This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Histology from a bone biopsy from proximal femur is given below of a 50 year old with bone pain.  What is your diagnosis? 
Select and explain. 
A. Osteomalacia, B. Paget’s disease, C. Osteoporosis, D. Osteosclerosis
B: Paget’s disease
Answer: B: Paget’s disease 
Explanation: Ref. Robbins Pathology. 9th edition. Page. 1191
 
Paget Disease

Diagnostic features are increased osteoclastic and osteoblastic activity with supportive radiologic findings
Acute: primarily woven bone; focal mosaic pattern of lamellar bone, resembles jigsaw puzzle with prominent irregular cement lines; osteoclasts present at surface of bone but don’t tunnel; in osteolytic phase, osteoclasts may have up to 100 nuclei
Chronic: thick trabeculae and thicker bones; fine fibrosis of marrow (Osteosclerotic stage)
The picture is also known as mosaic pattern of bone