Metastases to pelvic lymph nodes from carcinoma in the pelvic cavity: diagnosis using thin-section CT

Oncologic Imaging of the Lymphatic System: Current Perspective with Multi-Modality Imaging and New Horizon

The lymphatic system is an anatomically complex vascular network that is responsible for interstitial fluid homeostasis, transport of large interstitial particles and cells, immunity, and lipid absorption in the gastrointestinal tract. This network of specially adapted vessels and lymphoid tissue provides a major pathway for metastatic spread. Many malignancies produce vascular endothelial factors that induce tumoral and peritumoral lymphangiogenesis, increasing the likelihood for lymphatic spread. Radiologic evaluation for disease staging is the cornerstone of oncologic patient treatment and management. Multiple imaging modalities are available to access both local and distant metastasis. In this manuscript, we review the anatomy, physiology, and imaging of the lymphatic system.

Patterns of lymph node metastasis in locally advanced cervical cancer

The aim of this study was to investigate patterns and locations of lymph node metastasis in locally advanced cervical cancers.A total of 244 consecutive patients with stage IIb cervical cancer were retrospectively evaluated. Contrast-enhanced CT scans were used for lymph node grading. Lymph nodes with the shortest axis (>1 cm) were categorized as positive and those between 0.5 and 1 cm were categorized as suspicious. All lymph nodes (LNs) were also classified by their anatomic locations.Nine hundred thirty-one LNs (136 positive and 795 suspicious) were identified. Sixty-three (25.8%) patients had positive LNs, and 153 (62.7%) patients had only suspicious LNs. The metastatic pattern was predictable traveling from level 1 (external iliac, internal iliac, obturator, and mesorectum groups) through level 2 (common iliac and presacral groups) to level 3 (para-aortic groups). In most groups, LNs were located within 1.0 cm of main blood vessels. Our novel findings were: presacral LNs metastases were rare (2/244, 0.82%); the left common iliac group (LCI) had significantly more enlarged nodes than the right common iliac group (P = 0.00); the LCI and left down-para-aortic group were further away from blood vessels than expected (1.2 cm and 1.4 cm, respectively); no additional margin was needed in anterolateral direction for external iliac groups.The lymph node metastatic patterns are relatively predicable. Different expansions from vessels should be used to include LNs for different groups. Presacral nodes metastases are rare, and further study is warranted to see whether this region can be excluded from nodal CTV.

Interpretation and reporting multiparametric prostate MRI: a primer for residents and novices

Multiparametric MRI has developed as a tool for prostate cancer lesion detection, characterization, staging, surveillance, and imaging of local recurrence. Given the disease frequency and the growing importance of imaging, as reliance on PSA declines, radiologists involved in prostate MRI imaging must become proficient with the fundamentals of multiparametric prostate MRI (T2WI, DWI, DCE-MRI, and MR spectroscopy). Interpretation and reporting must yield accuracy, consistency, and add value to clinical care. This review provides a primer to novices and trainees learning about multiparametric prostate MRI. MRI technique is presented along with the use of particular MRI sequences. Relevant prostate anatomy is outlined and imaging features of prostate cancer with staging are discussed. Finally structured reporting is introduced, and some limitations of prostate MRI are discussed.

Nodal staging

Lymph node metastases are a poor prognostic indicator in many tumours and therefore accurate identification during staging is important prior to commencing treatment. The presence of lymph node metastases can significantly alter patient management and therefore accurate diagnosis of the presence and extent of nodal disease can help optimise patient management. In this review, the radiologic features that aid in the differentiation of malignant and benign lymph nodes are discussed. The keys to successful interpretation on cross-sectional computed tomography (CT) and magnetic resonance imaging of nodal metastases are highlighted. The clinical role of positron emission tomography-CT imaging for nodal staging is discussed and emerging imaging techniques that may further improve nodal staging accuracy are surveyed.

Comparison of CT and MRI for presurgical characterization of paraaortic lymph nodes in patients with pancreatico-biliary carcinoma

AIM: To determine the accuracy of computed tomography (CT) and magnetic resonance (MR) for presurgical characterization of paraaortic lymph nodes in patients with pancreatico-biliary carcinoma.

