Spinal angiolipoma (SAL) occurs in approximately 0.04% to 1.2% of all spinal tumors^{17,23,28,30,32,37)}. SAL is a benign tumor made up of adipose tissues and vasculature^{1,16,22,23,27-30,32,34,35,38,39,42)}. Although the tumor is usually found within the thoracic epidural space, SAL is sometimes found within the lumbar epidural space. It is also found within the cervical and sacral epidural space, though rarely^{9,18,32,35,38)}. Usually, SAL grows slowly and compresses the spinal cord or root, causing symptoms gradually^{4,12,18,31,40,46)}. SAL can be subdivided into two types, non-infiltrating and infiltrating^{1,18,23,32,33,35,40)}. The non-infiltrating type of SAL is easily dissected from the surrounding dura and adjacent tissue because it is encapsulated. In contrast, the infiltrating type is not encapsulated, making total removal difficult^{1,23,33,39,42)}. Magnetic resonance imaging (MRI) has an important role in diagnosing SAL, but the gold standard for diagnosis is pathological diagnosis^{1,4,18,23,32,38)}. The main treatment in SAL cases is surgical removal. Even when infiltrating type is subtotally removed, the prognosis is good^{18,27,33,39,40)}. We report a case of a patient with SAL complaining of cord compression symptoms arising from the thoracic level.

An 81-year-old male patient came to our clinic complaining of numbness in both legs lasting one year. The patient complained of both thigh pain and numbness in both feet. His big toe dorsiflexion motor grades (both toes) were 3+ with gait disturbance. The diagnosis was difficult not only due to the rarity of this type of tumor but also due to the patient’s history of brain meningioma. In August 2019, the patient underwent a craniotomy to remove a meningioma. This explains why the possibility of the post-operative spinal seeding of epidural meningioma could not be ruled out. After admission, MRI imaging showed a hyperintense mass in both T2 (Fig. 1A) and T1 (Fig. 1B) imaging at the T11 and T12 levels. It also showed homogenous enhancement in T1-contrast enhanced image (Fig. 1C). The mass was compressing the cord at that level and had spread to the neural foramina. Based on the patient’s history and the MRI imaging findings, we suspected an epidural meningioma.

We carried out surgical tumor removal. Pedicle screws were inserted at the T11-T12 level. Laminectomy and facetectomy were done. An Encapsulated mass with easily identifiable margins was exposed and removed. Postoperative MRI confirmed that the mass was completely removed (Fig. 2). Pathology revealed adipocytes with abundant vasculature, making the final diagnosis SAL (Fig. 3). The patient recovered well. His preoperative myelopathy symptoms were gradually relieved. In June 2023, approximately five months after surgery, the patient visited an outpatient clinic. Symptoms he complained of before the surgery, such as gait disturbance, motor weakness, and numbness in both feet, had disappeared.

SAL was first reported 1890 by Berenbruch and was defined as ‘spinal angiolipoma’ in 1961 by Howard and Helwig^{6,13,25,35,39)}. Benvenutti-Regato et al.⁵⁾ reported that there were 178 cases of SAL up to 2015. We found 51 more reported cases (Table 1) since 2016, making a total of 229 reported cases. Of the 51 cases, 31 were reported at the thoracic level, 13 at the lumbar level, one at the sacral level, four at the thoracolumbar level, and two at the lumbosacral level. According to Rkhami et al.³⁰⁾, 78% of SALs are found at the thoracic level, followed by 10% at the lumbar level and, less than 1% at the cervical or sacral level.

The tumor is commonly found in the posterior cord at thoracic levels. The symptoms are related to the compression of the thoracic spinal cord^31,40). Common symptoms include lower limb weakness, sensory changes, and numbness^31,40). Symptom progression can vary widely among patients, ranging from simple back pain to acute paraplegia^18,31,40).

According to Josephs et al.¹⁷⁾, several factors related to the growth of SAL are trauma, weight gain, and hormones³⁰⁾. Obesity and pregnancy can promote SAL growth by stimulating hormones that affect the growth of adipose tissue^{4,9,23,25,28,31,38)}.

Differential diagnoses of SAL include arteriovenous malformations, nerve sheath tumors, meningioma, metastasis, chronic extradural hematoma, and lymphoma^{4,12,24,25,29)}. Among them, the growth patterns of spinal epidural meningiomas are commonly the en plaque, dumbbell or fusiform type^24,44). The mass may extend toward the intervertebral foramen with a characteristic dura tail^24,44). Out of the three common shapes, the fusiform-shaped meningioma must be differentiated from SAL^24,44). Our patient’s imaging study revealed a mass at the thoracic level. The shape was fusiform with slight dural thickening extending to the intervertebral foramen (Fig. 1). Based on the imaging study and the patient's history of meningioma, we preoperatively suspected a case of spinal meningioma.

MRI is the most valuable tool for diagnosing SAL before surgery^{1,4,19,23,27,38,46)}. Though tumors display variable intensity across T1 and T2, they are usually hyperintense in both T1 and T2-, and homogenously enhanced in T1 images^{1,8,18,29,30,38,39)}. However, in SAL cases with profuse vasculature, T1 displays hypointensity and T2 displays hyperintensity^39,41,42,46).

SAL can be subdivided into two types. The first is the non-infiltration type. This subtype is more common and is commonly found within the dorsal epidural space; it is encapsulated, distinguishing it from the surrounding tissue^{1,28,32,38,42)}. Therefore, this type can be completely removed^{1,18,28,32,33,35,38,42,46)}. The second type is the infiltration type, which is less common. This type is commonly found on the ventral side of the spinal cord. It is difficult to distinguish from the surrounding tissue. It usually invades the vertebral body because it is not encapsulated^{1,18,28,32,33,35,38,42,46)}. SAL usually shows a good prognosis with no additional treatments needed, even when the tumor is subtotally removed^{1,4,12,16,18,21,27,29,31,46)}. However, Wang and Tang³⁹⁾ reported that myelopathy can recur in cases of incomplete removal due to dura infiltration.

Total resection is the treatment of choice. Most patients of surgically removed SAL are relieved of neurologic symptoms^{1,4,8,18,19,21,22,42,43)}.

The choice of surgical method depends on the tumor’s axial localization (ventral or dorsal) and the involvement of the intervertebral foramen⁴⁵⁾. The tumor is usually located dorsally without involvement of the intervertebral foramen^{1,28,32,38,42)}. In such cases, total resection is relatively easy without dura injury ⁴⁵⁾. However, in cases of a ventral location with the involvement of the intervertebral foramen, wider resection is necessary⁴⁵⁾. In our case, the wide resection method with laminectomy and facetectomy was selected, as the tumor was located dorsally-, but invaded the intervertebral foramen. After removal of the tumor, screw fixation was performed for spine stability.

Pathologically, SAL shows a characteristic appearance of mature adipocytes and abnormal vascular elements, including capillaries, thin- or thick-walled vessels, and small arteries^{4,20,37,39,42,46)}. Furthermore, mature fat tissue and blood vessels usually exist at 1:3 to 2:3 ³⁹⁾.

SAL is a rare benign tumor composed of fat tissue and vasculature. The case reported here was the non-infiltration type with a clear margin. After the tumor was completely removed, the patient was discharged with improved myelopathy symptoms. Treatment for SAL involves surgical resection. The prognosis is good after surgery.