Dr. Nielsen Non-neoplastic Lecture Flashcards
Eburnation
Loss / roughening of articular cartilage
Histologic hallmarks of degenerative joint disease/osteoarthritis
- Osteophytes
- Fibrillation of articular cartilage
- Duplication of tidemark
- Eburnation
- Subchondral sclerosis
- Subchondral/subarticular cysts
- (Rarely) subarticular sterile neutrophilic pseudoabscesses
What is the tidemark?
The watershed zone of the articular cartilage.
The tissue above the tidemark gets its nutrition from the synovial fluid, the tissue below the tidemark gets its nutrition from the bone vasculature.
The articular cartilage below the tidemark is mineralized due to the presence of calcium in the blood.
In osteoarthritis, you can get duplication or triplication of the tidemark.
What is cloning/clustering?
> 1 chondrocyte per lacuna
Sign of osteoarthritis.
How can you distinguish osteophytic replacement of articular cartilage vs native articular cartilage?
Only native articular cartilage will have a tidemark
Osteophyte cartilage will also often have a fibrous cap
Calcium pyrophosphate crystal deposition
Commonly seen in degenerative joint disease as well as pseudogout. You may just see them within spaces in the articular cartilage.
The crystals often dissolve in standard staining preparations, leaving behind rhomboid spaces. You may catch them intact as basophilic rhomboid crystals.
Features of osteomyelitis
Acute inflammation
Osteoclastic activity
Osteonecrosis
Avascular necrosis of bone
Yellow, wedge-shaped, and with separation of the cortical bone from trabeculae.
Subchondral insufficiency fracture
Traumatic or metabolic in etiology
Presents with pain, X-ray may be completely normal, but MRI shows a linear defect along the base of the articular cartilage.
May progress to rapidly destructive osteoarthritis.
Should be treated conservatively – many will recover and not need a hip replacement.
Main feature of osteoporosis on histology
Spacing out and thinning of the trabeculae.
Rather than looking like a web or meshwork on histology, you just see columns without connecting bridges.
Fracture callus
Can be cellular, atypical, and mitotically active.
Cartilage has a slight fibrous look – this is a give-away. Neoplastic lesions always have either hyaline cartilage or myxoid cartilage, never fibrocartilage.
Features of prolapsing or protruding intervertebral disks
Similar to those of cartilage in osteoarthritis
Crowding/clustering of chondrocytes
Fibrillation of cartilage
Vascular ingrowth into fibrocartilage
Calcium pyrophosphate crystal deposits
Synovial cyst
Intact and degenerated elements of ligamentum flavum with elastin fibers. Forms a pseudocyst.
Basically, pseudocystic degenerated ligamentum flavum.
Vertebral compression fracture or stress fracture
You have your normal trabecular bone, but then in-between/interconnecting you have additional woven bone and granulation tissue.
Hyperparathyroidism
Paratrabecular fibrosis
Osteoclastic activity that dips into trabecular bone (dissecting osteitis or tunneling)
Osteitis fibrosis
A very severe consequence of hyperparathyroidism that mimics fibrous dysplasia of bone, but is systemic and involves numerous body sites.
Associated with VERY high PTH or PTHrP. This is the kind of thing you see in parathyroid carcinoma.
Osteopetrosis
Occurs when there is a defect in osteoclastic activity, resulting in unrestrained osteoblastic bone deposition.
The histologic picure is an overgrowth of bland-looking mineralized cartilage admixed with bone. Basically, extension of the growth plate into the trabecular bone.
Associated with diffuse sclerosis of bone grossly and on imaging, and the “Sandwich sign” (shown) on X-ray imaging of vertebrae.
Loose body
Fragments of detached, mineralized tissue within the joint space. May become caught in the synovium and re-implant, in which case they may grow further and cause symptoms analogous to osteoarthritis:
Pain, joint locking, and swelling.
On sectioning, there is a central nidus with concentric deposition of fibro-cartilage around it and an outer layer of synovium. This is a gross diagnosis.
Synovial chondromatosis
Hyaline-type cartilagenous proliferation.
Grossly, gray-glistening nodules with focal endochondral ossification.
Where do the mesenchymal stem cells reside?
Within the periosteum, within fat pads, and some within the bone marrow
