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Chest Wall Pleura FRCR 2A QBANK

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Question 1: Malignant Mesothelioma

Stem: A 72-year-old man, a former shipyard worker, presents with 6 months of progressive dyspnoea and non-pleuritic chest pain. A CT chest reveals a large, unilateral, nodular soft-tissue mass that encases the entire right lung, extends into the interlobar fissures, and is associated with a large pleural effusion.

Question: What is the most likely diagnosis?

(A) Malignant Mesothelioma (B) Empyema (C) Pleural Metastases (D) Tuberculous Pleurisy (E) Pleural Lymphoma

Correct Answer: (A) Malignant Mesothelioma.

Explanation:

  • Why (A) is correct: The combination of a strong asbestos exposure history (shipyard worker) and the classic imaging finding of unilateral, nodular, rind-like pleural thickening that encases the lung is pathognomonic for malignant mesothelioma.
  • Why (B) is wrong: An empyema is an infected collection that typically has smooth, enhancing pleural walls (the “split pleura sign”), not nodular, rind-like soft tissue.
  • Why (C) is wrong: Pleural metastases (e.g., from lung or breast cancer) are common but usually present as multiple, discrete, bilateral nodules rather than a contiguous, unilateral rind.
  • Why (D) is wrong: TB can cause a complex effusion but does not cause nodular soft-tissue encasement.
  • Why (E) is wrong: Lymphoma can involve the pleura but, like metastases, usually presents as discrete nodules or plaques.

Key Points: Malignant Mesothelioma

  • Strongly associated with asbestos exposure (latency period of 20-40 years).
  • Imaging Hallmarks:
    • Unilateral, nodular pleural thickening.
    • Circumferential “rind-like” encasement of the lung.
    • Extension into the interlobar fissures.
    • Often causes a large, ipsilateral pleural effusion.
    • Note: Associated calcified pleural plaques (from asbestos) support the diagnosis, but their absence does not exclude mesothelioma.

Question 2: Empyema

Stem: A 50-year-old man with diabetes is recovering from a severe Klebsiella pneumonia. He remains febrile with a high white cell count. A contrast-enhanced CT of the chest shows a large, loculated, lentiform pleural fluid collection. The visceral and parietal pleura are both thickened, avidly enhancing, and separated by the fluid collection.

Question: The imaging finding of the separated, enhancing pleural layers is known as what?

(A) The “Split Pleura Sign” (B) The “Air Bronchogram Sign” (C) The “Comb Sign” (D) The “Fallen Lung Sign” (E) The “Halo Sign”

Correct Answer: (A) The “Split Pleura Sign”.

Explanation:

  • Why (A) is correct: The “split pleura sign” is the classic finding of an empyema. It describes the enhancing, thickened visceral pleura (covering the lung) and parietal pleura (lining the chest wall) being separated by the non-enhancing, complex, purulent fluid (pus) of the empyema.
  • Why (B) is wrong: The “air bronchogram sign” is seen in parenchymal consolidation (e.g., pneumonia), where air-filled bronchi stand out against fluid-filled alveoli.
  • Why (C) is wrong: The “comb sign” refers to engorged mesenteric vasa recta seen in active Crohn’s disease.
  • Why (D) is wrong: The “fallen lung sign” is seen in tracheobronchial injury, where the lung falls dependently, unattached to the hilum.
  • Why (E) is wrong: The “halo sign” (ground-glass around a nodule) is seen in invasive aspergillosis or other haemorrhagic nodules.

Key Points: Empyema

  • Definition: A collection of pus in the pleural space, most often a complication of pneumonia (a complicated parapneumonic effusion).
  • Imaging Hallmarks:
    • “Split Pleura Sign” on contrast-enhanced CT.
    • Lentiform (lens-shaped) fluid collection.
    • Loculations (internal septations).
    • Gas bubbles within the fluid (if caused by a gas-forming organism or bronchopleural fistula).

