Fibrous dysplasia - femur

Case contributed by Assoc Prof Frank Gaillard

Presentation

Past history of breast cancer. Known metastatic disease, including to spine. Staging CT demonstrated abnormality in the left proximal femur.

Patient Data

Age: 60 years
Gender: Female

There is substantial bony lucency in the intertrochanteric region of the left femoral neck extending proximally along the neck and distally along the shaft. There is some endosteal scalloping and distal sclerosis.

Multiple static images were obtained to cover the whole body. The study shows moderately increased tracer uptake worrisome for osteoblastic bony metastasis in the right 6th rib, T9 on the right side and L1 on the left side. 

The left proximal femur does not demonstrate convincing increased activity. 

Low grade tracer uptake consistent with degenerative arthritis is noted in both sacroiliac joints and right acromio-clavicular joint.

CT of the proximal femur demonstrates non-aggressive features, with a narrow zone of transition and slight expansion of the bone. No extra-osseous mass or fracture. Some matrix mineralization is present. 

At the proximal left femoral metaphysis and diaphysis, a 4.6 x 14.3 cm intramedullary mass demonstrates predominantly isointense T1 and high T2 signal with respect to muscle, with an area of bony sclerosis and septation at its distal aspect. There are areas of mild patchy internal contrast enhancement, and features suggestive of bony expansion. No internal fluid-fluid levels, cortical breech or adjacent soft tissue mass identified. There is sparing of the femoral head.

A smaller, slightly ill-defined intramedullary lesion of similar signal characteristics is identified (incompletely seen) at the superoposterior acetabulum, measuring. This also does not demonstrate cortical breech or an
adjacent soft tissue mass.

Under general anesthetic a bone biopsy was performed. 

Histology

MICROSCOPIC DESCRIPTION: Sections include focally calcified fibrous tissue.  A single mildly atypical polyhedral cell with vacuolated cytoplasm is present. CAM5.2 immunohistochemistry is negative.

DIAGNOSIS: Left proximal femur lesion bone biopsy: Fibrosis.  No evidence of malignancy.

Case Discussion

This case illustrates the need for multi-modality imaging, and highlights the importance of not assuming all lesions in a patient with known metastases are due to that one pathology. 

This patient was followed up for a year before succumbing to cerebral metastatic disease. The femur lesion remained unchanged over that time. 

Case courtesy of Dr Patsy Robertson. 

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