Spinal brown tumors as a rare cause of spinal cord compression: Report of case series.

Introduction

Brown tumor (BT) is a rare but distinct histopathological lesion that occurs in patients with hyperparathyroidism. It was found in less than 5 % of patients with primary hyperparathyroidism while the incidence in secondary hyperparathyroidism is 1.5 % to 13 %, frequently in end stage renal failure [ [1] , [2] , [3] , [4] ].

They are presented with unique or multiple lesions and mostly located in the bone of extremities and large bone like mandible, ribs, sternum and rarely in the spine. Their clinical manifestations are usually progressive and depend on the location. Spinal cord compression due to spinal BT is rare [ 1 , 5 ] and the treatment in such case should begin immediately when it is clinically suspected to avoid further deterioration of neurological status and negative consequences [ 1 , 5 , 6 ].

We report four cases of spine Brown tumors revealed by spinal cord compression appropriately treated in our department and we discuss their clinical, radiological, diagnostic, and treatment aspects, with a review of the literature.

Methods

This retrospective study includes four cases of Brown tumors revealed by spinal cord compression and rapidly operated in our neurosurgery department between 2014 and 2024. Data were collected from medical records, including demographic characteristics, clinical presentation, radiological findings (CT scan, MRI), surgical management, histopathological analysis, and postoperative outcomes.

Inclusion criteria: Patients diagnosed with Brown tumors associated with spinal cord compression requiring urgent surgical intervention.

Exclusion criteria: Absence of histopathological confirmation and patients who were not operated or refused surgery.

This study has been reported in accordance with all the criteria in the PROCESS guidelines [ 7 ].

Results

We herein report four cases of brown tumors of the spine revealed by spinal cord compression, each presenting with varying degrees of neurological impairment.

Case 1

The first case involved a 42-year-old woman with end-stage renal disease (ESRD) on hemodialysis for seven years. She suffered from a progressive C7 neuralgia over six months. Neurological examination revealed paraparesis graded at 4/5 in lower limbs with brisk deep tendon reflexes. Imaging showed C7 vertebral body compression with a butterfly-shaped vertebra appearance, hypertrophy of the right hemi lamina of C7, and significant anterior cord compression on MRI ( Fig. 1 ). Laboratory findings confirmed severe hyperparathyroidism, with markedly elevated PTH (3399 pg/mL), hypercalcemia (2.89 mmol/L), and high alkaline phosphatase (609 U/L). The patient underwent C6-C7 discectomy and partial resection of the C7 vertebral body via an anterior approach, revealing friable bone with a brownish lesion. Stabilization was achieved using semi-constrained cervical plate and titanium mesh cage. Histopathology confirmed a brown tumor of C7 associated with hyperparathyroidism, and the patient experienced significant relief from neuralgia with a parathyroidectomy scheduled for definitive treatment.

Case 2

The second case was a 66-year-old male who had previously undergone parathyroidectomy for primary hyperparathyroidism. He presented with progressive heaviness in the lower limbs, intermittent spinal claudication, back pain, and difficulty holding objects over an eight-month period. Examination showed right lower limb paresis (3/5 strength) and gait impairment requiring assistance. Cervical CT imaging revealed an osteosclerotic lesion located in the posterior arch of C7 with intracanalar extension, causing spinal cord compression ( Fig. 2 ). Laboratory tests were within normal limits, with calcium, phosphate, and PTH levels all normal, though alkaline phosphatase was slightly elevated (150 U/L), and ESR was increased (50 mm/h). The patient underwent C7 laminectomy with lesion excision, and histopathological analysis confirmed a brown tumor.

Postoperatively, he experienced marked relief from cervical pain and paresthesia, but one-year later developed pulmonary adenocarcinoma, ultimately leading to death from cancer-related complications.

