Diffusion-weighted imaging of retroperitoneal malignant peripheral nerve sheath tumor in a patient with neurofibromatosis type 1

A rare case of plexiform neurofibroma of the liver in a patient without neurofibromatosis type 1

Plexiform neurofibroma is mainly associated with neurofibromatosis type 1 and is seldom observed in the liver. Its occurrence in the liver without neurofibromatosis type 1 is even rarer. We report an extremely rare case of plexiform neurofibroma of the liver diagnosed by laparoscopic biopsy in a patient without neurofibromatosis type 1. The patient was a 35-year-old man who had neither clinical signs nor any family history of neurofibromatosis type 1. Abdominal ultrasonography, as part of a health screening, had detected a hepatic tumor. Subsequent contrast ultrasonography, computed tomography, and magnetic resonance imaging showed the tumor extending from the retroperitoneal space around the aorta to the hepatic hilum and distal portal branches in the right hepatic lobe, gallbladder, and left hepatic lobe. ¹⁸F-fluorodeoxyglucose positron emission tomography showed no abnormal accumulation. Histopathological examination of the tumor obtained laparoscopically led to a diagnosis of plexiform neurofibroma. Because the patient was asymptomatic with no features of malignancy, he was only monitored and managed. At follow-up 10 years later, computed tomography showed a decrease in tumor size. It is important to recognize that, while rare, plexiform neurofibroma can occur without neurofibromatosis type 1. We recommend follow-up instead of unreasonable surgery in such cases.

Evaluation of (18)F-FDG PET and MRI in differentiating benign and malignant peripheral nerve sheath tumors

OBJECTIVE

To compare 18F-FDG PET/CT and MRI for differentiating benign and malignant peripheral nerve sheath tumors (BPNSTs and MPNSTs) and correlate imaging characteristics with histopathology.

MATERIALS AND METHODS

Patients with pathologically proven PNSTs undergoing 18F-FDG PET/CT were retrospectively reviewed. PET/CTs and, if available, MRIs were analyzed, noting multiple imaging characteristics and likely pathology (benign or malignant).

RESULTS

Thirty-eight patients with 23 BPNSTs and 20 MPNSTs were analyzed. MPNSTs had higher SUVmax (10.1 ± 1.0, 4.2 ± 0.4, p < 0.0001), metabolic tumor volume (146.5 ± 39.4, 21.7 ± 6.6 cm(3), p = 0.01), total lesion glycolysis (640.7 ± 177.5, 89.9 ± 23.2 cm(3)*g/ml, p = 0.01), and SUVmax/LiverSUVmean (5.3 ± 0.5, 2.0 ± 0.2, p < 0.0001). All lesions with SUVmax < 4.3 were benign. All lesions with SUVmax > 8.1 were malignant. SUVmax cutoff of 6.1 yielded 90.0 % sensitivity and 78.3 % specificity for MPNSTs. SUVmax/LiverSUVmean cutoff of 3.0 yielded 90.0 % sensitivity and 82.6 % specificity. MPNSTs more commonly had heterogeneous FDG activity (p < 0.0001), perilesional edema (p = 0.004), cystic degeneration/necrosis (p = 0.015), and irregular margins (p = 0.004). There was no difference in lesion size, MRI signal characteristics, or enhancement. Expertly interpreted MRI had 62.5-81.3 % sensitivity and 94.1-100.0 % specificity while PET had 90.0-100.0 % sensitivity and 52.2-82.6 % specificity for diagnosing MPNSTs.

CONCLUSIONS

FDG PET and MRI play a complementary role in PNST evaluation. Multiple metabolic parameters and MRI imaging characteristics are useful in differentiating BPNSTs from MPNSTs. This underscores the potential critical role of PET/MRI in these patients.

Practical Issues for Retroperitoneal Sarcoma

Background

Retroperitoneal sarcoma is rare. Using initial specimens on biopsy, a definitive diagnosis of histological subtypes is ideal but not always achievable.

Methods

A retrospective institutional review was performed for all cases of adult retroperitoneal sarcoma from 1996 to 2015. A review of the literature was also performed related to the distribution of retroperitoneal sarcoma subtypes. A meta-analysis was performed.

Results

Liposarcoma is the most common subtype (45%), followed by leiomyosarcoma (21%), not otherwise specified (8%), and undifferentiated pleomorphic sarcoma (6%) by literature review. Data from Moffitt Cancer Center demonstrate the same general distribution for subtypes of retroperitoneal sarcoma. A pathology-based algorithm for the diagnosis of retroperitoneal sarcoma is illustrated, and common pitfalls in the pathology of retroperitoneal sarcoma are discussed.

Conclusions

An informative diagnosis of retroperitoneal sarcoma via specimens on biopsy is achievable and meaningful to guide effective therapy. A practical and multidisciplinary algorithm focused on the histopathology is helpful for the management of retroperitoneal sarcoma.

Diffusion-weighted MRI findings of treated and untreated retroperitoneal fibrosis

PURPOSE

We aimed to evaluate diffusion-weighted imaging (DWI) findings in patients with treated and untreated retroperitoneal fibrosis (RPF).

