Use of imaging in the management of malignant pleural mesothelioma

Conspicuity of malignant pleural mesothelioma in contrast enhanced MDCT - arterial phase or late phase?

BACKGROUND

To determine if late phase is superior to arterial phase intraindividually regarding conspicuity of MPM in contrast enhanced chest MDCT.

METHODS

28 patients with MPM were included in this retrospective study. For all patients, chest CT in standard arterial phase (scan delay ca. 35 s) and abdominal CT in portal venous phase (scan delay ca. 70 s) was performed. First, subjective analysis of tumor conspicuity was done independently by two radiologists. Second, objective analysis was done by measuring Hounsfield units (HU) in tumor lesions and in the surrounding tissue in identical locations in both phases. Differences of absolute HUs in tumor lesions between phases and differences of contrast (HU in lesion - HU in surrounding tissue) between phases were determined. HU measurements were compared using paired t-test for related samples. Potential confounding effects by different technical and epidemiological parameters between phases were evaluated performing a multiple regression analysis.

RESULTS

Subjective analysis: In all 28 patients and for both readers conspicuity of MPM was better on late phase compared to arterial phase. Objective analysis: MPM showed a significantly higher absolute HU in late phase (75.4 vs 56.7 HU, p < 0.001). Contrast to surrounding tissue was also significantly higher in late phase (difference of contrast between phases 18.5 HU, SD 10.6 HU, p < 0.001). Multiple regression analysis revealed contrast phase and tube voltage to be the only significant independent predictors for tumor contrast.

CONCLUSIONS

In contrast enhanced chest-MDCT for MPM late phase scanning seems to provide better conspicuity and higher contrast to surrounding tissue compared to standard arterial phase scans.

CT appearances of pleural infection: analysis of the Second Multi-centre Intra-pleural Sepsis Trial (MIST 2) cohort

AIM

To determine the prevalence of pleural abnormalities and describe the computed tomography (CT) features observed in a well-characterised population of patients with pleural infection.

MATERIALS AND METHODS

A retrospective study of a subgroup of patients from the Second Multi-centre Intra-pleural Sepsis Trial (MIST 2) trial was carried out. Patients were diagnosed with pleural infection on robust clinical criteria. CT examinations were assessed by three observers independently for the presence of predefined features. Planned subgroup comparisons of patients with and without evidence of parenchymal infection were performed.

RESULTS

Eighty-one patients were included. Parietal pleural thickening and enhancement were seen in 98.7% of patients. Visceral pleural changes were observed in most, including several previously undescribed features. Consolidation was observed in 61.7% of patients and there was a significant association of parenchymal consolidation with CT evidence of small airways infection (p<0.001) and visceral pleural thickening and enhancement (p<0.05). Features of parenchymal infection were absent in one third of patients.

CONCLUSION

This study provides a comprehensive account of the parietal pleural, visceral pleural, and parenchymal changes of pleural infection on CT. Parenchymal infection is absent in a significant proportion of patients with pleural infection, suggesting that a pneumonic process may not be necessary for the development of pleural infection.

The role of imaging in malignant pleural mesothelioma: an update after the 2018 BTS guidelines

Malignant pleural mesothelioma (MPM) is a primary malignancy of the pleura and is associated with a poor outcome. The symptoms and signs of malignant mesothelioma present late in the natural history of the disease and are non-specific, making the diagnosis challenging and imaging key. In 2018, the British Thoracic Society (BTS) updated the guideline on diagnosis, staging, and follow-up of patients with MPM. These recommendations are discussed in this review of the current literature on imaging of MPM. It is estimated MPM will continue to cause serious morbidity and mortality in the UK late into the 21st century, and internationally, people continue to be exposed to asbestos. We aim to update the reader on current and future imaging strategies, which could aid early diagnosis of pleural malignancy and provide an update on staging and assessment of tumour response.

Pleural tumours and tumour-like lesions

There are various neoplasms and tumour-like conditions of the pleura. Mesothelioma is perhaps the most widely recognised; however, there are many others that are more common and should be considered. Understanding the similarities and differences can be helpful in managing the patient with a newly found pleural lesion. We will discuss clinical symptoms at presentation and describe the imaging findings associated with these tumours, starting with conventional radiology, and correlating with computed tomography and combined positron-emission tomography (PET)/computed tomography (CT). Finally, imaging characteristics that help differentiation between the benign and malignant varieties will be reviewed.

