Mohs Micrographic Surgery — MCQs
A 10 cm tumor is found on the anterior surface of the thigh. What is the most appropriate procedure to obtain a diagnosis?
Which of the following nevi has the highest risk of malignant transformation to melanoma?
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Shave biopsy is not done in:
Unna boot is used for the treatment of which condition?
Which of the following is NOT true regarding patch testing?
A 45-year-old farmer presents with a 3-year history of itchy, erythematous papular lesions on the face, neck, 'V' area of the chest, and the dorsum of the hands and forearms. The lesions are more severe in the summer and improve significantly in the winter. What is the most appropriate diagnostic test for this condition?
Patch test is done to document which type of hypersensitivity?
A 19-year-old man develops a rash in the groin area. On examination, it is a large well-demarcated area of tan-brown discoloration around his left inguinal area. There is some scaling of the lesion when brushed with a tongue depressor. Which of the following is the most appropriate initial diagnostic test?
What is the best method to treat large port-wine hemangiomas?
Mohs Micrographic Surgery Indian Medical PG Practice Questions and MCQs
Question 1: A 10 cm tumor is found on the anterior surface of the thigh. What is the most appropriate procedure to obtain a diagnosis?
- A. Incision biopsy (Correct Answer)
- B. Excision biopsy
- C. FNAC
- D. USG
Explanation: ***Incision biopsy*** - An **incision biopsy** is most appropriate for a large tumor (10 cm) to obtain a tissue diagnosis without performing a potentially morbid or disfiguring complete excision upfront. - It involves removing a representative section of the tumor for histopathological analysis, providing adequate tissue for diagnosis, grading, and subtyping. - This allows definitive treatment planning based on confirmed histopathology. *Excision biopsy* - **Excision biopsy** is generally reserved for smaller tumors (typically <3-5 cm) that can be completely resected with acceptable cosmetic and functional outcomes. - Excision of a 10 cm tumor on the thigh would be a significant surgical procedure, potentially causing substantial morbidity, without a prior definitive diagnosis. - Could compromise subsequent definitive surgery if margins are inadequate. *FNAC* - **FNAC (Fine Needle Aspiration Cytology)** provides only cytological diagnosis, which is insufficient for definitive diagnosis, grading, and subtyping of soft tissue tumors, especially sarcomas. - It misses crucial architectural features and tissue patterns needed for accurate classification. - May yield inadequate or non-diagnostic samples from large heterogeneous tumors. *USG* - **USG (Ultrasound)** is an imaging modality, not a tissue diagnosis procedure. - While useful for characterizing mass features (size, location, vascularity, solid vs cystic), it cannot provide histopathological diagnosis. - The question specifically asks for a procedure to "obtain a diagnosis," which requires tissue sampling for microscopic examination.
Question 2: Which of the following nevi has the highest risk of malignant transformation to melanoma?
- A. Congenital nevus (Correct Answer)
- B. Dermal nevus
- C. Junctional nevus
- D. Lentigo nevus
Explanation: ***Junctional nevus*** - Junctional nevi are located at the **epidermal-dermal junction** and have a higher potential for **malignant transformation into melanoma** compared to other types of nevi [1,2]. - They often present as flat, pigmented lesions, making them distinguishable and more likely to undergo **dysplastic changes** associated with melanoma [1,4]. *Dermal nevus* - Dermal nevi are located deeper in the **dermis** and have a **lower risk** of transformation into melanoma [2]. - They are usually dome-shaped and lack the architectural changes that indicate a potential for malignancy [3]. *Lentigo nevus* - Lentigo nevi are generally benign pigmented lesions that result from **increased melanocyte activity** and are not typically associated with melanoma. - Although they can appear in sun-exposed areas, their risk for malignant transformation remains **minimal**. *Congenital nevus* - Congenital nevi can vary in size and may have some potential for **melanoma transformation**, but this risk is generally lower than that for junctional nevi. - Larger congenital nevi have a higher risk, yet they do not specifically relate to **common malignant transformation** compared to junctional nevi. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1146-1150. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 649-650. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 648-649.
