Bone and Soft Tissue Pathology Practice Questions

Q: Not a true statement about Osteoclastoma

Originates in the metaphyseal region of bones. ***Originates in the metaphyseal region of bones*** - Giant cell tumors (**osteoclastoma**) are typically found in the **epiphyseal region** of long bones, particularly around the knee (distal femur and proximal tibia), rather than the metaphysis [1]. - While they can extend into the metaphysis, their origin is characteristically **epiphyseal** after skeletal maturity [1]. *Benign bone tumor* - **Giant cell tumors** are considered **benign but locally aggressive** tumors [1]. - They have a potential for **local recurrence** and, rarely, **malignant transformation** or distant metastasis (typically to the lungs). *Usually solitary* - **Giant cell tumors** are almost always **solitary lesions** [1]. - Multifocal involvement is exceedingly rare and should prompt investigation for underlying syndromes or alternative diagnoses. *Common in age between 20-40 years* - Giant cell tumors typically occur in skeletally mature individuals, with a peak incidence in the **third and fourth decades of life** (20-40 years old). - They are rare before skeletal maturity because the epiphysis has not yet fused. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1205-1206.

Q: A 50-year-old male patient presented with weakness of bilateral lower limbs which was symmetrical (distal weakness >> proximal muscle weakness) for 1 month. On examination, certain skin and nail changes were noted. Patient also complained of myalgia and arthralgia. Lab findings: Raised creatinine kinase levels, Raised ANA antibody titre. Muscle biopsy was done from the quadriceps femoris muscle. CD4+ cells were found in the cellular infiltrate. IHC study of which protein is a very sensitive diagnostic test for the above condition?

Myxovirus resistance protein. ***Myxovirus resistance protein*** - The clinical presentation suggests **dermatomyositis** or **polymyositis**, characterized by symmetrical muscle weakness, skin/nail changes, myalgia, arthralgia, and elevated CK/ANA [1]. - In these conditions, **Type I interferon (IFN-I)** activation occurs, leading to increased expression of **myxovirus resistance protein A (MxA)**, which serves as a highly sensitive biomarker. *Adenovirus resistance protein* - This is not a recognized or specific biomarker for **inflammatory myopathies** like dermatomyositis or polymyositis. - While adenoviruses can cause muscle inflammation in certain contexts, related resistance proteins are not used for diagnosis in this manner. *Parvovirus resistance protein* - Parvovirus B19 can cause myositis, but "parvovirus resistance protein" is not a specific or sensitive diagnostic marker for **idiopathic inflammatory myopathies**. - The associated immune response and biomarkers would relate more directly to the viral infection itself. *Papovavirus resistance protein* - **Papovaviruses** (e.g., human papillomavirus, JC virus) are not typically associated with **idiopathic inflammatory myopathies**. - There is no "papovavirus resistance protein" that serves as a diagnostic biomarker for the presented clinical picture.

Q: Which of the following is the most important infiltrate in rheumatoid arthritis?

Macrophages. ***Macrophages*** - **Macrophages** are crucial in rheumatoid arthritis synovium due to their role in producing **pro-inflammatory cytokines** like TNF-̑, IL-1, and IL-6, which drive joint destruction [1], [2]. - They also contribute to the **pannus formation** and degrade cartilage and bone through the release of proteases [1]. *Dendritic cells* - While present in the synovium, **dendritic cells primarily function as antigen-presenting cells**, initiating T-cell responses. - Their direct contribution to tissue damage and chronic inflammation is less prominent than that of macrophages. *CD4+ Helper cells* - **CD4+ T helper cells** orchestrate the immune response by activating B cells and macrophages, but they are not the primary effector cells causing direct tissue damage [3]. - They secrete cytokines that promote inflammation but do not directly participate in tissue degradation. *Neutrophils* - **Neutrophils are abundant in the synovial fluid** during acute flares, contributing to inflammation and breakdown of cartilage through the release of enzymes. - However, their role in the chronic, sustained synovial inflammation and tissue destruction characteristic of RA is less significant compared to macrophages. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 677-678. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 105-106. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1212.

Q: Malignant peripheral nerve sheath tumour showing which of the following differentiation is termed as 'Triton tumour'?

Rhabdomyoblastic. ***Rhabdomyoblastic*** - A **Triton tumour** is a specific subtype of **malignant peripheral nerve sheath tumour (MPNST)** characterized by the presence of **rhabdomyosarcomatous differentiation** [1]. - This differentiation means that the tumour cells express features of **skeletal muscle differentiation**, making it a challenging diagnosis due to its aggressive nature and mixed histological features [1], [2]. *Cartilaginous* - The presence of **cartilaginous differentiation** in an MPNST would lead to a diagnosis of an **MPNST with heterologous chondrosarcomatous differentiation**, not a Triton tumour. - While MPNSTs can show heterologous elements, cartilage is not the characteristic feature of a Triton tumour [1]. *Glandular* - If an MPNST exhibits **glandular differentiation**, it would be termed an **MPNST with heterologous glandular differentiation** [1]. - This is a distinct subtype and does not correspond to the definition of a Triton tumour. *Osseous* - An MPNST with **osseous differentiation** (bone formation) would be classified as an **MPNST with heterologous osteosarcomatous differentiation** [1]. - This is another example of heterologous differentiation but is not what defines a Triton tumour. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1250-1251. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1224-1225.