METHODS: Two radiologists independently evaluated CT and MR imaging of 31 patients who had undergone lymphadenectomy (9 metastatic and 22 non-metastatic paraaortic nodes). Receiver operating characteristic (ROC) curve analysis was performed using a five point scale to compare CT with MRI. To re-define the morphologic features of metastatic nodes, we evaluated CT scans from 70 patients with 23 metastatic paraaortic nodes and 47 non-metastatic ones. The short axis diameter, ratio of the short to long axis, shape, and presence of necrosis were compared between metastatic and non-metastatic nodes by independent samples t-test and Fisher’s exact test. P < 0.05 was considered statistically significant.

RESULTS: The mean area under the ROC curve for CT (0.732 and 0.646, respectively) was slightly higher than that for MRI (0.725 and 0.598, respectively) without statistical significance (P = 0.940 and 0.716, respectively). The short axis diameter of the metastatic lymph nodes (mean = 9.2 mm) was significantly larger than that of non-metastatic ones (mean = 5.17 mm, P < 0.05). Metastatic nodes had more irregular margins (44.4%) and central necrosis (22.2%) than non-metastatic ones (9% and 0%, respectively), with statistical significance (P < 0.05).

CONCLUSION: The accuracy of CT scan for the characterization of paraaortic nodes is not different from that of MRI. A short axis-diameter (> 5.3 mm), irregular margin, and presence of central necrosis are the suggestive morphologic features of metastatic paraaortic nodes.

The potential of nanoparticle-enhanced imaging

Accurate lymph node staging in genitourinary malignancy is an important component in the diagnostic algorithm and therapeutic planning. A promising new method for lymph node staging is lymphotrophic nanoparticle enhanced magnetic resonance imaging. This novel technique uses ultrasmall superparamagnetic iron oxide particles, which localize in lymph nodes and provide detailed characterization of these nodes independent of typically accepted size criteria. This review provides a brief overview of the presently accepted methods for noninvasive lymph node staging and thoroughly discusses lymphotrophic nanoparticle enhanced MR imaging: a technique that can be used for accurate detection of lymph node metastases and will likely play a major role in noninvasive lymph node staging in genitourinary cancer in the near future.

Cross-sectional imaging of nodal metastases in the abdomen and pelvis

Accurate nodal staging is important for the management of patients with abdominal and pelvic malignancies. Local and nodal staging using cross-sectional imaging can influence treatment planning. The measurement of nodal size is still the most widely used criteria for discriminating between benign and malignant nodes. However, knowledge of the pathways of nodal spread, the treatment history, and careful analysis of nodal characteristics can improve nodal assessment. An appreciation of normal structures that may simulate nodal disease is also important. The potential for further improving nodal staging accuracy by positron emission tomography and magnetic resonance lymphography is discussed.

Clinical presentation, imaging, and staging of anal cancer

Perianal symptoms are common, and benign anorectal conditions have clinical features not too dissimilar to those associated with anal canal carcinoma. To avoid delayed diagnosis, physicians need to be cognizant of the possibility of anal canal carcinoma, which can be effectively treated with chemoradiation therapy without the need for mutilating surgery. Appropriate imaging studies should be obtained for accurate staging of the disease and for follow-up examinations after definitive treatment.

MR evaluation of normal retroperitoneal and pelvic lymph nodes

PURPOSE

To establish guidelines for normal retroperitoneal and pelvic lymph node size at magnetic resonance imaging (MRI) by correlation with computed tomographic (CT) and lymphangiographic (LAG) data.

MATERIALS AND METHODS

Twelve patients previously studied with pre- and post-LAG CT to determine normal pelvic lymph node size [ 1 ] were examined with MRI. All were on surveillance for stage I testicular tumour (minimum follow-up 10 years). Three observers recorded blind the site, size and number of nodes in the retroperitoneum and pelvis at 11 sites. The results were validated with previous CT imaging.

RESULTS

Eight hundred and fifteen nodes in 12 patients were visible on the MRI initially, and a further 44 nodes were identified after comparison with post-LAG CT. More nodes were seen on MRI than on CT. The 95th centile values for maximum short axis diameter (MSAD) of pelvic lymph nodes were common iliac and obturator 4 mm, external and internal iliac 5 mm and hypogastric 6 mm. In the retroperitoneum the 95th centile MSAD values were retrocrural, high left para-aortic, paracaval and interaortocaval 3 mm, post-caval 4 mm and low left para-aortic 5 mm.