MR Imaging of Pleural Neoplasms

The pleura may be affected by primary tumors or metastatic spread of intrathoracic or extrathoracic neoplasms. Primary pleural neoplasms represent ∼10% of all pleural tumors, and malignant lesions are more common than benign lesions. The most common primary tumors include malignant pleural mesothelioma and solitary fibrous tumor. Although pleural neoplasms may initially be evaluated with computed tomography (CT) and/or fluorodeoxyglucose positron emission tomography (PET)/CT, magnetic resonance (MR) imaging is complementary to these other imaging modalities for disease staging and evaluation of patients. In this article, we discuss the etiology, clinical presentation, and imaging of pleural neoplasms, with specific attention given to the role of MR imaging.

Early and delayed phases of contrast-enhanced CT for evaluating patients with malignant pleural effusion. Results of pairwise comparison by multiple observers

OBJECTIVE

To compare images from early and delayed phases of contrast-enhanced thoracic CT for assessing pleural thickening or nodules in a series of patients with malignant pleural effusions.

METHODS

Blinded images from 36 patients with malignant pleural effusions showing pleural lesions in both early (35 s delayed) and delayed (70 s delayed) phases of thoracic and abdominal contrast-enhanced CT scan were retrospectively assessed by six observers. First, images were individually scored in a six-point scale grading the quality of visualization of pleural findings such as pleural thickening or nodules. This was followed by a paired analysis, where the readers had to choose the one showing the highest quality between two images presented together corresponding to both phases of the same patient showing the same pleural lesion. When possible, contrast attenuation of the abnormal pleura was measured. Statistical analysis was performed by using paired t-test and χ ².

RESULTS

Mean attenuation of pleural lesions was significantly higher in the delayed phase (76.0 ± 25.1 vs 57.5 ± 20.7, p < 0.001). Mean score and score of individual images was statistically significant better for the delayed phase for all observers. In the paired analysis, all the readers preferred the delayed phase over the early phase in 77.8 to 91.7% of the cases.

CONCLUSION

Delayed phase of contrast-enhanced CT is preferable to early phase for evaluating pleural findings. Advances in knowledge: Pleural attenuation is greater for the delayed phase compared with the early phase of contrast-enhanced chest CT. In the pairwise comparison, all the observers prefer the delayed phase over the early phase for pleural evaluation.

Early Contrast Enhancement: A novel magnetic resonance imaging biomarker of pleural malignancy

INTRODUCTION

Pleural Malignancy (PM) is often occult on subjective radiological assessment. We sought to define a novel, semi-objective Magnetic Resonance Imaging (MRI) biomarker of PM, targeted to increased tumour microvessel density (MVD) and applicable to minimal pleural thickening.

MATERIALS AND METHODS

60 consecutive patients with suspected PM underwent contrast-enhanced 3-T MRI then pleural biopsy. In 58/60, parietal pleura signal intensity (SI) was measured in multiple regions of interest (ROI) at multiple time-points, generating ROI SI/time curves and Mean SI gradient (MSIG: SI increment/time). The diagnostic performance of Early Contrast Enhancement (ECE; which was defined as a SI peak in at least one ROI at or before 4.5 min) was compared with subjective MRI and Computed Tomography (CT) morphology results. MSIG was correlated against tumour MVD (based on Factor VIII immunostain) in 31 patients with Mesothelioma.

RESULTS

71% (41/58) patients had PM. Pleural thickening was <10 mm in 49/58 (84%). ECE sensitivity was 83% (95% CI 61-94%), specificity 83% (95% CI 68-91%), positive predictive value 68% (95% CI 47-84%), negative predictive value 92% (78-97%). ECE performance was similar or superior to subjective CT and MRI. MSIG correlated with MVD (r = 0.4258, p = .02).

DISCUSSION

ECE is a semi-objective, perfusion-based biomarker of PM, measurable in minimal pleural thickening. Further studies are warranted.