Case 3

The third case involved a 36-year-old male with a history of malignant hypertension, ESRD on hemodialysis since 2009, and a rejected kidney transplant. He presented with acute-onset back pain, progressive lower limb weakness, and urinary incontinence over two weeks. Examination revealed paraparesis (3/5 strength), tactile hypoesthesia in a ‘stocking’ distribution, and brisk deep tendon reflexes. Imaging showed L1 vertebral compression, with an osteolytic lesion and posterior cortical blowout on Standard X-ray and on CT, leading to spinal cord compression. MRI confirmed an expansive L1 vertebral lesion extending posteriorly to the pedicles and superiorly to T12 ( Fig. 3 ). Laboratory tests indicated advanced chronic kidney disease with secondary hyperparathyroidism, including elevated PTH (400 pg/mL), serum creatinine (800 μmol/L), and alkaline phosphatase (300 U/L). Due to rapid neurological deterioration, the patient underwent emergency T12-L1 laminectomy. The postoperative course was uneventful, with improvement in motor strength, restored independent ambulation, and amelioration of urinary dysfunction. Post-operative MRI shows posterior decompression ( Fig. 4 ). Patient then underwent posterior long segment fixation with pedicle screws. Histopathological study confirms the diagnosis of spinal brown tumor showing the presence of bone resorption, clusters of multinucleated giant cells and hemosiderin deposition ( Fig. 5 ). Long-term follow-up with recent X-ray after six years shows vertebral cortical mineralization ( Fig. 4 ).

Case 4

The final case was a 40-year-old female with chronic hepatitis C (treated with interferon) and ESRD on hemodialysis for 10 years. She presented with progressive intermittent spinal claudication over six weeks, without sphincter disturbances. Neurological examination revealed spastic paraparesis, posterior cord syndrome, and a sensory level at T10. Imaging ( Fig. 6 ) demonstrated a lytic process affecting the posterior arch of T11 on CT and a low T1-signal lesion with mass effect on the spinal cord on MRI. Given the severity of spinal cord compression, emergency T10-T11 laminectomy was performed, with complete removal of the lesion. Intraoperatively, the tumor appeared reddish-gray, friable, and minimally hemorrhagic. Histopathological analysis revealed bone resorption with giant cells, spindled mononuclear cells, vascularized stroma, hemorrhage, and hemosiderin deposition, consistent with a spinal brown tumor ( Fig. 7 ). The postoperative course was favorable, with progressive motor improvement and complete resolution of back pain.

Discussion

Summary of our series

In our retrospective study, we report 4 cases of BTs over a period of eleven years in two males and two females with mean age of 46 years old (ranging from 36 to 66 years). Three of our patients are on long term ESRD with secondary hyperparathyroidism and one with primary hyperparathyroidism, recently operated by parathyroidectomy for parathyroid adenoma. All patients presented with spinal cord compression syndrome. Radiological investigations showed osteolytic lesion located in cervical region in two cases: in thoracic in one case and in lumbar in the remaining case. The lesion affects the vertebral body in two cases and the posterior arch in two cases with extension to the canal compressing the spinal cord in all cases. Laboratory finding showed elevation of PTH, alkaline phosphate and calcium in all patients with secondary hyperparathyroidism and normal PTH with slight elevation of alkaline phosphate in the case with primary Hyperparathyroidism. All patients underwent surgical decompression via posterior approach in three case and anterior in one case. All patients manifested good post-operative recovery. Table 1 summarized the diagnosis, treatment, and outcome of our patients.

Literature review

Natural history and physiopathology

BTs are not true tumors, but a reactive bone lesion resulting from increased PTH in Hyperparathyroidism [ 1 , 2 ]. Hyperparathyroidism is a condition characterized by elevated serum parathyroid hormone levels [ 8 ]. This hormonal increase stimulates osteoclast activity [ 1 ], leading to bone changes such as trabecular resorption, fibrous tissue proliferation, hemorrhage, and hemosiderin deposition [ 3 , 9 ]. The accumulation of hemosiderin gives the tissue its distinctive brown color, which is the origin of the term “brown tumor” (BT) [ 1 , 9 ]. BT occurs in less than 5 % of cases of primary hyperparathyroidism, while its prevalence in secondary hyperparathyroidism ranges from 1.55 % to 13 % [ 1 , 2 ].

The clinical course of hyperparathyroidism was described for the first time by Von Recktinghausen in 1891 through clinical-pathological series [ 4 , 10 ] and was related to the presence of bone tumors caused by the intense activity of the parathyroid glands [ 2 ]. This tumor corresponds to the condition of osteitis fibrosa cystica, a term created by Erdheim and Wood in 1930 [ 2 ].

The etiology of the brown tumor is directly related to the osteoclastomatosis of the bone tissue related to hyperparathyroidism [ 4 , 10 ], as a direct effect of the high level of parathormone on the release of osteoclasts [ 6 ].

