Heterotopic ossification

Heterotopic ossification is an uncommon pathology specimen that may be considered a ditzel.

General

• Definition of heterotopic ossification: bone formation in soft tissue.
• Injury at site.
• May be seen in the context of tetraplegia.

Clinical:

• +/-Joint stiffness.
• +/-Swelling.
• +/-Pain.

Gross

• Firm nodule.

Microscopic

Features:

• Lamellar bone - has layering/lines (best seen with polarized light).
• +/-Skeletal muscle (within the marrow space).

DDx:

• Myositis ossificans - inflammation, cellular.
• Osteosarcoma, extraskeletal.
• Osteochrondroma - at joint, has cartilage.^{[citation needed]}

Sign out

Lesion, Distal Phalanx of Right Little Finger, Excision:
- Dermal ossification without cartilage in benign skin with a thick keratin layer.
- NEGATIVE for evidence of malignancy.

Block letters

LESION ("HETEROTOPIC OSSIFICATION"), RIGHT FEMUR, EXCISION:
- BONE -- CONSISTENT WITH MUSCLE HETEROTOPIC OSSIFICATION.
- NEGATIVE FOR MALIGNANCY.

Micro

The sections show laminar bone with a marrow space containing adipose tissue and benign skeletal muscle. The osteocytes show no nuclear atypia. No mitotic activity is appreciated.

See also

• Ditzels.
• Bone.
• Cutaneous calcification.