Bone and soft tissue tumours
Bone tumours, soft tissue sarcomas and skin cancers (FCPS Part 1)
Bone tumours by age, site and X-ray sign, soft tissue sarcomas, BCC, SCC, melanoma and xeroderma pigmentosum for FCPS Part 1. Location within the bone and the cell of origin answer most questions on these tumours.
Reading a bone lesion
- Three clues identify most bone tumours: age, position in the bone (epiphysis, metaphysis or diaphysis) and X-ray behaviour. A narrow sclerotic margin means slow growth (usually benign); a wide, permeative margin with sunray spicules, Codman triangle or onion-skin periosteal reaction means aggressive growth.
- Commonest malignant bone lesion in adults: metastases, from breast, prostate, lung, kidney and thyroid. Most are lytic (kidney, thyroid, lung); prostate and some breast metastases are sclerotic. The spine is the commonest site; complications are pathological fracture, hypercalcaemia and cord compression.
- Multiple myeloma is the commonest primary bone malignancy in older adults: punched-out lytic lesions, and the bone scan is often negative because there is no osteoblastic response, so use a skeletal survey, MRI or PET.
| Site in bone | Typical tumours |
|---|---|
| Epiphysis | Giant cell tumour (after the growth plate closes), chondroblastoma (before) |
| Metaphysis | Osteosarcoma, osteochondroma, simple and aneurysmal bone cysts, non-ossifying fibroma |
| Diaphysis | Ewing sarcoma, adamantinoma, fibrous dysplasia |
| Vertebrae | Osteoblastoma (posterior elements), haemangioma, chordoma (sacrum and clivus), metastases, myeloma |
Benign bone tumours
| Tumour | Patient and site | Key points |
|---|---|---|
| Osteochondroma | Adolescents; metaphysis near the knee or proximal humerus | Commonest benign bone tumour; cartilage-capped outgrowth pointing away from the joint; suspect chondrosarcoma if it grows after skeletal maturity or the cap exceeds 2 cm; multiple in hereditary exostoses (EXT1/2) |
| Osteoid osteoma | Ages 10–25; cortex of femur or tibia | Night pain relieved by aspirin or NSAIDs (the nidus makes prostaglandins); nidus under 1.5 cm with dense sclerosis; radiofrequency ablation |
| Osteoblastoma | Young adults; vertebrae, posterior elements | Histologically like osteoid osteoma but over 2 cm, pain not relieved by aspirin, can cause scoliosis or nerve compression |
| Enchondroma | Phalanges of the hand | Commonest hand bone tumour; multiple in Ollier disease, with haemangiomas in Maffucci syndrome (higher sarcoma risk) |
| Giant cell tumour | Ages 20–40; epiphysis of distal femur, proximal tibia, distal radius | Eccentric lytic "soap-bubble" lesion reaching subchondral bone; locally aggressive and recurs; RANKL-driven, so denosumab helps |
| Simple bone cyst | Children; proximal humerus | "Fallen fragment" sign after fracture |
| Aneurysmal bone cyst | Under 20 | Expansile, blood-filled, fluid levels on MRI |
| Fibrous dysplasia | Any | Ground-glass matrix; McCune–Albright syndrome |
- Paget disease of bone: disorganised remodelling with thick but weak bone, fractures, deformity, high-output cardiac failure from vascular shunts, and a risk of secondary osteosarcoma in old age.
Malignant bone tumours
| Tumour | Age and site | Hallmarks |
|---|---|---|
| Osteosarcoma | 10–25, metaphysis around the knee; second peak in the elderly with Paget disease or irradiation | Tumour makes osteoid; sunburst spicules, Codman triangle; raised ALP; RB1 (retinoblastoma survivors) and TP53 (Li–Fraumeni); lung metastases; neoadjuvant chemotherapy and limb salvage |
| Ewing sarcoma | 5–20, diaphysis and pelvis | Small round blue cells, CD99, t(11;22) EWS–FLI1; onion-skin periosteal reaction; fever, high ESR, mimics osteomyelitis; radiosensitive |
| Chondrosarcoma | 40–70, pelvis, proximal femur, ribs | "Ring and arc" (popcorn) calcification, endosteal scalloping; resists chemotherapy and radiotherapy, so wide excision is the only cure |
| Chordoma | Adults, sacrum, clivus | Notochord remnant; physaliphorous cells |
- Biopsy is planned with the sarcoma centre that will do the resection, along a track that can be removed with the tumour.
