Spinal Extradural Angiolipoma: A Report of Two Cases and Review of Literature

Abstract

Spinal extradural angiolipomas (SEALs) are rare, benign neoplasms composed of mature adipocytes and vascular elements. They are often noninfiltrating and located in the posterior aspect of the spinal canal at the level of thoracic/dorsal vertebrae. Back pain, progressive paraparesis, and sensory disturbance in lower limbs are the typical symptoms. Here, we discuss two cases of SEALs presenting with subacute paraparesis. The magnetic resonance imaging of one patient was reported to be suggestive of spinal metastasis/plasmacytoma/sarcoma, while the other was reported as a spinal extradural hematoma. After laminectomy, both lesions were recognized as encapsulated extradural tumors and en-bloc resection was done. Postoperatively, the neurological deficits improved and there was no recurrence on 2-year follow-up. Histopathology characterized both of them to be extradural angiolipomas. Current experience and literature support curative surgical resection as the gold standard. The prognosis is excellent in most cases, even if total resection is not feasible. It is due to the slow-growing nature of the tumor and absence of malignant transformation.

Keywords

angiolipomas - epidural - laminectomy - spinal cord compression - neoplasms - paraparesis

Introduction

Extradural tumors of the spine usually arise from hematologic malignancies like lymphoma, multiple myeloma, or from metastasis. Primary extradural tumors are mostly osseous in origin, like aneurysmal bone cyst, giant cell tumor, osteosarcoma, chordoma, etc.[1] Spinal extradural angiolipomas (SEALs) are extremely rare, benign, extradural lesions. They constitute approximately 0.04 to 1.2% of all spinal tumors and 2 to 3% of spinal extradural lesions.[2] Only approximately 120 cases were reported from 1800 to 2020 to the best of our knowledge. These tumors are more common in females, usually diagnosed in the fifth decade of life.[3] They are usually located in the posterior surface of the dura. The tumor often molds itself to the epidural space (noninfiltrating) with occasional “nipple-like projections” extending into the intervertebral foramina.[4] Most of the time SEALs are noninfiltrating but can rarely infiltrate the adjacent bony structure of the spine. Also, infiltrating angiolipoma tends to localize in the anterior epidural compartment. Nonetheless, both have excellent prognosis after surgical removal.[5]

Case Report

Case 1

A 55-year-old male presented with complaints of back pain along the dorsal and lumbar regions for the past 10 days. He also experienced lower limb weakness and progressive difficulty in walking during the last 10 days. He had a history of slip and fall 15 days back. There was no history of bowel or bladder disturbance. On examination, bilateral lower limbs were hypertonic and hyper-reflexic with a positive Babinski sign. The muscle power was 3/5 (Medical Research Council [MRC] grade) in both lower limbs. Hypoesthesia was present below the T4 (thoracic) dermatome level. Magnetic resonance imaging (MRI) revealed a well-defined T2 hyperintense extradural lesion measuring 6.4 × 1.1 × 1.7 cm in the D2–D5 (dorsal/thoracic spine) level, situated in the posterior epidural space. The lesion compressing the spinal cord also showed avid post-contrast enhancement ([Fig. 1]). The lesion was reported to be suggestive of metastatic deposit/sarcoma/plasmacytoma. We proceeded with laminectomy from D2 to D5 levels, which revealed a reddish-brown, well-defined, sausage-like mass over the dura mater ([Fig. 2]). It was easily mobilized from the dura and complete surgical excision was done. Postoperatively, neurological deficit improved and the patient started walking with assistance on POD (postoperative day) 3 before gaining full motor power and sensations by 3 months. Histopathology revealed the encapsulated tumor to be made of proliferating capillary and cavernous blood spaces admixed with mature adipose tissue. There was no evidence of pleomorphism, mitosis or necrosis, and the tumor was reported as an angiolipoma ([Fig. 3]).

Fig. 1 (A) Green arrow pointing the well-defined T2-hyperintense extradural mass extending from the D2 to D5 level in the posterior aspect of the spinal canal. (B) Yellow arrow pointing the mass with avid post-contrast enhancement.

Fig. 2 Intraoperative images showing (A) the tumor after laminectomy and (B) the dura after excision of the tumor.

Fig. 3 Histopathology image showing proliferating capillary and cavernous blood spaces admixed with mature adipose tissue that were divided by hyalinized fibrous septa.

Case 2

A 47-year-old female presented with complaints of inability to walk, paresthesia of both lower limbs, and gait disturbance for the past 2 weeks. There was no history of incontinence. The patient also gave an unreliable history of a trivial fall from standing height 3 days before. On examination, the patient had spastic paraparesis (MRC grade 3/5) associated with exaggerated deep tendon reflexes, ankle clonus, and bilateral Babinski signs. Light touch, position, and vibration sensations were decreased below the level of the umbilicus. MRI revealed an extradural lesion of size 4 × 1 × 0.7 cm extending from D8–D10 in the posterior aspect of the spinal canal ([Fig. 4]). The lesion was isointense on T1 and hyperintense on T2-weighted sequences and was reported to have features suggestive of subacute epidural hematoma. We proceeded with laminectomy in view of neurological deficit. Intraoperatively, the lesion was recognized as a brown, elastic, soft extradural tumor of the above-mentioned dimensions. The lesion was nonadherent to the dura and was excised in toto. Postoperatively, neurological deficits improved, and the patient started walking with assistance and was discharged on POD 5. The patient came with full motor power and sensations during the follow-up visit after 2 months. Histopathological examination revealed the tumor to be an angiolipoma with vascular elements and adipose tissue.

Fig. 4 Arrow pointing the well-defined T2-hyperintense, extradural lesion in the posterior aspect of spinal canal extending from the D8 to D10 level.