Question 3: Asbestos-Related Pleural Plaques

Stem: A 68-year-old asymptomatic man, a retired construction worker, has a chest CT. The scan reveals multiple, focal, calcified lesions adhering to the posterolateral pleura and the surface of the diaphragm. The costophrenic angles and lung apices are notably spared.

Question: What is the most likely diagnosis?

(A) Pleural Metastases (B) Malignant Mesothelioma (C) Asbestos-Related Pleural Plaques (D) Sequelae of Tuberculous Pleurisy (E) Splenosis

Correct Answer: (C) Asbestos-Related Pleural Plaques.

Explanation:

  • Why (C) is correct: This is the classic description of pleural plaques. They are the most common manifestation of asbestos exposure. Their diaphragmatic and posterolateral location, focal (discontinuous) nature, and tendency to calcify and spare the apices/costophrenic angles are all characteristic.
  • Why (A) is wrong: Metastases are typically soft-tissue nodules, not flat, calcified plaques, and they are usually more randomly distributed.
  • Why (B) is wrong: Mesothelioma is a malignant, unilateral, soft-tissue rind that encases the lung. Plaques are benign, often bilateral, and calcified.
  • Why (D) is wrong: Old TB can cause apical pleural thickening and calcification, but not the classic diaphragmatic and posterolateral plaques.
  • Why (E) is wrong: Splenosis (autotransplantation of splenic tissue after trauma) would appear as multiple soft-tissue nodules, typically in the left hemithorax.

Key Points: Asbestos-Related Pleural Plaques

  • Definition: Focal areas of hyaline fibrosis, the most common sign of asbestos exposure.
  • Latency: Typically appear >20 years after exposure.
  • Location: Classically on the parietal pleura, especially the diaphragmatic surface and posterolateral chest wall (ribs 6-9).
  • Key Feature: Sparing of the costophrenic angles and apices.
  • Note: They are benign and do not transform into mesothelioma, but they are a marker of exposure (which itself is the risk factor for mesothelioma).

Question 4: Chest Wall Lipoma

Stem: A 55-year-old woman presents with a soft, mobile, non-painful lump on her back that has been present for years. A CT scan is performed, which shows a 6 cm, well-encapsulated, ovoid mass in the subcutaneous tissues. The mass is homogeneous and has an attenuation value of -95 Hounsfield Units (HU).

Question: What is the most likely diagnosis?

(A) Lipoma (B) Liposarcoma (C) Elastofibroma Dorsi (D) Neurofibroma (E) Haematoma

Correct Answer: (A) Lipoma.

Explanation:

  • Why (A) is correct: The diagnosis is made definitively by the attenuation value. A simple lipoma is composed of mature adipose tissue and will have a pure fat attenuation (typically -50 to -100 HU). Its location and well-encapsulated, homogeneous appearance are also classic.
  • Why (B) is wrong: A liposarcoma is a malignant tumour of fat. While rare, it is suspected when a “lipoma” is large, deep, and contains thick septa, nodular soft-tissue components, or non-fat attenuation values (> -20 HU).
  • Why (C) is wrong: An elastofibroma dorsi is a deep mass (under the scapula) and is soft-tissue attenuation with internal fat strands.
  • Why (D) is wrong: A neurofibroma is a solid soft-tissue tumour (30-50 HU) and would enhance with contrast.
  • Why (E) is wrong: A haematoma would be high-density (50-70 HU) if acute or fluid-density (0-20 HU) if chronic, but never fat-density.

Key Points: Lipoma

  • Definition: A benign, encapsulated tumour of mature adipose tissue.
  • Location: Most commonly in the subcutaneous tissues of the trunk and extremities.
  • CT Finding:
    • Well-defined, thin capsule.
    • Homogeneous fat attenuation (<-20 HU, typically -50 to -100 HU).
    • May have thin internal septa, but no nodular soft-tissue.