Question 3: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 4: Shave biopsy is not done in:
- A. Seborrheic keratoses
- B. Basal cell carcinoma
- C. Melanoma (Correct Answer)
- D. Viral warts
Explanation: ***Melanoma*** - **Shave biopsy is absolutely contraindicated for suspected melanoma** because it does not provide sufficient depth to accurately measure **Breslow thickness**, which is the most important prognostic factor. - An **excisional biopsy with 1-3mm margins** down to subcutaneous fat is the gold standard to ensure complete histological evaluation and accurate staging. - Inadequate depth sampling can lead to **understaging, incorrect prognosis, and inappropriate treatment planning**. *Basal cell carcinoma* - Shave biopsy **can be performed** for basal cell carcinoma and is commonly used for diagnostic purposes, especially for **superficial and nodular types**. - While punch or excisional biopsy may be preferred for morpheaform or infiltrative subtypes to assess depth, shave biopsy is not contraindicated and provides adequate tissue for diagnosis in most cases. *Seborrheic keratoses* - **Shave biopsy is ideal** for seborrheic keratoses as they are **benign, superficial epidermal growths**. - The technique allows for complete removal and histological confirmation with excellent cosmetic outcomes. *Viral warts* - **Shave biopsy can be used** for diagnosis and treatment of viral warts, particularly for **exophytic lesions**. - The superficial nature of warts makes shave excision an appropriate and effective method.
Question 5: Unna boot is used for the treatment of which condition?
- A. Diabetic foot ulcer
- B. Varicose ulcers (Correct Answer)
- C. Ankle instability
- D. Calcaneum fracture
Explanation: **Explanation:** The **Unna boot** is a specialized compression dressing used primarily for the management of **venous stasis ulcers (varicose ulcers)**. It consists of a zinc oxide-impregnated bandage, often containing calamine and glycerin, which is wrapped around the lower leg from the base of the toes to just below the knee. **Why it is the correct answer:** The mechanism of action is based on **compression therapy**. As the bandage dries, it becomes semi-rigid. When the patient walks, the calf muscles contract against this rigid barrier, significantly enhancing the **musculovenous pump** efficiency. This reduces venous hypertension, decreases edema, and promotes the healing of chronic venous ulcers. **Analysis of Incorrect Options:** * **Diabetic foot ulcer:** These are primarily neuropathic or ischemic. Treatment focuses on offloading pressure (e.g., total contact casts) and revascularization, rather than the semi-rigid compression provided by an Unna boot. * **Ankle instability:** This requires mechanical stabilization via braces, taping, or surgical intervention to protect ligaments, not a medicated compression wrap. * **Calcaneum fracture:** Fractures require rigid immobilization (plaster casts) or surgical fixation. An Unna boot does not provide sufficient structural support for bone healing. **High-Yield Clinical Pearls for NEET-PG:** * **Composition:** Zinc oxide (promotes healing), Calamine (soothes skin), and Glycerin. * **Contraindication:** It should **not** be used in patients with severe Peripheral Arterial Disease (ABI < 0.5) as compression can worsen ischemia. * **Application:** It is typically changed once a week. * **Gold Standard:** While Unna boots are classic, multilayer compression wraps are now often considered the gold standard for venous ulcers.
Question 6: Which of the following is NOT true regarding patch testing?
- A. Used to diagnose allergic contact dermatitis
- B. Readings are typically taken after 48 hours
- C. False negative results can occur in patients with angry back syndrome (Correct Answer)
- D. The T.R.U.E. test is a type of patch test
Explanation: **Explanation:** **1. Why Option C is the correct answer (The False Statement):** **Angry Back Syndrome** (also known as **Excited Skin Syndrome**) refers to a state of skin hyper-reactivity where a strong positive reaction at one patch test site triggers non-specific positive reactions at other sites. Therefore, it leads to **false-positive** results, not false-negative results. This occurs because the skin's threshold for irritation is lowered globally due to a localized severe inflammatory response. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** Patch testing is the **gold standard** for diagnosing Type IV (delayed-type) hypersensitivity reactions, specifically **Allergic Contact Dermatitis (ACD)**. * **Option B:** In a standard protocol, patches are applied for **48 hours**, removed, and the first reading is taken. a second reading is typically taken at **72–96 hours** to identify delayed reactions. * **Option D:** The **T.R.U.E. test** (Thin-layer Rapid Use Epicutaneous test) is a widely used, standardized, ready-to-use patch testing system containing common allergens impregnated into polyester patches. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Type IV Hypersensitivity (Cell-mediated). * **Prick Test vs. Patch Test:** Prick tests are for Type I (IgE-mediated) reactions (e.g., asthma, urticaria), while Patch tests are for Type IV. * **Grading (ICDRG):** * **+:** Weak (non-vesicular) reaction (erythema, infiltration). * **++:** Strong (vesicular) reaction. * **+++:** Extreme (bullous) reaction. * **IR:** Irritant reaction (usually sharply demarcated, "burned" appearance). * **Contraindication:** Testing should not be done during an acute flare-up of dermatitis or if the patient is on high-dose systemic corticosteroids (usually >15-20mg prednisolone).
