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10. Pathology and Oncology MCQs

Practice Set 182 of 351

This practice set contains high-yield board review questions covering key concepts in 10. Pathology and Oncology. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3621

Topic: 10. Pathology and Oncology

A 25-year-old female with known Ollier disease presents with new-onset deep-seated pain in her proximal humerus. Radiographs show an enlarging lucent lesion with endosteal scalloping. What is the estimated lifetime risk of malignant transformation to chondrosarcoma in patients with Ollier disease?

. Less than 1%
. 5-10%
. 25-40%
. Over 90%
. 0%; Ollier disease is strictly benign

Correct Answer & Explanation

. 25-40%

Explanation

Correct Answer: CWhile solitary enchondromas have a very low risk of malignant transformation (<1%), patients with Enchondromatosis (Ollier disease) have a significantly higher risk, often cited between 25% and 40%. In Maffucci syndrome, the risk of skeletal and extra-skeletal malignancy is even higher.

Question 3622

Topic: Bone Tumors

Maffucci syndrome is distinguished from Ollier disease by the presence of which of the following clinical features?

. Autosomal dominant inheritance pattern
. Soft tissue hemangiomas
. Precocious puberty
. Polyostotic fibrous dysplasia
. Blue sclera and dentinogenesis imperfecta

Correct Answer & Explanation

. Soft tissue hemangiomas

Explanation

Correct Answer: BMaffucci syndrome is characterized by multiple enchondromas (similar to Ollier disease) plus soft tissue hemangiomas (often spindle-cell hemangiomas). Both conditions are non-hereditary and result from somatic mutations (IDH1 or IDH2).

Question 3623

Topic: 10. Pathology and Oncology
A 9-year-old girl presents with a 'ground-glass' lesion in the femoral neck and large, irregular café-au-lait spots with 'Coast of Maine' borders. Which molecular mechanism is responsible for this condition?
. Inactivation of the TSC1 gene
. Constitutive activation of the alpha subunit of the Gs stimulatory protein
. Loss of function in the NF1 tumor suppressor gene
. Mutation in the FGFR3 receptor
. Defect in the COL1A1 gene

Correct Answer & Explanation

. Constitutive activation of the alpha subunit of the Gs stimulatory protein

Explanation

The patient has McCune-Albright syndrome (fibrous dysplasia, café-au-lait spots, and endocrinopathies). This is caused by a somatic mutation in the GNAS1 gene, which leads to constitutive activation of the Gs-alpha protein, resulting in overproduction of intracellular cAMP and anarchic bone development.

Question 3624

Topic: Bone Tumors

A 14-year-old patient with polyostotic fibrous dysplasia presents with a progressive varus deformity of the proximal femur (Shepherd's crook deformity). What is the most appropriate surgical strategy to prevent recurrence?

. Isolated curettage and bone grafting with allograft
. Valgus osteotomy and fixation with a dynamic hip screw
. Valgus osteotomy and stabilization with an intramedullary nail
. External fixation with gradual distraction osteogenesis
. Observation until skeletal maturity

Correct Answer & Explanation

. Valgus osteotomy and stabilization with an intramedullary nail

Explanation

Correct Answer: CFor the Shepherd's crook deformity in Fibrous Dysplasia, the gold standard is a valgus-producing osteotomy to improve mechanical alignment, stabilized by an intramedullary device. Intramedullary nails are preferred over plates because they provide better support for the entire weakened diaphysis and are less likely to fail in the 'ground-glass' bone.

Question 3625

Topic: 10. Pathology and Oncology

Dysplasia Epiphysealis Hemimelica (Trevor disease) is best described as:

. A malignant transformation of an enchondroma
. An osteochondroma-like overgrowth arising from an epiphysis
. A generalized failure of primary spongiosa resorption
. A form of dwarfism involving the rhizomelic segments
. A vitamin D resistant metabolic bone disease

Correct Answer & Explanation

. An osteochondroma-like overgrowth arising from an epiphysis

Explanation

Correct Answer: BTrevor disease (DEH) is a rare developmental disorder characterized by asymmetric osteochondromatous overgrowth of one or more epiphyses. It most commonly affects the medial side of the ankle or knee joints.

Question 3626

Topic: 10. Pathology and Oncology

An adult patient with Multiple Hereditary Exostoses (MHE) undergoes an MRI for a rapidly enlarging pelvic mass. Which of the following MRI findings is most suggestive of malignant transformation to chondrosarcoma?

