case_images: PMC10995294_01
case_images: Clinical history and representative radiological images. (A) Clinical course and diagnostic work-up of the described case. Day 0 is defined as the day when paralysis of extension of the right foot was evident for the patient. (B) Representative coronal and axial MRI images of the right tigh, showing an inhomogeneous contrast-enhancing lesion (red arrows). The brown box depicts a close-up image of the axial tumor expansion (C) Representative axial and coronal CT image of the initial CT scan on day 4 revealing no further nodular DLBCL lesions. (D) Representative axial and coronal CT image 17 days post-surgery showing novel malignant lesions in the ventral right femoral compartment (top orange arrow) as well as in the right inguinal region (bottom violet arrow).
case_images: fonc-14-1354073-g001.jpg
case_images: PMC10995294_01_fonc-14-1354073-g001.jpg
case_images: f1
case_images: The electromyogram showed pathological spontaneous activity of the M. tibialis anterior and the M. gastrocnemius, consistent with an axonal injury to the right sciatic nerve ( Figure 1A ). In total, imaging was suggestive of a malignant process and compatible with a MPNST ( Figure 1B ). The initial CT scan did not show additional contrast-enhancing lesions in particular in the caudal pelvic region and no enlarged lymph nodes ( Figure 1C ). A lumbar puncture was unremarkable with no evidence of malignant cells ( Figure 1A ). Moreover, based on the localization and the lack of other lymphoma manifestations as shown in  Figure 1C , the diagnosis corresponding to a primary extranodal manifestation of a DLBCL was made. As shown in  Figure 1D , the second CT scan 17 days after surgery revealed new nodular lymphoma manifestations in the inguinal region as well as in the right-sided frontal femoral compartment in line with a progression to systemic disease(see orange signs in  Figure 1D ). We acknowledge, that this may have provided additional information on the dignity of the lesion and treatment response or might have helped to identify small systemic manifestations not visible on standard CT/MRI scan ( Figure 1C, D ).
case_images: Histopathology. (A, B) Hematoxylin and eosin (H&E) stained cross section of the sciatic nerve showing a highly cellular neoplasm growing diffusely in between and within the nerve fascicles. (Original magnifications x5 and x100. Scale bars = 3,75 mm and 170 microm). (C) The tumor is composed of medium- to large-sized lymphoid cells with open nuclear chromatin, a single to multiple prominent eccentric nucleoli, and variable amounts of basophilic cytoplasm. Note the high mitotic activity. (Original magnification x400. Scale bar = 45 microm). (D) The tumor cells show strong CD20 expression by immunohistochemistry, consistent with a B-cell origin. (Original magnification x100. Scale bar = 170 microm). (E) MIB1 staining showing a proliferation rate of more than 90%, in line with the abundance of mitotic figures in the H&E stain. The non-proliferating cells in between are mostly endothelial cells and fibroblasts. (Original magnification x200. Scale bar = 75 microm). (F) A neuron specific enolase stain highlighting the reduced number of remaining nerve fibers. (Original magnification x100. Scale bar = 170 microm).
case_images: fonc-14-1354073-g002.jpg
case_images: PMC10995294_01_fonc-14-1354073-g002.jpg
case_images: f2
case_images: Histologically, the resected sciatic nerve was diffusely infiltrated by a highly cellular neoplasm composed of medium- to large-sized lymphoid cells with round to slightly convoluted nuclei with open nuclear chromatin, a single to multiple prominent nucleoli, and variable amounts of basophilic cytoplasm ( Figure 2 ).