Clinical Profile:

•A 32 year old man presented to orthopaedic department with complaints of continuous backache in the lumbosacral region since 2 months. There is associated tingling numbness in both lower limbs. Patient also has history of urinary retention since 2 weeks. A Foley’s catheter was inserted for the same.

•Patient also complains of associated significant loss of weight in the last 2 months.

•No history of fever, jaundice.

•No history of constipation or obstipation.

•On clinical examination, the abdomen of the patient is soft and non-tender.

•All routine blood investigations are unremarkable.

•Radiological investigations like radiograph of lumbosacral spine, ultrasound of abdomen and pelvis and contrast enhanced CT of abdomen and pelvis were advised to look for the cause of the above symptoms.

Radiological Investigations:

•A plain radiograph of lumbosacral spine was taken in AP and lateral view.(figure 1a and 1b)

•It shows an approximately 3x2cm sized geographic osteolytic lesion in the lower part of sacrum involving S2-S4 vertebra in the midline with a wide zone of transition. No surrounding sclerosis or matrix mineralisation seen.

•There is a well defined soft tissue opacity seen in the left pelvis which is displacing the bowel loops to the right side.

•Rest of the bones are normal. Both sacroiliac joints and hip joints are normal.

A contrast enhanced CT scan was advised for further evaluation.

•On CT, there is a well defined heterogeneously enhancing mass lesion seen arising from the sacrum at S2-S4 level measuring 14.2x11.3x15.3cm.(figure 2d)

•There are few hypoattenuating areas seen within the mass lesions suggestive of fluid-filled cavities. There are few foci of matrix mineralisation seen within the soft tissue component of tumor suggestive of osteoid formation.

•The mass is causing destruction of the cortex of sacrum(figure 2b and 2c) and extending anteriorly into the pre-sacral region with mass effect on rectum and urinary bladder.

•The fat planes with rectum are effaced but maintained with urinary bladder.

•The lesion is seen to extend posteriorly into the sacral canal causing osteolytic destruction of sacral body.

•MR imaging of the pelvis is done for further evaluation.

•Multiplanar multiecho MRI of the pelvis was done for further evaluation of the lesion.

•T1 and T2 non-fat saturated and fat saturated images show heterogenous signal intensity of the soft tissue of the mass lesion with its origin from the sacrum. The lesion is overall hyperintense on T2.

•There is destruction of the lower part of the sacrum.

•There are few hyperintensities in T1 and T2 suggestive of sites of haemorrhage. The fat planes with the rectum are lost, whereas with bladder, they are maintained(figure 3a,3b,3c and 3d)

•Sagittal, coronal and axial images of post-gadolinium enhanced MR show heterogenous enhancement of the mass with few unenhanced areas of haemorrhage and necrosis.(figure 3e,3f and 3g)

•Presacral mass biopsy was advised for a definitive diagnosis. Under all aseptic precautions, with written informed consent, a CT guided biopsy was performed under local anaesthesia from posterolateral region and samples were sent for routine microscopic and histopathological analysis.(figure 4)

Pathological diagnosis

Telangiectatic osteosarcoma

Discussion:

An approach to presacral masses :

•A wide variety of benign and malignant conditions arise from various elements of pre-sacral region.

•The involvement of sacrum(destructive or re-modelling) and the presence of soft tissue component may help in narrowing the differentials

•Demographic features are also important. Congenital and developmental tumors occur in younger patients, and tumors like chondrosarcomas occur in older patients.

Specific imaging features aid in the diagnosis.

Differentials of pre-sacral masses

•Based on the origin of tumor, the following are the differentials of pre-sacrsal masses which are usually encountered at imaging:

1.Osteochondral -

•Benign- Osteoma, simple bone cyst, aneursmal bone cyst, giant cell tumor

•Malignant- Ewing sarcoma, osteosarcoma, chondrosarcoma

2.Neurogenic –

•Benign- Neurofibroma, ependymoma, neuroblastoma, schwannoma, dural ectasia, anterior sacral meningocele

•Malignant- Neurofibrosarcoma, chordoma, malignant schwannoma

3. Mesenchymal-

•Benign- Hemangioma, fibroma or fibrosis, myelolipoma, solitary fibrous tumor, Castleman disease

•Malignant- Soft-tissue sarcoma, lymphoma, gastrointestinal stromal tumor

4. Congenital or developmental-

•Benign- Retrorectal cystic hamartoma, rectal duplication cyst, epidermoid cyst, dermoid cyst

•Malignant- Teratocarcinoma, teratoma, yolk sac tumor

5. Others- metastatic disease, desmoplastic round cell tumor, inflammatory, infectious.

Differentiating features of pre-sacral masses

1.Osteochondral tumors.