. A cartilage cap thickness of 5 mm
. Presence of internal 'popcorn' calcifications
. A cartilage cap thickness exceeding 2 cm
. The lesion is pedunculated rather than sessile
. The lesion is located in a distal phalanx

Correct Answer & Explanation

. A cartilage cap thickness exceeding 2 cm

Explanation

Correct Answer: CIn a skeletally mature patient, a cartilage cap thickness greater than 1.5 to 2.0 cm on MRI is highly suspicious for malignant transformation into secondary chondrosarcoma. Other signs include new pain, growth after skeletal maturity, and associated soft tissue masses.

Question 3627

Topic: Bone Tumors
A 9-year-old girl presents with a pathologic proximal femur fracture, precocious puberty, and large, irregular "coast of Maine" café-au-lait spots. The underlying pathophysiology involves which of the following?
. Inactivating mutation in the EXT1 gene
. Activating mutation of the GNAS gene increasing intracellular cAMP
. Mutation in the Gsa protein decreasing intracellular cAMP
. Chromosomal translocation t(11;22)
. Mutation in the RUNX2 gene

Correct Answer & Explanation

. Activating mutation of the GNAS gene increasing intracellular cAMP

Explanation

McCune-Albright syndrome is characterized by polyostotic fibrous dysplasia, endocrine abnormalities, and café-au-lait spots. It is caused by a somatic activating mutation in the GNAS gene, leading to elevated cAMP levels.

Question 3628

Topic: Bone Tumors
A 9-year-old girl presents with precocious puberty, café-au-lait spots with irregular borders, and a "shepherd's crook" deformity of the proximal femur. Which of the following accurately describes the underlying molecular defect?
. Post-zygotic activating mutation in the GNAS1 gene
. Germline inactivating mutation in the EXT1 gene
. Germline mutation in the NF1 gene
. Post-zygotic mutation in the PIK3CA gene
. Inactivating mutation in the PTEN gene

Correct Answer & Explanation

. Post-zygotic activating mutation in the GNAS1 gene

Explanation

McCune-Albright syndrome is characterized by polyostotic fibrous dysplasia, café-au-lait spots (Coast of Maine), and endocrinopathies like precocious puberty. It is caused by a somatic (post-zygotic) activating mutation in the GNAS1 gene.

Question 3629

Topic: Bone Tumors
A 9-year-old girl is diagnosed with McCune-Albright syndrome after presenting with polyostotic fibrous dysplasia, a large café-au-lait macule with irregular borders, and early breast development. The GNAS1 gene mutation in this disorder results in the overactivity of which of the following signaling pathways?
. Wnt/beta-catenin pathway
. Transforming growth factor-beta (TGF-beta) pathway
. cAMP generation via the Gs-alpha protein
. Receptor tyrosine kinase signaling
. MAP kinase signaling pathway

Correct Answer & Explanation

. cAMP generation via the Gs-alpha protein

Explanation

McCune-Albright syndrome is caused by a somatic activating mutation in the GNAS1 gene. This leads to constitutive activation of the Gs-alpha protein, resulting in unregulated overproduction of intracellular cAMP, which drives the endocrine and skeletal abnormalities.

Question 3630

Topic: Bone Tumors
An 8-year-old girl with precocious puberty and large café-au-lait spots presents with a progressive 'shepherd's crook' deformity of the proximal femur. What is the most appropriate surgical management for this deformity?
. Curettage and autologous bone grafting
. Bisphosphonate therapy alone
. Valgus-producing osteotomy with intramedullary nailing
. Proximal femoral replacement
. Open reduction and internal fixation with a dynamic hip screw

Correct Answer & Explanation

. Valgus-producing osteotomy with intramedullary nailing

Explanation

The diagnosis is McCune-Albright syndrome (Fibrous Dysplasia). Lesions resorb bone grafts and often cause plate/screw failure; the gold standard is valgus-producing osteotomy stabilized with an intramedullary nail.

Question 3631

Topic: Bone Tumors

A 5-year-old boy presents with a hard, painless swelling on the medial aspect of his right ankle, limiting range of motion. Radiographs show an irregular, lobulated bony mass arising exclusively from the medial epiphysis of the distal tibia. What is the most likely diagnosis?

. Osteochondroma
. Ollier disease
. Trevor disease (Dysplasia Epiphysealis Hemimelica)
. Chondrodysplasia punctata
. Melorheostosis

Correct Answer & Explanation

. Trevor disease (Dysplasia Epiphysealis Hemimelica)

Explanation

Trevor disease (Dysplasia Epiphysealis Hemimelica) is characterized by an asymmetric osteochondroma-like overgrowth arising from an epiphysis, most commonly affecting the ankle or knee in young children.

Question 3632

Topic: 10. Pathology and Oncology

Which of the following is a common early sign of infection following flexor tendon repair, requiring prompt evaluation?

