PMC9826804_01
Plain x-ray of the distal femur showing non-destructive lytic lesion.
gr1.jpg
PMC9826804_01_gr1.jpg
f0005
MRI images showing the lesion from left to right: T1 weighted image, T2 weighted image, PD weighted image.
gr2.jpg
PMC9826804_01_gr2.jpg
f0010
MRI was ordered and it showed a well-defined heterogenies non-aggressive lesion in the distal femur with low signal on t1 weighted images and mixed signal on t2 and PD images measuring 7 x 4 x 3 cm (Fig. 2). while a simple bone cyst doesn't correlate with the age of the patient and ABCs usually have a characteristic MRI appearance -multiple fluid lines- and tend to be more expansile and aggressive, chondromyxoid fibroma might be the most probable diagnosis but it is usually more demarcated from the adjacent bone with a scalloped and a sclerotic rim. Malignant bone lesions don't have that subtle hideous presentation, and of course infection the great mimicker of lesions is a possibility, however there is no local nor systemic symptoms of infection and the labs were within normal limits.
A, B: benign osseous and fibroadipose tissues. C: edematous fibrous tissue with mild inflammatory infiltrate and multinucleate giant cells. From the CT guided biopsy.
gr3.jpg
PMC9826804_01_gr3.jpg
f0015
A follow-up x-ray 6 months post-surgery.
gr4.jpg
PMC9826804_01_gr4.jpg
f0020
So we went for surgery with extensive curettage and reconstruction of the gap left behind, however the visual look of the lesion intra-operatively was not correlating with ABC so the decision of marginal resection was made and the gap was filled with bone cement and the bone was prophylactically fixed with an anatomical distal femur plate (Fig. 4).
Histological study showing pink laminated gelatinous membrane suggesting hydated cyst within bone.
gr5.jpg
PMC9826804_01_gr5.jpg
f0025
The resected tissue was send again for histological study and came in as fragments of bony and inflamed fibrotic tissue showing granulation tissue formation and fragments of pink acellular laminated material suggestive of germinal layer of the hydatid cyst (Fig. 5).