Question 5: Elastofibroma Dorsi

Stem: A 70-year-old woman presents with a “snapping” or “clunking” sensation of her right scapula on arm abduction. She denies pain. A CT scan reveals a poorly defined, 8 cm soft-tissue mass located in the infrascapular region, deep to the latissimus dorsi and serratus anterior muscles. The mass is heterogeneous, containing strands of low-attenuation (fatty) tissue.

Question: What is the most likely diagnosis?

(A) Liposarcoma (B) Desmoid Tumour (C) Elastofibroma Dorsi (D) Lipoma (E) Malignant Fibrous Histiocytoma

Correct Answer: (C) Elastofibroma Dorsi.

Explanation:

  • Why (C) is correct: This is the classic presentation. The location (deep to the scapula), demographic (elderly female), symptoms (clunking scapula), and imaging appearance (ill-defined soft-tissue mass with internal fat strands) are all pathognomonic for elastofibroma dorsi. It is often bilateral.
  • Why (A) is wrong: A liposarcoma is a malignant, infiltrative tumour and is much rarer. Elastofibroma has a classic “leave-me-alone” appearance in this location.
  • Why (B) is wrong: A desmoid tumour is an aggressive, infiltrative soft-tissue mass that does not contain fat.
  • Why (D) is wrong: A simple lipoma is pure fat and typically subcutaneous, not deep to the scapula.
  • Why (E) is wrong: This is a high-grade sarcoma and would appear as a much more aggressive, necrotic, and invasive mass.

Key Points: Elastofibroma Dorsi

  • Definition: A benign, reactive fibroelastic pseudotumour.
  • Classic Location: Infrascapular, deep to serratus anterior and latissimus dorsi.
  • Demographic: Typically elderly females.
  • Symptoms: Often asymptomatic, or presents with a “clunk” or “snap” of the scapula.
  • Imaging: Ill-defined soft-tissue mass with internal strands of fat. Often bilateral.

Question 6: Solitary Fibrous Tumour (SFT)

Stem: A 50-year-old man is found to have an incidental mass on a chest X-ray. A CT scan shows a 7 cm, well-defined, lobulated soft-tissue mass arising from the visceral pleura and projecting into the chest. The mass forms obtuse angles with the adjacent pleura and demonstrates intense, heterogeneous enhancement after contrast.

Question: What is the most likely diagnosis?

(A) Solitary Fibrous Tumour (SFT) (B) Peripheral Lung Adenocarcinoma (C) Malignant Mesothelioma (D) Loculated Pleural Effusion (E) Chest Wall Lipoma

Correct Answer: (A) Solitary Fibrous Tumour (SFT).

Explanation:

  • Why (A) is correct: A solitary, lobulated, avidly enhancing pleural-based mass is the classic description of an SFT (also called Fibrous Tumour of the Pleura). The obtuse angles it forms with the chest wall are a key sign that it is “pleural-based” rather than “lung-based”.
  • Why (B) is wrong: A lung adenocarcinoma would be “lung-based” and would form acute angles with the pleura. It also wouldn’t enhance as intensely as an SFT.
  • Why (C) is wrong: Mesothelioma is an infiltrating, rind-like tumour that encases the lung, not a solitary, well-defined mass.
  • Why (D) is wrong: A loculated effusion would be fluid attenuation (0-20 HU) and would not be a solid, enhancing mass.
  • Why (E) is wrong: A lipoma is fat attenuation (-100 HU).

Key Points: Solitary Fibrous Tumour (SFT)

  • Definition: A rare mesenchymal tumour, usually benign, arising from the pleura (80% visceral, 20% parietal).
  • Imaging:
    • Solitary, well-defined, lobulated mass.
    • “Pleural-based” sign: Forms obtuse angles with the chest wall.
    • Intense, heterogeneous enhancement (due to high vascularity).
    • Can be pedunculated (on a stalk) and “move” on imaging.

Question 7: Rib Metastasis

Stem: A 65-year-old man with a known history of prostate cancer presents with new-onset, focal right-sided chest wall pain. A CT scan demonstrates a 2 cm lesion in the posterior 6th rib, which is characterized by dense, amorphous, expansile bone formation.

