Pseudoaneurysm within a desmoid tumor in an extremity: report of 2 cases.

Desmoid tumor is considered a benign neoplasm, yet substantial morbidity can result from local invasion of structures adjacent to the tumor or from complications related to its treatment. We report two patients with extremity desmoid tumor who were each found at MRI to have an unsuspected pseudoaneurysm within their tumor after prior treatments (surgery and systemic therapy in one, surgery alone in the other). Such a pseudoaneurysm probably results from weakening of an arterial wall by adjacent desmoid tumor, as well as from local trauma. Due to the potential risk for life-threatening rupture of a pseudoaneurysm, one patient underwent surgical repair and the other, coil embolization. To our knowledge the presence of pseudoaneurysm has been reported within a few cases of abdominal desmoid tumor but not within an extremity desmoid tumor. This diagnosis has not been reported to have been made at MRI, either.

A molecular study of synovial chondromatosis.

Synovial chondromatosis (SC) is a rare benign cartilaginous neoplasm in which recurrent fibronectin 1 (FN1) and activin receptor 2A (ACVR2A) gene rearrangements have been recently reported. Triggered by a case of malignant transformation in SC (synovial chondrosarcoma) showing a novel KMT2A-BCOR gene fusion by targeted RNA sequencing, we sought to evaluate the molecular abnormalities in a cohort of 27 SC cases using a combined methodology of fluorescence in situ hybridization (FISH) and/or targeted RNA sequencing. Results showed that FN1 and /or ACVR2A gene rearrangements were noted in 18 cases (67%), with an FN1-ACVR2A fusion being confirmed in 15 (56%) cases. Two cases showed only FN1 gene rearrangement, without other abnormalities. A novel FN1-NFATc2 gene fusion was noted in one case by RNA sequencing. The remaining nine cases showed no abnormalities in FN1 and ACVR2A genes. No additional cases showed BCOR gene alterations. In conclusion, this study confirms that FN1-ACVR2A fusion is the leading pathogenetic event in SC, at even higher frequency than previously reported. FISH methodology emerges as an appropriate tool in the identification of FN1 and ACVR2A gene abnormalities, which can be used in challenging cases. Further studies are needed to determine the recurrent potential of BCOR abnormalities in this disease.

High-Signal Bladder Urine at T1-Weighted MR Imaging Performed 1-7 Days After a Prior Gadolinium-Enhanced MRI: Prevalence and Correlation with Renal Function.

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 eGFR for each patient. A positive scan was defined as one with bladder urine T1-weighted signal higher than that of muscle. RESULTS: Twenty-five (9%) of 267 study group scans were positive; this included 68% (n=19) of scans obtained 12-24 hours after gadolinium-based contrast material administration, 21% (n=3) after 25-36 hours, 7% (n=2) after 37-48 hours, and 3% (n=1) after 49-72 hours. No positive scan occurred after 72 hours or in the control group. Mean eGFR in positive scans obtained more than 36 hours after gadolinium-based contrast material administration was significantly lower than in negative scans in the same timeframe (37 ml/min versus 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 decreased eGFR. ADVANCES IN KNOWLEDGE: Increased signal is occasionally present on bladder urine MRI performed up to 3 days post gadolinium-based contrast material administration. When higher signal is visible more than 36 hours after gadolinium-based contrast material administration it is associated with decreased eGFR.

Plexiform fibrohistiocytic tumor: imaging features and clinical findings.

