NEET MDS Lessons
Oral Pathology
Non-epithelial cysts (not true cysts)
Solitary bone cyst
Radiology
The solitary bone cyst appears as a well-defined but non-corticated radiolucency. Typically, it has little effect
on adjacent structures and 'arches' up between the roots of teeth .
The inferior dental canal may not be displaced, but the cortical margins of the canal may be lost where it overlies the lesion. Expansion is rare.
Pathology
The cyst is lined by fibrovascular tissue that often includes haemosiderin and multinucleate giant cells.
Aneurysmal bone cyst
Radiology
The aneurysmal bone cyst typically presents as a fairly well-defined radiolucency. Sometimes it has a multilocular appearance because of the occurrence of internal bony septa and opacification. Marked expansion is a feature.
Pathology
The predominant feature of an aneurysmal bone cyst is the presence of blood-filled spaces of variable size lying in a stroma rich in fibroblasts, multinucleate giant cells and haemosiderin. Deposits of osteoid are also seen
Garre’s Osteomyelitis (Chronic Osteomyelitis with Proliferative Perosteitis)
- Chronic Non Suppurative Sclerosing Osteitis/ Periostitis Ossificans.
- Non suppurative productive disease characterized by a hard swelling.
- Occurs due to low grade infection and irritation
- The infectious agent localizes in or beneath the periosteal covering of the cortex & spreads only slightly into the interior of the bone.
- Occurs primarily in young persons who possess great osteogenic activity of the periosteum.
Clinical Features
- Uncommonly encountered, described in tibia and in the head and neck region, in the mandible.
- Typically involves the posterior mandible & is usually unilateral.
- Patients present with an asymptomatic bony, hard swelling with normal appearing overlying skin and mucosa.
- On occasion slight tenderness may be noted
- pain is most constant feature
- The increase in the mass of bone may be due to mild toxic stimulation of periosteal osteoblasts by attenuated infection.
Radiographic features
- Laminations vary from 1 – 12 in number, radiolucent separations often are present between new bone and original cortex. (“onion skin appearance”)
- Trabeculae parallel to laminations may also be present.
Histologic Features
- Reactive new bone.
- Parallel rows of highly cellular & reactive woven bone in which the individual trabeculae are oriented perpendicular to surface.
- Osteoblasts predominate in this area.
D/D for Garre’s Osteomyelitis
- Ewing's sarcoma
- Caffey’s disease
- Fibrous dysplasia
- Osteosarcoma
Treatment
- Removal of the offending cause.
- Once inflammation resolves, layers of the bone consolidate in 6 – 12 months, as the overlying muscle helps to remodel.
- If no focus of infection evident, biopsy recommended.