1. What questions would you like to ask?
HPI
22 yo previously healthy F comes to the clinic complaining of right shoulder pain that has gotten progressively worse over the past 6 weeks.
What questions would you like to ask?

2. HPI
+ R shoulder pain, worse with movement. + R shoulder swelling. +intermittent low grade fevers. Recently noticed a bump over the shoulder.
- history of recent falls or trauma to the shoulder
Denies pain/discomfort anywhere else

3. Differential Diagnosis?
PMH: asthma
PSH: appendectomy
Family Hx: none
Social: Graduate student. Social drinker. Denies smoking and illicits. Sexually active with her boyfriend.
Meds: rescue albuterol
Allergies: pollen, dust
Differential Diagnosis?

4. Differential Diagnosis
Rotator cuff tear
Sub acromial bursitis
Sub acromial impingement
Osteomyelitis
Soft tissue/bone tumor

5. PE Vitals: AVSS CV, Pulm, Abd: WNL
Musc: swollen R shoulder without erythema. No warmth to touch. Tender to palpation over proximal arm/shoulder. Difficult to assess ROM secondary to pain. Neurovascularly intact distal R shoulder.
Labs:
CBC, BMP: normal
ESR: 5
Alkaline phosphatase:260

6. XRAY

7. XRAY

8. MRI: Coronal FAST STIR

9. Histology

10. Histology

11. Histology

12. Osteosarcoma
Multiple subtypes (intramedullary, parosteal, periosteal, telangiectatic)
Intramedullary osteosarcoma is the most common primary sarcoma of bone
usually occurs in children and young adults with bimodal distribution of occurrence
majority occur in the second decade of life
second peak in occurrence is in elderly patients with Paget's disease
most common site is the distal femur and proximal tibia 
other sites include proximal humerus, proximal femur, and pelvis
Radiographs: classic “sun burst” appearance
Abnormal Labs: Elevated alkaline phosphatase may be 2-3x’s normal value
Orthobullets.com/pathology
Miller’s review of orthopaedics

13. Characteristic Features
blastic and destructive lesion  sun-burst or hair on end pattern of matrix mineralization
periosteal reaction (Codman's triangle)

14. Histology
tumor cells show significant atypia, and produce "lacey" osteoid 
stroma cells show malignant characteristics with atypia, high nuclear to cytoplasmic ratio, and abnormal mitotic figures  
Giant cells may be present in giant cell rich osteosarcoma often confused with giant cell tumor of bone

15. Prognosis 76% long-term survival with modern treatment
poor prognostic factors :
advanced stage of disease (most predictive of survival)
response to chemotherapy (as judged by percent tumor necrosis of resected specimen)
tumor site and size
expression of P-glycoprotein
high serum alkaline phosphatase 
high lactic dehydrogenase
vascular involvement
surgical margins
Orthobullets.com/pathology
Miller’s review of orthopaedics