OBJECTIVE: To describe the imaging features of plexiform fibrohistiocytic tumor and its associated clinical findings. MATERIALS AND METHODS: An institutional database was searched to identify all patients with a pathological diagnosis of plexiform fibrohistiocytic tumor. The electronic medical record was reviewed for relevant clinical data. Radiologic images of the primary tumor site were reviewed by two radiologists to assess primary, residual, or recurrent tumor with respect to tumor location, size, morphology, MR signal characteristics and enhancement, and involvement of adjacent structures. RESULTS: Thirteen patients with imaging of the primary tumor site were identified [eight female, five male; mean age, 15.9 years (range, 3-41 years)]. Plexiform fibrohistiocytic tumor typically manifested as a solitary, painless, firm, slow-growing lesion centered in the subcutaneous tissues, with a predilection for the upper extremity or head and neck region. Most tumors had a purely plaque-like or infiltrative morphology at MRI; some demonstrated no round or oval mass. Tumors were predominantly isointense to muscle on T1-weighted imaging and hyperintense on fluid-sensitive imaging, and enhanced after gadolinium contrast administration. Five patients (38%) had residual tumor after initial surgery, resembling postoperative changes. No patient had recurrent tumor. One patient (8%) developed metastases to local lymph nodes and to the lung. No patient died from plexiform fibrohistiocytic tumor. CONCLUSIONS: Plexiform fibrohistiocytic tumor often manifests as a plaque-like or infiltrative process, sometimes without a round or oval mass, most commonly in the subcutaneous tissues of the upper extremity or head and neck region. Residual tumor is often present after initial surgery, and may be indistinguishable from postoperative changes.

Undifferentiated pleomorphic sarcoma: indolent, tail-like recurrence of a high-grade tumor.

Recurrence of a soft tissue sarcoma typically manifests as a round or oval mass at imaging, and recurrent high-grade soft tissue sarcomas generally enlarge relatively rapidly. We present a case of high-grade undifferentiated pleomorphic sarcoma in the calf of a 48-year-old male that recurred as a thin, curvilinear "tail" of enhancing tissue at magnetic resonance imaging (MRI), with extremely indolent growth over a 7-year period. The unusual imaging finding of a slowly enlarging "tail" should not be dismissed as postoperative changes, even for a high-grade soft tissue sarcoma.

Prostate cancer bone metastases on staging prostate MRI: prevalence and clinical features associated with their diagnosis.

PURPOSE: Bone lesions on prostate MRI often raise concern about metastases. This study aimed to evaluate the prevalence of bone metastases on staging prostate MRI and evaluate associations between their MRI features and clinical/pathologic characteristics. METHODS: Retrospective, IRB-approved study of 3765 patients undergoing prostate MRI for newly diagnosed PCa between 2000 and 2014. The reference standard to calculate the prevalence of bone metastases was bone biopsy and/or ≥1-year follow-up after MRI. In a subsample of 228 patients, the MRI characteristics of bone lesions were recorded by two radiologists independently. Associations between MRI and clinical/pathologic findings, including National Comprehensive Cancer Network (NCCN) risk categories, were calculated. RESULTS: 57/3765 patients (1.5%, 95% CI 1.2-2.0%) had bone metastases. No patient with NCCN low-risk PCa (Gleason < 7, PSA < 10 ng/mL, cT1-2a) had bone metastases. In the subsample, ≥1 bone lesion was present on MRI in 74% (95% CI 0.67-0.79) and 72% (95% CI 0.66-0.78) of patients (R1 and R2). Larger lesion diameter (OR 1.33/1.19; p < 0.001 for both readers) and the absence of intralesional fat (OR 0.07/0.11; p = 0.004/0.002 for R1/R2) were significantly associated with bone metastases. CONCLUSION: Bone lesions are common in prostate MRI, but only rarely represent metastases. MRI should be interpreted in the context of clinical features that influence the likelihood of metastatic disease.

Infiltrative pattern of carcinomatosis in extremity muscles on MRI.

Carcinomas can cause an unusual, infiltrative pattern of metastatic carcinoma in extremity muscles on MRI. To assess this pattern, reports of MRI exams of 907 consecutive patients with a diagnosis of carcinoma were reviewed retrospectively to identify those that mentioned muscle metastasis or myositis in an extremity. Thirty-six (4%) of those reports described muscle metastasis (n=18) or myositis (n=18); based on medical record review and imaging follow-up, 17 cases represented metastases. Metastases manifested as an infiltrative carcinomatosis pattern in five patients, resulted from primary esophageal or gastric adenocarcinomas, and often were misdiagnosed as myositis.

