa and CTa models showed the best ability to differentiation in training and validation group (AUCs of 0.867 and 0.806 for PETa model, AUCs of 0.891 and 0.759 for CTa model, respectively).

CONCLUSION

Models based on clinical, SUV, and radiomic features of ¹⁸ F-FDG PET/CT images could accurately discriminate breast carcinoma from breast lymphoma.

Whole body FDG-PET/CT for the assessment of bone marrow infiltration in patients with newly diagnosed lymphoma

BACKGROUND

Positron emission tomography-computed tomography (PET-CT) and bone marrow biopsy are currently the common clinical examination of lymphoma infiltration. The aim of this research is to evaluate the value of PET-CT in diagnosis of bone marrow infiltration, clinical staging and pathological typing of lymphoma.

METHODS

153 cases were analyzed retrospectively to compare the consistency of PET-CT and bone marrow biopsy. We analyzed the sensitivity, accuracy and specificity of PET-CT in different clinical pathology of lymphoma.

RESULTS

The PET-CT sensitivity in detecting bone marrow infiltration is 54.3% with a specificity of 80.5% and accuracy of 74.5%. In aggressive B-cell lymphoma (DLBCL, HG-BL) and MZL, PET-CT results of bone marrow infiltration showed high accuracy of 88.1% and 83.3% respectively. The median value of SUVmax in the patients detected to have bone marrow infiltration by BMB was significantly higher than patients with BMB negative results among subgroups of aggressive B-cell lymphoma, MZL and T-NHL (p<.05).

CONCLUSION

PET-CT is significant in detecting bone marrow infiltration in certain pathological types of lymphoma. However pathological inconsistencies still exist between bone marrow biopsy and PET-CT, thus PET-CT cannot completely replace biopsy.

Three-Dimensional Texture Analysis Based on PET/CT Images to Distinguish Hepatocellular Carcinoma and Hepatic Lymphoma

Objectives: This study compared the diagnostic ability of image-based parameters with texture parameters in the differentiation of hepatocellular carcinoma (HCC) and hepatic lymphoma (HL) by positron emission tomography–computed tomography (PET/CT).

Methods: Patients with pathological diagnosis of HCC and HL were included in this study. Image-based and texture parameters were obtained by manual drawing of region of interest. Receiver operating characteristic (ROC) was used to test the diagnostic capacity of each parameter. Binary logistic regression was used to transform the most discriminative image-based parameters, texture parameters, and the combination of these parameters into three regression models. ROC was used to test the diagnostic capacity of these models.

Result: Ninety-nine patients diagnosed with HCC (n = 76) and HL (n = 23, 10 primary HL, 13 secondary HL) by histological examination were included in this study (From 2011 to 2018, West China hospital). According to the AUC and p-value, 2 image-based parameters and five texture parameters were selected. The diagnostic ability of texture-based model was better than that of image-based model, and after combination of those two groups of parameters the diagnostic capacity improved.

Conclusion: Texture parameters can differentiate HCC from HL quantitatively and improve the diagnostic ability of image-based parameters.

Infiltrative Renal Masses: Clinical Significance and Fidelity of Documentation

BACKGROUND

The prevalence of infiltrative renal masses (IRMs) and fidelity of documentation of infiltrative features remain unclear.

OBJECTIVE

To investigate the prevalence/significance of IRMs and assess whether infiltrative features were documented preoperatively.

DESIGN, SETTING, AND PARTICIPANTS

A total of 522 patients with renal tumors managed with partial/radical nephrectomy (2012-2014) whose pathology demonstrated locally advanced and/or aggressive histology were analyzed. Preoperative computed tomography/magnetic resonance imaging was retrospectively/independently reviewed by two radiologists. IRMs were required to have a poorly defined interface with parenchyma and nonelliptical shape in one or more distinct/unequivocal areas. Infiltrative features were defined as extensive or focal.

INTERVENTION

Partial/radical nephrectomy.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Cancer-specific mortality (CSM) was estimated using cumulative-incidence analysis. Significant and independent predictors of CSM were evaluated using Cox proportional hazard analysis.

RESULTS AND LIMITATIONS

Median tumor size was 6.9cm; renal cell carcinomas (RCCs) predominated (92%). Image review confirmed 133 IRMs (25%), including 103 RCCs; 59 had sarcomatoid or poorly differentiated features. IRMs were larger and more often symptomatic compared than non-IRMs, and disseminated disease was also more common for IRMs (all p<0.001). Overall, 109 IRMs were imaged at our center; 42 were documented as IRMs in preoperative radiology reports, while infiltrative features were not documented in 67 (61%). Only four (6%) of these 67 were documented as infiltrative by the surgical team. Infiltrative features were more often focal in undocumented IRMs. On multivariable analysis, infiltrative features, disseminated disease, and non-RCC histology were independent predictors of CSM (hazard ratio or HR [95% confidence interval {CI}]=1.73 [1.21-2.47], 2.98 [2.10-4.23], and 2.79 [1.86-4.62], respectively). Among IRMs, extensive infiltrative features and disseminated disease were associated with CSM (HR [95% CI]=1.98 [1.27-3.07] and 2.35 [1.52-3.63], respectively), while documentation status failed to show an association. Excluding patients with disseminated disease or residual cancer after surgery, recurrence rates were 62% for IRMs versus 22% for non-IRMs (p<0.001), and there was again no significant difference between documented and undocumented IRMs (p=0.36). Limitations include a retrospective design.