Spectrum of CT Findings in Thoracic Extranodal Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma (NHL) frequently manifests in extranodal structures in the chest, often in the form of secondary involvement but occasionally as primary disease. Because staging and treatment are affected by the presence of extranodal disease at imaging, radiologists' interpretation and management of suspicious findings are critical to patient care. Unfortunately, owing to considerable imaging overlap with other diseases, primary extranodal lymphoma is difficult to diagnose with imaging alone. Radiologists should have a heightened degree of suspicion in patients at risk (including patients with immune compromise, autoimmune diseases, or a history of stem cell or solid organ transplant) or with particular imaging appearances (including the vertebral wraparound sign, nonresolving consolidation, an infiltrative soft-tissue mass, and lesions demonstrating vascular encasement without invasion). For patients with known NHL, positron emission tomography/computed tomography (PET/CT) using fluorine 18 (¹⁸F)-labeled fluorodeoxyglucose (FDG) is now preferred for routine staging in most cases. CT remains heavily used, and identification of subtle extranodal involvement with CT can be improved with use of intravenous contrast material and careful review of multiplanar images. Pericardial effusion, pleural soft tissue (even when mild), mass-like consolidation, perilymphatic nodularity, and new lytic bone lesions are particularly suggestive of secondary involvement in a patient with known NHL. Magnetic resonance imaging is a helpful problem-solving tool when equivocal findings would change staging and treatment. This comprehensive review illustrates the spectrum of CT manifestations of extranodal NHL in the chest, including the pleura, lung, airways, heart, pericardium, esophagus, chest wall, and breast. ^©RSNA, 2017.

Can CT and MR Shape and Textural Features Differentiate Benign Versus Malignant Pleural Lesions?

RATIONALE AND OBJECTIVES

The study aimed to identify a radiomic approach based on CT and or magnetic resonance (MR) features (shape and texture) that may help differentiate benign versus malignant pleural lesions, and to assess if the radiomic model may improve confidence and accuracy of radiologists with different subspecialty backgrounds.

MATERIALS AND METHODS

Twenty-nine patients with pleural lesions studied on both contrast-enhanced CT and MR imaging were reviewed retrospectively. Three texture and three shape features were extracted. Combinations of features were used to generate logistic regression models using histopathology as outcome. Two thoracic and two abdominal radiologists evaluated their degree of confidence in malignancy. Diagnostic accuracy of radiologists was determined using contingency tables. Cohen's kappa coefficient was used to assess inter-reader agreement. Using optimal threshold criteria, sensitivity, specificity, and accuracy of each feature and combination of features were obtained and compared to the accuracy and confidence of radiologists.

RESULTS

The CT model that best discriminated malignant from benign lesions revealed an AUC_CT = 0.92 ± 0.05 (P < 0.0001). The most discriminative MR model showed an AUC_MR = 0.87 ± 0.09 (P < 0.0001). The CT model was compared to the diagnostic confidence of all radiologists and the model outperformed both abdominal radiologists (P < 0.002), whereas the top discriminative MR model outperformed one of the abdominal radiologists (P = 0.02). The most discriminative MR model was more accurate than one abdominal (P = 0.04) and one thoracic radiologist (P = 0.02).

CONCLUSION

Quantitative textural and shape analysis may help distinguish malignant from benign lesions. A radiomics-based approach may increase diagnostic confidence of abdominal radiologists on CT and MR and may potentially improve radiologists' accuracy in the assessment of pleural lesions characterized by MR.

Response evaluation in mesothelioma: Beyond RECIST

Malignant pleural mesothelioma (MPM) typically demonstrates a non-spherical growth pattern, so it is often difficult to accurately categorize change in tumour burden using size-based tumour response criteria (e.g., WHO (World Health Organisation), RECIST (Response Evaluation Criteria in Solid Tumours) and modified RECIST). Functional imaging techniques are applied to derive quantitative measurements of tumours, which reflect particular aspects of the tumour pathophysiology. By quantifying how these measurements change with treatment, it is possible to observe treatment effects. In this review, we survey the existing roles of CT and MRI for the management of MPM, including the currently applied size measurement criteria for the assessment of treatment response. New functional imaging techniques, such as positron emission tomography (PET), diffusion-weighted MRI (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) that may potentially improve the assessment of treatment response will be highlighted and discussed.