How Sure Are You, Doctor? A Standardized Lexicon to Describe the Radiologist's Level of Certainty.

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.

Acute myonecrosis on MRI: etiologies in an oncological cohort and assessment of interobserver variability.

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.

EWSR1-PBX3: a novel gene fusion in myoepithelial tumors.

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.

ZFP36-FOSB fusion defines a subset of epithelioid hemangioma with atypical features.

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.

Benign mural nodules within fluid collections at MRI after soft-tissue sarcoma resection.

OBJECTIVE: The purpose of this study was to determine the prevalence and clinical significance of nodules within fluid collections on MRI after surgical resection of soft-tissue sarcoma. MATERIALS AND METHODS: This retrospective study included 175 patients who underwent resection of primary soft-tissue sarcoma and whose postoperative MRI reports mentioned fluid. Images were reviewed to determine the presence of fluid collections of 1 cm or greater in diameter in the surgical bed and any nodule (measuring ≥ 0.7 cm) within the collection. Signal intensity and characteristics of each collection and rim and presence of septa or blood products were recorded. Size, signal intensity, and contrast enhancement of nodules were reviewed. Nodules were classified as benign or malignant on the basis of histologic results or clinical or MRI follow-up. RESULTS: Fluid collections were present in 75 patients. Of those, 45 collections (60%) showed homogeneous fluid signal intensity and 30 (40%) were heterogeneous; septa were present in 45 (60%) and blood products in 12 (16%). Most collections showed a thin rim (59%) and rim enhancement (88%). Nodules were present along the inner wall of six (8%) collections. Four (66%) nodules enhanced and two (33%) were T1 hyperintense. At follow-up MRI, two nodules were stable in size, one decreased, and three resolved. Nodules in three patients were biopsied; all were benign. Two other patients had no recurrence at follow-up, and another died at 3 months. CONCLUSION: A nodule within a postoperative fluid collection at MRI after soft-tissue sarcoma resection generally does not represent tumor recurrence; short-interval follow-up MRI is recommended rather than immediate biopsy.

Imaging and management of a small cell lung cancer metastasis/adrenal adenoma collision tumor: a case report and review of the literature.

OBJECTIVE: We report a case of an adrenal collision tumor composed of a small cell lung carcinoma metastasis and a benign adrenal adenoma identified preoperatively on FDG-PET, CT and MRI and confirmed pathologically. METHODS: The patient's history, preoperative imaging characteristics, postoperative course, and histopathology are described. A review of the literature addressing adrenal collision tumors is provided. RESULTS: A 47-year-old female was found to have a left upper lobe lung mass and an adrenal lesion on imaging. FDG-PET, CT and MRI of the adrenal suggested a metastatic lesion adjacent to an adrenal adenoma. CT-guided biopsy of the adrenal gland was consistent with a small cell lung cancer metastasis. The patient underwent systemic chemotherapy and had complete resolution of the left upper lobe mass. Post-treatment FDG-PET demonstrated a persistently enlarged adrenal gland with decreased but persistent FDG uptake. The patient underwent adrenalectomy and pathologic examination demonstrated a small cell lung cancer/adenoma collision tumor. CONCLUSIONS: This case and a review of the literature demonstrate that FDG, CT and MR imaging can all characterize the separate components of collision tumors within the adrenal gland.

Biopsy of suspicious bone lesions in patients with a single known malignancy: prevalence of a second malignancy.

