Sarcomatous transformation of @entity470 and XXXX mutation-positive metastatic @entity2220 , masquerading as a primary @entity242 of the proximal femur.

@entity1 @entity4562 @entity242 @entity470 @entity5 @entity2 @entity9512 @entity876 @entity158 @entity3 @entity2220 @entity7457
We investigated a case of metastatic @entity2220 at the left proximal femur, masquerading as a primary @entity242 . A 72-year-old @entity1 presented with @entity158 in her left thigh in conjunction with a mass that had been gradually growing over a few months. She was being treated with @entity4562 for @entity2220 positive for the @entity470 ( @entity470 ) mutation @entity9512 , and had multiple bone @entity3 . The @entity2220 and @entity3 had stabilized with the treatment. The metastatic lesions in the bone had also received radiation; however, a @entity5 in the proximal femur kept growing despite treatment. A biopsy specimen from the proximal femur revealed the proliferation of spindle-shaped cells without an epithelial glandular component. The @entity1 underwent en bloc resection of the proximal femur that was replaced by prosthesis. Histologically, the resected @entity5 was entirely composed of pleomorphic cells and @entity5 giant cells exhibiting no apparent glandular structures. @entity5 cells were diffusely positive for @entity876 and focally positive for epithelial markers and @entity470 , but were negative for @entity7457 , suggesting an initial diagnosis of primary @entity242 . Genetic examination revealed mutations in @entity470 and @entity876 that were of the same type as the @entity2 , leading to the final diagnosis of the femoral mass as a sarcomatous transformation of metastatic @entity2220 . However, secondary genetic alterations that might explain the acquired resistance to @entity4562 could not be found in the proximal @entity5 . The @entity1 remains alive and the remaining lesions are well controlled.