Recent advances in the understanding of parathyroid hormone (PTH) dynamics have underscored its role not only in calcium‑phosphorus metabolism [ 10 ] but also in direct skeletal remodeling and vascular calcification, particularly in patients with chronic kidney disease (CKD) [ 10 , 11 ]. Elevated PTH promotes osteoclastic activity, leading to high-turnover bone disease and the development of osteolytic lesions such as brown tumors [ 11 ]. Molecular studies have further highlighted the involvement of the RANK/RANKL/OPG axis and Wnt signaling in the pathogenesis of secondary hyperparathyroidism-related bone changes [ 11 ].

Clinical manifestations

The clinical expression of spinal brown tumors (SBT) compression is similar to the other spinal etiologies when the tumor compresses the canal [ 2 , 3 , 12 ]. The following symptoms can occur: radiation pain, spinal pain, neurological deficit, and autonomic dysfunction. Moreover, nocturnal pain, which is exacerbated when coughing or standing, may be seen [ 1 , 2 ]. Spinal cord compression syndrome in BTs is found to be rare [ 1 , 2 ].

Differential diagnosis

Brown tumors may clinically mimic other spinal lesions, for example, infections, bone hydatid cysts, metastases, multiple myeloma, giant cell tumors, Ewing's sarcoma, no ossifying fibroma, and osteoblastoma [ 8 , 9 ]. There are currently no definitive clinical patterns suggestive of spinal brown tumors by which in the case of earlier diagnosis and management could be achieved [ 12 ]. We highlight the importance of early diagnosis and detection of spine cord compression and the difficulty of differential diagnosis specially knowing that the history of arthralgia, back pain and neuralgia is common in patient with ESRD. This difficulty in diagnosis leads to delayed scanning of the spine and delayed management of spine BT increasing the risk of motor deficit and neurological complication. Therefore, these early symptoms are necessary to raise the index of suspicion of spinal BT and to make a differential diagnosis [ 4 , 11 , 13 ].

Radiological characteristics

The typical radiographic appearance of SBT is a mixed lytic and sclerotic lesion, which occasionally may be associated with trabeculation or multi-cystic changes, and with a soft-tissue mass in its periphery [ 14 , 15 ]. Differentiation from primary or secondary malignancies or other bone disorders, especially metastatic bone disease or multiple myeloma, using clinical and imaging features is usually a difficult task [ 1 , 6 , 15 ]. Spinal brown tumors most likely mimic primary tumors radiologically; thus, in the absence of any earlier skeletal involvement, the possibility of a spinal brown tumor due to primary hyperparathyroidism is quite low. On CT scans, bone tumors (BTs) typically show up as well-defined, hyperdense, expansile lesions with areas shown the destruction of the bone. The bone cortex may appear thinned or destroyed [ 15 ]. The contrast-enhanced CT scans show strong enhancement due to the highly vascular character of these tumors. On MRI, BTs usually appear as either iso- or hypointense on T1-weighted images and can vary between hyper- or hypointense on T2-weighted images [ 2 , 15 ]. The tumor often shows intense enhancement after contrast [ 8 ].

Laboratory findings

Laboratory test results show elevations in levels of markers of increased osteoclast activity [ 1 , 10 ]. In primary hyperparathyroidism, patients typically present with elevated serum calcium (hypercalcemia), low serum phosphorus (hypophosphatemia), and elevated or inappropriately normal parathyroid hormone (PTH) levels [ 10 ]. Urinary calcium excretion is typically elevated, reflecting the increased bone resorption, and alkaline phosphatase may be elevated due to the increased bone turnover [ 10 ]. Secondary hyperparathyroidism, most often due to chronic kidney disease or vitamin D deficiency, is seen as elevated PTH with normal or low serum calcium and elevated or low phosphorus, depending on the etiology [ 9 , 10 ]. Low vitamin D is prevalent, and the ratio of calcium/creatinine clearance can be low. These biochemical derangements lead to hyperparathyroidism, and the resultant excess osteoclast activity leads to bone resorption, micro-hemorrhages, and vascularized, giant cell-rich lesions characteristic of brown tumors [ 4 , 6 ].

Histologic features

Microscopically, BT tumor nodules are comparable with the appearance of an older, woven, primary bone and bone tissue tumor [ 6 , 11 ]. Histologically, bone lesions consist mainly of reactive fibrous tissue with histiocytes, osteoclasts, osteoclastic giant cell response, and osteoblastic rimming [ 6 ]. Immune-histochemical shows positive TRAP stain (tartrate-resistant acid phosphatase), H-resembling cells and the application of sodium fluorescein may reveal large osteoclasts [ 1 , 2 , 4 ].