Malignant Pleural Mesothelioma: Accuracy of CT Against Immunohistochemical Test Among the Mexican Population

BACKGROUND AND AIMS

Malignant pleural mesothelioma (MPM) is associated with occupational and environmental exposure to asbestos. The incidence is expected to increase as the use of asbestos is not prohibited in many countries, such as in Mexico. We undertook this study to determine sensitivity, specificity, predictive values and likelihood ratios of computed tomography (CT) in a sample from Mexican population with suspected MPM and other pleuropulmonary diseases.

METHODS

CT films of 38 patients suspected of having MPM were analyzed. A single observer was blinded to MPM diagnoses. The frequencies of ten CT findings were identified. A cut-off point of ≥5 CT findings was established to determine high MPM probability. Sensitivity, specificity, predictive values and likelihood ratio of the CT against biopsy using immunohistochemical testing (IHC) for MPM were calculated.

RESULTS

Of the 38 patients, 31 had MPM and seven had lung adenocarcinoma. The five key findings were mediastinal pleural thickening 96.7% (n = 30), nodular pleural thickening 93.3% (n = 29), pleural mass 83.9% (n = 26), diminished lung 70.9% (n = 22) and contracted hemithorax 70.9% (n = 22). Sensitivity 96.8% (83.2-99.4), specificity 85.7% (42.2-97.6), positive likelihood ratio 6.7 (1.1-41.6), and negative likelihood ratio of 0.04 (0.01-0.2) were reported.

CONCLUSIONS

Sensitivity and specificity in this study was greater than previously reported, 96.8% and 85.7 vs. 93.2 and 65.6%, respectively. CT is an easily accessible and useful tool that should be incorporated into the medical education of general physicians to improve MPM diagnosis of suspected cases.

HER1-targeted 86Y-panitumumab possesses superior targeting characteristics than 86Y-cetuximab for PET imaging of human malignant mesothelioma tumors xenografts

Malignant mesothelioma (MM), a rare form of cancer is often associated with previous exposure to fibrous minerals, such as asbestos. Asbestos exposure increases HER1-activity and expression in pre-clinical models. Additionally, HER1 over-expression is observed in the majority of MM cases. In this study, the utility of HER1-targeted chimeric IgG₁, cetuximab, and a human IgG₂, panitumumab, radiolabeled with ⁸⁶Y, were evaluated for PET imaging to detect MM non-invasively in vivo, and to select an antibody candidate for radioimmunotherapy (RIT).

Methods

Radioimmunoconjugates (RICs) of cetuximab and panitumumab were prepared by conjugation with CHX-A’’-DTPA followed by radiolabeling with ⁸⁶Y. The HER1 expression of NCI-H226, NCI-H2052, NCI-H2452 and MSTO-211H human mesothelioma cells was characterized by flow cytometry. In vivo biodistribution, pharmacokinetic analysis, and PET imaging were performed in tumor bearing athymic mice.

Results

In vivo studies demonstrated high HER1 tumor uptake of both RICs. Significant reduction in tumor uptake was observed in mice co-injected with excess mAb (0.1 mg), demonstrating that uptake in the tumor was receptor specific. Significant differences were observed in the in vivo characteristics of the RICs. The blood clearance T_½α of ⁸⁶Y-cetuximab (0.9–1.1 h) was faster than ⁸⁶Y-panitumumab (2.6–3.1 h). Also, the tumor area under the curve (AUC) to liver AUC ratios of ⁸⁶Y-panitumumab were 1.5 to 2.5 times greater than ⁸⁶Y-cetuximab as observed by the differences in PET tumor to background ratios, which could be critical when imaging orthotopic tumors and concerns regarding radiation doses to normal organs such as the liver.

Conclusion

This study demonstrates the more favorable HER1-targeting characteristics of ⁸⁶Y-panitumumab than ⁸⁶Y-cetuximab for non-invasive assessment of the HER1 status of MM by PET imaging. Due to lower liver uptake, panitumumab based immunoconjugates may fare better in therapy than corresponding cetuximab based immunoconjugates.

Multidetector CT imaging of pleura: comparison of two contrast infusion protocols

OBJECTIVES

Imaging of the pleura by multidetector CT (MDCT) can be challenging. There is no clear evidence or guidelines on contrast infusion parameters for imaging pleura. We compared two contrast protocols for assessing pleural pathology on MDCT.