CONCLUSION

MRI criteria for normal retroperitoneal and pelvic lymph node size are defined. Adoption of these recommendations may improve the sensitivity of MRI for the detection of nodal metastases.

Detection of pelvic lymph node metastases in gynecologic malignancy: a comparison of CT, MR imaging, and positron emission tomography

OBJECTIVE

Accurate assessment of lymph node status before treatment is critical in the treatment of gynecologic cancers because the 5-year survival and treatment of women is influenced by lymph node involvement. The aims of this study were to investigate the ability of X-ray CT, MR imaging, and (18)F-FDG positron emission tomography (PET) to detect pelvic lymph node metastases by comparing imaging with histopathologic findings after lymph node dissection.

MATERIALS AND METHODS

Eighteen patients with gynecologic cancers were studied by all three imaging methods before surgery. The images were initially reviewed with routine diagnostic conditions and then, subsequently, by two observers who were unaware of the clinical and histopathologic findings of the patients. The nodal sites were split into upper (aortic to common iliac bifurcations) and lower (common iliac bifurcations to inguinal ligament) iliac chains. All observers' results were statistically analyzed with specificity, sensitivity, positive and negative predictive values, Fisher's exact test (individual observers) or chi-square test (combined observers), and Cohen's kappa test.

RESULTS

Eight of 18 patients had lymph node metastases at histology. Findings of all three modalities agreed in full in only one patient. CT correctly revealed 10 node-negative patients, whereas MR imaging was correct in eight of these patients. (18)F-FDG PET correctly depicted one patient with lymph nodes negative for tumor. CT was the most specific imaging modality (97.0%), with MR imaging and PET rendering values of 90.7% and 77.3%, respectively, but sensitivity of all modalities was low (CT, 48.1%; MR imaging, 53.7%; PET, 24.5%). Observer agreement for each modality was good; kappa values among all observers were 0.88 for CT, 0.85 for MR imaging, and 0.72 for PET.

CONCLUSION

CT is the most specific modality for detecting lymph nodes positive for tumor in gynecologic cancers, whereas MR imaging is the most sensitive. The poor results of PET in the pelvis are attributed to urinary (18)F-FDG in the ureters or bladder, which may mask or imitate lymph node metastases.

Comparison of dynamic helical CT and dynamic MR imaging in the evaluation of pelvic lymph nodes in cervical carcinoma

OBJECTIVE

This study compares dynamic helical CT with dynamic MR imaging in the evaluation of pelvic lymph nodes in cervical carcinoma.

SUBJECTS AND METHODS

Women with biopsy-proven cervical carcinoma prospectively underwent dynamic helical CT and MR imaging before surgery. A metastatic node on CT and MR imaging was defined as a rounded soft-tissue structure greater than 10 mm in maximal axial diameter or a node with central necrosis. Imaging results were compared with pathology, and receiver operating characteristic curves for size and shape were plotted on a hemipelvis basis. Nodal density and signal intensity on CT and MR images, respectively, were reviewed for differences between benign and malignant disease.

RESULTS

A total of 949 lymph nodes were found at pathology in 76 hemipelves in 43 women, of which 69 lymph nodes (7%) in 17 hemipelves (22%) were metastatic. Sensitivity, specificity, positive and negative predictive values, and accuracy of helical CT and MR imaging in the diagnosis of lymph node metastasis on a hemipelvis basis was 64.7%, 96.6%, 84.6%, 90.5%, and 89.5% and 70.6%, 89.8%, 66. 7%, 91.4%, and 85.5%, respectively. Receiver operating characteristic curves for helical CT and MR imaging gave cutoff values of 9 and 12 mm in maximal axial diameter, respectively, in the prediction of metastasis. Central necrosis had a positive predictive value of 100% in the diagnosis of metastasis. Signal intensity on MR imaging and density-enhancement pattern on CT in patients with metastatic nodes did not differ from those in patients with negative nodes.

CONCLUSION

Helical CT and MR imaging show similar accuracy in the evaluation of pelvic lymph nodes in patients with cervical carcinoma. Central necrosis is useful in the diagnosis of metastasis in pelvic lymph nodes in cervical cancer.