Dermatopathology Practice Questions

Q: A patient presents with multiple, pearly papules on the face. Biopsy reveals a malignant tumor. Which of the following microscopic features would most likely be observed?

Palisading nuclei. **Explanation:** The clinical presentation of **pearly papules** on the face, often with telangiectasia, is the classic description of **Basal Cell Carcinoma (BCC)**, the most common skin cancer. **Why the correct answer is right:** The hallmark histopathological feature of BCC is the presence of nests or islands of basaloid cells (cells with large, dark nuclei and scant cytoplasm). At the periphery of these nests, the nuclei align themselves in a parallel, fence-like arrangement known as **peripheral palisading**. Additionally, a characteristic "retraction artifact" (clefting) is often seen between the tumor nests and the surrounding stroma. **Why the incorrect options are wrong:** * **A. Cytoplasmic viral inclusions:** These are characteristic of viral infections like Molluscum Contagiosum (Henderson-Patterson bodies) or HPV (koilocytes), not malignant tumors like BCC. * **B. Keratin:** While BCC can occasionally show focal keratinization (Basosquamous variant), **Keratin pearls** are the pathognomonic feature of **Squamous Cell Carcinoma (SCC)**. * **C. Melanin:** While "Pigmented BCC" exists, melanin is the defining feature of **Melanoma**. In a general question about pearly papules, palisading is the more specific diagnostic marker for BCC. **High-Yield NEET-PG Pearls:** * **Most common site:** Upper 2/3rd of the face (above the line joining the earlobe to the angle of the mouth). * **Risk Factor:** Chronic UV exposure; also associated with **Gorlin Syndrome** (PTCH gene mutation). * **Behavior:** Locally invasive ("Rodent ulcer") but rarely metastasizes. * **Treatment of choice:** Surgical excision or Mohs Micrographic Surgery (for high-risk areas).

Q: An epidermal cyst is lined by which type of epithelium?

Stratified squamous epithelium. **Explanation:** An **epidermal cyst** (also known as an epidermal inclusion cyst or sebaceous cyst) is the most common cutaneous cyst. It originates from the follicular infundibulum. 1. **Why the correct answer is right:** The wall of an epidermal cyst is composed of **stratified squamous epithelium** that is identical to the surface epidermis. This lining includes a distinct **granular cell layer**. As the cells mature and shed into the cyst cavity, they form laminated layers of **keratin**, which constitutes the "cheesy" white material found inside. 2. **Why the incorrect options are wrong:** * **Transitional epithelium:** Found in the urinary tract (urothelium); it allows for stretching. It is not found in cutaneous cysts. * **Columnar epithelium:** Typically lines the gastrointestinal tract or respiratory tract. While found in some developmental cysts (like bronchogenic cysts), it does not line epidermal cysts. * **Cuboidal epithelium:** Found in glandular ducts or the thyroid. It is not a feature of true epidermal cysts. **High-Yield Clinical Pearls for NEET-PG:** * **Punctum:** A characteristic central pore or "opening" is often visible on the surface, representing the plugged follicle. * **Histology Tip:** The presence of a **granular layer** distinguishes an epidermal cyst from a **pilar cyst** (trichilemmal cyst), which lacks a granular layer and undergoes "abrupt keratinization." * **Gardner Syndrome:** Multiple epidermal cysts, especially in unusual locations (like the face or scalp), are a clinical marker for Gardner Syndrome (associated with familial adenomatous polyposis). * **Rupture:** If the cyst wall ruptures, the keratin acts as an irritant, leading to a painful foreign-body giant cell reaction (pseudoinflammation).

Q: Which of the following is a melanocytic marker?

