Page 602 - Concise Pathology for Exam Preparation ( PDFDrive )

21 Musculoskeletal System 587

Nests and sheets
of round cells

Bone

FIGURE 21.16. Section from Ewing sarcoma showing a cellular, infiltrative neoplasm consist-
ing of sheets of round cells with scant cytoplasm arranged in irregular nests/lobules separated
by fibrovascular septae (H&E; 4003).

Q. What are the different pathways of spread of tumours to bone?
Ans. Pathways of spread of tumours to bone:
• Direct
• Lymphatic or haematogenous
• Intraspinal seeding

Q. Enumerate the common tumours which metastasize to bone.
Ans. Metastatic cancers are the most frequent malignant tumours found in bone. They are
by far more common than primary bone tumours and are characterized by the following
features:
• Eighty percent metastases to bone comes from breast, lungs, prostate and kidney. Wilms’
tumour, neuroblastoma and rhabdomyosarcoma are the main sources of bony metasta-
ses in children.
• Metastasis is usually multifocal and has a predilection for the haematopoietic marrow
sites in the axial skeleton (vertebrae, pelvis, ribs and cranium) and proximal long bones.
Metastases to long bones distal to the elbows and knees and the small bones of the
hands and feet are rare. Occasionally, metastases may appear as solitary lesions (particu-
larly true for lung, kidney and thyroid cancer).
• Carcinoma of prostate, breast and carcinoid tumour gives rise to pure osteoblastic
metastases.
• Pure lytic metastases is seen in carcinoma of kidney, lungs, GIT and malignant
melanoma.

Q. Enumerate the various cystic lesions of bone. Describe their
clinical and pathological features.

Ans. Cystic lesions of bone include
1. Solitary (simple, unicameral) bone cyst or SBC
• Benign lesion occurring in children and adolescents.
• Most frequently located in the metaphysis of humerus and femur.

mebooksfree.com