METHODS

This was a prospective study in which consecutive patients with MDCT for suspected pleural disease on chest radiograph were randomised into two groups. The first group received 150 ml of intravenous contrast at a rate of 2.5 ml s(-1) and the second group received 100 ml at 2 ml s(-1). Images were acquired after a 60 s delay. Hounsfield units of the pleura, thoracic aorta, main pulmonary artery, portal vein and superior mesenteric artery were measured and analysed by two independent readers.

RESULTS

40 patients (20 in each group) who had pleural enhancement on MDCT were included for final analysis. The mean pleural enhancement value was 83 HU (Group A) vs 59 HU (Group B) (p = 0.0004). The mean aortic enhancement was 241 HU (A) vs 141 HU (B) (p<0.0001); main pulmonary artery enhancement was 208 HU (A) vs 139 HU (B) (p<0.0002); portal venous enhancement was 169 HU (A) vs 115 HU (B) (p<0.0001); and the superior mesenteric artery enhancement was 215 HU (A) vs 128 HU (B) (p<0.0001).

CONCLUSION

Enhancement of the pleura and major vessels was significantly higher in the group receiving more contrast at a greater infusion rate. This technique of a single scan through the entire pleural surface with a delayed acquisition is promising. When pleural disease is suspected, contrast infusion protocols should be modified to achieve the best results and clinicians should be encouraged to specifically request a "pleural CT".

Assessment of therapy responses and prediction of survival in malignant pleural mesothelioma through computer-aided volumetric measurement on computed tomography scans

PURPOSE

The purposes of this study were (1) to calculate the tumor volume in patients with malignant pleural mesothelioma using computed tomography (CT) scan images and a computer-aided measurement technique and (2) to investigate whether the baseline volume, or volume change after chemotherapy, predicts patient survival.

METHODS

We compiled the clinical characteristics and outcome from 30 patients enrolled in two clinical trials at our cancer center in which the patients were treated with induction chemotherapy followed by surgery and radiation. CT scans of 30 patients were obtained at baseline and after two cycles of chemotherapy. Tumor volumes were calculated using a semiautomated computer algorithm. Overall survival was measured using a landmark time at 3 months post-treatment start date such that all patients had already received two cycles of chemotherapy and a follow-up scan. Association of volume changes with overall survival were determined by a Cox Proportional Hazards Model or log-rank test. The relationship between both pre and postoperative clinical stage and baseline tumor volume was analyzed using the rank sum test.

RESULTS

The median baseline tumor volume was 473 cm(3) (range, 61 cm(3)-2108 cm(3)). Patients with high preoperative stages (III and IV) had larger baseline tumor volume than those with low preoperative stages (I and II) (p = 0.05). Patients with baseline volumes smaller than 619 cm(3) tended to survive longer than those with baseline volumes larger than or equal to 619 cm(3) (p = 0.07). Percentage change of tumor volume from baseline to first follow-up CT after two cycles of chemotherapy was significantly associated with overall survival (hazard ratio: 1.94 [95% confidence interval, 1.05-3.60], p = 0.04). Whereas the relative change in modified RECIST measurements was not significantly associated with overall survival (hazard ratio: 1.06 [95% confidence interval, 0.96-1.16], p = 0.25). By classifying changes of tumor volumes between two scans into two groups, i.e., "increase" and "decrease," a significant difference in survival was found between those who increased and decreased after two cycles of chemotherapy (p = 0.03).

CONCLUSIONS

Changes in tumor volume after two cycles of chemotherapy predicted overall survival in patients with malignant pleural mesothelioma. Tumor volume at baseline was shown to be associated with preoperative clinical stage and survival. Computer-aided volumetric measurements may enable more reliable therapeutic response assessment and could provide additional prognostic information.

Localized pleural mesothelioma causing cranial vena cava syndrome in a dog

A 9-year-old female crossbred dog was presented to the Hospital Universitario Veterinario Rof Codina (Universidad de Santiago de Compostela, Lugo, Spain) for acute onset of severe, progressive swelling of the head, neck, and cranial trunk. Survey radiographs and ultrasonography revealed a large, heterogeneous mass in the cranial mediastinum, compressing or growing into a large blood vessel within the cranial mediastinum and displacing the heart dorsocaudally. At postmortem examination, the mass was diagnosed as a large, localized mesothelioma. Localized mesotheliomas are rare neoplasms in dogs but should be considered as a possible differential diagnosis for cranial vena cava syndrome. The anatomic distribution and clinical features of mesothelioma in the present report are similar to other cases in humans.