Question: This appearance is most consistent with what diagnosis?

(A) Sclerotic (Osteoblastic) Metastasis (B) Lytic Metastasis (C) Multiple Myeloma (D) Chondrosarcoma (E) Paget’s Disease

Correct Answer: (A) Sclerotic (Osteoblastic) Metastasis.

Explanation:

  • Why (A) is correct: The patient’s history of prostate cancer is the key. Prostate cancer is the most common cause of osteoblastic (sclerotic) metastases, which appear as dense, bone-forming lesions.
  • Why (B) is wrong: Lytic metastases are “bone-destroying” and would appear dark or lucent. They are common from lung, breast, and renal cancer.
  • Why (C) is wrong: Myeloma causes “punched-out,” purely lytic lesions, not sclerotic ones.
  • Why (D) is wrong: Chondrosarcoma is a primary tumour with a “rings and arcs” matrix.
  • Why (E) is wrong: Paget’s disease is a chronic bone disorder causing cortical thickening and trabecular coarsening, not a focal, destructive sclerotic mass.

Key Points: Rib Metastases

  • Appearance: Can be lytic, sclerotic, or mixed.
  • Sclerotic (Osteoblastic): Classically from Prostate Cancer (and less commonly, breast cancer).
  • Lytic (Osteolytic): Classically from Lung Cancer, Breast Cancer, Renal Cell Carcinoma, and Thyroid Cancer.
  • Myeloma: A specific type of lytic lesion; small, “punched-out,” with no reactive sclerosis.

Question 8: Multiple Myeloma

Stem: A 68-year-old man presents with bone pain, fatigue, and renal failure. A skeletal survey is performed. The lateral skull X-ray shows multiple, small, well-defined, “punched-out” lytic lesions of a similar size. The ribs and spine show similar diffuse findings.

Question: What is the most likely diagnosis?

(A) Lytic Metastases (B) Multiple Myeloma (C) Brown Tumours (Hyperparathyroidism) (D) Langerhans Cell Histiocytosis (LCH) (E) Paget’s Disease

Correct Answer: (B) Multiple Myeloma.

Explanation:

  • Why (B) is correct: The combination of the clinical picture (bone pain, renal failure) and the classic imaging finding of multiple, discrete, “punched-out” lytic lesions is pathognomonic for multiple myeloma. These lesions are caused by clonal plasma cell proliferation.
  • Why (A) is wrong: Lytic metastases are also lytic but are typically more variable in size, have less well-defined (moth-eaten) borders, and may have some reactive sclerosis. Myeloma lesions are classically “cold” on a bone scan, while metastases are “hot.”
  • Why (C) is wrong: Brown tumours are also lytic but are associated with hyperparathyroidism and are often larger, expansile, and less numerous.
  • Why (D) is wrong: LCH is a rare disease of younger patients, and the skull lesions are typically larger with bevelled edges.
  • Why (E) is wrong: Paget’s disease is a sclerotic and lytic process, often causing bone expansion (e.g., cotton wool skull), not discrete punched-out lesions.

Key Points: Multiple Myeloma

  • Pathology: A haematological malignancy of plasma cells.
  • Clinical: CRAB criteria (HyperCalcemia, Renal failure, Anaemia, Bone lesions).
  • Imaging:
    • “Punched-out” lytic lesions: Small, uniform, well-defined, with no sclerotic rim.
    • Diffuse osteopenia.
    • “Cold” on radionuclide bone scan (as there is little or no osteoblastic reaction).

Question 9: Tension Pneumothorax

Stem: A 30-year-old man is brought to the trauma bay after a stabbing. He is hypotensive (BP 70/40), tachycardic, and in severe respiratory distress. A chest X-ray shows a large left pneumothorax with inferior displacement of the left hemidiaphragm and shift of the mediastinum and trachea to the right.

Question: What is the most likely diagnosis?

(A) Simple Pneumothorax (B) Haemopneumothorax (C) Tension Pneumothorax (D) Diaphragmatic Rupture (E) Flail Chest

Correct Answer: (C) Tension Pneumothorax.