•Giant cell tumor- Lytic, expansile, often eccentrically located, vascular with substantial enhancement

• Ewing sarcoma- Aggressive, permeative bone lysis, osseous expansion, sclerosis, soft-tissue mass

•Osteosarcoma- Densely mineralized matrix, soft-tissue mass

•Chondrosarcoma- Chondroid matrix (rings and arcs), cartilaginous neoplasm, high water content (indicated by low attenuation at CT and high SI on T2W images)

2. Neurogenic tumors

•Neurofibroma- Target appearance on T2W images (central area of low SI with a high-SI rim), low attenuation at CT

•Schwannoma- Remodeling or erosion through sacral bone, heterogeneous mass with thin pseudocapsule and small cystic areas

•Paraganglioma- Vascular tumor with intense enhancement and flow voids, hemorrhage common, cap sign related to hemorrhage (low-SI rim at MR imaging)

•Chordoma- Destructive lytic lesion, large presacral soft-tissue component, high SI on T2W images

3. Mesenchymal tumors-

•Hemangioma- Areas of fat and hemorrhage (increased SI on T1W images), increased SI on T2W with flow voids, phleboliths

•Myelolipoma- Macroscopic fat, low attenuation at CT, high SI on T1W images that drops out with fat suppression

•Solitary fibrous tumor- Well circumscribed, vascular with intense enhancement

•Retroperitoneal fibrosis- Fibrotic plaque centered over lower lumbar spine, hypo- to isointense on T1W and T2W images, soft-tissue attenuation at CT

•Gastrointestinal stromal tumor- Central areas of hemorrhage, necrosis, or cyst formation

4. Developmental cyst -Thin walled, uni- or multilocular, low attenuation at CT, high SI on T2W images, no internal enhancement

5. Germ cell tumor- Fat (low attenuation at CT and high SI on T1W images)

•Telangiectatic osteosarcoma is a subtype of osteosarcoma which constitutes for about 2.5% to 12% of all osteosarcomas.(1)

•It is believed to originate from transformed osteoblast or from stem cells that derive from mesenchymal tissue(2).

•A majority of the tumour consists of blood filled cavities, and hence it is often a close differential of aneurysmal bone cyst., however, the septa surrounding the blood filled spaces shows nodular enhancement with presence of malignant cells that produce osteoid(3).

•Clinical features include local tenderness or pain or as a soft tisse mass(2).

•

•These osteosarcomas often occur in the metaphyseal region of long bones. Most frequently affected site is the distal femur(2). Other sites that are involved are proximal tibia, proximal femur, fibula, mid femur, mid humerus and mandible.

•Telangiectatic osteosarcoma of the spine is and exceedingly rare entity. It accounts for 0.08% of all primary osteosarcomas(4).

•The aggressive osteolytic nature of this tumour is the radiographic hallmark. There could be few islands of osteoid formation within the tumour.

•This tumour has a poorer prognosis as compared to other types of osteosarcomas(2)

•The preferred treatment modality for this tumour is pre-operative neo-adjuvant chemotherapy followed by surgical resection of the tumor.(5)

References

1.MurpheyMD, wan Jaovisidha S, Temple HT, Gannon FH, Jelinek JS, Malawer MM. Telangiectatic osteosarcoma: radiologic-pathologic comparison. Radiology2003; 229(2): 545–553.

2.Telangiectatic Osteosarcoma: Radiologic and Pathologic Findings,Federico Discepola, Thomas I. Powell, Ayoub Nahal https://doi.org/10.1148/rg.292085150

3.MetcalfDJ, Nightingale TD, Zenner HL, et al. Formation and function of Weibel-Palade bodies. J Cell Sci2008; 121(pt 1): 19–27.

4.Telangiectatic osteosarcoma of the spine: a case report R. Amritanand, K. Venkatesh, R. Cherian, A. Shah, and G. D. Sundararaj doi: 10.1007/s00586-008-0672-3

5.Presacral Masses: Multimodality Imaging of a Multidisciplinary Space, Kendra S. Hain, Perry J. Pickhardt , Meghan G. Lubner, Christine O. Menias, Sanjeev Bhalla, https://doi.org/10.1148/rg.334115171.