1. Musculoskeletal system
SYLLABUS:
RBP(Robbins Basic Pathology) Chapters:
The Musculoskeletal System

2. Musculoskeletal system
56 Chondroma
57 Chondrosarcoma
58 Osteoma
60 Ostosarcoma
187 Aneurysmal bone cyst
189 Eosinophilic granuloma

3. - well circumscribed nodules of cartilage
Chondroma
- well circumscribed nodules of cartilage
- hyaline matrix
- cytologically benign neoplastic chondrocytes residing in lacunae

4. Chondroma

5. Chondroma

6. - sometimes two or more nuclei per lacuna
Chondrosarcoma
- sheets or ill-defined nodules of cartilage with variable nuclear atypia (enlarged, pleomorphic, hyperchromatic nuclei)
- sometimes two or more nuclei per lacuna
- invasion of trabecular bone
- soft tissue lesions usually with abundant myxoid stroma or spindle cells

7. Chondrosarcoma

8. Chondrosarcoma

9. -dense, mature, lamellar bone
Osteoma
-dense, mature, lamellar bone

10. Osteoma

11. Osteoma

12. - minimal diagnostic requirement is malignant calcified osteoid
Ostosarcoma
- minimal diagnostic requirement is malignant calcified osteoid
- cytologic malignant features include enlarged, hyperchromatic, pleomorphic, mitotically active nuclei, possibly atypical mitoses
- architecture extremely variable: - sheets of osteoid with osteoblast lacunae and little fibrous stroma - thin osteoid trabeculae and more stroma - rare foci of osteoid in irregular islands or rosettes
- may have cartilage, and giant cells

13. Ostosarcoma

14. Ostosarcoma

15. About half of cases have areas of precursor lesion (wide variety).
Aneurysmal bone cyst (ABC)
Probably rather a degenerative change that can occur in many lesions than an independent lesion.
About half of cases have areas of precursor lesion (wide variety).
- multiple blood filled lakes
- fibrous and bony septa
- many giant cells often in a row beneath the surface
- no cytologic atypia
- foci of osteoid and bone

16. Aneurysmal bone cyst

17. Aneurysmal bone cyst

18. Eosinophilic granuloma (Langerhans' cell histiocytosis of bone, Histiocytosis X)
- a variety of cell types, but only Langerhans' cell is diagnostic
- number of Langerhans' cells present is variable
- prototypical Langerhans' cells have abundant, powdery, eosinophilic cytoplasm and characteristic bean-shaped nuclei with grooves and indentations, may or may not have well-demarcated cell borders
- variable numbers of ordinary histiocytes and sometimes foam cells
- common secondary components include eosinophils, may form aggregates surrounded by histiocytes and Langerhans' cells, neutrophils, lymphocytes and plasma cells

19. Eosinophilic granuloma

20. Eosinophilic granuloma