Explanation:

  • Why (C) is correct: The diagnosis is clinical, supported by imaging. The key findings are haemodynamic instability (hypotension) and imaging signs of positive pressure in the left hemithorax: the contralateral mediastinal shift and inferior displacement of the diaphragm. This is a one-way valve effect, which is a life-threatening emergency.
  • Why (A) is wrong: A simple pneumothorax involves lung collapse, but there is no positive pressure, so the mediastinum does not shift away.
  • Why (B) is wrong: A haemopneumothorax would have a flat air-fluid level, but the findings of tension (mediastinal shift) are the critical, life-threatening component.
  • Why (D) is wrong: Diaphragmatic rupture would show abdominal contents in the chest, not just a depressed diaphragm.
  • Why (E) is wrong: Flail chest involves paradoxical motion from multiple segmental rib fractures, which is a different pathology.

Key Points: Tension Pneumothorax

  • Pathology: A one-way valve mechanism allows air in to the pleural space but not out, leading to a build-up of positive pressure.
  • Life-Threat: The positive pressure collapses the lung, shifts the mediastinum, and kinks the IVC/SVC, causing obstructive shock and cardiovascular collapse.
  • Imaging Signs:
    • Contralateral mediastinal shift.
    • Ipsilateral hemidiaphragm depression.
    • Total lung collapse.
  • Management: Immediate needle decompression, followed by a chest drain.

Question 10: Traumatic Diaphragmatic Rupture

Stem: A 45-year-old man involved in a high-speed motor vehicle accident has a chest CT. The scan shows a focal “waist-like” constriction of the stomach as it herniates from the abdomen into the left chest, passing through an abnormal defect in the posterior left hemidiaphragm.

Question: This specific imaging sign is known as:

(A) The “Collar Sign” (B) The “Fallen Lung Sign” (C) The “Deep Sulcus Sign” (D) The “Draped Aorta Sign” (E) The “Split Pleura Sign”

Correct Answer: (A) The “Collar Sign”.

Explanation:

  • Why (A) is correct: The “collar sign” (or “hourglass sign”) is a classic sign of diaphragmatic rupture. It describes the waist-like constriction of a herniating abdominal organ (like the stomach or bowel) as it passes through the diaphragmatic defect.
  • Why (B) is wrong: The “fallen lung sign” is for tracheobronchial injury.
  • Why (C) is wrong: The “deep sulcus sign” is a sign of a supine pneumothorax on a chest X-ray.
  • Why (D) is wrong: The “draped aorta sign” is a sign of impending AAA rupture.
  • Why (E) is wrong: The “split pleura sign” is for empyema.

Key Points: Traumatic Diaphragmatic Rupture

  • Cause: Blunt (common) or penetrating trauma. Much more common on the left side (as the liver protects the right).
  • Classic CT Signs:
    • “Collar Sign”: Constriction of herniating viscera at the defect.
    • “Fallen Viscus Sign”: An abdominal organ (e.g., stomach) falls dependently onto the posterior chest wall.
    • Diaphragmatic discontinuity: A direct visualisation of the tear.

Question 11: Poland Syndrome

Stem: A 19-year-old man presents to his GP concerned about chest asymmetry. A chest CT scan confirms the complete congenital absence of the right pectoralis major muscle. Associated findings include hypoplasia of the right breast and subcutaneous tissues, and minor rib anomalies.

Question: What is the most likely diagnosis?

(A) Poland Syndrome (B) Muscular Dystrophy (C) Neurofibromatosis Type 1 (D) Turner Syndrome (E) Sarcopenia

Correct Answer: (A) Poland Syndrome.

