1. Parosteal lipoma of proximal radius-A rare case report
Presenting author :Dr.Bursupalle Mahesh Reddy mdrd pg
Coauthor:Dr.Onteddu Joji Reddy,mdrd,prof&hod
Dept of Radiodiagnosis
Kurnool Medical College
Kurnool
Andhra Pradesh

2. INTRODUCTION Parosteal lipoma is an extremely rare benign tumor
composed mainly of mature adipose tissue with a bony
component.
The most common locations for this tumor are the femur,
proximal radius, humerus, tibia, clavicle and pelvis.
It affects, almost exclusively, adults over 40 years, of either sex.

3. AIM It is among the rarest neoplasias of skeleton, accounting
for less than 0.1% of primary bone tumors and 0.3% of all lipomas.
To convey its rarity ,benignity and extreme rare malignant
transformation and complete cure after resection,iam
presenting this as case report.

4. MATERIALS AND METHODS
A 80 yr old male patient presented with a painless swelling on the proximal part of the left forearm.
 The swelling was a slow growing, painless, nontender, immobile mass which was not fixed to skin.

5.  X-ray showing radiolucent shadow of fat density with bony excrescences adherent to left proximal radius.
CECT showing non enhancing hypodense lesion of fat density with  osseous excrescences abutting the left proximal radius .

6. MRI revealed a large well defined, nonenhancing, heterointense, predominantly fat intensity lesion with a small area of signal loss corresponding to calcification in lateral aspect of proximal left radius, seen completely separate from the adjacent muscles.

7. RESULTS
The tumor was resected along with periosteum and then sent to biopsy.
Biopsy revealed both osteal and fat components.

8. DISCUSSION
Parosteal lipoma is situated directly on the cortex of bone.
Thought to arise from mesenchymal cells in the periosteum, parosteal lipomas share histopathologic features with the commonly occurring soft-tissue lipomas, and cytogenetic evidence suggests a common histopathogenesis

9. Depending on the degree of chondroid modulation and enchondral ossification 1. parosteal lipomas may rest directly on the cortex without cartilage or bone elements; 2. may have a narrow bony stalk with a lucent lipomatous cap, mimicking a pedunculated exostosis;

10. 3.may have a densely ossified broad-based osteochondromatous element beneath a thin lipomatous cap, simulating a sessile exostosis
4.may have patches of chondroid and bone scattered throughout the lipomatous mass.

11. On CT and MR imaging, parosteal lipomas have a homogeneous lobulated appearance and are adherent to the surface of the adjacent bone.
When present, osseous excrescences may mimic osteochondromas, but the former lack the contiguity of the marrow space with the underlying bone that is characteristic of the latter.

12. Parosteal lipomas that gain clinical attention are those that compress neurovascular bundles and cause motor and sensory function deficits
. Common sites of involvement include the proximal forearm and the sciatic nerve.

13. The treatment of parosteal lipoma is complete surgical resection along with periosteum.
The nerve must also be separated from the parosteal lipoma and care must be taken to spare it during surgical excision.

14. CONCLUSION
•      These soft tissue tumors are benign with extremely rare malignant transformation and an excellent prognosis with ‘no’ recurrence.

15. T1w image coronal view showing hyperintense lesion with signal void adherent to left proximal radius

16. IRFSE image axial view showing fat suppression with signal void adherent to left proximal radius

17.  X-ray showing radiolucent shadow of fat density with bony excrescences adherent to left proximal radius.

18. CT showing hypodense lesion of fat density with  osseous excrescences abutting the left proximal radius .