. Slight numbness in the fingertip.
. Mild swelling that resolves with elevation.
. Serous drainage from the wound with no associated pain.
. Increasing pain, erythema, swelling, and warmth around the surgical site.
. Inability to achieve full passive range of motion.

Correct Answer & Explanation

. Increasing pain, erythema, swelling, and warmth around the surgical site.

Explanation

The classic signs of infection (rubor, tumor, dolor, calor - redness, swelling, pain, warmth) are crucial indicators. Increasing pain, erythema, swelling, and warmth around the surgical site, especially if accompanied by fever or purulent drainage, are clear signs of a potential infection and warrant immediate evaluation and treatment. Numbness could be nerve irritation, mild swelling is common post-op, serous drainage without pain is often normal, and limited passive ROM points to stiffness/adhesions, not typically early infection.

Question 3633

Topic: Bone Tumors

A 35-year-old male with a history of X-linked recessive spondyloepiphyseal dysplasia tarda presents with worsening joint pain and stiffness in his hips and knees. Which of the following is a known long-term complication associated with this condition?

. Progressive arthropathy
. Osteosarcoma
. Recurrent pathological fractures
. Avascular necrosis of the scaphoid
. Charcot neuroarthropathy

Correct Answer & Explanation

. Progressive arthropathy

Explanation

Correct Answer: Progressive arthropathySpondyloepiphyseal dysplasia tarda (SEDt) is an osteochondrodysplasia that can be associated with progressive arthropathy, leading to significant joint pain and stiffness in adulthood.

Question 3634

Topic: 10. Pathology and Oncology

A 35-year-old male with a history of X-linked recessive Spondyloepiphyseal Dysplasia Tarda presents to the orthopedic clinic. Which of the following long-term musculoskeletal complications is most strongly associated with this condition as the patient ages?

. Progressive arthropathy
. Recurrent pathological fractures
. Malignant transformation to chondrosarcoma
. Severe heterotopic ossification

Correct Answer & Explanation

. Progressive arthropathy

Explanation

Correct Answer: Progressive arthropathySpondyloepiphyseal dysplasia tarda is frequently associated with progressive arthropathy, particularly affecting the hips and spine, leading to early-onset osteoarthritis and significant morbidity in adulthood.

Question 3635

Topic: 10. Pathology and Oncology

Which of the following immune cells is characterized by its ability to directly lyse virally infected cells and tumor cells without prior sensitization or the need for MHC presentation, playing a crucial role in the initial defense against these threats?

. Neutrophils
. Macrophages
. Natural Killer (NK) cells
. B lymphocytes
. CD4+ T lymphocytes

Correct Answer & Explanation

. Natural Killer (NK) cells

Explanation

Natural Killer (NK) cells are cytotoxic lymphocytes of the innate immune system. They can recognize and kill virally infected cells and tumor cells directly, primarily by sensing a lack of MHC class I molecules or the presence of activating ligands on target cells, without the need for specific antigen presentation. Neutrophils and macrophages are phagocytes, B lymphocytes produce antibodies, and CD4+ T lymphocytes are helper cells in the adaptive immune response.

Question 3636

Topic: 10. Pathology and Oncology

Regarding the adaptive immune system's response to infection, which of the following statements accurately differentiates the primary role of CD4+ T helper cells from CD8+ cytotoxic T lymphocytes (CTLs)?

. CD4+ T cells directly kill virus-infected cells, while CD8+ T cells primarily activate B cells.
. CD4+ T cells recognize antigens presented on MHC Class I, while CD8+ T cells recognize antigens on MHC Class II.
. CD4+ T cells regulate and enhance other immune responses, while CD8+ T cells directly kill target cells.
. CD4+ T cells are responsible for antibody production, while CD8+ T cells produce cytokines.
. CD4+ T cells are part of the innate immunity, while CD8+ T cells are part of the adaptive immunity.

Correct Answer & Explanation

. CD4+ T cells regulate and enhance other immune responses, while CD8+ T cells directly kill target cells.

Explanation

CD4+ T helper cells (Th cells) primarily recognize antigens presented on MHC Class II molecules by antigen-presenting cells (APCs). Their main role is to regulate and enhance various immune responses by secreting cytokines, which activate B cells, macrophages, and CD8+ T cells. CD8+ cytotoxic T lymphocytes (CTLs) primarily recognize antigens presented on MHC Class I molecules and are responsible for directly killing target cells (e.g., virally infected cells, tumor cells) through cytotoxic mechanisms.

Question 3637

Topic: 10. Pathology and Oncology

Which of the following cytokines is known for its potent anti-inflammatory and immunosuppressive properties, playing a key role in dampening immune responses and promoting immune tolerance, often produced by regulatory T cells and macrophages?

