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Benign notochordal tumor — Clinical Guidelines

Overview

Benign notochordal cell tumor (BNCT) is a rare, benign intraosseous lesion originating from notochordal cells. Often mistaken for chordoma due to similar anatomical locations and histological features, BNCT typically presents as a benign entity without malignant potential, although it may occasionally mimic more aggressive conditions clinically. Patients affected span a wide age range but are predominantly adults, with common sites including the sacro-coccygeal region, base of the skull, cervical, and lumbar vertebrae. Accurate diagnosis is crucial in day-to-day practice to avoid unnecessary aggressive treatments, ensuring appropriate management and patient outcomes. 1 2 3

Pathophysiology

The pathophysiology of BNCT revolves around the persistence or aberrant differentiation of notochordal cells within bone tissue. Normally, notochordal cells contribute to the formation of the intervertebral discs during embryonic development but typically degenerate postnatally. In BNCT, these cells fail to undergo complete regression, leading to the formation of benign masses. Histologically, these tumors exhibit characteristics reminiscent of notochordal tissue, including physaliphorous cells, but lack the invasive and proliferative features seen in chordomas. The exact molecular mechanisms driving this persistence or aberrant differentiation remain under investigation, though genetic and epigenetic factors likely play significant roles. 3 4

Epidemiology

The incidence of BNCT is relatively low, with most cases being incidental findings during autopsies or unrelated surgical procedures. Reported cases suggest a slight female predominance, with affected individuals ranging from young adults to middle-aged patients, though specific age and sex distributions vary. Geographic distribution does not appear to show significant regional clustering based on current literature. Longitudinal trends indicate an increasing recognition of BNCT due to advancements in imaging techniques, which facilitate earlier detection. However, precise prevalence figures are limited due to the rarity and often asymptomatic nature of the condition. 1 3

Clinical Presentation

BNCT often presents subclinically, with most lesions discovered incidentally through imaging studies performed for other reasons. When symptomatic, patients typically report subacute or chronic back pain localized to the affected vertebral region, without significant neurological deficits. Larger tumors may cause more pronounced symptoms such as localized tenderness, swelling, or, rarely, vertebral instability. Red-flag features include rapid growth, neurological deficits, or significant bone destruction, which warrant urgent evaluation to rule out more aggressive conditions like chordoma. 1 2 3

Diagnosis

Diagnosis of BNCT involves a combination of clinical, radiological, and histopathological evaluations to distinguish it from chordoma and other mimickers. Key diagnostic criteria include:

Imaging Findings: MRI often shows lesions with low T1 and high T2 signal intensities, confined to bone without soft tissue extension. CT may reveal lytic or sclerotic patterns depending on the lesion's characteristics. 1 3

Histological Examination: Biopsy or surgical resection specimens must demonstrate notochordal cell features, including physaliphorous cells, without evidence of atypical mitotic activity or invasion. Immunohistochemical staining typically shows positivity for vimentin and S-100 protein, but negativity for epithelial markers like cytokeratin. 1 3 4

Differential Diagnosis:

- Chordoma: Characterized by more aggressive histological features, including atypical mitoses and infiltrative growth patterns. - Osteonecrosis: Typically shows signs of bone marrow edema and fat stranding on MRI, lacking the characteristic notochordal cell morphology. - Giant Cell Tumor of Bone: Exhibits multinucleated giant cells and more aggressive behavior histologically. - Intraosseous Ganglion Cyst: Usually presents with fluid-fluid levels on imaging and lacks notochordal cell markers. 1 2 3

Management

Initial Management

Conservative Approach: For asymptomatic or minimally symptomatic lesions, regular imaging follow-up is recommended to monitor for any changes in size or characteristics. 2

- Follow-up Imaging: MRI or CT scans every 6-12 months initially, adjusting based on lesion stability.

Surgical Intervention

Indicated for: Symptomatic lesions, atypical imaging patterns, or diagnostic uncertainty requiring histopathological confirmation.

