Sacral mass in a teenager - Scrimmage between neoplasia and infection: A case report with imaging appearances of mimics

Chandrika Sachar; Aakanksha Agarwal; Rahul Dev

doi:10.4103/JME.JME_79_21

CASE REPORT

Year : 2022 | Volume : 3 | Issue : 1 | Page : 67-70

Sacral mass in a teenager - Scrimmage between neoplasia and infection: A case report with imaging appearances of mimics

Chandrika Sachar, Aakanksha Agarwal, Rahul Dev
Department of Radiodiagnosis and Imaging, AIIMS, Rishikesh, Uttarakhand, India

Date of Submission	15-Aug-2021
Date of Decision	06-Nov-2021
Date of Acceptance	06-Nov-2021
Date of Web Publication	28-Apr-2022

Correspondence Address:
Dr. Rahul Dev
Department of Radiodiagnosis and Imaging, AIIMS, Room No. 13, Trauma Block, Rishikesh - 249 203, Uttarakhand
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JME.JME_79_21

How to cite this article:
Sachar C, Agarwal A, Dev R. Sacral mass in a teenager - Scrimmage between neoplasia and infection: A case report with imaging appearances of mimics. J Med Evid 2022;3:67-70

How to cite this URL:
Sachar C, Agarwal A, Dev R. Sacral mass in a teenager - Scrimmage between neoplasia and infection: A case report with imaging appearances of mimics. J Med Evid [serial online] 2022 [cited 2023 Jun 3];3:67-70. Available from: http://www.journaljme.org/text.asp?2022/3/1/67/344298

Introduction

Ewing's sarcoma is a rare and malignant mesenchymal tumour, that accounts for <10% of primary bony sarcomas. Together with osteosarcoma, they are the most common primary malignant bone tumours in children occurring in the first two decades with a male predominance.^[1] Primary Ewing's sarcoma of sacrum presents late in the course of disease with features secondary to involvement of adjacent neural structures, vertebral columns and pelvic organs.

Case Report

A 17-year-old male presented with complaints of weakness in bilateral lower limbs for 3 months and low backache for 2 months with bowel and bladder incontinence. There was no history of trauma or any significant medical or surgical illness in the child or his family. Local examination revealed tenderness over the left sacroiliac joint, paraspinal muscles and the sacrum. Fullness was noted overlying the sacral region with limitation of movements, decreased power (Grade 3/5) in both lower limbs with low tone and reduced sensations bilaterally. Neurological examination revealed spastic gait and neurogenic bladder.

A radiograph of the lumbosacral spine revealed a lytic lesion involving the sacrum. There were no associated calcifications. To further characterise the lesion a contrast-enhanced magnetic resonance imaging (MRI) study was performed. On MRI, an ill-defined altered signal intensity lesion was seen involving predominantly left half of the S1-S3 vertebrae including their posterior elements with further extension to involve the left transverse process of the L5 vertebra and the iliac surface of the left sacroiliac joint across the joint space. The lesion showed T1 and T2 iso-hypointense signals with areas of T2 hyperintensities within and diffusion restriction with corresponding low apparent diffusion coefficient values [Figure 1]. There was associated heterogeneous enhancement on post-contrast images. A breach in the posterior cortex of sacral vertebrae was seen with severe spinal canal stenosis and secondary neural compression. Evaluation of computed tomography (CT) scan images done at a different centre showed irregular large lytic destructive lesions with associated soft-tissue component involving the sacrum, more on the left side [Figure 2]. The lesion was extending into the spinal canal, causing spinal canal stenosis. No calcifications were noted within the lesion.

Figure 1: Ewing's sarcoma: Sagittal T2 (a), T1 (b), coronal T2FS (c) and axial T2 (white arrow in d) magnetic resonance images show the area of altered signal intensity in the left side of sacrum showing predominantly hyperintense, hypointense and hyperintense signal abnormality respectively. Corresponding DWI (e) high signal and apparent diffusion coefficient signal (f) were seen, with heterogeneous enhancement on post-contrast images (black star in g). There is the involvement of corresponding posterior elements as well as the iliac surface of the left sacroiliac joint (black arrow in d)

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Figure 2: Ewing's sarcoma: Non-contrast computed tomography images in sagittal (a), coronal (b) and axial planes (c) revealed an irregular large lytic soft-tissue density lesion (black arrow in c) involving the sacrum, extending into the spinal canal, causing spinal canal stenosis. No calcifications were noted within the mass

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Based on imaging findings and clinical parameters, the possibility of a neoplastic aetiology, like Ewing's sarcoma was suggested with an infective aetiology being a probable differential diagnosis. Image-guided biopsy was performed for this lesion with the histopathological examination (HPE) suggesting features of malignant small round blue cell tumour compatible with Ewing's sarcoma of the sacrum.

