David M. Panicek

Objective: To determine the prevalence of high-signal bladder urine at T₁ weighted MRI performed 1–7 days after injection of gadolinium-based contrast material and to assess for correlation with altered renal function. Methods: The study group consisted of 267 patients who underwent MRI that included the bladder 1–7 days after a prior gadolinium-enhanced MRI. A control group consisted of 200 patients who underwent pelvic MRI and had not received gadolinium-based contrast material within the prior month. One reader recorded the relative T₁ weighted signal intensity of bladder urine and calculated the estimated glomerular filtration rate (eGFR) for each patient. A positive scan was defined as one with bladder urine T₁ weighted signal higher than that of muscle. Results: 25 (9%) of 267 study group scans were positive; this included 68% ( n = 19) of scans obtained 12–24 h after gadolinium-based contrast material administration, 21% ( n = 3) after 25–36 h, 7% ( n = 2) after 37–48 h, and 3% ( n = 1) after 49–72 h. No positive scan occurred after 72 h or in the control group. Mean eGFR in positive scans obtained more than 36 h after gadolinium-based contrast material administration was significantly lower than in negative scans in the same timeframe (37 vs 76 ml/min, respectively; p = 0.01). Conclusion: High T₁ weighted signal in bladder urine occasionally is present on MRI performed up to 3 days after gadolinium-based contrast material administration, presumably reflecting residual excreted gadolinium-based contrast material. When visible more than 36 hours after gadolinium-based contrast material administration, such increased signal is associated with low eGFR. Advances in knowledge: Increased signal is occasionally present in bladder urine at MRI performed up to 3 days after gadolinium-based contrast material administration. When higher signal is visible more than 36 hours after contrast administration, it is associated with decreased eGFR.

OBJECTIVE. A standardized lexicon to specify the radiologist's level of certainty in a radiologic diagnosis can decrease the confusingly large number of words and phrases currently used for that purpose. Such a lexicon furthermore can minimize ambiguity and facilitate clearer communication among radiologists, referring physicians, and patients. CONCLUSION. We would like to share our experience with the lexicon that we developed in 2009. For ease of communication, the lexicon itself is included in each radiology report.

Objective To determine the etiologies of myonecrosis in oncology patients and to assess interobserver variability in interpreting its MRI features. Materials and methods Pathology records in our tertiary cancer hospital were searched for proven myonecrosis, and MRIs of affected regions in those patients were identified. MRI reports that suggested myonecrosis were also identified. Each MRI was reviewed independently by 2 out of 6 readers to assess anatomical site, size, and signal intensities of muscle changes, and the presence of the previously reported stipple sign (enhancing foci within a region defined by rim enhancement). The stipple sign was assessed again, weeks after a training session. Cohen kappa and percentage agreement were calculated. Medical records were reviewed for contemporaneous causes of myonecrosis. Results MRI reports in 73 patients suggested the diagnosis of myonecrosis; pathological proof was available in another 2. Myonecrosis was frequently associated with radiotherapy (n = 34 patients, 45 %); less frequent causes included intraoperative immobilization, trauma, therapeutic embolization, ablation therapy, exercise, and diabetes. Myonecrosis usually involved the lower extremity, the pelvis, and the upper extremity; mean size was 13.0 cm. The stipple sign was observed in 55–100 % of patients at first assessment (κ = 0.09–0.42; 60–80 % agreement) and 55–100 % at second (κ = 0.0–0.58; 72–90 % agreement). Enhancement surrounded myonecrosis in 55–100 % patients (κ = 0.03–0.32; 58–70 % agreement). Conclusion Myonecrosis in oncology patients usually occurred after radiotherapy, and less commonly after intraoperative immobilization, trauma, therapeutic embolization, ablation therapy, exercise, or diabetes. Although interobserver variability for MRI features of myonecrosis exists (even after focused training), a combination of findings facilitates diagnosis and conservative management.

With current shifts in our health care system and a growing national discussion around the concept of the value of imaging, it is time for radiologists and nuclear medicine physicians to recognize and accept our role in the multidisciplinary oncology team.

Many musculoskeletal abnormalities in the pelvis are first seen by body imagers while reviewing pelvic cross-sectional studies, and some of these abnormalities may mimic malignancy or another aggressive process. This article describes nine musculoskeletal pseudotumours and interpretative pitfalls that may be seen on CT, MRI and ultrasound imaging of the pelvis. Awareness of these pitfalls and pseudotumours may help avoid misdiagnosis and prevent inappropriate intervention or management.

The genetics of myoepithelial tumors (ME) of soft tissue and bone have recently been investigated, with EWSR1‐related gene fusions being seen in approximately half of the tumors. The fusion partners of EWSR1 so far described include POU5F1, PBX1, ZNF444 and, in a rare case, ATF1. We investigated by RNA sequencing an index case of EWSR1‐rearranged ME of the tibia, lacking a known fusion partner, and identified a novel EWSR1‐PBX3 fusion. The fusion was further validated by reverse transcriptase polymerase chain reaction and fluorescence in situ hybridization (FISH). To evaluate if this is a recurrent event, an additional cohort of 22 EWSR1‐rearranged ME cases lacking a fusion partner were screened by FISH for abnormalities in PBX3 gene. Thus, two additional cases were identified showing an EWSR1‐PBX3 gene fusion. One of them was also intraosseous involving the ankle, while the other occurred in the soft tissue of the index finger. The morphology of the EWSR1‐PBX3 fusion positive cases showed similar findings, with nests or sheets of epithelioid to spindle cells in a partially myxoid to collagenous matrix. All three cases showed expression of S100 and EMA by immunohistochemistry. In summary, we report a novel EWSR1‐PBX3 gene fusion in a small subset of ME, thereby expanding the spectrum of EWSR1‐related gene fusions seen in these tumors. This gene fusion seems to occur preferentially in skeletal ME, with two of the three study cases occurring in intraosseous locations.

Epithelioid hemangioma (EH) is a benign neoplasm with distinctive vasoformative features, which occasionally shows increased cellularity, cytologic atypia, and/or loco‐regional aggressive growth, resulting in challenging differential diagnosis from malignant vascular neoplasms. Based on two intraosseous EH index cases with worrisome histologic features, such as the presence of necrosis, RNA sequencing was applied for possible fusion gene discovery and potential subclassification of a novel atypical EH subset. A ZFP36‐FOSB fusion was detected in one case, while a WWTR1‐FOSB chimeric transcript in the other, both were further validated by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT‐PCR). These abnormalities were then screened by FISH in 44 EH from different locations with seven additional EH revealing FOSB gene rearrangements, all except one being fused to ZFP36. Interestingly, 4/6 penile EH studied showed FOSB abnormalities. Although certain atypical histologic features were observed in the FOSB‐rearranged EH, including solid growth, increased cellularity, mild to moderate nuclear pleomorphism, and necrosis in 3/9 cases, no overt sarcomatous areas were discerned to objectively separate the lesions from the fusion‐negative EH. No patient has developed recurrence to date, but the follow‐up was relatively limited and short to draw definitive conclusions regarding behavior. Although FOSB‐rearranged EH do not show significant morphologic overlap with SERPINE1‐FOSB fusion‐positive pseudomyogenic hemangioendothelioma, FOSB oncogenic activation is emerging as an important event in these benign and intermediate groups of vascular tumors.