Bone metastases

Origin and classification

Musculoskeletal tumors include neoplasms of bone, cartilage, muscle, and connective tissue. The World Health Organization (WHO) places metastatic disease into the broad category of "Other mesenchymal bone tumors" (along with lipomas, fibrous dysplasia, and simple bone cysts).

A classic example of a tumor that produces secondary bone deposits is retinoblastoma. Although its lymphatic metastases affect the parotid, submandibular, and cervical nodes, the hematogenous route of spread leads to the formation of lesions in the cranial bones and tubular bones of the extremities. The extension of this tumor beyond the eyeball sharply worsens the prognosis, and patient death most commonly results specifically from metastases.

Examination of patients over 40 years of age

If a bone neoplasm is detected in a patient over 40 years of age, the clinician's strategy aims to rule out metastatic involvement from an undiscovered primary tumor. A comprehensive evaluation is ordered to locate the lesion:

• Collection of complaints and a thorough physical examination.
• Diagnostic imaging: radiography of the affected bones, bone scintigraphy (skeletal scan), and computed tomography (CT) of the chest, abdomen, and pelvis.
• Laboratory diagnostics: complete blood count and blood biochemistry.
• Oncoscreening: PSA (prostate-specific antigen) testing for men to rule out prostate cancer, and mammography for women to rule out breast cancer.

Further strategy depends on the results. If a solitary lesion is identified (no other foci), the patient is consulted by an oncologist, and a biopsy is performed to confirm or rule out primary osteosarcoma. If other lesions are detected, a biopsy is also performed to confirm the metastatic nature of the process and search for the primary organ.

Obtaining morphological material

Differential diagnosis of bone and soft tissue tumors requires morphological evaluation of the substrate. There are several methods for tissue acquisition:

1. Tumor surface scraping: used to prepare smears on glass slides for subsequent cytological examination.
2. Tumor puncture: allows obtaining cellular material for smear preparation and cytology.
3. Biopsy: the most definitive and informative method, as it enables a full histological examination of the tumor's tissue architecture.

Staging of musculoskeletal tumors

Evaluation of any neoplasm includes determining the grade (Grade) and stage (Stage).

• Tumor Grade: reflects the aggressiveness of the lesion. Evaluation is based on histological presentation and imaging signs of destruction. The scale includes 0 (benign), low (low), intermediate (intermediate), and high (high, 3 points) grades.
• Stage: describes the anatomical extent. It can be localized, with regional or distant metastases.

In musculoskeletal oncology, two main staging systems are used. The universal TNM (AJCC) system accounts for tumor size (T), lymph nodes (N), and the presence of metastatic disease (M). Alternatively, the Enneking staging system (Enneking Staging System) is used. This specialized system comprehensively evaluates histological Grade, exact anatomical location of the lesion, and current metastatic status, which directly impacts treatment planning.

Class and exam questions

What else to study on this topic

• Criteria for tumor grade (Grade 0–3)
• Hematogenous and lymphatic pathways of retinoblastoma metastasis
• Differential diagnosis of maxillofacial tumors
• Genetic features and pathogenesis of Wilms tumor (WT-1 and WT-2 genes)
• Preparation of a tumor patient for surgery under general anesthesia

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.