HMB-45. **Explanation:** **HMB-45 (Human Melanoma Black-45)** is a highly specific monoclonal antibody used in immunohistochemistry (IHC) to identify melanocytic lesions [1]. It reacts against **gp100**, a glycoprotein found in the stage II premelanosomes of melanocytes. It is particularly useful in diagnosing malignant melanoma, as it typically stains fetal melanocytes and melanoma cells, but is usually negative in normal adult resting melanocytes and intradermal nevi (except for "blue nevi"). **Analysis of Incorrect Options:** * **CD99 (MIC2):** This is a cell surface glycoprotein and a classic marker for **Ewing’s Sarcoma** and Primitive Neuroectodermal Tumors (PNET). It is also seen in lymphoblastic lymphoma and synovial sarcoma. * **NMP-22 (Nuclear Matrix Protein 22):** This is a tumor marker used primarily in the screening and monitoring of **Bladder Cancer** (Urothelial carcinoma) via urine samples. * **CA-125 (Cancer Antigen 125):** This is a well-known tumor marker for **Ovarian Cancer** (specifically epithelial types like serous cystadenocarcinoma). **High-Yield Clinical Pearls for NEET-PG:** * **Other Melanocytic Markers:** Apart from HMB-45, other high-yield markers include **S-100** (most sensitive but least specific), **Melan-A (MART-1)**, **Tyrosinase**, and **SOX10** (highly sensitive for spindle cell and desmoplastic melanomas). * **HMB-45 Utility:** It is excellent for distinguishing melanoma from other "small round blue cell tumors" or undifferentiated carcinomas [1]. * **Negative Marker:** Remember that **Desmoplastic Melanoma** is often negative for HMB-45 but positive for S-100 and SOX10. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1146-1152.

Question 1

A 74-year-old woman has noted increasing size and number of darker brown patches on the dorsum of each hand for the past 15 years. They do not change with sun exposure, are nonpruritic, and non-tender. On examination, these 0.5- to 1-cm lightly pigmented lesions are flat. Which of the following is the most likely microscopic finding in these lesions?

Accepted Answer

Basal melanocytic hyperplasia

Answer

Dermal nevus cells

Answer

Loss of melanin in surrounding skin

Answer

Mast cell proliferation

Question 2

Which mutation is seen in malignant melanoma?

Accepted Answer

CDKN2A

Answer

N-MYC

Answer

RB gene

Answer

p53

Question 3

A patient presents with multiple, pearly papules on the face. Biopsy reveals a malignant tumor. Which of the following microscopic features would most likely be observed?

Accepted Answer

Palisading nuclei

Answer

Cytoplasmic viral inclusions

Answer

Keratin

Answer

Melanin

Question 4

A 60-year-old diabetic female presented with a burning sensation aggravated by spicy food. Intraoral examination revealed multiple periodontal abscesses and a keratotic area in a lace pattern with occasional erosive areas within the lace pattern. What histological feature would be expected?

Accepted Answer

Saw-tooth rete ridges

Answer

Elongated rete ridges

Answer

Flattened rete ridges

Answer

Bulbous rete ridges

Question 5

An epidermal cyst is lined by which type of epithelium?

Accepted Answer

Stratified squamous epithelium

Answer

Transitional epithelium

Answer

Columnar epithelium

Answer

Cuboidal epithelium

Question 6

Which of the following is NOT true about dysplastic nevus syndrome?

Accepted Answer

It is inherited in an autosomal recessive pattern.

Answer

Approximately half of such patients develop melanoma by age 60.

Answer

It is associated with mutations in BRAF and NRAS.

Answer

It is a disorder characterized by numerous dysplastic nevi.

Question 7

A 66-year-old woman presents with a 6-month history of scaling and abnormal pigmentation of the skin. Her past medical history is significant for the treatment of thyroid cancer 1 year ago. Biopsy of lesional skin shows atrophy of the epidermis and dense fibrosis of the dermis, which displays dilated superficial blood vessels. These pathologic findings are most likely caused by previous exposure to which of the following?

Accepted Answer

Radiation therapy

Answer

Chemotherapy

Answer

Corticosteroids

Answer

Organic iodine

Question 8

Which of the following is a melanocytic marker?

Accepted Answer

HMB-45

Answer

CD99

Answer

NMP-22

Answer

CA-125

Question 9

Which is the most severe form of malignant melanoma?

Accepted Answer

Nodular infiltrating type melanoma

Answer

Superficially spreading melanoma

Answer

Melanoma arising in lower limb

Answer

Melanoma arising in choroid

Question 10

Which type of carcinoma is characterized by no or minimal metastasis?

Accepted Answer

Basal cell carcinoma

Answer

Squamous cell carcinoma

Answer

Melanoma

Answer

Leydig's cell carcinoma

Dermatopathology — MCQs

Dermatopathology — MCQs

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