Question 7: A 45-year-old farmer presents with a 3-year history of itchy, erythematous papular lesions on the face, neck, 'V' area of the chest, and the dorsum of the hands and forearms. The lesions are more severe in the summer and improve significantly in the winter. What is the most appropriate diagnostic test for this condition?
- A. Patch test (Correct Answer)
- B. Skin biopsy
- C. Intradermal prick test
- D. Estimation of IgE levels in blood
Explanation: ### Explanation **Diagnosis: Parthenium Dermatitis (Airborne Contact Dermatitis)** The clinical presentation of itchy, erythematous papules in a "photo-distributed" pattern (face, neck, 'V' area of chest, and dorsum of hands/forearms) in a farmer, with seasonal exacerbation in summer, is classic for **Parthenium Dermatitis**. This is a type of **Airborne Contact Dermatitis (ABCD)** caused by the weed *Parthenium hysterophorus*. **1. Why Patch Test is the Correct Answer:** Parthenium dermatitis is a **Type IV (Delayed-type) Hypersensitivity reaction**. The gold standard for diagnosing Type IV hypersensitivity is the **Patch Test**. It identifies the specific allergen (usually the sesquiterpene lactone in Parthenium) responsible for the T-cell mediated allergic response. **2. Why Other Options are Incorrect:** * **Skin Biopsy:** While it may show features of eczematous dermatitis (spongiosis), it is non-specific and cannot identify the causative allergen. * **Intradermal Prick Test:** This is used to diagnose **Type I (Immediate) Hypersensitivity** (e.g., asthma, allergic rhinitis). It is not used for contact dermatitis. * **Estimation of IgE levels:** IgE is a marker for Type I hypersensitivity and atopic conditions. It has no diagnostic value in Type IV hypersensitivity reactions like ABCD. **Clinical Pearls for NEET-PG:** * **Distribution:** Unlike true photodermatitis, ABCD often involves the **upper eyelids, nasolabial folds, and retroauricular areas** (the "shadow regions"), as pollen/dust can settle there. * **Common Allergen:** In India, *Parthenium hysterophorus* (Congress grass) is the most common cause. * **Management:** Avoidance of the allergen is key. Topical steroids and sun protection are used for symptomatic relief. In chronic cases, azathioprine may be used as a steroid-sparing agent.
Question 8: Patch test is done to document which type of hypersensitivity?
- A. Type I hypersensitivity
- B. Delayed type hypersensitivity (Correct Answer)
- C. Autoimmune disease
- D. Immunocomplex deposition
Explanation: ### Explanation **Correct Answer: B. Delayed type hypersensitivity** The **Patch Test** is the gold standard diagnostic tool for **Allergic Contact Dermatitis (ACD)**. ACD is a classic example of **Type IV Hypersensitivity** (also known as Delayed-type Hypersensitivity). * **Mechanism:** This reaction is **T-cell mediated** (specifically Th1 cells) rather than antibody-mediated. When an allergen contacts the skin of a sensitized individual, memory T-cells recognize the antigen, leading to the release of cytokines and subsequent inflammation. * **Timing:** Because it takes time for T-cell recruitment and cytokine production, the reaction typically peaks at **48 to 72 hours**, which is why patch test readings are performed at these intervals. --- ### Why other options are incorrect: * **A. Type I Hypersensitivity:** This is an immediate, IgE-mediated reaction (e.g., Anaphylaxis, Urticaria). It is tested using the **Skin Prick Test**, not the Patch Test. * **C. Autoimmune Disease:** While some autoimmune skin diseases (like Pemphigus) are diagnosed via Immunofluorescence (DIF/IIF), the patch test specifically identifies external allergens, not auto-antibodies against self-antigens. * **D. Immunocomplex Deposition:** This refers to **Type III Hypersensitivity** (e.g., SLE, Vasculitis). These are typically diagnosed via skin biopsy and direct immunofluorescence showing granular deposits (e.g., Lumpy-bumpy pattern). --- ### High-Yield Facts for NEET-PG: * **Standard Series:** The most commonly used series globally is the **European Standard Series**; in India, it is the **ISDR (Indian Standard Series)**. * **Commonest Allergen:** Globally, **Nickel** (found in artificial jewelry) is the most common allergen. In India, **Parthenium** (Congress grass) is a frequent cause of airborne contact dermatitis. * **Reading Schedule:** Readings are usually taken at **48 hours** (removal of patches) and **72 or 96 hours** (delayed reading). * **Open Patch Test:** Used for substances with potential irritancy or volatile compounds.