. Interleukin-1 (IL-1)
. Interleukin-6 (IL-6)
. Tumor Necrosis Factor-alpha (TNF-alpha)
. Interleukin-10 (IL-10)
. Interferon-gamma (IFN-gamma)

Correct Answer & Explanation

. Interleukin-10 (IL-10)

Explanation

Interleukin-10 (IL-10) is a well-known anti-inflammatory cytokine. It is primarily produced by regulatory T cells (Tregs), macrophages, and other immune cells, and it plays a critical role in limiting and terminating inflammatory responses. IL-10 inhibits the production of pro-inflammatory cytokines, suppresses antigen presentation, and generally dampens immune cell activation, thereby contributing to immune tolerance. The other cytokines listed are generally pro-inflammatory.

Question 3638

Topic: 10. Pathology and Oncology
A 30-year-old male presents with acute onset of joint pain and swelling following a recent bout of urethritis (Reiter's Syndrome/Reactive Arthritis). This condition is often associated with HLA-B27. Which class of MHC molecules does HLA-B27 belong to, and what is its primary function in antigen presentation?
. MHC Class II; presents exogenous antigens to CD4+ T cells.
. MHC Class I; presents endogenous antigens to CD8+ T cells.
. MHC Class II; presents endogenous antigens to CD8+ T cells.
. MHC Class I; presents exogenous antigens to CD4+ T cells.
. MHC Class III; involved in complement activation.

Correct Answer & Explanation

. MHC Class I; presents endogenous antigens to CD8+ T cells.

Explanation

HLA-B27 is an allele of MHC Class I molecules. MHC Class I molecules are expressed on virtually all nucleated cells and primarily present endogenous antigens (peptides derived from intracellular proteins, including viral or bacterial antigens processed within the cell) to CD8+ cytotoxic T lymphocytes. This interaction is critical for immune surveillance against intracellular pathogens and tumor cells. In reactive arthritis, it's thought that specific peptides from bacterial pathogens presented by HLA-B27 might trigger an autoimmune response.

Question 3639

Topic: Bone Tumors

A patient undergoing chemotherapy for osteosarcoma develops neutropenia. This significantly increases their risk of bacterial infections. Which of the following is the predominant mechanism by which neutrophils combat bacterial pathogens?

. Producing large quantities of antibodies to neutralize bacteria.
. Presenting bacterial antigens to T lymphocytes.
. Phagocytosis, degranulation of antimicrobial substances, and formation of neutrophil extracellular traps (NETs).
. Secreting anti-inflammatory cytokines to dampen the immune response.
. Directly lysing infected host cells using perforin and granzymes.

Correct Answer & Explanation

. Phagocytosis, degranulation of antimicrobial substances, and formation of neutrophil extracellular traps (NETs).

Explanation

Neutrophils are the most abundant granulocytes and are crucial first responders to bacterial infections. Their primary mechanisms of action include: 1) Phagocytosis: engulfing and destroying bacteria; 2) Degranulation: releasing antimicrobial substances (e.g., defensins, lysozyme) from their granules into phagolysosomes or extracellularly; and 3) Formation of Neutrophil Extracellular Traps (NETs): releasing decondensed chromatin decorated with antimicrobial proteins to trap and kill pathogens. They do not primarily produce antibodies, present antigens, or directly lyse host cells.

Question 3640

Topic: 10. Pathology and Oncology

A novel immunotherapy for musculoskeletal tumors is being investigated, focusing on enhancing anti-tumor immunity. Which of the following is a primary mechanism by which tumor cells often evade immune surveillance?

. Overexpression of MHC Class I molecules, making them highly visible to T cells.
. Increased production of co-stimulatory molecules (e.g., B7-1, B7-2).
. Downregulation of MHC Class I molecules and expression of immune checkpoint ligands (e.g., PD-L1).
. Secretion of pro-inflammatory cytokines that enhance T-cell activation.
. Activation of the complement system to destroy themselves.

Correct Answer & Explanation

. Downregulation of MHC Class I molecules and expression of immune checkpoint ligands (e.g., PD-L1).

Explanation

Tumor cells employ various strategies to evade immune surveillance. A common mechanism is the downregulation of MHC Class I molecules, which makes them less visible to CD8+ cytotoxic T lymphocytes (the primary anti-tumor immune cells). Additionally, many tumors express immune checkpoint ligands such as PD-L1 (Programmed Death-Ligand 1), which binds to PD-1 on T cells, leading to T-cell exhaustion and inhibition of the anti-tumor immune response. This is why checkpoint inhibitors are an effective form of cancer immunotherapy.

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