Surgical management and medical treatment

For primary hyperparathyroidism, parathyroidectomy is indicated in the instance of a raised parathyroid hormone level as the hyperparathyroidism was to blame for the destruction of bone [ 2 , 10 ].

Supplementation with calcium and vitamin D is an extremely effective therapy for secondary hyperparathyroidism of renal disease [ 4 , 8 , 16 ]. Optimization of homeostasis of calcium and phosphorus with pharmaceuticals and diet is the first step in secondary hyperparathyroidism management [ 8 , 10 , 16 ].

Because of the aggressive nature of the clinical course of spinal Brown Tumors and because they are often encountered in thoracic spine, spinal brown tumors are treated with surgical excision and hyperparathyroidism treatment simultaneously or later [ 10 , 14 , 16 ]. The goal of the surgery is to decompress the spinal cord and stabilize through internal fixation, particularly in compression fracture of a pathological vertebra and kyphosis to prevent neurological deterioration [ 6 , 12 , 16 ].

The optimal timing of parathyroidectomy in relation to spinal decompression surgery remains a matter of clinical judgment. Some authors suggest that preoperative parathyroidectomy may reduce recurrence of osseous lesions and enhance bone healing [ 16 ]; however, in patients with acute or progressive neurological deficits, spinal decompression must be prioritized [ 11 , 12 , 16 ]. Our approach aligns with this strategy: we performed urgent surgical decompression in all symptomatic patients and referred them postoperatively to endocrinology and nephrology for further hormonal management, including consideration of parathyroidectomy when appropriate. This reflects a pragmatic, multidisciplinary model supported by current nephrology and endocrine practice guidelines. [ 16 ].

Finally, the principles of therapy of surgical treatment need to be tailored individually based on the patient's clinical condition, life expectancy, and the stage of any underlying illness [ 3 , 11 , 12 ].

Short and long term prognosis

In general, most brown tumors regress spontaneously after parathyroidectomy and normalization of biochemical abnormalities over several years [ 4 , 5 ]. No cases of malignant transformation have been reported. The presence of hyperparathyroidism at the time of surgery causes more diffuse bone disease and residual poor-quality bone after surgery, leading to a slower recovery of neurological function, loss of vertebral height, kyphosis, postoperative fractures, and ultimately poor long-term quality of life [ 5 , 6 ]. Parathyroidectomy should lead to a decrease in serum calcium and PTH concentration within 24 h after surgery [ 4 ]. Uncorrected hyperparathyroidism is a predisposing factor for recurrence. After parathyroidectomy, radiographic ossification of the brown tumor occurs within a few months to a few years [ 4 , 15 ].

Our findings align with those reported in the literature, reinforcing the current understanding of brown tumors in the context of hyperparathyroidism. However, our study is distinctive in that it presents a case series of four patients, in contrast to previous literature which has only documented isolated case reports. To our knowledge, this is the second case-series of spinal brown tumors. This strengthens the significance of our contribution. Nevertheless, our study has certain limitations, primarily its retrospective nature and the challenges in ensuring long-term follow-up. The latter was hindered by COVID-19 restrictions and patient reluctance to return for consultations.

Conclusion

Although BTs are benign, spine involvement can lead to spinal cord compression with neurological deterioration, then early screening in patient with ESRD or parathyroid adenoma through biochemical tests and bone imaging is crucial for timely diagnosis and management.

Despite its rarity, BTs should be kept in mind in case of spinal cord compression caused by spine osteolytic lesion in the ESRD or parathyroidism cases.

Author contribution

Ghassen Elkahla: Data collection, analysis, and manuscript writing, review, approval.

Ahmed Amine Daoued: Data collection, analysis, and manuscript writing, review, approval.

Amine Trifa: Data interpretation, literature review, and manuscript writing, approval.

Kais Maamri: Verification and Fact-Checking, approval.

Samiha Mabrouk: Pathology interpretation and photomicrography, approval.

Mehdi Darmoul: Study concept and design, supervision and conceptual guidance, review, approval.

Consent

Written informed consent was obtained from the patients for publication of this case series and accompanying images.

A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

Our institution does not require ethical approval for reporting individual cases (We maintained a high level of respect for both anonymity and confidentiality when presenting the patient in our case series.)

Guarantor

Ph.D Professor Mehdi Darmoul

Research registration number

This is not a research study.

Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work the author(s) used CHATGPT in order to improve readability and language. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Conflict of interest statement

The author declares no conflicts of interest.

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