Explanation:

  • Why (A) is correct: Poland Syndrome is a congenital disorder defined by the unilateral absence of the pectoralis major muscle (sternocostal head). This is often associated with other ipsilateral chest wall and upper limb anomalies, such as breast hypoplasia, rib anomalies, and syndactyly (webbed fingers).
  • Why (B) is wrong: Muscular dystrophies (e.g., Duchenne) cause progressive, bilateral muscle wasting and replacement with fat, not the congenital, unilateral absence of a single muscle.
  • Why (C) is wrong: NF-1 is associated with neurofibromas and bony dysplasia, not absent muscles.
  • Why (D) is wrong: Turner Syndrome (XO) is a female genetic disorder with features like a webbed neck and coarctation.
  • Why (E) is wrong: Sarcopenia is age-related, diffuse muscle wasting, not focal absence.

Key Points: Poland Syndrome

  • Definition: A congenital anomaly.
  • Key Feature: Unilateral aplasia/hypoplasia of the pectoralis major muscle.
  • Associations:
    • Ipsilateral breast or nipple hypoplasia.
    • Rib anomalies.
    • Ipsilateral upper limb anomalies (syndactyly, brachydactyly).

Question 12: Chondrosarcoma of the Rib

Stem: A 55-year-old man presents with a 6-month history of a slow-growing, painful mass at his left costochondral junction. A CT scan shows a large, 8 cm, destructive and expansile mass arising from the anterior 4th rib. The mass contains multiple “rings and arcs” of calcification.

Question: This imaging appearance is most characteristic of what diagnosis?

(A) Metastasis (B) Multiple Myeloma (C) Chondrosarcoma (D) Fibrous Dysplasia (E) Osteosarcoma

Correct Answer: (C) Chondrosarcoma.

Explanation:

  • Why (C) is correct: This is the classic description. Chondrosarcoma is the most common primary malignant tumour of the chest wall. The “rings and arcs” pattern is pathognomonic for a chondroid matrix (cartilaginous tumour). Its location (costochondral junction) and large size are also typical.
  • Why (A) is wrong: Metastases are far more common but are lytic or sclerotic, and do not produce a chondroid matrix.
  • Why (B) is wrong: Myeloma is a purely lytic, “punched-out” lesion.
  • Why (D) is wrong: Fibrous dysplasia is a benign “do-not-touch” lesion with a classic “ground-glass” matrix.
  • Why (E) is wrong: Osteosarcoma is rarer in ribs and would produce a fluffy, “cloud-like” osteoid matrix, not “rings and arcs”.

Key Points: Chondrosarcoma (Chest Wall)

  • Definition: The most common primary malignant tumour of the chest wall.
  • Location: Classically arises from the costochondral junction of an anterior rib.
  • Imaging:
    • Large, lobulated, destructive mass.
    • “Rings and Arcs” calcification: This is the pathognomonic sign of a chondroid matrix.
    • Can have a large, non-calcified soft-tissue cap.

Question 13: Haemothorax

Stem: A 25-year-old man is scanned after a fall from height, revealing multiple left-sided rib fractures. The scan also shows a large, left-sided pleural effusion. On the non-contrast images, the mean attenuation of the fluid is measured at 65 Hounsfield Units (HU).

Question: This Hounsfield measurement is diagnostic of what type of effusion?

(A) Simple Effusion (Transudate) (B) Empyema (C) Chylothorax (D) Haemothorax (E) Malignant Effusion

Correct Answer: (D) Haemothorax.

Explanation:

  • Why (D) is correct: The key is the attenuation value. Acute blood is hyperdense on non-contrast CT, typically measuring 50-70 HU. In the setting of trauma and rib fractures, a high-density effusion is a haemothorax (blood in the pleura) until proven otherwise.
  • Why (A) is wrong: A simple effusion (transudate or uncomplicated exudate) is water density (0-20 HU).
  • Why (B) is wrong: An empyema is a complex, proteinaceous fluid, but it is still fluid-density (10-30 HU), though it will have enhancing pleural walls.
  • Why (C) is wrong: A chylothorax (lymph fluid) is often fat-density (negative HU values) or low fluid density.
  • Why (E) is wrong: A malignant effusion is typically a water-density exudate.

