Dermatology Board Certification Exam 2026: ABD Professional
Practice Test — Medical Dermatology, Dermatopathology, Skin
Oncology, Paediatric Dermatology, Immunohematology & Clinical
Management — 190 Multiple-Choice Questions with Answers &
Detailed Rationales
SECTION 1: BASIC SCIENCE AND DERMATOPATHOLOGY (Questions 1-25)
Question 1
A 45-year-old woman presents with a pearly, translucent papule with telangiectasias on her
nasal tip. Histopathology reveals nests of basaloid cells with peripheral palisading and
retraction artifact. Which molecular pathway is most commonly dysregulated in this
condition?
A. RAS-MAPK signaling pathway
B. Hedgehog signaling pathway
C. Wnt/β-catenin signaling pathway
D. PI3K-AKT-mTOR signaling pathway
Correct Answer: B
Explanation: Basal cell carcinoma pathogenesis involves dysregulation of the Hedgehog
signaling pathway, typically through PTCH1 mutations, leading to constitutive activation of
Smoothened. Clinical pearl: Hedgehog inhibitors like vismodegib target this pathway.
Question 2
A 32-year-old man presents with hypopigmented macules on his trunk that fluoresce coral-
red under Wood's lamp examination. KOH preparation reveals short hyphae and spores.
What is the causative organism?
,A. Trichophyton rubrum
B. Microsporum canis
C. Malassezia furfur
D. Epidermophyton floccosum
Correct Answer: C
Explanation: Malassezia furfur causes tinea versicolor, presenting with hypopigmented or
hyperpigmented macules showing coral-red fluorescence and "spaghetti and meatballs"
appearance on KOH. Best practice: Treat with selenium sulfide or topical azoles.
Question 3
A 28-year-old woman presents with violaceous, flat-topped papules on her wrists and
ankles. Histopathology shows a band-like lymphocytic infiltrate at the dermoepidermal
junction with saw-tooth rete ridges. Which condition is most likely?
A. Discoid lupus erythematosus
B. Lichen planus
C. Psoriasis vulgaris
D. Pityriasis rosea
Correct Answer: B
Explanation: Lichen planus classically presents with the 6 P's: purple, polygonal, planar,
pruritic, papules, and plaques. Histology shows band-like lymphocytic infiltrate and saw-
tooth rete ridges. Clinical pearl: Associated with hepatitis C.
Question 4
,A 55-year-old man presents with a rapidly growing, ulcerated nodule on his scalp. Biopsy
reveals atypical spindle cells with numerous mitoses and prominent vascularity. Which
immunohistochemical marker would most likely be positive?
A. S100 protein
B. CD34
C. Cytokeratin 20
D. Melan-A
Correct Answer: B
Explanation: This describes angiosarcoma, which expresses CD34, CD31, and factor VIII-
related antigen. Clinical pearl: Angiosarcoma can be associated with chronic lymphedema or
prior radiation therapy.
Question 5
A 3-year-old boy presents with grouped, translucent, 1-2 mm vesicles on an erythematous
base in the diaper area. Tzanck smear reveals multinucleated giant cells. What is the most
likely causative organism?
A. Varicella-zoster virus
B. Herpes simplex virus type 1
C. Coxsackievirus A16
D. Human papillomavirus
Correct Answer: B
, Explanation: Herpes simplex virus causes grouped vesicles with multinucleated giant cells on
Tzanck smear. In children, HSV-1 is common in the diaper area from autoinoculation. Best
practice: Confirm with viral culture or PCR.
Question 6
A 62-year-old woman presents with a slowly growing, flesh-colored, dome-shaped nodule
with central crateriform invagination on her face. Histopathology shows lobules of basaloid
cells with ductal differentiation. Which condition is most likely?
A. Basal cell carcinoma
B. Squamous cell carcinoma
C. Keratoacanthoma
D. Trichoblastoma
Correct Answer: C
Explanation: Keratoacanthoma presents as a rapidly growing nodule with a central keratin-
filled crater, often on sun-exposed skin. Clinical pearl: May spontaneously regress but is
often treated to exclude SCC.
Question 7
A 40-year-old man presents with generalized erythroderma, lymphadenopathy, and
circulating Sézary cells. Skin biopsy shows epidermotropism with Pautrier microabscesses.
What is the most likely diagnosis?
