WBR0765

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Musculoskeletal/Rheumatology
Prompt	[[Prompt::A 14 year old girl is brought by her mother to the physician's office for facial asymmetry and a limp on the right side. Her past medical history is significant for McCune-Albright syndrome. Physical examination is remarkable for facial asymmetry, breast enlargement, and multiple cafe-au-lair spots on her skin. Xray of the right proximal femur shows a "ground glass" appearance and findings consistent with a "shepherd's crook". The physician tells the patient and her mother that her condition is caused by a disease of the bone marrow stromal cells and abnormal production of fibroosseous masses of tissue. Bone biopsy of the bone lesions will most likely show which of the following findings?]]
Answer A	AnswerA::Spindle-shaped cells with multi-nucleated giant cells
Answer A Explanation	AnswerAExp::Giant cell tumor (osteoclastoma) is characterized on pathology by spindle-shaped cells with multi-nucleated giant cells
Answer B	AnswerB::"Chinese characters" made of bone trabecular
Answer B Explanation	AnswerBExp::Fibrous dysplasia of bone is characterized by pathology by "Chinese characters", which are curvilinear trabeculae, made of bone trabeculae.
Answer C	AnswerC::Small blue anaplastic cells
Answer C Explanation	AnswerCExp::Ewing's sarcoma is characterized on pathology by small blue anaplastic cells.
Answer D	AnswerD::High grade spindle cells that produce osteoid matrix with no cartilage connections
Answer D Explanation	AnswerDExp::Osteoid sarcoma is characteriezd on pathology by high grade spindle cells that produce osteoid matrix with no cartilage connections
Answer E	AnswerE::Small circumscribed irregular trabeculae and sclerotic nidus of woven bone
Answer E Explanation	AnswerEExp::Osteoid osteoma is characterized by small circumscribed irregular trabeculae and sclerotic nidus of woven bone.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Fibrous dysplasia (FD) of the bone is a rare congenital disease caused by mutations in cAMP regulating protein Gs-alpha. As such, bone marrow stromal cells will cause abnormal production of fibroosseous masses of tissue instead of bone. Bone will thus be replaced by fibroblasts, collagen, and irregular bony trabeculae. The most common form of FD is monostotic, i.e. involving only one bone. In many cases, the bone findings are incidental during radiological work-up, whereas in other cases patients present with a limp due to involvement of the proximal femur or a bulging mass from the ribs. The lesion in FD may be painless or painful. Less commonly, patient have polyostotic involvement. The latter form might be associated with several endocrinopathies in the minority of cases, such as McCune-Albright, which might manifest in young girls as precocious puberty and cafe-au-lait spots. Craniofacial involvement in FD is common, involving the skull base. The disease might be extensive causing severe damage, including visual and auditory disturbances, or present with facial asymmetry, or be clinically not evident whatsoever. On radiological work-up, ground glass appearance of bone is characteristic. If the proximal femur is involved, it appears as a pathognomonic "Sheperd's crook". On pathology, FD appears as "Chines letters", or curvilinear trabeculae, that involve bone trabeculae. Educational Objective: Bone lesions in fibrous dysplasia appear as "Chinese letters" in bone trabeculae. Reference: Leet AI, Collins MT. Current approach to fibrous dysplasia of bone and McCune-Albright syndrome. J Child Orthop. 2007;1(1):3-17. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::fibrous, WBRKeyword::dysplasia, WBRKeyword::bone, WBRKeyword::chinese, WBRKeyword::Chinese, WBRKeyword::letters, WBRKeyword::characters, WBRKeyword::character, WBRKeyword::letter, WBRKeyword::pathological, WBRKeyword::pathology, WBRKeyword::mccune albright, WBRKeyword::McCrune, WBRKeyword::Albright, WBRKeyword::McCune-Albright, WBRKeyword::precocious, WBRKeyword::puberty, WBRKeyword::menarch, WBRKeyword::breast, WBRKeyword::enlargement, WBRKeyword::endocrinopathy, WBRKeyword::endocrinopathies, WBRKeyword::skull, WBRKeyword::proximal, WBRKeyword::femur, WBRKeyword::sheperd, WBRKeyword::sheperd's, WBRKeyword::crook, WBRKeyword::ground, WBRKeyword::glass, WBRKeyword::xray
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