Q: Muscle biopsy shows ragged red fibers on modified Gomori trichrome stain. Which enzyme defect is most likely?

Complex I. ***Complex I*** - **Ragged red fibers** on modified Gomori trichrome stain are the pathological hallmark of **mitochondrial myopathies** [1] - **Complex I (NADH-CoQ reductase) deficiency** is the **most common cause** of mitochondrial disease, accounting for approximately 30-40% of all cases - Complex I deficiency is the **most frequent cause of ragged red fibers** in muscle biopsies - Associated clinical features include progressive muscle weakness, exercise intolerance, lactic acidosis, and encephalomyopathy (Leigh syndrome) [1] - The ragged red appearance results from subsarcolemmal accumulation of abnormal mitochondria attempting to compensate for defective oxidative phosphorylation *Complex II* - **Complex II (succinate dehydrogenase) deficiency** is a relatively rare cause of mitochondrial myopathy - More commonly associated with hereditary paraganglioma-pheochromocytoma syndromes and certain cancers - Can cause ragged red fibers but is much less common than Complex I deficiency - The only complex entirely encoded by nuclear DNA (not mitochondrial DNA) *Complex III* - **Complex III (ubiquinol-cytochrome c reductase) deficiency** is a rare cause of mitochondrial disease - Can present with myopathy and ragged red fibers, but accounts for only a small percentage of mitochondrial disorders - Associated with exercise intolerance and multisystem involvement when present *Complex IV* - **Complex IV (cytochrome c oxidase, COX) deficiency** can cause mitochondrial myopathy with ragged red fibers [1] - However, it is **less common than Complex I deficiency** as a cause of ragged red fibers - COX-deficient fibers can be identified using specific COX histochemical staining [1] - Associated with Leigh syndrome and other encephalomyopathies, but not the **most likely** cause when ragged red fibers are present **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1305-1306.

Q: A 60-year-old man presents with severe joint pain and swelling, and his uric acid levels are elevated. Which histological feature is characteristic of this condition?

Tophi with needle-shaped crystals. ***Tophi with needle-shaped crystals*** - The presence of **tophi**, which are aggregations of **monosodium urate crystals**, is pathognomonic for **gout**, especially in cases with elevated uric acid and severe joint pain [1]. - These crystals often appear **needle-shaped** under polarized light microscopy and are surrounded by a **foreign body giant cell reaction** [1]. *Chondrocyte necrosis* - **Chondrocyte necrosis** is more characteristic of **osteoarthritis** or other forms of cartilage damage, where the cartilage cells die due to mechanical stress or degenerative processes. - While it can be seen in advanced joint disease, it is not specific to the **hyperuricemia** and crystal deposition seen in gout. *Pannus formation* - **Pannus formation** is a hallmark of **rheumatoid arthritis**, where inflamed synovial tissue invades and erodes cartilage and bone. - It is composed of aggressive **fibroblasts, macrophages**, and **lymphocytes**, and is distinct from the crystal deposits found in gout. *Synovial hyperplasia* - **Synovial hyperplasia** (thickening of the synovial lining) is a common feature in many inflammatory arthropathies, including **gout, rheumatoid arthritis**, and other conditions [1]. - It is a **non-specific** finding and does not differentiate gout from other joint diseases as effectively as **urate crystal deposition** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1216-1220.

Q: A patient with multiple fractures and blue sclerae is suspected of having osteogenesis imperfecta. What genetic mutation is most commonly associated with this condition?

COL1A1. ***COL1A1*** - **Osteogenesis imperfecta** is primarily caused by mutations in the genes encoding **Type I collagen**, specifically **COL1A1** and **COL1A2**. - Mutations in **COL1A1** account for the **majority of cases** (~60-70%), with COL1A2 mutations responsible for most remaining cases, and lead to defective collagen synthesis or structure, resulting in brittle bones and other connective tissue abnormalities like **blue sclerae** [1]. - The defective collagen weakens bone matrix, leading to the characteristic **multiple fractures** with minimal trauma [2]. *BRCA1* - **BRCA1** is a tumor suppressor gene associated with an increased risk of developing **breast cancer** and **ovarian cancer**. - Mutations in **BRCA1** play no role in the pathogenesis of osteogenesis imperfecta or collagen synthesis. *RB1* - **RB1** is a tumor suppressor gene linked to **retinoblastoma**, a rare childhood eye cancer, and other malignancies. - Mutations in **RB1** are not involved in collagen synthesis or bone formation. *P53* - **P53** is a critical tumor suppressor gene often termed the "guardian of the genome," playing a role in cell cycle arrest, apoptosis, and DNA repair. - While fundamental in cancer biology, mutations in **P53** are not associated with osteogenesis imperfecta. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-672. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1188.

Q: A young patient is diagnosed with osteosarcoma. Which region of the long bones is most commonly affected?