Question 9: A 19-year-old man develops a rash in the groin area. On examination, it is a large well-demarcated area of tan-brown discoloration around his left inguinal area. There is some scaling of the lesion when brushed with a tongue depressor. Which of the following is the most appropriate initial diagnostic test?
- A. Punch biopsy of skin
- B. Tzanck smear
- C. Potassium hydroxide (KOH) preparation of scrapings (Correct Answer)
- D. Blood culture for fungi
Explanation: ### Explanation The clinical presentation of a **well-demarcated, tan-brown, scaly lesion** in the inguinal area of a young man is highly suggestive of a superficial fungal infection, most likely **Tinea cruris** (jock itch). **1. Why KOH Preparation is Correct:** The **Potassium Hydroxide (KOH) preparation** is the gold standard initial diagnostic test for suspected fungal infections of the skin. When skin scrapings are treated with 10–20% KOH, the alkaline solution dissolves keratinocytes and debris, allowing for the clear visualization of fungal elements like **septate hyphae** or spores under a microscope. The "scaling when brushed" (positive scratch sign) indicates active fungal shedding or associated pityriasis, making KOH the most efficient and cost-effective bedside tool. **2. Why Other Options are Incorrect:** * **Punch Biopsy:** This is an invasive procedure used for deep inflammatory conditions or suspected malignancies. It is not indicated for a simple, superficial scaly rash. * **Tzanck Smear:** This is used for the diagnosis of **herpetic infections** (HSV, VZV) to look for multinucleated giant cells, not fungal infections. * **Blood Culture:** This is used for systemic/disseminated fungal infections (e.g., Candidemia). Superficial dermatophytosis does not involve the bloodstream. **3. High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** If the lesion showed **coral-red fluorescence** under Wood’s lamp, the diagnosis would be **Erythrasma** (caused by *Corynebacterium minutissimum*). * **Tinea Cruris vs. Candidiasis:** Tinea cruris typically **spares the scrotum**, whereas Candidal intertrigo involves the scrotum and presents with **satellite lesions**. * **Treatment:** First-line treatment for localized Tinea cruris is topical antifungals (e.g., Clotrimazole, Terbinafine). Avoid topical steroids as they lead to **Tinea incognito**.
Question 10: What is the best method to treat large port-wine hemangiomas?
- A. Radiotherapy
- B. Tattooing
- C. Excision with skin grafting
- D. Pulsed dye laser (Correct Answer)
Explanation: **Explanation:** **Pulsed Dye Laser (PDL)** is the gold standard treatment for Port-Wine Stains (PWS). The underlying medical concept is **Selective Photothermolysis**. The PDL (typically 585 or 595 nm) targets the chromophore **oxyhemoglobin** within the dilated dermal capillaries. The pulse duration is shorter than the thermal relaxation time of the vessels, allowing for targeted destruction of the vascular malformation without damaging the surrounding dermis. This results in significant lightening of the lesion with a very low risk of scarring. **Analysis of Incorrect Options:** * **Radiotherapy (A):** Historically used but now contraindicated due to the high risk of radiation-induced dermatitis, secondary malignancies (e.g., basal cell carcinoma), and permanent skin atrophy. * **Tattooing (B):** This involves injecting skin-colored pigments to mask the lesion. It is rarely used today because the pigment often looks unnatural, can shift over time, and does not address the underlying vascular pathology. * **Excision with skin grafting (C):** Port-wine stains are often large and involve the face. Surgical excision leads to significant scarring and "patchwork" cosmetic results, making it inferior to non-invasive laser therapy. **Clinical Pearls for NEET-PG:** * **Timing:** Treatment should ideally start in **infancy** (as early as weeks old) because the skin is thinner, the lesion is smaller, and the response to PDL is superior. * **Associated Syndromes:** Always rule out **Sturge-Weber Syndrome** (if the PWS involves the V1/V2 distribution of the trigeminal nerve) and **Klippel-Trenaunay Syndrome** (if involving an extremity with hypertrophy). * **Progression:** Unlike strawberry hemangiomas, PWS are **vascular malformations** that do not involute; they grow proportionately with the child and may become thickened or nodular (blebbing) in adulthood.
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