Classification of primary bone tumours

Primary bone tumours can be classified according to the tissue of differentiation, using the WHO system. Tumours are classified as:

  • cartilage tumours (eg osteochondroma, chondrosarcoma)
  • osteogenic tumours (eg osteoid osteoma, osteosarcoma)
  • fibrogenic tumours (eg desmoplastic fibroma, fibrosarcoma)
  • fibrohistiocytic tumours (eg benign fibrous histiocytoma, malignant fibrous histiocytoma)
  • Ewing sarcoma/Primitive Neuroectodermal tumour (PNET)
  • Haemopoetic tumours (eg plasma cell myeloma)
  • Giant cell tumour of bone
  • Notochordal tumours (eg chordoma)
  • Vascular tumours (eg haemangioma)
  • Smooth muscle tumours (eg leiomyosarcoma)
  • Lipogenic tumours (eg lipoma, liposarcoma)
  • Neural tumours (eg neurilemmoma)
  • Miscellaneous tumours (eg adamantinoma)
  • Miscellaneous lesions (eg aneurysmal bone cyst)
  • Joint lesions (eg synovial chondromatosis)
For more information look here.
A simpler classification can also be helpful:
  • Cartilage forming tumours
  • Bone forming tumours
  • Fibrous tumours
  • Non-matrix producing tumours

Seven questions to ask when looking at an x-ray

A good approach to looking at an X-ray demonstrating an abnormality in the bone is to ask seven questions:
  1. Where is the lesion?
  2. How large is the lesion?
  3. What is the lesion doing to the bone?
  4. What is the bone doing in response?
  5. Is the lesion making matrix?
  6. Is the cortex eroded?
  7. Is there a soft tissue mass?
(from Levesque et al. A Clinical Guide to Primary Bone Tumours)

What are anatomical compartments?

The concept of anatomical compartments in the limb is attributed to Enneking. The idea is that these osteofascial envelopes tend to contain the growth of sarcomas and therefore consideration should be given to removing the whole compartment when operating. Furthermore, it is obvious that biopsies should not cross (and therefore contaminate) uninvolved compartments. Where these barriers are obvious, for example in the thigh, the tumour is said to be in an intracompartmental site. Other sites with less obvious barriers (for example the popliteal fossa) are classified as extracompartmental.

This concept is used in the MSTS staging system and the classification of surgical margins.

Examples of intra- and extracompartmental sites:

Intracompartmental sites Extracompartmental sites
Intra-articular
Superficial to deep fascia
Osteofascial compartments Extrafascial planes or spaces
– Ray of hand or foot – Mid- and hindfoot
– Posterior calf – Popliteal space
– Anterolateral leg – Groin/femoral triangle
– Anterior thigh – Intrapelvic
– Medial thigh – Mid hand
– Posterior thigh – Antecubital fossa
– Buttocks – Axilla
– Volar forearm – Periclavicular
– Dorsal forearm – Paraspinal
– Anterior arm – Head and neck
– Posterior arm
– Periscapular

Tumours which arise within a compartment and expand outside it are also classified as extracompartmental. For example, an osteosarcoma of the distal femur with an associated soft tissue mass would be classified as an MSTS 2B if not metastatic.

 

Limitations of this approach include the fact that although the margins of a compartment might be clear in an axial section, often the superior and inferior limits of the compartment are less well defined.

Referral guidelines for suspected primary bone tumours

NICE guidance suggests the following:

1.13 Bone cancer and sarcoma
General recommendations
1.13.1 A patient who presents with symptoms suggesting bone cancer or
sarcoma should be referred to a team specialising in the
management of bone cancer and sarcoma, or to a recognised bone
cancer centre, depending on local arrangements.
1.13.2 If a primary healthcare professional has concerns about the
interpretation of a patient’s symptoms and/or signs, a discussion
with the local specialist should be considered.
1.13.3 Patients with increasing, unexplained or persistent bone pain or
tenderness, particularly pain at rest (and especially if not in the
joint), or an unexplained limp should be investigated by the primary
healthcare professional urgently. The nature of the investigations
will vary according to the patient’s age and clinical features.
• In older people metastases, myeloma or lymphoma, as well as
sarcoma, should be considered.

