Spinal epidural calcified chondroid mesenchymal neoplasm mimicking epidural abscess: a case report

Abstract

Introduction

Calcified chondroid mesenchymal neoplasm (CCMN) is a recently defined chondroid matrix-producing tumor characterized by distinctive morphology, chondroblastoma-like calcification, and recurrent FN1-receptor tyrosine kinase gene fusions [1]. The evolving classification of CCMN overlaps with soft tissue chondroma, chondroid synoviocytic neoplasm, and cellular tophaceous calcium pyrophosphate dihydrate (CPPD) lesions [2, 3]. Reported CCMNs arise predominantly in the distal extremities and temporomandibular joint. To our knowledge, no prior spinal cases of CCMN have been reported [4, 5].

This case report describes a thoracic epidural lesion with histopathologic features morphologically consistent with CCMN. Recognition of CCMN in such an atypical anatomic location has important diagnostic implications, especially when more common pathologies, such as spinal abscess in this case, are initially suspected.

Case report

A 40-year-old male presented with severe progressive mid-back pain that radiated to his right hip and flank. He reported a 1-week history of fever prior to the onset of the pain that had resolved by the time of presentation (97.9°F). Neurological examination was non-focal except for localized pain over the thoracic spine.

Laboratory evaluation demonstrated a white blood cell count (WBC) of 3.6 × 10³/μl, CRP <0.4 mg/dl, and ESR 21 mm/h. Blood cultures were negative for 5 days, and no fever was documented during the hospitalization. Serum calcium (9.7 mg/dl), magnesium (2.1 mg/dl), phosphorus (2.8 mg/dl), and alkaline phosphatase (60 U/L) were within normal limits. Serum uric acid and parathyroid hormone levels were not obtained. There was no documented history of gout or pseudogout. Preoperative computed tomography (CT) demonstrated a hyperdense T10–T12 spinal canal lesion causing moderate-to-severe stenosis. Magnetic resonance imaging (MRI) demonstrated a 3.4 cm posterior/right epidural lesion extending from mid-T10 to upper T12, with severe canal stenosis and cord compression (Fig. 1). The patient underwent T9–T12 laminectomy and decompression for suspected epidural abscess. CT and MRI were obtained on the day of presentation, followed by operative decompression the next day.

Figure 1

Preoperative imaging. (A) CT demonstrating a hyperdense collection within the spinal canal extending from T10 to T12 with associated canal stenosis. (B) Sagittal T2–weighted MRI demonstrating the epidural lesion and associated cord compression. (C) Sagittal contrast-enhanced T1-weighted MRI demonstrating marginal enhancement of the posterior epidural lesion extending from approximately T10–T12. (D) Axial contrast-enhanced T1-weighted MRI at T10–11 demonstrating the posterior/right epidural lesion (arrow) with marginal enhancement and associated spinal cord (^*) compression.

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Following T9–T12 laminectomy, a white, curd-like epidural lesion was identified beneath the ligamentum flavum in the posterior epidural space that was highly adherent to the dura. No direct relationship between the epidural lesion and the facet joints was identified. The epidural lesion was carefully dissected and removed piecemeal, with a small component densely adherent to the dura left in situ to avoid dural injury. The resected specimen consisted of multiple tissue fragments measuring 3.3 × 2.5 × 0.6 cm in aggregate. During T9–10 transpedicular decompression, a large, calcified disc herniation with ventral canal extension was also identified and decompressed. Empiric cefepime and vancomycin were initiated intraoperatively for suspected epidural abscess. Blood and intraoperative tissue cultures were negative.

Histopathologic examination demonstrated a calcified spindle cell lesion with chondroid differentiation and morphologic features compatible with CCMN (Figs 2 and 3). The lesion contained bland spindle cells within a chondromyxoid background, with grungy calcification and fractured blocky chondroid material. Assessment of multinodular architecture and other classic morphologic features was limited by the small, fragmented specimen. Trabecular bone and fibrocartilage with trilineage marrow hematopoiesis represented adjacent tissue included in the resection specimen rather than a component of the lesion. The lesional cells were immunohistochemically negative for SATB2, SSTR2, CD56, S100, and SOX10. The nuclear expression of INI1/SMARCB1 and BRG1/SMARCA4 was uniformly retained. Molecular testing for an FN1-receptor tyrosine kinase fusion by FISH was negative. However, the assay was unvalidated and the final pathologic diagnosis remained unchanged. Polarized light microscopy for crystal identification was not performed.