METHODS

We analyzed magnetic resonance imaging examinations of 44 RPF patients (36 male, 8 female), of which 15 were untreated and 29 were under therapy. Qualitative DWI and T1 postcontrast signal intensities and the largest perivascular extent of RPF were compared between treated and untreated groups and correlated to erythrocyte sedimentation rate and C-reactive protein values. Quantitative DWI signal intensities and apparent-diffusion-coefficients were calculated in regions-of-interest, together with a relative index between signal intensities of RPF and psoas muscle in 15 untreated patients and 14 patients under treatment with remaining perivascular fibrosis of more than 5 mm.

RESULTS

The extent of RPF in untreated patients was significantly larger compared with the extent of RPF in treated patients (P <0.0001). DWI signal intensities were significantly higher in untreated patients than in patients under therapy (mean, 27 s/mm2 vs. 20 s/mm2; P = 0.009). The calculated DWI-index was significantly higher in untreated patients than in patients under therapy (P = 0.003).

CONCLUSION

Our data show significant differences in the DWI findings (b800 signal intensities and relative DWI-index) of patients with treated and untreated RPF. DWI is a promising technique in the assessment of disease activity and the selection of patients suitable for medical therapy.

Diffusion-weighted MRI in the follow-up of chronic periaortitis

OBJECTIVE

To evaluate the usefulness of diffusion-weighted MRI (DWI) for the assessment of the intraindividual follow-up in patients with chronic periaortitis (CP) under medication.

METHODS

MRI data of 21 consecutive patients with newly diagnosed untreated disease were retrospectively examined before and after medical therapy, with a median follow-up of 16 weeks. DWI parameters [b800 signal, apparent diffusion coefficient (ADC) values] of the CP and psoas muscle were analysed together with the extent and contrast enhancement. Pre- and post-treatment laboratory inflammation markers were acquired parallel to each MR examination.

RESULTS

Statistically significant lower b800 signal intensities (p ≤ 0.0001) and higher ADC values (p ≤ 0.0001) were observed after medical treatment within the fibrous periaortic tissue. Extent and contrast enhancement of the CP showed also a statistically significant decrease (p ≤ 0.0001) in the follow-up examinations, while the control parameters within the psoas muscle showed no differences.

CONCLUSION

DWI seems to be a useful method for the evaluation of response to treatment without contrast agents. The technique may be helpful in the assessment of disease activity to guide further therapeutic strategies.

ADVANCES IN KNOWLEDGE

DWI detects significant differences in the intraindividual follow-up of CP under medical therapy.

Diagnosis and management of an isolated pediatric plexiform neurofibroma involving the hepatic and celiac plexus using multimodality approach: problem solving with diffusion-weighted magnetic resonance imaging

Plexiform neurofibroma with involvement of the gastrointestinal tract is a very rare entity in children. Here, we present a rather unique case of a 9-year-old boy with no clinical signs or features of neurofibromatosis type 1. A periportal mass lesion was incidentally found after performing an ultrasound in this previously healthy child. Computed tomographic scan was subsequently performed which showed a low-density mass in a periportal distribution with extension along the celiac axis. Because the findings were nonspecific, a pre- and postcontrast magnetic resonance imaging of the abdomen was performed which included diffusion-weighted imaging. The lesion was then confirmed to be a plexiform neurofibroma with open biopsy. Management of plexiform neurofibromas varies widely. Given the extensive nature of the lesion, managing the patient with follow-up rather than surgical excision was favored.

A retroperitoneal NF1-independent malignant peripheral nerve sheath tumor with elevated serum CA125: case report and discussion

Malignant peripheral nerve sheath tumors (MPNSTs) are usually located in the trunk, extremities, head, or neck, and most occur with neurofibromatosis type 1 (NF1; von Recklinghausen's disease). No biomarkers have previously been found to be associated with their progression. Retroperitoneal NF1-independent MPNSTs are rare; they are considered to be less aggressive and to have better prognoses compared to NF1-related tumors. Currently, en bloc excision is the only consensus treatment approach. In a 27-year-old male with a giant retroperitoneal MPNST and no stigmata or family history of neurofibromatosis type-1 (NF1), a remarkable elevation of serum CA125 was detected. The high-grade tumor displayed a striking progression: the primary lesion, 25 cm in diameter, recurred in its previous site as a 17-cm MPNST less than 50 days after total excision. Subsequent treatment with microwave ablation and huachansu, a traditional Chinese medication, proved ineffective, and the patient died within 3 months. Our case suggests that retroperitoneal MPNSTs can deteriorate rapidly even if NF1 independent, that aggressive treatment may not benefit large high-grade MPNSTs, and that novel and effective treatment is urgently needed. Our case also suggests the possibility of using serum tumor markers in the early detection and monitoring of MPNSTs.

Diffusion-weighted imaging of an atypical teratoid/rhabdoid tumor of the cervical spine

Spinal atypical teratoid/rhabdoid tumor (AT/RT) is a rare, aggressive malignant neoplasm of the central nervous system usually seen in young children and infants. We present diffusion-weighted imaging (DWI) findings for an intradural extramedullary AT/RT in the cervical spine of a 6-year-old boy. High signal on DWI and low apparent diffusion coefficients may represent high cellularity of the tumor. These findings indicated a highly malignant tumor.