CONCLUSIONS

Twenty-five percent of locally advanced/histologically aggressive renal tumors exhibited infiltrative features, although many were not documented as IRMs. Among this high-risk surgical population, infiltrative features were independent predictors of CSM, irrespective of whether they were documented or not. Our data suggest that infiltrative features should be assessed and documented routinely during evaluation of renal masses.

PATIENT SUMMARY

Infiltrative renal masses may be more common than previously appreciated, although many were not documented as infiltrative during preoperative evaluation. Our data suggest that infiltrative features have a strong impact on prognosis and should be assessed and documented routinely during radiologic and clinical evaluation of renal masses.

Differential diagnostic ability of 18F-FDG PET/CT radiomics features between renal cell carcinoma and renal lymphoma

BACKGROUND

The aim of this study is to determine the differential diagnostic value of texture parameters of PET/CT on renal cell carcinoma and renal lymphoma.

METHODS

Twenty renal lymphoma and 18 renal cell carcinoma (RCC) patients were analyzed in this study. The pathological information and basic characteristics were extracted from the electronic medical record system of our hospital. We used LIFEx package to extract data from the radiomics images. Receiver operating characteristic analysis and binary logistic regression analysis was applied in determining the diagnostic accuracy of texture parameters as well as the synthetic parameter, of which the sensitivity and specificity was improved.

RESULTS

There were 14 (two in Histogram, two in Grey Level Co-occurrence Matrix, five in Grey-Level Run Length Matrix, five in Grey-Level Zone Length Matrix) out of the texture parameters showing an area under the curve (AUC) >0.7 and P<0.05. Synthesized parameters of each section showed even higher differentiation ability, with AUC varying from 0.725 to 1.000.

CONCLUSIONS

Texture analysis of ¹⁸F-FDG PET/CT could effectively differentiate between RCCs and renal lymphomas.

The Complete Spectrum of Infiltrative Renal Masses: Clinical Characteristics and Prognostic Implications

OBJECTIVE

To analyze the full spectrum of patients presenting with radiologically-identified infiltrative renal masses (IRMs), including those managed surgically or otherwise, with focus on clinical presentation/prognosis.

METHODS

All 280 patients presenting with radiologically-identified renal mass with infiltrative features (2008-2017) were retrospectively reviewed. Poorly-defined interface between tumor and parenchyma and irregular shape (nonelliptical) in one or more distinct/unequivocal areas were required for classification as IRM. IRM was confirmed in 265 and clinical characteristics and outcomes were assessed.

RESULTS

Median age/tumor size were 65-years/6.9 cm, respectively, and 225 patients (85%) were R.E.N.A.L. = 10-12. Overall, 181 patients (68%) presented symptomatically, locally-advanced cancer (cT3-T4) was observed in 176 (66%) and disseminated disease and/or lymphadenopathy (>2 cm) in 181(68%). Clinical/radiographic findings were suggestive of etiology and could direct evaluation, but were nonspecific for definitive diagnosis. Renal-mass biopsy was performed in 103 patients and diagnostic in 97 (94%). Renal surgery was only performed in 82 patients (31%) and partial nephrectomy in 3 (1.1%). Overall, 72 patients (27%) received systemic chemotherapy and 59 (22%) targeted therapy. Final-diagnosis was renal cell carcinoma in 94 patients (35%), including 49 with highly-aggressive histology (sarcomatoid/rhabdoid/collecting-duct/medullary/unclassified). High-grade urothelial-carcinoma was found in 70 (26%), and lymphoma/metastatic cancer in 26 (10%)/25 (9%), respectively. Overall, 153 patients (58%) died; 138 (52%) cancer-related at median of 5 months. The majority of patients with renal cell carcinoma, urothelial-carcinoma, and renal metastasis died, almost exclusively cancer-related, at medians of 8, 3, and 2 months, respectively.

CONCLUSION

Our series includes the full spectrum of IRMs and confirms predominance of symptomatic, poorly-differentiated, highly-lethal malignancies. Our study highlights the overriding importance of identifying infiltrative features, a simple radiologic diagnosis, during assessment of renal masses.