Discussion

Spinal angiolipomas are most commonly found at the thoracic level. The patients mostly present with complaints of back pain, progressive paraparesis, hyper-reflexia, and sensory changes in the lower extremities.[6] [7] The time between onset and diagnosis of symptoms in most cases is 1 year or less.[8] Subacute paraparesis can develop in extramedullary lesions, where symptoms progress due to the slow growth of the tumor.[4] Extradural angiolipomas receive their vascular supply from the recurrent radicular arteries. Interestingly, these lesions occur predominantly in the mid-thoracic region, which is a relatively avascular zone of the spinal cord.[9]

Acute deterioration of neurological status can occur as a result of rapid increase in tumor volume due to vascular causes such as thrombosis, intratumoral hemorrhage, or “steal phenomenon,” resulting in acute compression of the spinal cord.[7] [10] Von Hanwehr et al have speculated that the enlargement of abnormal vessels can lead to tumor expansion. Further, degeneration of tumor vessel walls might lead to changes in tumor blood supply and hemorrhage with resultant epidural compression. Events like blood volume and extracellular fluid volume changes that occur in pregnancy and alterations in fat mobilization patterns (due to hormonal changes) also may cause an increase in tumor mass. All these can accelerate the symptoms of SEALs.[7] [9]

Si et al have classified spinal angiolipomas into two types: type I—intraspinal: type IA: without lipomatosis, type IB: with lipomatosis; type II—dumbbell-shaped (both intra and extra-dural). Both our cases were type IA, which has a good outcome compared with type IB. It is because type IB-associated lipomatosis remnants may cause spinal cord compression even after excision of angiolipoma.[2] Computed tomography (CT) shows a hypo- to hyperdense mass depending on the amount of vascular component or the presence of calcification. Angiolipoma can be suspected in the presence of erosive bone changes with hypo/hyperdense mass in the epidural space. However, CT-scan findings are nonspecific.[9] [11] MRI is the modality of choice to detect SEALs. The fat content of angiolipoma appears hyperintense in both T1- and T2-weighted images, while the vascular component is isointense in T1- and hyperintense in T2-weighted sequences, respectively. Type IA tumor appears as a homogeneous lesion that is isointense or hypointense (occasionally) on T1 and hyperintense on T2 images.[2] The degree of central hypointensity on T1-weighted images is predictive of the tumor vascularity.[6] On fat suppression sequences, the abnormal intensities within the fatty tumor may be enhanced. There is an avid post-contrast enhancement.[2] The vascular component of the type IB tumor has a similar appearance as described above, while the lipomatosis component appears hyperintense in both T1- and T2-weighted sequences. Lipomatosis appears hypointense in the fat suppression sequence and does not show contrast enhancement.[2]

These tumors are highly vascular, composed of proliferating capillary and cavernous blood spaces admixed with mature adipose tissue. Both components do not display cytological atypia, mitosis, or nuclear pleomorphism.[12] Various theories have been proposed on the histopathogenesis of angiolipomas. They are speculated to arise from abnormal primitive pluripotent mesenchymal cells. Angiolipomas are suggested by some authors to be true hamartomas.[8]

It is imperative to distinguish angiolipoma from its close differentials histopathologically. When the fat component predominates, abnormal pericytic proliferation and complex branching patterns of the capillaries within the tumor distinguish angiolipoma from lipoma.[13] Similarly, the presence of identifiable adipocytes rules out a vertebral body hemangioma extending into the extradural space.[14] Liposarcoma is a possible differential diagnosis to be considered, as pleomorphic and myxoid liposarcomas have been reported to occur in the intradural and extradural space. The absence of pleomorphic lipoblasts with areas of high-grade sarcoma may help in ruling out the pleomorphic variant. Also, well-differentiated liposarcoma without pleomorphism can be identified against angiolipoma by the presence of lipoblasts.[12] [15] The presence of a myxoid background, a distinctive “chicken wire” pattern of blood vessels, and some signet ring-like (mononuclear) lipoblasts are mandatory for the myxoid variant to be considered. In all, the bland histology of angiolipoma is not easily confused with the above differentials.[16]

Total surgical resection is the mainstay of treatment, as most extradural angiolipomas are noninfiltrating and are completely removable by laminectomy. The majority of patients have excellent outcomes after surgery, with complete recovery from paraplegia.[17] In the case of infiltrative angiolipoma, the goal is to achieve a complete excision, which may not be feasible in some instances. In such scenarios, treatment must focus on removing the epidural part and cord decompression. Even adjuvant radiotherapy is not indicated as the tumors grow slowly and usually do not recur.[5] [18]

Conclusion

SEALs pose a diagnostic challenge to both the surgeons and radiologists, as they are seldom encountered in day-to-day practice and also mimic other spinal lesions. MRI is the diagnostic modality of choice. T2-weighted, fat-suppressed, and post-contrast images can reliably point toward the diagnosis. Current experience and literature support curative surgical resection to avoid progression of symptoms and relieve the neurological deficit. In the case of infiltrating angiolipomas, total resection to provide adequate decompression can be challenging. However, prognosis is excellent in most cases due to the slow-growing nature of the tumor and absence of malignant transformation.

Conflict of Interest

None declared.

Authors' Contributions

The concept and design of the study were contributed by T.E.S.K., while the acquisition of data was carried out by T.E.S.K. and A.M. The analysis and interpretation of data were undertaken by T.E.S.K., V.K.S., and G.D.G. The initial drafting of the article was completed by T.E.S.K., V.K.S., and G.D.G., with critical revisions provided by T.E.S.K. and A.M. All authors reviewed and approved the final version of the article. Photomicrographs were prepared by N.V.

Patients' Consent

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

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Publication History

Article published online:
24 March 2025