Soft tissue tumours
- Lipoma is the commonest soft tissue tumour.
- Sarcoma red flags needing urgent ultrasound or MRI: over 5 cm, deep to fascia, growing, painful, or recurring after excision.
- Adult sarcomas: undifferentiated pleomorphic sarcoma, liposarcoma (thigh, retroperitoneum; MDM2), leiomyosarcoma, synovial sarcoma (young adults near the knee; t(X;18)), MPNST (NF1), angiosarcoma after radiation or chronic lymphoedema (Stewart–Treves), Kaposi sarcoma (HHV-8).
- Rhabdomyosarcoma is the commonest childhood soft tissue sarcoma (head and neck, orbit, genitourinary tract). The embryonal botryoid variant (sarcoma botryoides) forms a grape-like mass protruding from the vagina or bladder of a young girl; small round blue cells crowd beneath the epithelium as a cambium layer. Skeletal muscle differentiation is shown by myogenin and MyoD1 (most specific) and desmin (which also stains smooth muscle).
- Sarcomas spread by blood to the lungs; nodes are rarely involved except in rhabdomyosarcoma, synovial, epithelioid, clear cell sarcoma and angiosarcoma. Treat with wide excision and radiotherapy; never shell out a lump that could be a sarcoma. Desmoid tumour (FAP, abdominal wall) is locally aggressive but never metastasises.
Skin cancers
| Feature | Basal cell carcinoma | Squamous cell carcinoma | Melanoma |
|---|---|---|---|
| Frequency | Commonest skin cancer | Second | Fewer cases, most deaths |
| Cell | Basal keratinocytes | Keratinocytes | Melanocytes (neural crest) |
| Look | Pearly rolled edge, telangiectasia, central ulcer (rodent ulcer); upper face, inner canthus, nose | Keratotic, crusted ulcer with everted edge; lower lip, ear, hands | ABCDE: asymmetry, border, colour variation, diameter over 6 mm, evolution |
| Spread | Local invasion; almost never metastasises | Nodes in a minority (lip, ear, immunosuppressed, Marjolin ulcer) | Lymphatic and blood-borne, to lungs, liver, brain |
| Precursors | None | Actinic keratosis, Bowen disease, burns and chronic ulcers (Marjolin ulcer), transplant immunosuppression, arsenic | Dysplastic naevi, giant congenital naevi |
| Treatment | Excision with 4 mm margin; Mohs surgery on the face | Excision with 4–6 mm margin | Excision biopsy, then wide excision by Breslow; sentinel node biopsy; anti-PD-1, BRAF/MEK inhibitors |
- Xeroderma pigmentosum: autosomal recessive (consanguinity is the clue) defect in nucleotide excision repair, which normally removes UV-induced thymine dimers. Children burn severely, freckle heavily and develop BCC, SCC and melanoma in the first decade.
- Melanoma subtypes: superficial spreading (commonest overall), nodular (early vertical growth, worst for its size), lentigo maligna (elderly face), acral lentiginous (palms, soles, nails; commonest in darker skin including South Asians; Hutchinson sign of nail fold pigment), uveal (liver metastases), and amelanotic.
- Amelanotic melanoma is a pink nodule with no pigment, so it is diagnosed late. Large atypical cells with prominent nucleoli are confirmed as melanoma by S-100 and SOX10 (sensitive) and HMB-45 and Melan-A (more specific).
- Breslow thickness (granular layer to deepest tumour cell, in mm) is the most important prognostic factor; then ulceration, mitotic rate and sentinel node status. Wide excision margins: in situ 0.5–1 cm, up to 1 mm 1 cm, 1–2 mm 1–2 cm, over 2 mm 2 cm.