Medical thoracoscopy vs CT scan-guided Abrams pleural needle biopsy for diagnosis of patients with pleural effusions: a randomized, controlled trial

BACKGROUND

In cases of pleural effusion, tissue samples can be obtained through Abrams needle pleural biopsy (ANPB), thoracoscopy, or cutting-needle pleural biopsy under the guidance of CT scan (CT-CNPB) for histopathologic analysis. This study aimed to compare the diagnostic efficiency and reliability of ANPB under CT scan guidance (CT-ANPB) with that of medical thoracoscopy in patients with pleural effusion.

METHODS

Between January 2006 and January 2008, 124 patients with exudative pleural effusion that could not be diagnosed by cytologic analysis were included in the study. All patients were randomized after the CT scan was performed. Patients either underwent CT-ANPB or thoracoscopy. The two groups were compared in terms of diagnostic sensitivity and complications associated with the methods used.

RESULTS

Of the 124 patients, malignant mesothelioma was diagnosed in 33, metastatic pleural disease in 47, benign pleural disease in 42, and two were of indeterminate origin. In the CT-ANPB group, the diagnostic sensitivity was 87.5%, as compared with 94.1% in the thoracoscopy group; the difference was not statistically significant (P = .252). No difference was identified between the sensitivities of the two methods based on the cause, the CT scan findings, and the degree of pleural thickening. Complication rates were low and acceptable.

CONCLUSION

We recommend the use of CT-ANPB as the primary method of diagnosis in patients with pleural thickening or lesions observed by CT scan. In patients with only pleural fluid appearance on CT scan and in those who may have benign pleural pathologies other than TB, the primary method of diagnosis should be medical thoracoscopy.

TRIAL REGISTRATION

clinicaltrials.gov; Identifier: NCT00720954.

Malignant pleural mesothelioma presenting as low back pain: diagnosed by bone scan coordinating with F-18 FDG PET/CT

STUDY DESIGN

Case report.

OBJECTIVE

We report malignant pleural mesothelioma (MPM) discovered in a Tc-99m MDP bone scan as a photopenic lesion in a 64-year-old man presenting with low back pain and diagnosed with F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT).

SUMMARY OF BACKGROUND DATA

Malignant pleural mesothelioma, an uncommon neoplasm with a poor prognosis, arises from mesothelial cells of the pleura. Typically, the patient presents with either chest pain or symptoms derived from a pleural effusion such as dyspnea, or both. Most cases of MPM are initially detected on chest radiographs and primarily diagnosed with a CT scan.

METHODS

Case study with bone scan and F-18 FDG PET/CT.

RESULTS

The Tc-99m MDP bone scan showed a photopenic defect occupying the left side of the T11 vertebra and implicated the existence of a tumor. Pathologic analysis of the paraspinal tumor indicated metastatic neoplastic cells, which we initially suspected originated from the gastrointestinal tract. The CT and magnetic resonance imaging showed no additional information about the primary malignancy; therefore, we did an F-18 FDG PET/CT study, which suggested malignant pleural mesothelioma.

CONCLUSION

The present case highlights both the value of a Tc-99m MDP bone scan when MPM presents, unusually, as low back pain, and the importance of carefully interpreting bone scan images, especially for photopenic defects. It also indicates the usefulness of F-18 FDG PET/CT study in MPM in a difficult histopathological diagnosis.

Problems in mesothelioma diagnosis

Many centres are now seeing increasing numbers of patients with malignant mesothelioma. This presents pathologists involved in making the diagnosis with a number of problems, which can be divided into those encountered in making the distinction between mesothelioma and benign changes and those experienced in separating mesotheliomas from other types of epithelial and connective tissue tumours. Immunohistochemistry plays a major role in helping to make the diagnosis, but it should be interpreted with due regard to the clinical setting and radiological features, and with a knowledge of the wide morphological variations seen in mesothelioma. This review identifies some of these problems and addresses the uses and limitations of immunohistochemistry in different situations. It includes a discussion of some of the less common variants of mesothelioma and other pleural-based tumours that enter into the differential diagnosis.