Concomitant occurrence of primary renal non-Hodgkin lymphoma and a colon cancer: A rare case report

RATIONALE

Primary renal lymphoma (PRL) is a rare malignancy due to the absence of lymphatic tissues in the kidney, and patients with PRL have been reported to have a poor prognosis due to its rapid invasiveness and limited treatment strategies. Colon cancer is the third most common cancer, and has a high mortality rate. Both malignant diseases predominantly affected elderly men; however, a case with concomitant occurrence of the 2 cancers is extremely rare.

PATIENT CONCERNS

A 78-year-old male patient with abdominal pain came to our hospital. Computed tomography (CT) indicated malignant masses in the left kidney, left adrenal gland, and the lower part of the descending colon.

DIAGNOSES

PRL and colon cancer were diagnosed based on pathological examinations.

INTERVENTIONS

The patient was treated with laparoscopic radical nephrectomy and laparoscopic radical resection of colon cancer.

OUTCOMES

The patient was then transferred to the intensive care unit (ICU) because of poor condition after surgery. He died 3 months after discharge without receiving any other treatment.

LESSONS

It is worth thinking about whether surgery was reasonable for elderly patients with double malignancies, or palliative treatment to improve the quality of life was more meaningful. This case also contributes to the understanding of the 2 malignancies and highlights the need to pay more attention to patients with multiple primary malignant neoplasms (MPMNs), explore genetic features, and investigate treatments with more survival benefits.

Ability of 18F-FDG PET/CT Radiomic Features to Distinguish Breast Carcinoma from Breast Lymphoma

Purpose. To investigate the value of SUV metrics and radiomic features based on the ability of 18F-FDG PET/CT in differentiating between breast lymphoma and breast carcinoma. Methods. A total of 67 breast nodules from 44 patients who underwent 18F-FDG PET/CT pretreatment were retrospectively analyzed. Radiomic parameters and SUV metrics were extracted using the LIFEx package on PET and CT images. All texture parameters were divided into six groups: histogram (HISTO), SHAPE, gray-level co-occurrence matrix (GLCM), gray-level run-length matrix (GLRLM), neighborhood gray-level different matrix (NGLDM), and gray-level zone-length matrix (GLZLM). Receiver operating characteristics (ROC) curves were generated to evaluate the discriminative ability of each parameter, and the optimal parameter in each group was selected to generate a new predictive variable by using binary logistic regression. PET predictive variable, CT predictive variable, the combination of PET and CT predictive variables, and SUVmax were compared in terms of areas under the curve (AUCs), sensitivity, specificity, and accuracy. Results. Except for SUVmin (p=0.971), the averages of FDG uptake metrics of lymphoma were significantly higher than those of carcinoma (p ≤ 0.001), with the following median values: SUVmean, 4.75 versus 2.38 g/ml (P < 0.001); SUVstd, 2.04 versus 0.88 g/ml (P=0.001); SUVmax, 10.69 versus 4.76 g/ml (P=0.001); SUVpeak, 9.15 versus 2.78 g/ml (P < 0.001); TLG, 42.24 versus 9.90 (P < 0.001). In the ROC curves analysis based on radiomic features and SUVmax, the AUC for SUVmax was 0.747, for CT texture parameters was 0.729, for PET texture parameters was 0.751, and for the combination of CT and PET texture parameters was 0.771. Conclusion. The SUV metrics in 18FDG PET/CT images showed a potential ability in the differentiation between breast lymphoma and carcinoma. The combination of SUVmax and PET/CT texture analysis may be promising to provide an effectively discriminant modality for the differential diagnosis of breast lymphoma and carcinoma, even for the differentiation of subtypes of lymphoma.

Genitourinary involvement of lymphomas on FDG-PET

Primary extranodal lymphomatous involvement of the genitourinary tract is rare and secondary extranodal involvement in disseminated disease occurs more frequently. Imaging of metabolic activity with 2-(fluorine-18) fluoro-2-deoxy-d-glucose (FDG) used in PET facilitates the identification of these extranodal sites of disease, particularly in the absence of structural lesions on conventional imaging modalities. Primary extranodal lymphoma affecting the genitourinary system is often caused by high-grade Non-Hodgkin's Lymphoma (NHL) with the most common subtype being diffuse large B-cell lymphoma (DLBCL). Although rare, the incidence of extranodal lymphoproliferative disease is increasing and a delay in diagnosis holds a poor prognosis. Familiarity with benign and physiological causes of FDG uptake, particularly due to the urinary tracer excretion is crucial in identifying sites of lymphomatous involvement in the genitourinary system. Additionally, non-lymphomatous malignancies are usually treated surgically, whereas lymphoma is primarily treated with chemotherapy and/or radiotherapy. Therefore, accurate identification and staging together with histological confirmation significantly impacts management of these patients. This article serves to review and illustrate the imaging findings on FDG-PET/CT of primary extranodal lymphoma affecting the genitourinary system.