- En bloc Resection: Preferred for larger or symptomatic tumors to ensure complete removal and histopathological assessment. - Minimally Invasive Techniques: Considered for smaller lesions to reduce morbidity, though complete resection remains critical. - Post-operative Care: Close monitoring for complications such as wound infection, nerve injury, or vertebral instability. 1 2 3

Complications Management

Neurological Deficits: Immediate referral to neurosurgery if new neurological deficits arise post-surgery.

Vertebral Instability: Consider spinal stabilization procedures if instability is noted.

Infection: Prompt antibiotic therapy if signs of infection are present. 2

Complications

Postoperative Complications: Include infection, nerve injury, and vertebral instability, particularly after extensive resections.

Recurrent Lesions: Rare but possible, necessitating vigilant follow-up imaging.

Referral Triggers: Persistent pain, neurological deficits, or imaging evidence of lesion progression should prompt specialist referral. 2 3

Prognosis & Follow-up

The prognosis for BNCT is generally favorable, with no reported cases progressing to malignancy in long-term follow-up studies. Prognostic indicators include lesion size, symptomatic status, and completeness of surgical resection. Recommended follow-up intervals typically involve:

Imaging Follow-up: MRI or CT scans every 6-12 months initially, extending to annually if stable.

Clinical Assessment: Regular patient evaluations for symptom recurrence or new neurological symptoms. 1 2

Special Populations

Pediatrics: BNCT in pediatric patients is exceedingly rare, but when encountered, conservative management is often sufficient due to the benign nature of the lesion.

Elderly Patients: Increased caution is advised due to higher risk of complications from surgical interventions; conservative management is preferred unless absolutely necessary.

Comorbidities: Patients with significant comorbidities may require tailored surgical approaches to minimize risks associated with anesthesia and surgery. 1 3

Key Recommendations

Diagnose BNCT through comprehensive imaging and histopathological confirmation, distinguishing it from chordoma and other mimickers. (Evidence: Moderate)

Initiate conservative management for asymptomatic or minimally symptomatic lesions, with regular imaging follow-up. (Evidence: Moderate)

Consider surgical intervention for symptomatic lesions or diagnostic uncertainty, prioritizing complete resection. (Evidence: Moderate)

Monitor for postoperative complications, particularly neurological deficits and vertebral instability, necessitating prompt specialist referral. (Evidence: Moderate)

Regular follow-up imaging and clinical assessments are essential to detect any changes in lesion characteristics or symptom recurrence. (Evidence: Moderate)

Tailor management strategies based on patient-specific factors, such as age and comorbidities, to minimize risks. (Evidence: Expert opinion)

Avoid aggressive treatments unless there is clear evidence of progression or atypical features suggesting malignancy. (Evidence: Moderate)

Educate patients on recognizing red-flag symptoms that may indicate complications or transformation. (Evidence: Expert opinion)

Collaborate with specialists (neurosurgery, orthopedic surgery) for complex cases requiring multidisciplinary care. (Evidence: Expert opinion)

Stay updated with evolving diagnostic criteria and management guidelines due to the evolving understanding of BNCT. (Evidence: Expert opinion)

References

1 Yamaguchi T, Iwata J, Sugihara S, McCarthy EF, Karita M, Murakami H et al.. Distinguishing benign notochordal cell tumors from vertebral chordoma. Skeletal radiology 2008. link 2 Terzi S, Mobarec S, Bandiera S, Gasbarrini A, Barbanti-Bròdano G, Alberghini M et al.. Diagnosis and treatment of benign notochordal cell tumors of the spine: report of 3 cases and literature review. Spine 2012. link 3 Lalam R, Cassar-Pullicino VN, McClure J, Singh J. Entrapped intralesional marrow: a hitherto undescribed imaging feature of benign notochordal cell tumour. Skeletal radiology 2012. link 4 Amer HZ, Hameed M. Intraosseous benign notochordal cell tumor. Archives of pathology & laboratory medicine 2010. link 5 Kyriakos M, Totty WG, Lenke LG. Giant vertebral notochordal rest: a lesion distinct from chordoma: discussion of an evolving concept. The American journal of surgical pathology 2003. link

Benign notochordal tumor