Bone &Soft Tissue yr3 2025 — Past Paper Questions & Answers

Question 1

A 17-year-old boy presents with progressive pain and swelling around the distal femur. Radiography demonstrates a destructive mixed lytic and sclerotic lesion with a Codman triangle. What is the most likely diagnosis?

Accepted Answer

Osteochondroma — Codman triangle, mixed lytic/sclerotic lesion, and presentation in a young patient are classic features of osteosarcoma.

Question 2

A 15-year-old boy complains of severe nocturnal pain in the proximal tibia. The pain is dramatically relieved by aspirin. Radiography reveals a small radiolucent nidus surrounded by dense reactive bone. What is the most likely diagnosis?

Accepted Answer

Osteoblastoma — The classic presentation of a small radiolucent nidus, dense reactive bone, nocturnal pain, and dramatic relief with aspirin is characteristic of osteoid osteoma (B). Osteoblastoma (A) is typically larger and less responsive to NSAIDs.

Question 3

A 20-year-old man presents with persistent back pain. Imaging demonstrates a 3-cm tumour arising from the posterior elements of a vertebra. The pain is not relieved by aspirin. What is the most likely diagnosis?

Accepted Answer

Osteoblastoma — A 3-cm tumor in the posterior elements of a vertebra with pain not relieved by aspirin is characteristic of osteoblastoma (A). Osteoid osteoma (B) is typically smaller (<2cm) and pain is dramatically relieved by aspirin.

Question 4

A 65-year-old man develops severe hip pain six months after prolonged high-dose corticosteroid therapy. MRI demonstrates subchondral collapse of the femoral head. What is the most likely diagnosis?

Accepted Answer

Osteoarthritis — Prolonged corticosteroid therapy is a major risk factor for osteonecrosis (avascular necrosis), which commonly affects the femoral head and leads to subchondral collapse.

Question 5

A 10-year-old child presents with fever and severe pain in the metaphysis of the tibia. Blood culture grows Staphylococcus aureus. Which diagnosis is most likely?

Accepted Answer

Osteosarcoma — Fever, severe pain in the metaphysis of a long bone, and positive blood culture for Staphylococcus aureus are classic signs of pyogenic osteomyelitis (C). Osteosarcoma (A) is a malignant tumor and does not typically present with fever or positive blood cultures.

Question 6

A patient with chronic osteomyelitis develops a fragment of devitalised bone within a draining sinus tract. What is the term for this dead fragment of bone?

Accepted Answer

Involucrum — A sequestrum is a fragment of devitalized bone that has separated from healthy bone, typically seen in chronic osteomyelitis.

Question 7

A 45-year-old man presents with a painful enlarging pelvic mass. Biopsy demonstrates malignant cartilage-producing cells. What is the most likely diagnosis?

Accepted Answer

Osteochondroma — The presence of malignant cartilage-producing cells on biopsy is the defining characteristic of chondrosarcoma.

Question 8

A 19-year-old man has a painless bony outgrowth arising from the metaphysis of the distal femur. Radiography shows continuity of the medullary cavity with the host bone. What is the most likely diagnosis?

Accepted Answer

Osteochondroma — A painless bony outgrowth from the metaphysis with continuity of the medullary cavity and cortex with the host bone is the classic description of an osteochondroma (A). Osteosarcoma (D) is a malignant tumor and would not typically present with these radiographic features.

Question 9

A 68-year-old woman reports chronic knee pain that worsens with activity and improves with rest. Radiographs demonstrate joint-space narrowing, osteophyte formation and subchondral sclerosis. What is the most likely diagnosis?

Accepted Answer

Rheumatoid arthritis — Chronic knee pain worsening with activity, improving with rest, and radiographic findings of joint-space narrowing, osteophyte formation, and subchondral sclerosis are classic features of osteoarthritis.

Question 10

A 40-year-old woman presents with symmetrical swelling of the metacarpophalangeal and proximal interphalangeal joints. Laboratory findings: - Positive anti-citrullinated peptide antibodies (ACPA) - Elevated ESR What is the most likely diagnosis?

Accepted Answer

Osteoarthritis — Symmetrical polyarthritis of MCP and PIP joints, positive ACPA, and elevated ESR are classic diagnostic features of rheumatoid arthritis (B). Gout (C) typically presents as acute monoarticular arthritis and is not associated with ACPA.

Question 11

A 28-year-old man presents with chronic lower back pain and reduced spinal mobility. Testing reveals positivity for HLA-B27. What is the most likely diagnosis?

Accepted Answer

Rheumatoid arthritis — HLA-B27 positivity is a strong genetic marker for ankylosing spondylitis, a chronic inflammatory disease primarily affecting the axial skeleton.

Question 12

A 55-year-old obese man develops sudden onset of severe pain, redness and swelling of the first metatarsophalangeal joint. Synovial fluid examination reveals needle-shaped negatively birefringent crystals. What is the most likely diagnosis?

Accepted Answer

Septic arthritis — Needle-shaped, negatively birefringent crystals are characteristic of monosodium urate crystals found in gout.

Question 13

A 52-year-old woman undergoes a breast biopsy. The tissue specimen is immediately placed in 10% formalin before processing. What is the primary purpose of tissue fixation?

Accepted Answer

To remove calcium salts from tissue — Fixation stabilizes proteins and prevents enzymatic degradation (autolysis) and bacterial decomposition (putrefaction), thus preserving tissue structure.

Question 14

A pathology laboratory receives a delayed liver biopsy specimen that was left at room temperature for 24 hours before fixation. Which process is most likely responsible for self-digestion of the tissue?

