Rodrigo Luna1, Laura M Fayad1,2,3, Fausto J Rodriguez3,4,5, Shivani Ahlawat6. 1. The Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins Medical Institutions, 600 North Wolfe Street, Baltimore, MD, 21287, USA. 2. Division of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 3. Division of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 4. Division of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 5. Division of Pathology - Neuropathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 6. The Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins Medical Institutions, 600 North Wolfe Street, Baltimore, MD, 21287, USA. sahlawa1@jhmi.edu.
Abstract
OBJECTIVE: To evaluate the frequency, clinico-pathologic and imaging features of malignant tumors in peripheral nerves which are of non-neurogenic origin (non-neurogenic peripheral nerve malignancy-PNM). MATERIALS AND METHODS: We retrospectively reviewed our pathology database for malignant peripheral nerve tumors from 07/2014-07/2019 and performed a systematic review. Exclusion criteria were malignant peripheral nerve sheath tumor (MPNST). Clinico-pathologic and imaging features, apparent diffusion coefficient (ADCmin), and standard uptake values (SUVmax) are reported. RESULTS: After exclusion of all neurogenic tumors (benign = 196, MPNST = 57), our search yielded 19 non-neurogenic PNMs (7%, n = 19/272), due to primary intraneural malignancy (16%, n = 3/19) and secondary perineural invasion from an adjacent malignancy (16%, n = 3/19) or metastatic disease (63%, n = 12/19). Non-neurogenic PNMs were located in the lumbosacral plexus/sciatic nerves (47%, n = 9/19), brachial plexus (32%, n = 6/19), femoral nerve (5%, n = 1/19), tibial nerve (5%, n = 1/19), ulnar nerve (5%, n = 1/19), and radial nerve (5%, n = 1/19). On MRI (n = 14/19), non-neurogenic PNM tended to be small (< 5 cm, n = 10/14), isointense to muscle on T1-W (n = 14/14), hyperintense on T2-WI (n = 12/14), with enhancement (n = 12/12), low ADCmin (0.5-0.7 × 10-3 mm2/s), and variable metabolic activity (SUVmax range 2.1-13.1). A target sign was absent (n = 14/14) and fascicular sign was rarely present (n = 3/14). Systematic review revealed 89 cases of non-neurogenic PNM. CONCLUSION: Non-neurogenic PNMs account for 7% of PNT in our series and occur due to metastases and primary intraneural malignancy. Although non-neurogenic PNMs exhibit a non-specific MRI appearance, they lack typical signs of neurogenic tumors such as the target sign. Quantitative imaging features identified by DWI (low ADC) and F18-FDG PET/CT (high SUV) may be helpful clues to the diagnosis.
OBJECTIVE: To evaluate the frequency, clinico-pathologic and imaging features of malignant tumors in peripheral nerves which are of non-neurogenic origin (non-neurogenic peripheral nerve malignancy-PNM). MATERIALS AND METHODS: We retrospectively reviewed our pathology database for malignant peripheral nerve tumors from 07/2014-07/2019 and performed a systematic review. Exclusion criteria were malignant peripheral nerve sheath tumor (MPNST). Clinico-pathologic and imaging features, apparent diffusion coefficient (ADCmin), and standard uptake values (SUVmax) are reported. RESULTS: After exclusion of all neurogenic tumors (benign = 196, MPNST = 57), our search yielded 19 non-neurogenic PNMs (7%, n = 19/272), due to primary intraneural malignancy (16%, n = 3/19) and secondary perineural invasion from an adjacent malignancy (16%, n = 3/19) or metastatic disease (63%, n = 12/19). Non-neurogenic PNMs were located in the lumbosacral plexus/sciatic nerves (47%, n = 9/19), brachial plexus (32%, n = 6/19), femoral nerve (5%, n = 1/19), tibial nerve (5%, n = 1/19), ulnar nerve (5%, n = 1/19), and radial nerve (5%, n = 1/19). On MRI (n = 14/19), non-neurogenic PNM tended to be small (< 5 cm, n = 10/14), isointense to muscle on T1-W (n = 14/14), hyperintense on T2-WI (n = 12/14), with enhancement (n = 12/12), low ADCmin (0.5-0.7 × 10-3 mm2/s), and variable metabolic activity (SUVmax range 2.1-13.1). A target sign was absent (n = 14/14) and fascicular sign was rarely present (n = 3/14). Systematic review revealed 89 cases of non-neurogenic PNM. CONCLUSION: Non-neurogenic PNMs account for 7% of PNT in our series and occur due to metastases and primary intraneural malignancy. Although non-neurogenic PNMs exhibit a non-specific MRI appearance, they lack typical signs of neurogenic tumors such as the target sign. Quantitative imaging features identified by DWI (low ADC) and F18-FDG PET/CT (high SUV) may be helpful clues to the diagnosis.
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