- Risk factors for melanoma: intermittent intense sunburn, fair skin, many naevi, family history (CDKN2A), immunosuppression, xeroderma pigmentosum. SCC follows cumulative sun exposure.
- Keratoacanthoma: crater with a keratin plug that grows over weeks; excise as for SCC. Merkel cell carcinoma: polyomavirus, elderly, aggressive.
Remember Epiphysis giant cell, metaphysis osteosarcoma, diaphysis Ewing, vertebral posterior elements osteoblastoma.
Exam trap BCC is locally destructive but almost never metastasises.
Exam trap Never shave or partly biopsy a suspected melanoma; Breslow depth would be lost.
How FCPS asks about this
- Commonest site of osteoblastoma: vertebrae, posterior elements.
- Grape-like vaginal mass in a young girl, myogenin positive: embryonal (botryoid) rhabdomyosarcoma.
- Burns since infancy, freckling, facial BCC in a child of a consanguineous family: xeroderma pigmentosum, defective nucleotide excision repair.
- Pink nodule of large atypical cells without melanin: amelanotic melanoma; S-100, SOX10 and HMB-45 positive.
- Bone tumour by site: giant cell tumour epiphysis; osteosarcoma metaphysis with sunburst and Codman triangle; Ewing diaphysis with onion skin and t(11;22).
- Pain relieved by aspirin in a young cortex lesion: osteoid osteoma; chondrosarcoma resists chemoradiotherapy.
- Most important prognostic factor in melanoma: Breslow thickness; acral lentiginous type is commonest in South Asians.
Test yourself on this topic
5 of the 35 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
An elderly woman has a slowly enlarging, well-defined, red scaly plaque on her shin. Biopsy shows full-thickness atypia of the epidermis with an intact basement membrane. What is the diagnosis?
Answer: Bowen disease (SCC in situ)
Bowen disease is squamous cell carcinoma in situ of the skin. Atypical keratinocytes replace the full thickness of the epidermis, but the basement membrane is intact, so there is no invasion. It appears as a slowly enlarging, well-defined red scaly plaque, often on the lower legs of older women, and can be mistaken for psoriasis or eczema. A small proportion progress to invasive SCC.
Bowen disease
- SCC in situ of skin
- Full-thickness atypia
- Basement membrane intact
- Red scaly plaque, often lower leg
Remember Single red scaly plaque that does not respond to steroids: biopsy for Bowen.
Exam trap A single 'psoriatic' plaque that fails to respond to treatment in an older person needs biopsy.
Why the other options are wrong
- Plaque psoriasis Shows regular acanthosis and parakeratosis without atypia.
- Basal cell carcinoma Nests of basaloid cells with palisading.
- Actinic keratosis Atypia is limited to the lower epidermis.
- Invasive squamous cell carcinoma Would show invasion through the basement membrane.
A 55-year-old man has had deep aching pain in the pelvis for a year. X-ray shows a large lytic lesion of the ilium with ring-and-arc calcification. Biopsy shows malignant cartilage. What is the tumour?
Answer: Chondrosarcoma
Chondrosarcoma is a malignant cartilage-forming tumour of middle and later adult life. It favours the axial skeleton and proximal limbs, especially the pelvis, shoulder girdle and proximal femur. The cartilage matrix calcifies in rings and arcs. It may arise new or from a pre-existing enchondroma or osteochondroma. It responds poorly to chemotherapy and radiotherapy, so wide surgical excision is the main treatment.
Chondrosarcoma
- Adults over 40
- Pelvis, proximal femur, shoulder
- Ring-and-arc calcification
- Treated by wide excision
Remember Older adult, pelvic cartilage tumour: chondrosarcoma.
Exam trap A cartilage lesion of a long bone that becomes painful in an adult may be turning into chondrosarcoma.
Why the other options are wrong
- Osteosarcoma Usually in adolescents, forms osteoid, around the knee.
- Ewing sarcoma Children and young adults; small round cells.
- Giant cell tumour Epiphyseal lesion of young adults; no cartilage matrix.