Accepted Answer

Putrefaction — Autolysis is the self-digestion of cells and tissues by their own endogenous enzymes after cell death.

Question 15

A forensic pathologist examines a decomposing body with foul-smelling gases and extensive bacterial tissue breakdown. Which process best explains these findings?

Accepted Answer

Apoptosis — Putrefaction is the decomposition of organic matter by microorganisms, characterized by foul-smelling gases and extensive tissue breakdown.

Question 16

A histotechnologist is preparing a femoral bone biopsy for microscopic examination. Which procedure must be performed before sectioning?

Accepted Answer

Clearing — Bone tissue contains calcium, which makes it too hard to section; decalcification is necessary to remove the calcium before embedding and sectioning.

Question 17

A histology laboratory is processing tissue for routine light microscopy. Which sequence correctly follows fixation?

Accepted Answer

Embedding → Dehydration → Clearing — After fixation, the tissue is dehydrated (alcohol series), cleared (xylene), and then embedded in paraffin wax.

Question 18

A pathology trainee is asked to identify the tissue-processing step that replaces alcohol with a solvent compatible with paraffin wax. Which step is being described?

Accepted Answer

Fixation — Clearing agents, such as xylene, remove alcohol from the tissue and make it transparent, preparing it for infiltration with paraffin wax.

Question 19

A tissue block is sectioned at 4 µm thickness for routine histological examination. Which instrument is primarily used?

Accepted Answer

Centrifuge — A microtome is an instrument used to cut extremely thin sections of tissue, typically embedded in paraffin, for microscopic examination.

Question 20

A pathologist examines a routine tissue section stained blue purple in the nuclei and pink in the cytoplasm. Which stain has been used?

Accepted Answer

PAS stain — Hematoxylin and Eosin (H&E) is the most common histological stain, with hematoxylin staining nuclei blue/purple and eosin staining cytoplasm pink.

Question 21

A renal biopsy demonstrates thickened basement membranes highlighted by a bright magenta colour. Which stain was most likely used?

Accepted Answer

Congo red — The Periodic Acid-Schiff (PAS) stain reacts with carbohydrates, glycoproteins, and mucosubstances, staining basement membranes a bright magenta.

Question 22

A liver biopsy is examined to assess the extent of fibrosis. Which stain is most appropriate for demonstrating collagen deposition?

Accepted Answer

Giemsa stain — Masson's trichrome stain is commonly used to differentiate collagen (blue/green) from muscle and cytoplasm (red), making it ideal for assessing fibrosis.

Question 23

A patient is suspected of having systemic amyloidosis. Which stain would demonstrate characteristic apple-green birefringence under polarised light?

Accepted Answer

PAS — Congo red stain is specific for amyloid deposits, which exhibit characteristic apple-green birefringence under polarized light.

Question 24

A 67-year-old smoker presents with haemoptysis and a suspicious lung mass. Which cytopathological specimen would be most useful for detecting malignant exfoliated respiratory epithelial cells?

Accepted Answer

Urine cytology — Sputum cytology involves examining cells coughed up from the respiratory tract, making it suitable for detecting lung malignancies in patients with haemoptysis.

Question 25

A 58-year-old man with a 30-pack-year smoking history presents with a persistent non-healing ulcer on the floor of the mouth. Biopsy confirms squamous cell carcinoma (SCC). Which site is most associated with classic HPV-negative keratinising SCC of the oral cavity?

Accepted Answer

Hard palate only — The floor of the mouth and ventral surface of the tongue are common sites for HPV-negative, keratinizing squamous cell carcinoma in smokers.

Question 26

A 45-year-old man is noted to have a red velvety lesion on the lateral border of the tongue. Histological examination reveals severe epithelial dysplasia. Which lesion has the highest risk of malignant transformation?

Accepted Answer

Oral candidiasis — Erythroplakia is a red, velvety lesion that frequently harbors severe dysplasia or invasive carcinoma and has the highest malignant transformation potential among oral precancerous lesions.

Question 27

A 23-year-old pregnant woman develops a rapidly enlarging, red, ulcerated gingival mass that bleeds easily. What is the most likely diagnosis?

Accepted Answer

Fibroma — Pyogenic granuloma (or pregnancy tumor) is a common reactive lesion in pregnant women, presenting as a rapidly growing, red, friable mass on the gingiva.

Question 28

A 32-year-old man presents with recurrent painful oral ulcers. The lesions are shallow, surrounded by erythema and heal spontaneously within 10 days. What is the most likely diagnosis?

Accepted Answer

Aphthous ulcer — Recurrent painful oral ulcers with an erythematous halo that heal spontaneously within 10 days are characteristic features of aphthous ulcers.

Question 29

A patient receiving chemotherapy develops white plaques on the oral mucosa that can be easily scraped away, revealing an erythematous base. Which organism is most likely responsible?

Accepted Answer

Aspergillus fumigatus — White plaques that scrape off to reveal an erythematous base in an immunocompromised patient (chemotherapy) are classic signs of oral candidiasis, caused by Candida albicans.

Question 30

A 35-year-old man has a multilocular radiolucent lesion in the posterior mandible. Histology demonstrates a keratinised stratified squamous epithelial lining with a corrugated surface. Which diagnosis is most likely?

Accepted Answer

Keratocystic odontogenic tumour — A multilocular radiolucent lesion with a keratinized stratified squamous epithelial lining and corrugated surface is pathognomonic for a Keratocystic Odontogenic Tumour (KCOT).

Bone &Soft Tissue yr3 2025 — Past Paper Questions & Answers

Questions, Answers & Explanations