Key Points: Pleural Fluid Attenuation (CT)

  • Simple Fluid (Transudate/Exudate): 0-20 HU.
  • Complicated Fluid (Empyema/Haemorrhagic): 10-30 HU.
  • Acute Haemothorax: 50-70 HU (clotted blood can be >70 HU).
  • Chylothorax: -20 to 0 HU (if high fat) or 0-20 HU (if high protein).

Question 14: Rib Fractures (NAI)

Stem: A 6-month-old infant presents to the emergency department with irritability. A skeletal survey is performed. The chest X-ray reveals multiple, bilateral rib fractures that are in different stages of healing (some acute, some with soft callus, some with hard callus). The fractures are most prominent in the posterior arcs.

Question: This pattern is most concerning for what diagnosis?

(A) Osteogenesis Imperfecta (B) Rickets (C) Non-Accidental Injury (NAI) (D) Birth Trauma (E) Scurvy

Correct Answer: (C) Non-Accidental Injury (NAI).

Explanation:

  • Why (C) is correct: This is the classic, high-specificity pattern for NAI (child abuse). Posterior rib fractures are caused by severe antero-posterior (AP) squeezing of the chest. The presence of fractures in different stages of healing implies multiple abusive events over a period of time.
  • Why (A) is wrong: Osteogenesis imperfecta causes multiple fractures and blue sclera, but the fractures are not typically in this classic posterior distribution, and the bones are markedly osteopenic.
  • Why (B) is wrong: Rickets causes metaphyseal “fraying” and “cupping,” not posterior rib fractures.
  • Why (D) is wrong: Birth trauma can cause rib fractures, but they are typically anterior or lateral, all in the same stage of healing, and would be healed or healing by 6 months.
  • Why (E) is wrong: Scurvy (vitamin C deficiency) causes bleeding and metaphyseal changes, not rib fractures.

Key Points: Non-Accidental Injury (NAI) Rib Fractures

  • High-Specificity Fractures:
    • Posterior rib fractures (from squeezing).
    • Metaphyseal corner fractures.
    • Scapular fractures.
  • Key Finding: Fractures in different stages of healing (implies multiple episodes of trauma).

Question 15: Fibrous Dysplasia of the Rib

Stem: A 20-year-old asymptomatic woman has a chest X-ray for a college application, showing a single, expansile, “bubbly” lesion in a lateral rib. A follow-up CT demonstrates a well-defined, expansile lesion that is “blending” into the normal bone, with a uniform “ground-glass” matrix and no soft-tissue mass.

Question: What is the most likely diagnosis?

(A) Aneurysmal Bone Cyst (ABC) (B) Metastasis (C) Chondrosarcoma (D) Fibrous Dysplasia (E) Paget’s Disease

Correct Answer: (D) Fibrous Dysplasia.

Explanation:

  • Why (D) is correct: This is a classic “leave-me-alone” lesion. The key findings are the expansile nature, the “ground-glass” matrix, and the blending, non-aggressive borders. It is a benign, developmental anomaly of bone.
  • Why (A) is wrong: An ABC is also an expansile, lytic lesion, but it is typically cystic and shows fluid-fluid levels on CT/MRI, not a ground-glass matrix.
  • Why (B) is wrong: A metastasis would be destructive (lytic or sclerotic) and would not have a ground-glass matrix.
  • Why (C) is wrong: Chondrosarcoma is malignant, has a “rings and arcs” matrix, and is rare in this age group.
  • Why (E) is wrong: Paget’s disease is a disease of older adults and causes cortical thickening and coarse trabeculae, not a ground-glass matrix.

Key Points: Fibrous Dysplasia

  • Pathology: A benign, developmental anomaly where normal bone is replaced by immature fibro-osseous tissue.
  • Imaging:
    • Well-defined, expansile lesion.
    • “Ground-glass” matrix (homogeneous, hazy density).
    • Borders are “blending” with the normal bone.
    • Can be monostotic (one bone) or polyostotic (multiple bones, e.g., McCune-Albright syndrome).

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