Ancient schwannomas (AS) are exceedingly rare variant of common schwannomas (CS). Only two cases involving the cauda equina region have been previously reported in literature. AS are typically associated with a higher histological degree of degenerative changes (Antoni B areas). It is of peculiar importance, according to our opinion, to outline that, because of their extremely slow growth (which explains the increase of the degenerative changes in respect to the CS) and their typical soft consistency in respect to their standard counterparts, AS usually imply an even better prognosis.
To the best of our knowledge, there are only 2 cases previously reported of AS involving cauda equina [
The authors report a case of AS involving cauda equina, an exceptionally rare lesion for an extremely rare location, and review all the relevant literature in order to outline clinical, radiological, and pathological remarks of this rare condition.
A 36-year-old man was admitted to our department complaining of one-year history of progressively worsening back pain with bilateral radiation to the anterior surface of the lower limbs, combined with paresthesias to both lower limbs and urinary incontinence for about a month. The neurological examination reported a bilateral fall of both lower limbs in Mingazzini maneuver and Patellar and Achilles hyporeflexia and bilateral sensory deficit of sacral dermatomes.
The patient underwent a lumbar spine MRI scan with TSE, FS, T1w, and T2w sequences and contrast enhanced T1 (Gadolinium) which demonstrated a voluminous intradural-extramedullary tumor (1.9 cm × 2.8 cm × 2.0 cm), with solid and cystic areas of heterogeneous intensity signal (Figures
(a) Sagittal and (b) axial preoperative contrast enhanced MRI scan. (c) Intraoperative image of the lesion at gross examination resembles an ordinary schwannoma. Note the “target” pattern in (a) and the finely heterogenous contrast enhancement in (b), consistent with the typical aspect of an ancient schwannoma.
The patient was operated on for D12-L1 laminotomy and en bloc resection of the lesion. Gross pathology was consistent with a spinal schwannoma (Figure
Histology showed a mesenchymal neoplasm, with an alternation of hypercellular (Antoni A) and hypocellular areas (Antoni B) presenting degenerative traits like multiple microcystic areas filled with a tenuously basophilic colloid material in H&E stain, surrounded by a loose hypocellular fibrillary stroma with rare necrotic areas.
The neoplasm was composed of spindle-cells with pyknotic nuclei and rare mitotic figures and a modest degree of nuclear pleomorphism. The neoplasm showed a remarkable S-100 immunoreactivity and a scarce reactivity for GFAP staining. The Ki67 immunoreactivity demonstrated an extremely low proliferating rate (less than 1%) (Figures
(a) H&E 40x, (b) Ki67, and (c) S-100 immunostaining of the lesion. Note the presence of microcystic areas (
Before writing this paper patient was consulted and gave informed written explicit consent to this report.
Ancient schwannoma is a rare variant of schwannoma (<1% of CS) [
Cauda equina tumors are rare entities with a total incidence of less than 6% among spinal primary neoplasms [
The cases reported in detail.
Author | Age | Sex | Location | Symptoms | Duration | Therapy | Recovery |
---|---|---|---|---|---|---|---|
Saiful Azli et al. [ |
54 | M | Conus medullaris-cauda equina | Worsening lumbar pain and sciatica | 2 years | Surgical | Complete |
Domínguez et al. [ |
39 | F | Intrasacral, cauda equina involvement | Lumbar pain | Not reported | Surgical | Complete |
Our case | 36 | M | Cauda equina | Lumbar pain and cruralgia | 1 year | Surgical | Complete |
Another case of AS was reported by Hayashi et al. [
These tumors are typically associated with a long lasting history of mild low back pain, progressively worsening over years [
Occasionally, the clinical onset may be a tumor hemorrhage [
As for any other primary spinal neoplasm, Gadolinium enhanced MRI is the current “gold standard” for radiological diagnosis [
The radiological appearance of the capsule and of the central “core” of the lesion is important in differentiating a CS from its “ancient” variant [
In AS, Antoni A and B areas are more finely admixed; thus, the resulting MRI appearance is of a circumscribed, rounded mass with heterogeneous contrast enhancement [
Because of the different pattern of contrast enhancement in respect to CS and the presence of multiple cystic areas, the differential diagnosis between AS and malignant neoplasms such as fibrous histiocytomas, malignant peripheral nerve sheath tumors, liposarcomas, or haemangiopericytomas can be quite difficult [
Macroscopically, the AS is not different from the standard schwannoma: but there are remarkable histological differences.
CS is a mesenchymal neoplasm composed of an alternation of bundles of spindle-shaped cells with pyknotic nuclei packed in pseudopalisades (Antoni A areas) and hypocellular areas with cells organized in ovular masses surrounded by a loose stroma (Antoni B areas); mitotic index is low but mitotic figures are commonly observed [
On the opposite, AS has a higher degree of degenerative phenomena involving Antoni B areas: microcysts, calcifications, intravasal thrombosis, necrosis, and hyalinosis are common findings. Nuclear pleomorphism is more pronounced than CS [
The aforementioned histological features are useful to perform the differential diagnosis between AS and mesenchymal malignant neoplasms. Furthermore the absence of local invasion involving the tumor capsule and neoplastic vessels and a low Ki67 immunoreactivity complete the diagnosis [
As for other intradural-extramedullary spinal neoplasms [
We strongly prefer laminotomy over laminectomy to approach an intradural-extramedullary lesion because of the risk of iatrogenic postoperative instability and spinal deformity. The incidence of postoperative instability in thoracolumbar spine can involve up to 25% of patients receiving two or more levels of laminectomies [
Ancient schwannomas are benign lesions characterized by a prevalence of Antoni B areas heterogeneously and finely admixed with Antoni A areas. It exceptionally involves cauda equina and only two other cases with cauda equina involvement have been previously reported. Surgical treatment is the gold standard for this condition.
Ancient schwannoma
Common schwannoma
Magnetic Resonance Imaging
T1 weighted MRI imaging
T2 weighted MRI imaging
Turbo spin echo
Fat suppressed
Hematoxylin and Eosin
Glial fibrillary acid protein.
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