Multidisciplinary treatment of malignant pleural mesothelioma

The incidence of malignant pleural mesothelioma (MPM) is increasing worldwide, and is predicted to peak in the next 10-20 years. Difficulties in MPM diagnosis and staging, especially of early disease, have thwarted the development of a universally accepted therapeutic approach. Single modality therapies (surgery, radiotherapy, chemotherapy) have generally failed to significantly prolong patient survival. As a result, multimodality treatment regimens have been developed. Radical surgery with extrapleural pneumonectomy and adjuvant treatments has become the preferred option in early disease, but the benefits of such an aggressive approach have been questioned because of significant treatment-related morbidity and mortality. In the past few years, there have been several major advances in the management of patients with MPM, including more accurate staging and patient selection, improvements in surgical techniques and postoperative care, novel chemotherapy regimens with definite activity such as antifolate (pemetrexed or raltitrexed)-platinum combinations, and new radiotherapy techniques such as intensity-modulated radiation therapy. Induction chemotherapy followed by surgery and adjuvant radiotherapy has shown promising results. A number of molecular alterations occurring in MPM have been reported, providing broader insights into its biology and leading to the identification of new targets for therapy. However, currently available treatments still appear to have modest results. Further studies are needed to provide evidence-based recommendations for the treatment of early and advanced stages of this disease.

Functional imaging: CT and MRI

Numerous imaging techniques permit evaluation of regional pulmonary function. Contrast-enhanced CT methods now allow assessment of vasculature and lung perfusion. Techniques using spirometric controlled multi-detector row CT allow for quantification of presence and distribution of parenchymal and airway pathology; xenon gas can be employed to assess regional ventilation of the lungs, and rapid bolus injections of iodinated contrast agent can provide a quantitative measure of regional parenchymal perfusion. Advances in MRI of the lung include gadolinium-enhanced perfusion imaging and hyperpolarized gas imaging, which allow functional assessment, including ventilation/perfusion, microscopic air space measurements, and gas flow and transport dynamics.

Current state and future directions of pleural mesothelioma imaging

The diagnosis, staging, and response assessment of mesothelioma pose unique challenges to radiologic imaging. No single, conventional imaging approach captures the information necessary to direct all aspects of patient management. Instead, the complexities of this unique disease demand the integration of elements cleverly adapted from different modalities. Imaging-based studies presented at the 8th International Conference of the International Mesothelioma Interest Group (IMIG) in October 2006 sought to further define the current practice and future potential of radiology for the mesothelioma patient. The imaging studies selected through a peer-review process for presentation at the 2006 IMIG Conference were intended to frame this research in the context of the unique imaging challenges presented by mesothelioma while stimulating dialogue on the future resolution of these challenges. This communication conveys the pitfalls and potential of pleural mesothelioma imaging based on work presented at the Conference. From diagnosis to response, PET/CT to molecular bioprobes, volumetric analysis to computerized tumor assessment, imaging promises to provide valuable insight for patients with mesothelioma and the physicians who treat them.

IMAGING DIAGNOSIS-CANINE THORACIC MESOTHELIOMA

A 12-year-old neutered female Pembroke Welsh Corgi had a 2-month history of a progressive, productive cough nonresponsive to therapy. Mild pleural effusion, right middle lung lobe collapse, and multiple subpleural nodular lesions were detected in thoracic radiographs and computed tomography (CT) images. Histopathologic diagnosis of the pleural nodules was mesothelioma. Mesothelioma should be considered in patients where pleural masses are detected in radiographs or CT images.

Exclusive intrapulmonary lepidic growth of a malignant pleural mesothelioma presenting with pneumothorax and involving the peritoneum

We report a rare case of malignant pleural mesothelioma presenting clinically with pneumothorax and histologically with an exclusive intrapulmonary lepidic growth. Neither intrathoracic nodules nor pleural thickening were found. The patient subsequently experienced acute abdominal pain with peritonitis and intestinal occlusion by peritoneal mesothelioma. The morphologic clues leading to the correct diagnosis of mesothelioma with prominent intrapulmonary growth are briefly discussed.

[Pleural mesothelioma: imaging contribution]

Imaging plays an essential role in management of patients of with pleural mesothelioma. In this article, we discuss the respective roles for ultrasonography, computed tomography, magnetic resonance imaging, and positon emission tomography for the diagnosis, staging, and postherapeutic evaluation of pleural mesothelioma.