Keywords
ossifying fibroma - monostotic - postpartum - thoracic spine
Introduction
Ossifying fibromas are very rare tumors. They commonly occur in women with a peak
incidence in the third and fourth decades. They more commonly occur in the mandible
and maxilla. They are uncommon in the spine, and the monostotic variant of the dorsal
spine is very rare. We report a case of an 18-year-old woman with D3 vertebral ossifying
fibroma. Clinical significance and management of this lesion are discussed with the
review of the literature.
Case Report
An 18-year-old postpartum woman presented with complaints of difficulty in walking
for 10 days. She gave birth to her first child 14 days earlier by normal vaginal delivery.
The antenatal course was uneventful. There was no history of trauma, drug abuse, or
physical exertion. The patient was able to walk for 4 days after delivery following
which she developed difficulty in walking, which was gradual in onset and progressive
in nature. Initially she walked with support but later could not do so even with support.
There was history of dull mid thoracic pain of moderate intensity for 10 days. There
was history of bladder retention and overflow incontinence for 8 days. There was no
history of tingling and paresthesias in both the lower limbs. There was no history
of fever. On examination, power was 0/5 (Medical Research Council [MRC] grading) in
both the lower limbs. All sensations were preserved. In T2W/STIR magnetic resonance
imaging (MRI) hyperintensity was noted involving the D3 vertebral body with posterior
cortical bulge with a decrease in vertebral body height. MRI contrast revealed intense
enhancement with paravertebral epidural components causing spinal canal narrowing
and cord compression ([Fig. 1A, B]). There was D3 vertebral body destruction with adjacent soft tissue thickening ([Fig. 2]). Computed tomography (CT)–guided biopsy was advised, which revealed a spindle cell
tumor. D3 and D4 laminectomy and excision biopsy of the lesion was done followed by
spinal stabilization. The specimen was sent for histopathologic examination (biopsy)
and immunohistochemistry. Ki-67 was sparsely positive (< 1%), indicating that the lesion was benign in nature
([Fig. 3]), and a diagnosis of ossifying fibroma was established. Postoperative period was
uneventful, and there was no improvement in the muscle strength (MRC 0/5). The patient
was later lost to follow-up.
Fig. 1 (A, B) T2W/STIR hyperintensity noted involving D3 vertebral body with posterior cortical
bulge with decrease in vertebral body height. Intense enhancement was noted with paravertebral
epidural components causing spinal canal narrowing and cord compression. MRI, magnetic
resonance imaging.
Fig. 2 D3 vertebral body destruction with adjacent soft tissue thickening. CT, computed
tomography.
Fig. 3 IHC: Sparsely Ki-67 positive (< 1%) indicating that the lesion was benign in nature.
Discussion
Ossifying fibroma was recognized by Lichtenstein in 1938.[1] It was first reported in the spine by Ohyama et al in 1992.[2] It is a component of the benign fibro-osseous lesion (BFOL). It is characterized
by replacement of normal bone by cellular fibrous tissue and newly formed osseous
or so-called cemento-osseous deposits. Skeletal involvement can be mono-ostotic/polyostotic
(associated with endocrine abnormalities). Ossifying fibroma accounts for 7% of benign
bone lesions, and prevalence of spinal involvement is very low particularly in monostotic forms.[3] It is more common in women. It occurs in patients before the age of 40 years with
a peak incidence in the third to the fourth decade.[4] It is more common in the mandibles and maxilla.[4] It also manifests in the calvarium (frontal and temporal) and long bones. The vertebral
body is more commonly involved due to a relative large amount of the cancellous bone.
Thoracic monostotic vertebrae involvement is extremely rare, which has been reported
in this case. It is caused by postzygotic mutation in guanine nucleotide stimulatory
protein (GNAS1) gene, grows slowly, and is asymptomatic initially; symptoms and signs
depend on the tumor location. Ossifying fibroma is usually static after growth ceases
but is reactivated with pregnancy.[5] There might be a rapid growth of the lesion because of the presence of hormone-specific
receptors in bone cells. Though gonadal steroids profoundly affect bony metabolism,
exacerbation of ossifying fibroma in pregnancy is a rare phenomenon.[6]
[7] Studies revealed a high-concentration estrogen receptor on osteogenic cells obtained
from abnormal areas of the skeleton of patients with monostotic variants.
Radiographically radiolucent lesions initially but gradually become radiopaque with
calcification. There is an expansion of the involved bone with presentation of thin
rim of the cortex. CT of ossifying fibroma shows multiple intracortical osteolysis
as lucencies with a characteristic sclerotic band. In MRI T1W images are of low signal.
T2W images are iso- to high-intensity signals and show enhancement with contrast.[8] Histologically lesions appear well circumscribed sharply delineated by host lamellar
bone. The classic characteristic pattern is that of curvilinear Chinese alphabet spicules
of woven bone separated abundant fibrous stroma.[9]
[10] Ki-67 index is sparse in ossifying fibroma.
Treatment
Treatment depends on the presence of symptoms. Asymptomatic patients are observed
every 6 months with serial radiographs. Surgery is indicated when there are persistent
pain, neurologic impairment, vertebral collapse, and instability/cord compression.[11] In a case of spinal involvement, consensus of management has not yet been achieved.
Conclusion
The thoracic monostotic spinal variant of ossifying fibroma is an extremely rare tumor,
which can present in the postpartum period because of the effect of hormones on the
tumor growth; hence, it should be kept in mind for evaluation of sudden onset of weakness
in the postpartum period.
Consent
The patient and her attendants have given consent for publication of article.