Figure 2

Haematoxylin and eosin (H&E) stain of tumor at 100× magnification. Long black arrows point to areas of calcification. The C marks the chondromyxoid background. The S marks the spindle cell component. The blue arrows mark the fractured blocky chondroid material.

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Figure 3

H&E stain of tumor at 200× magnification. The S marks the spindle cell component. The arrows mark the fractured blocky chondroid material.

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The patient’s postoperative course was uncomplicated, and his symptoms resolved. MRI obtained 3 weeks postoperatively demonstrated no definite residual inflammatory fluid collection. At 1-year follow-up, MRI demonstrated no significant residual canal stenosis (Fig. 4). The patient remained asymptomatic at 18-month clinical follow-up.

Figure 4

One-year postoperative thoracic spine MRI. Representative sagittal (A) and axial (B) images demonstrating postoperative changes following T9–T12 decompression and instrumentation, without significant residual canal stenosis. Evaluation of the operative levels is partially limited by metallic susceptibility artifact.

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Discussion

CCMN remains a rare soft-tissue neoplasm, with reported cases arising in soft tissue or joints and no primary intraosseous cases identified to date [6]. Feng et al. identified 92 cases in a pooled review [4]. Recent reports involving the masticator space and perineum further expand its recognized anatomic spectrum, as does the present spinal epidural location [7, 8].

The differential diagnosis included crystal deposition disease and other calcified spinal lesions. Spinal tophaceous CPPD disease can mimic an epidural infectious process, while tophaceous gout can also involve the spine [9]. The patient had normal calcium, magnesium, and phosphorus, and no history of gout or pseudogout. Uric acid and parathyroid hormone levels were not obtained. Polarized light microscopy was not performed, precluding definitive exclusion of crystal deposition disease. Despite reported fever one week before presentation, the patient remained afebrile without leukocytosis and with negative blood and tissue cultures.

Phosphaturic mesenchymal tumour, another FN1-fusion-associated neoplasm with potential axial involvement, was also considered. The absence of SATB2, SSTR2, and CD56 expression with normal phosphorus and alkaline phosphatase argued against it. Other spinal causes of epidural calcification included ligamentum flavum ossification or calcification and synovial cyst. Imaging demonstrated intradiscal calcifications and a separate calcified T9–10 disc herniation, which was decompressed intraoperatively. The dorsal epidural lesion beneath the ligamentum flavum was distinct from this disc pathology. Clusterin and CSF1 were not evaluated, limiting distinction from chondroid synoviocytic neoplasm.

Diagnosis requires integration of imaging, histology, and molecular findings. Although FN1 fluorescence in situ hybridization (FISH) was negative, the assay was unvalidated, and FN1 alterations are not identified in all morphologically defined CCMNs [10]. The nosologic boundaries of CCMN remain debated, with Nishino et al. questioning whether morphologically similar lesions lacking characteristic molecular alterations may represent established neoplastic or reactive entities [11]. Without validated molecular confirmation or polarized light evaluation, definitive classification of this lesion remains limited.

Recurrence has been reported primarily following incomplete resection. Feng et al. identified two recurrences among 30 cases with 2–72 months of follow-up, both after incomplete excision [4]. Kallen et al. reported one recurrence following incomplete excision among 15 patients (mean follow-up 14.4 months, range 2–30 months) [5]. Given the small residual component adherent to the dura in our patient, continued surveillance is warranted.

This case represents, to our knowledge, the first reported spinal lesion morphologically consistent with CCMN. Its presentation as a calcified epidural lesion mimicking infection highlights the diagnostic challenge of CCMN in an atypical location and may help avoid misdiagnosis of calcified epidural lesions.

Conflicts of interest

The authors have no relevant financial or non-financial interests to disclose.

Funding

No funds, grants, or other support were received.

Data availability

Data supporting the findings of this case report are available from the corresponding author upon reasonable request, subject to applicable patient privacy restrictions.

Ethical approval

Institutional Review Board approval was exempted because this case report included fewer than three patients.

Consent

The patient provided informed consent for the procedure.

References