Discussion

Plain radiographs are inadequate in evaluating the sacrum, thus cross-sectional imaging is embarked on for the identification and characterisation of sacral pathologies.^[2] The diagnosis of sacral pathology is delayed as the patient presents with nonspecific clinical features like low back pain and usually presents late to the hospital when the tumour becomes large enough to cause neurological symptoms.

Considering the patient's age and clinical presentation a long list of differential diagnoses can be proposed [Table 1]. Infective aetiology includes tuberculosis [Figure 3] and non-tubercular osteomyelitis, while neoplastic aetiology includes giant cell tumour [Figure 4], aneurysmal bone cyst [Figure 5], Chordoma [Figure 6], Ewing's sarcoma [Figure 1] and [Figure 2], and lymphoma.

Table 1: Aetiological differentials of sacral bony lesions

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Figure 3: Tuberculosis: Sagittal T2 (a) and T2FS (b) magnetic resonance images showing a hyperintense lesion involving the left side of the sacrum with contiguous involvement of left sacroiliac joint and left iliac bone. Axial post-contrast images (c and d) at the same level show predominantly peripheral post-contrast enhancement (white arrow in c) and abscess formation (black star in d) consistent with inflammatory changes

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Figure 4: Giant cell tumour: Sagittal T2 (a) and T2FS (white star in b) magnetic resonance images show an expansile heterointense lesion arising from the sacrococcygeal region. Corresponding T1 (c) and T1 post-contrast coronal images show lesions having T1 hyperintense areas consistent with haemorrhage with heterogenous post-contrast enhancement. Axial T2 images depict the heterogeneity of the lesion (e) with similar post-contrast enhancement pattern (black star in f)

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Figure 5: Aneurysmal bone cyst: Sagittal T2 (a), T1 (b) and coronal T2FS (white arrow in c) magnetic resonance images showing a lesion in left sacral ala appearing heterointense with both hypo and hyperintense areas within. On axial T2 images, the lesion shows internal fluid-fluid levels suggesting recurrent haemorrhage (white star in d), with heterogenous predominantly peripheral post-contrast enhancement (black star in e)

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Figure 6: Chordoma: Sagittal T2 (a), T1 (b) and coronal T2FS (white arrow in c) magnetic resonance images showing a heterointense lesion arising from sacrum in the midline with T2 and T2FS hyperintense and T1 hypointense areas respectively, depicting necrosis with the anteroinferior displacement of the rectum. On axial T2 images (white star in d) the lesion shows heterointense signal with post-contrast enhancement of the large solid component (black star in e)

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Differentiation among these lesions requires imaging and guided biopsy providing HPE confirmation. The presence of extensive soft-tissue involvement and locoregional abscess formation points towards an infective origin of the lesion, commonly either tubercular or pyogenic. Among the tumoral differentials, giant cell tumour and chordoma are two entities that show prominent tumour stains on angiography.^[2] This feature helps in both diagnosis and treatment in the form of pre-operative embolisation of these lesions. Metastasis from renal cell carcinoma should also keep kept in mind when encountered with vascular blush in sacral tumour and requires imaging exclusion. Aneurysmal bone cyst shows characteristic fluid levels which are seldom seen in the sacral location of the tumour. However present in a smaller subset of cases, they are pathognomic and help in the exclusion of other entities.^[3]

Ewing's sarcoma is a rare malignant small round cell neoplasm of undifferentiated mesenchymal origin.^[4] It is usually seen in the second or third decades of life, with the incidence being 0.5%.^[5] Ewing's sarcoma of the sacrum usually presents as a lytic lesion, with a large presacral soft-tissue component soft tissue, few of them having associated bony sclerosis. It can show both intra-dural and extra-dural components.^[6]

On HPE, uniform small cells with a high nucleus to cytoplasmic ratio and round to oval nuclei with finely dispersed chromatin and indistinct nucleoli are seen.^[4] The immunohistochemistry shows positivity for various neurofilaments such as CD-99 and S-100 are present. The presence of these typical histological features confers a better prognosis and less incidence of metastatic disease than atypical features.^[7]

MRI is considered to be the imaging modality of choice, as it gives a better evaluation of both soft tissue and bony extent of disease, neurovascular involvement, as well as the intraspinal extension of the disease.^[8] MRI is also a prime modality for assessing the response to treatment. CT scan is used for demonstration of bony destruction, associated sclerosis and to assess associated soft-tissue calcification/ossification.

Management of Ewing's sarcoma depends on tumour size and its extension, especially into spinal canal and involvement of neurovascular bundle. Treatment modalities include surgery, chemotherapy, radiotherapy individually or in a combination.

Ewing's sarcoma of the sacrum is a rare tumour and should be a differential diagnosis in patients with low backache presenting in the first two decades of life. MRI can help in the early detection of this disease, but confirmation can be established only on HPE. The mainstay of management includes surgical excision followed by adjuvant chemotherapy or radiotherapy. Imaging, therefore, plays an important role in evaluating sacral lesions and helps in differentiating from other infective or neoplastic aetiologies as well as guiding treatment and subsequent follow-up.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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