- Plasmacytoma Lytic, but made of plasma cells, not cartilage.
A 30-year-old has knee pain. X-ray shows an eccentric lytic 'soap bubble' lesion in the distal femoral epiphysis reaching the joint surface. What is the most likely tumour?
Answer: Giant cell tumour
Giant cell tumour of bone occurs at 20–40 years after the growth plate closes, in the epiphysis of long bones (around the knee, distal radius). It is lytic, eccentric and expansile ('soap bubble'), extending to subchondral bone. Histology shows osteoclast-like giant cells. It is locally aggressive and recurs after curettage; rarely it metastasises to the lungs. Denosumab (RANKL inhibitor) is used in some cases.
Giant cell tumour
- Age 20–40
- Epiphysis (after fusion)
- Soap bubble, eccentric
- Osteoclast-like giant cells
- Locally aggressive
Remember Grown-up epiphysis with soap bubbles.
Exam trap Before skeletal maturity, an epiphyseal lesion is more likely a chondroblastoma.
Why the other options are wrong
- Osteosarcoma Metaphysis; sunburst, Codman triangle; adolescents.
- Ewing sarcoma Diaphysis; onion skin; children.
- Osteochondroma Bony outgrowth from the metaphysis.
- Simple bone cyst Metaphysis in children; fallen fragment sign.
A 16-year-old boy has severe night pain in his upper tibia that is relieved dramatically by ibuprofen. X-ray shows a small lucent nidus under 1.5 cm surrounded by dense sclerosis. What explains the response to ibuprofen?
Answer: The nidus makes prostaglandins
Osteoid osteoma is a small benign bone-forming tumour of adolescents and young adults, most often in the femur and tibia. The nidus of woven bone and osteoid is richly innervated and produces large amounts of prostaglandin E₂, which causes pain, especially at night, and stimulates the reactive sclerosis around it. NSAIDs block COX and give striking relief. Radiofrequency ablation of the nidus is curative.
Osteoid osteoma
- Young patient, night pain
- Nidus under 1.5 cm with sclerosis
- Nidus makes PGE₂
- Relieved by NSAIDs; ablation cures
Remember Night pain relieved by NSAIDs: osteoid osteoma.
Exam trap A spinal osteoid osteoma can present as painful scoliosis in a teenager.
Why the other options are wrong
- Ibuprofen shrinks the tumour NSAIDs relieve pain but do not shrink the nidus.
- It lowers marrow pressure Not the mechanism.
- It blocks osteoclast activity Not the main reason for pain relief.
- It treats a bone infection There is no infection.
A 4-year-old girl has a grape-like mass protruding from the vagina. Biopsy shows small round blue cells forming a dense layer beneath the surface epithelium, staining for desmin and myogenin. What is the tumour?
Answer: Embryonal rhabdomyosarcoma
Rhabdomyosarcoma is the commonest soft tissue sarcoma of childhood and shows skeletal muscle differentiation, so it stains for desmin, myogenin and MyoD1. The embryonal botryoid subtype grows under mucosal surfaces of hollow organs such as the vagina and bladder, forming grape-like polyps. A dense band of tumour cells beneath the epithelium (the cambium layer) is characteristic. Multimodal treatment gives good survival.
Botryoid rhabdomyosarcoma
- Child, grape-like mucosal mass
- Cambium layer under epithelium
- Desmin, myogenin positive
- Skeletal muscle differentiation
Remember Grapes from the vagina of a small child: rhabdomyosarcoma.
Exam trap Myogenin and MyoD1 are more specific for rhabdomyosarcoma than desmin, which also stains smooth muscle.
Why the other options are wrong
- Ewing sarcoma Small round cells, but CD99-positive and in bone.
- Yolk sac tumour Germ cell tumour with Schiller-Duval bodies and raised AFP.
- Neuroblastoma Small round cells in rosettes, from adrenal or sympathetic chain.
- Clear cell adenocarcinoma Occurs in young women exposed to DES in utero.
Where this sits in the CPSP syllabus
- Surgery & Allied, Paper 2: Oncology, Bone and soft tissue tumours; skin cancers
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