DPM Podiatric Pathology 1 — Questions and Answers

Question 1: What is the most common benign soft tissue tumor found in the foot?

Neuroma
Lipoma (Correct answer)
Fibroma
Sarcoma

Correct answer: Lipoma

A lipoma is a benign tumor composed of mature fat cells, making it the most common benign soft tissue tumor found in the body, including the foot. These tumors are typically soft, movable, and painless, growing slowly over time. While other benign tumors can occur, lipomas are statistically the most prevalent in the soft tissues of the foot.

Question 2: Which pathogen is most commonly associated with plantar warts?

Staphylococcus aureus
Candida albicans
Human papillomavirus (Correct answer)
Pseudomonas aeruginosa

Correct answer: Human papillomavirus

Plantar warts, which are common lesions on the soles of the feet, are caused by an infection with the Human papillomavirus (HPV). Specific strains of HPV, particularly types 1, 2, 4, and 63, are responsible for these growths. The virus enters the skin through small cuts or abrasions, leading to the characteristic rough, grainy texture of the wart.

Question 3: Which condition is characterized by the triad of arthritis, urethritis, and conjunctivitis and can affect the foot?

Gout
Psoriatic arthritis
Reactive arthritis (Correct answer)
Rheumatoid arthritis

Correct answer: Reactive arthritis

Reactive arthritis is an autoimmune condition triggered by an infection elsewhere in the body, often gastrointestinal or genitourinary. It is classically characterized by the triad of arthritis (inflammation of joints, commonly affecting the feet and ankles), urethritis (inflammation of the urethra), and conjunctivitis (inflammation of the eyes). This specific combination of symptoms distinguishes it from other forms of arthritis.

Question 4: Which bone tumor is most often found in the metaphyseal region of long bones and may involve the calcaneus?

Chondroblastoma (Correct answer)
Osteosarcoma
Giant cell tumor
Ewing sarcoma

Correct answer: Chondroblastoma

Chondroblastoma is a rare, benign bone tumor that typically arises in the epiphysis or apophysis of long bones, but can extend into the metaphysis. While it's most common in the knee and shoulder, it can also involve the calcaneus (heel bone) in the foot. Its characteristic location in the metaphyseal region of long bones, including those of the foot, makes it a key diagnostic consideration.

Question 5: What histological feature is most characteristic of diabetic foot ulcers?

Lymphocytic infiltration
Necrosis with bacterial colonies (Correct answer)
Caseating granulomas
Fibroblast proliferation

Correct answer: Necrosis with bacterial colonies

Diabetic foot ulcers are characterized by poor circulation, neuropathy, and impaired immune response, making them highly susceptible to infection. Histologically, these ulcers frequently show tissue necrosis (dead tissue) along with the presence of bacterial colonies, indicating a significant infectious component. This combination contributes to the slow healing and high risk of complications associated with diabetic foot ulcers.

Question 6: Which of the following is a hallmark microscopic finding in gouty arthritis affecting the toe joints?

Calcium pyrophosphate crystals
Amyloid deposits
Monosodium urate crystals (Correct answer)
Keratin pearls

Correct answer: Monosodium urate crystals

Gouty arthritis is caused by the deposition of monosodium urate crystals in the joints, particularly the first metatarsophalangeal joint of the big toe. These needle-shaped crystals trigger an intense inflammatory response, leading to acute pain, swelling, and redness. The microscopic identification of these specific crystals in synovial fluid or tissue is diagnostic for gout.

Question 7: Which type of ulcer is most commonly associated with peripheral arterial disease in the foot?

Venous ulcer
Arterial ulcer (Correct answer)
Diabetic neuropathic ulcer
Pressure ulcer

Correct answer: Arterial ulcer

Peripheral arterial disease (PAD) results in reduced blood flow to the extremities, particularly the feet and legs. This lack of oxygen and nutrients leads to the formation of arterial ulcers, which are typically painful, located on the toes or bony prominences, and have a 'punched-out' appearance. Unlike venous ulcers, arterial ulcers are characterized by poor circulation and often require revascularization for healing.

Question 8: What is the most likely diagnosis for a rapidly growing, painful lesion on the foot with frequent bleeding?

Melanoma
Kaposi's sarcoma
Pyogenic granuloma (Correct answer)
Basal cell carcinoma

Correct answer: Pyogenic granuloma

A pyogenic granuloma is a common, benign vascular lesion that presents as a rapidly growing, reddish, often pedunculated (stalk-like) papule or nodule. It is highly vascular and prone to frequent bleeding, even with minor trauma. Its rapid growth and tendency to bleed are key diagnostic features, distinguishing it from other lesions like melanoma or basal cell carcinoma which typically grow slower and may not bleed as readily.

Question 9: Which fungal infection is most commonly responsible for onychomycosis in the toenails?

Candida glabrata
Epidermophyton floccosum
Trichophyton rubrum (Correct answer)
Malassezia furfur

Correct answer: Trichophyton rubrum

Trichophyton rubrum is the most common dermatophyte responsible for causing onychomycosis, a fungal infection of the toenails. This fungus thrives in warm, moist environments and typically invades the nail plate from the hyponychium, leading to thickening, discoloration, and crumbling of the nail. It accounts for a significant majority of all onychomycosis cases worldwide.

DPM Podiatric Pathology 1

What is the most common benign soft tissue tumor found in the foot?