Metaphysis. ***Correct: Metaphysis*** - The **metaphysis** is the most common site for osteosarcoma development due to its rich vascular supply and high rate of osteoblastic activity during bone growth. - This region is actively growing and undergoing rapid cell division, making it more susceptible to malignant transformation. - Osteosarcoma most commonly affects the metaphyseal region around the knee (distal femur and proximal tibia). *Incorrect: Epiphysis* - The **epiphysis** is the end part of a long bone, initially separated from the main bone by cartilage but later fused with it. - While other tumors like **chondroblastoma** and **giant cell tumor** can occur here, osteosarcoma is rarely found in this region. *Incorrect: Diaphysis* - The **diaphysis** is the main shaft of a long bone, consisting of compact bone. - While other bone tumors like **Ewing sarcoma** commonly affect the diaphysis, osteosarcoma is less frequent in this area compared to the metaphysis. *Incorrect: Articular surface* - The **articular surface** is covered with cartilage and is involved in joint articulation. - Tumors rarely originate directly from the articular cartilage or surface, and osteosarcoma has no predilection for this region.

Q: A patient presents with blue sclera and a history of frequent fractures. Which genetic disorder should be suspected based on these findings?

Osteogenesis imperfecta. ***Osteogenesis imperfecta*** - **Blue sclera** is a classic sign due to the thinness of the sclera revealing the underlying choroidal veins, and **frequent fractures** are caused by defective collagen synthesis. - This disorder is a group of genetic conditions primarily affecting **type I collagen**, which is crucial for bone and connective tissue formation. *Marfan syndrome* - Characterized by tall stature, **arachnodactyly**, long limbs, and abnormalities of the **cardiovascular system** (e.g., aortic dissection) and eyes (e.g., lens dislocation). - While it affects connective tissue, it does not typically present with blue sclera or bone fragility as primary symptoms. *Ehlers-Danlos syndrome* - Features include **skin hyperextensibility**, **joint hypermobility**, and tissue fragility, often leading to easy bruising and poor wound healing [1]. - Unlike osteogenesis imperfecta, **blue sclera** and recurrent fractures are not hallmark features [1]. *Rickets* - A condition caused by **vitamin D deficiency** leading to impaired bone mineralization, resulting in bone softening and deformities. - It does not involve blue sclera and is typically seen in children, while osteogenesis imperfecta is a genetic disorder presenting from birth.

Question 1

Not a true statement about Osteoclastoma

Accepted Answer

Originates in the metaphyseal region of bones

Answer

Benign bone tumor

Answer

Usually solitary

Answer

Common in age between 20-40 years

Question 2

A 50-year-old male patient presented with weakness of bilateral lower limbs which was symmetrical (distal weakness >> proximal muscle weakness) for 1 month. On examination, certain skin and nail changes were noted. Patient also complained of myalgia and arthralgia. Lab findings: Raised creatinine kinase levels, Raised ANA antibody titre. Muscle biopsy was done from the quadriceps femoris muscle. CD4+ cells were found in the cellular infiltrate. IHC study of which protein is a very sensitive diagnostic test for the above condition?

Accepted Answer

Myxovirus resistance protein

Answer

Adenovirus resistance protein

Answer

Parvovirus resistance protein

Answer

Papovavirus resistance protein

Question 3

In rheumatoid arthritis, which type of cells are prominently involved in the pathogenesis?

Accepted Answer

CD4+ helper cells

Answer

Lymphocyte

Answer

Macrophages

Answer

Dendritic cells

Question 4

Which of the following is the most important infiltrate in rheumatoid arthritis?

Accepted Answer

Macrophages

Answer

Dendritic cells

Answer

CD4+ Helper cells

Answer

Neutrophils

Question 5

Malignant peripheral nerve sheath tumour showing which of the following differentiation is termed as 'Triton tumour'?

Accepted Answer

Rhabdomyoblastic

Answer

Cartilaginous

Answer

Glandular

Answer

Osseous

Question 6

Muscle biopsy shows ragged red fibers on modified Gomori trichrome stain. Which enzyme defect is most likely?

Accepted Answer

Complex I

Answer

Complex IV

Answer

Complex II

Answer

Complex III

Question 7

A 60-year-old man presents with severe joint pain and swelling, and his uric acid levels are elevated. Which histological feature is characteristic of this condition?

Accepted Answer

Tophi with needle-shaped crystals

Answer

Chondrocyte necrosis

Answer

Pannus formation

Answer

Synovial hyperplasia

Question 8

A patient with multiple fractures and blue sclerae is suspected of having osteogenesis imperfecta. What genetic mutation is most commonly associated with this condition?

Accepted Answer

COL1A1

Answer

BRCA1

Answer

RB1

Answer

P53

Question 9

A young patient is diagnosed with osteosarcoma. Which region of the long bones is most commonly affected?

Accepted Answer

Metaphysis

Answer

Epiphysis

Answer

Diaphysis

Answer

Articular surface

Question 10

A patient presents with blue sclera and a history of frequent fractures. Which genetic disorder should be suspected based on these findings?

Accepted Answer

Osteogenesis imperfecta

Answer

Marfan syndrome

Answer

Ehlers-Danlos syndrome

Answer

Rickets

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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