OBJECTIVE: The probability that a suspicious bone lesion in a patient with one known malignancy is actually due to a second, previously unknown primary malignancy has been reported to be 2-8%. We sought to determine this prevalence as well as that of benign diagnoses in a larger number of patients in a tertiary cancer center. MATERIALS AND METHODS: The medical records of 482 consecutive patients (254 women and 228 men) with only one known primary malignancy each (excluding nonmelanoma skin cancer) and who underwent biopsy of a suspicious bone lesion were retrospectively reviewed. The results of bone biopsy were classified as benign, metastasis of the known primary malignancy, due to a second primary malignancy, or nondiagnostic or indeterminate. RESULTS: In 103 of 482 (21%) patients, bone biopsy results were benign, 316 (66%) were due to metastases of the known malignancy, 15 (3%) were due to a second malignancy, and 48 (10%) were nondiagnostic or indeterminate. Second malignancies included osteosarcoma (n = 4); soft-tissue sarcoma (n = 2); lymphoma (n = 2); plasma cell malignancy (n = 2); and lung cancer, thyroid cancer, renal cancer, chondrosarcoma, and carcinoma of unknown primary (n = 1 each). CONCLUSION: In 3% of patients with one known malignancy and a suspicious bone lesion, the lesion was due to a previously unknown second malignancy; in 21% of patients, the lesion was benign. Bone biopsy is recommended in the management of patients with one known cancer and a suspicious bone lesion only if the presence of a second malignancy would alter clinical management.

Intra- and interobserver variability in CT measurements in oncology.

PURPOSE: To assess variability of computed tomographic (CT) measurements of lesions of various sizes and margin sharpness in several organs taken by readers with different levels of experience, as would be found in routine clinical practice. MATERIALS AND METHODS: In this institutional review board-approved, HIPAA-compliant retrospective study, 17 radiologists with varying levels of experience independently obtained bidimensional orthogonal axial measurements of 80 lymph nodes, 120 pulmonary lesions, and 120 hepatic lesions, categorized by size and margin sharpness. Repeat measurements were performed 2 or more weeks later. Intraclass correlation coefficients and Bland-Altman plots were used to assess intra- and interobserver variability. RESULTS: For long- and short-axis measurements, respectively, overall intraobserver agreement rates were 0.957 (95% confidence interval [CI]: 0.947, 0.966) and 0.945 (95% CI: 0.933, 0.955); interobserver agreement rates were 0.954 (95% CI: 0.943, 0.963) and 0.941 (95% CI: 0.929, 0.951). Both intra- and interobserver agreement differed by lesion size, margin sharpness, location, and reader experience. Agreement ranged from 0.847 to 0.886 for lesions 20 mm or larger versus 0.745-0.785 for lesions smaller than 10 mm, 0.961 to 0.975 for smooth margins versus 0.924-0.942 for irregular margins, 0.955 to 0.97 for lung lesions versus 0.884-0.94 for lymph nodes, and 0.95 to 0.97 for attending radiologists versus 0.928-0.945 for fellows. Measurement variability decreased with increasing lesion size; 95% limits of agreement for short-axis measurements were -11.6% to 6.7% for lesions smaller than 10 mm versus -6.2% to 4.7% for lesions 20 mm or larger. CONCLUSION: Overall intra- and interobserver variability rates were similar; in clinical practice, serial CT measurements can be safely performed by different radiologists. Smooth margins, larger lesion size, and greater reader experience resulted in a higher consistency of measurements. Depending on lesion size, increases of 4%-6% or greater in long axis and 5%-7% or greater in short axis and decreases of -6% to -10% or greater in long axis and -6% to -12% or greater in short axis at CT can be considered true changes rather than measurement variation, with 95% confidence.

Musculoskeletal tumors and tumor-like conditions: common and avoidable pitfalls at imaging in patients with known or suspected cancer: Part A: benign conditions that may mimic malignancy.

A wide range of musculoskeletal tumors and tumor-like conditions may be encountered when patients undergo radiological examinations. The imaging features of certain normal, reactive, benign neoplastic, inflammatory, traumatic, and degenerative processes in the musculoskeletal system may mimic malignant tumor; misinterpretation of the imaging findings can lead to inappropriate clinical management of the patient. This review describes and illustrates a number of such mimics that we have commonly encountered in our oncological imaging practice, and provides suggestions for avoiding each of these pitfalls. Because many orthopaedic surgeons interpret radiological images themselves, they need to be as aware as radiologists about these issues.