A 3D navigation-guided surgical resection of a rare case of sacral spine mesenchymal chondrosarcoma: a case report

Abstract

Background: Chondrosarcomas are a group of heterogeneous malignant cartilaginous neoplasms that arise from preexisting benign precursors. They can be divided into conventional (primary) chondrosarcomas, which account for 90% of cases, and nonconventional chondrosarcomas, which account for the remaining 10%. Mesenchymal chondrosarcoma (MCS) is a rare high-grade soft tissue tumor variant of nonconventional chondrosarcoma that is histologically characterized by a biphasic pattern of atypical cartilage with small round cells.

Case description: A 23-year-old female known case of ovarian cyst presented with a two-year history of low back pain and constitutional symptoms. Pelvic magnetic resonance imaging (MRI) with contrast showed a well-defined lesion with intermediate to high signals located at the right wing of the upper sacrum, at the level of S1-S2. The patient underwent a combined ultrasound and computed tomography-guided biopsy under local anesthesia and the immunochemical profile was positive for CD99 and S100 biomarkers. The patient underwent a two-stage procedure for a wide marginal tumor resection. Stage 1 was performed with an anterior approach; identification of the tumor margins was done followed by designing the cuts of the sacrum to achieve wide margins around the tumor. Stage 2 was performed with a posterior approach exposing L3 vertebrae down to the sacrum. Utilizing O-Arm Navigation for posterior margin allocation in addition to instrumentation. After 12 months post-operation, follow up revealed no evidence of recurrence.

Conclusions: Limitation in accessibility to the axial skeleton and the neurovascular component, poses a challenge to treatment. Therefore, using neuro-navigation system and optimal adjuvant therapy should be studied further to improve the prognosis.

Keywords: 3D neuro-navigation; Mesenchymal chondrosarcoma (MCS); case report; spine; surgical resection.

Figure 1

A plain pelvic X-ray anteroposterior view showing heterogeneity of the right sacral ala bone (arrow) with lytic and destructive changes.

Figure 2

A T2-weighed pelvic MRI showing an intermediate to high signal following IV gadolinium administration: (A) sagittal plane; (B) coronal plane. A few intra-lesional hypointense signal foci are present, in keeping with calcification/chondroid matrix. The mass measures 5.1 cm proximal-distal × 5.0 cm medial-lateral × 4.4 cm anterior-posterior. The mass is abutting the right iliac side of the sacroiliac joint, however the joint remains intact (arrows). There is loss of the anterior cortex. MRI, magnetic resonance imaging.

Figure 3

Abdominal and pelvis CT scan: (A) coronal plane, (B) axial plane, (C) sagittal plane, showing a well-circumscribed soft tissue lytic lesion within the superior right sacral ala which measures 5.5 cm × 4.2 cm (arrows). It shows enhancing soft tissue with some calcification centrally. It has caused some remodeling of the contour of the medial right iliac wing with no invasion into it. CT, computed tomography.

Figure 4

A bone scan. This is a baseline study showing uniform activity throughout the skeleton. A small rounded focus of activity seen anterior to the right sacroiliac joint (arrows). 20 mCi radiotracer technetium-99m was injected. mCi, millicuries.

Figure 5

Intra-operative anterior view after the osteotomies were made showing vessel loops used to identify and protect the L5 nerve roots and the major vessels. The arrow shows superior cut at level lower wedge of L5.

Figure 6

Intra-operative images showing the use of the O-arm 3D neuronavigation system during the posterior approach. (A) Illustrates the surgeon using the navigation probe to identify the level of vertebra to assist with the posterior cut and pedicel screw placement. (B) Showing on demand imaging from the monitor demonstrating the anterior cut that was made during the anterior approach of the procedure at the level of S1 (arrow), alongside using navigated instrumentation to assist in pedicle screws placement with sufficient medial margin. 3D, 3-dimensional.

Figure 7

Post-operative lumbar spine X-ray. (A) Anteroposterior view and (B) lateral view, which presents interval insertion of pedicle screws involving L3, L4, L5, S1, and bilateral sacroiliac fixation. The resected tumor location is indicated in the right sacral ala bone (arrow).

Figure 8

Histopathology assessment for the tumor specimen. (A) Macroscopic examination of an en bloc gross specimen measuring 10 cm from proximal to distal, 9 cm from anterior to posterior and 4 cm from medial to lateral. A well-circumscribed mass, soft-to-firm, tan-white, homogenous. The proximal, distal, lateral and medial margins of the specimen were all negative for the tumor. (B) Microscopic examination using H&E stain under ×400 magnification of the CT-guided biopsy showed undifferentiated small blue cells with hemangiopericytoma like vascular pattern mixed with islands of mature appearing, well differentiated hyalin cartilage (WHO grade 3). H&E, hematoxylin and eosin; CT, computed tomography; WHO, World Health Organization.