A. Psoriasis vulgaris
B. Atopic dermatitis
C. Sézary syndrome
Practice Test — Medical Dermatology, Dermatopathology, Skin
Oncology, Paediatric Dermatology, Immunohematology & Clinical
Management — 190 Multiple-Choice Questions with Answers &
Detailed Rationales
SECTION 1: BASIC SCIENCE AND DERMATOPATHOLOGY (Questions 1-25)
Question 1
A 45-year-old woman presents with a pearly, translucent papule with telangiectasias on her
nasal tip. Histopathology reveals nests of basaloid cells with peripheral palisading and
retraction artifact. Which molecular pathway is most commonly dysregulated in this
condition?
A. RAS-MAPK signaling pathway
B. Hedgehog signaling pathway
C. Wnt/β-catenin signaling pathway
D. PI3K-AKT-mTOR signaling pathway
Correct Answer: B
Explanation: Basal cell carcinoma pathogenesis involves dysregulation of the Hedgehog
signaling pathway, typically through PTCH1 mutations, leading to constitutive activation of
Smoothened. Clinical pearl: Hedgehog inhibitors like vismodegib target this pathway.
Question 2
A 32-year-old man presents with hypopigmented macules on his trunk that fluoresce coral-
red under Wood's lamp examination. KOH preparation reveals short hyphae and spores.
What is the causative organism?
,A. Trichophyton rubrum
B. Microsporum canis
C. Malassezia furfur
D. Epidermophyton floccosum
Correct Answer: C
Explanation: Malassezia furfur causes tinea versicolor, presenting with hypopigmented or
hyperpigmented macules showing coral-red fluorescence and "spaghetti and meatballs"
appearance on KOH. Best practice: Treat with selenium sulfide or topical azoles.
Question 3
A 28-year-old woman presents with violaceous, flat-topped papules on her wrists and
ankles. Histopathology shows a band-like lymphocytic infiltrate at the dermoepidermal
junction with saw-tooth rete ridges. Which condition is most likely?
A. Discoid lupus erythematosus
B. Lichen planus
C. Psoriasis vulgaris
D. Pityriasis rosea
Correct Answer: B
Explanation: Lichen planus classically presents with the 6 P's: purple, polygonal, planar,
pruritic, papules, and plaques. Histology shows band-like lymphocytic infiltrate and saw-
tooth rete ridges. Clinical pearl: Associated with hepatitis C.
Question 4
,A 55-year-old man presents with a rapidly growing, ulcerated nodule on his scalp. Biopsy
reveals atypical spindle cells with numerous mitoses and prominent vascularity. Which
immunohistochemical marker would most likely be positive?
A. S100 protein
B. CD34
C. Cytokeratin 20
D. Melan-A
Correct Answer: B
Explanation: This describes angiosarcoma, which expresses CD34, CD31, and factor VIII-
related antigen. Clinical pearl: Angiosarcoma can be associated with chronic lymphedema or
prior radiation therapy.
Question 5
A 3-year-old boy presents with grouped, translucent, 1-2 mm vesicles on an erythematous
base in the diaper area. Tzanck smear reveals multinucleated giant cells. What is the most
likely causative organism?
A. Varicella-zoster virus
B. Herpes simplex virus type 1
C. Coxsackievirus A16
D. Human papillomavirus
Correct Answer: B
, Explanation: Herpes simplex virus causes grouped vesicles with multinucleated giant cells on
Tzanck smear. In children, HSV-1 is common in the diaper area from autoinoculation. Best
practice: Confirm with viral culture or PCR.
Question 6
A 62-year-old woman presents with a slowly growing, flesh-colored, dome-shaped nodule
with central crateriform invagination on her face. Histopathology shows lobules of basaloid
cells with ductal differentiation. Which condition is most likely?
A. Basal cell carcinoma
B. Squamous cell carcinoma
C. Keratoacanthoma
D. Trichoblastoma
Correct Answer: C
Explanation: Keratoacanthoma presents as a rapidly growing nodule with a central keratin-
filled crater, often on sun-exposed skin. Clinical pearl: May spontaneously regress but is
often treated to exclude SCC.
Question 7
A 40-year-old man presents with generalized erythroderma, lymphadenopathy, and
circulating Sézary cells. Skin biopsy shows epidermotropism with Pautrier microabscesses.
What is the most likely diagnosis?
A. Psoriasis vulgaris
B. Atopic dermatitis
C. Sézary syndrome