Specific recommendations
Bone tumours
1.13.4 A patient with a suspected spontaneous fracture should be referred
for an immediate X-ray.
1.13.5 If an X-ray indicates that bone cancer is a possibility, an urgent
referral should be made.
1.13.6 If the X-ray is normal but symptoms persist, the patient should be
followed up and/or a repeat X-ray or bone function tests or a referral
requested.

The UK guidance on the management of bone sarcomas states the following:

The most common symptom of a primary bone tumour is pain which may be nonmechanical or night pain. The presence of bone pain at night should always be considered to be a “red flag” symptom leading to further investigation. The presence of bone swelling or a soft-tissue mass may occur later. The average duration of symptoms is 3 months although a history of 6 months or longer is not uncommon [1315]. The presence of pain or a palpable mass arising from any bone should cause concern and lead to further investigation of which a plain X-ray is the first investigation of choice. The presence of any of the following on the X-ray is suggestive, but not diagnostic of a bone tumour and should also lead to further investigation:
  • bone destruction,
  • new bone formation,
  • periosteal swelling,
  • soft tissue swelling.
Referral forms for the London Sarcoma Service can be found here.
The North of England Bone and Soft Tissue Tumour Service has a fax for urgent referrals: 0191 223 1328. A referral form for professionals can be found here.

References UK guidelines for the management of bone sarcomas. NICE referral guidelines for suspected cancer 2005

The Musculoskeletal Tumour Society staging system

The MSTS (Enneking) staging system for sarcomas is another exam classic.  This is a very straightforward system which allows the user to describe the extent of the tumour locally and systemically. Tumours are either low grade (Stage 1, <15% risk of metastasis), high grade (Stage 2, >15% risk of metastasis) or metastatic (Stage 3).

Intracompartmental tumours are classified as “A” and extracompartmental tumours as “B”.

For example, an osteosarcoma of the distal femur, which has an associated soft tissue mass but no detectable metastases would be staged as “2B” in this system.

Other systems include the AJCC system for staging.

Reference:

Enneking WF, Spanier SS, Goodman MA. Current concepts review. The surgical staging of musculoskeletal sarcoma. J Bone Joint Surg Am 1980;62(6):1027-30.

The five presenting complaints of musculoskeletal tumours

According to Levesque et al in their excellent book “A clinical guide to Primary Bone Tumours”, the five ways in which patients with musculoskeletal tumours present are:

  1. A soft tissue mass
  2. A painless bony mass
  3. A bone tumour as an incidental finding
  4. A painful bone lesion
  5. A pathological fracture
The approach to each clinical scenario has a different emphasis.

What is a tumour?

A growth or swelling, which enlarges by cellular proliferation more rapidly than surrounding normal tissue and continues to enlarge after the initiating stimuli cease. Usually lacks structural organization and functional coordination with normal tissues and serves no useful purpose to the host organism.

Taking a history

Taking a history from a patient with a suspected bone or soft tissue tumour requires a different emphasis from the rest of orthopaedics. Particular features to note include:

  • Length of history (is this a preexisting mass that has changed?)
  • Rate of growth
  • Pain history (site, character, severity, radiation, modifying factors, periodicity – is there mechanical or night pain?)
  • Previous surgery at the site of interest (ie is this a local recurrence?)
  • History of  malignancy (could this be a metastasis?)
  • History of a predisposing condition (eg Hereditary Multiple Exostoses)
  • Previous radiotherapy
  • Family history (think  inherited disorders like Li Fraumeni syndrome)
  • Symptoms suggestive of malignancy (eg weight loss, lethargy)