Parakeratosis most frequently occurs in which of the following conditions?
Q62
Acantholytic cells in pemphigus are derived from:
Q63
Pautrier's microabscess is a histological feature of which disease?
Q64
Birbeck granules in the cytoplasm are characteristic of which cells?
Q65
A 27-year-old woman has developed areas of scaling skin over the past month. On physical examination, there are 1- to 3-cm light pink plaques covered with silvery scale on her arms and torso. A punch biopsy of one lesion, examined microscopically, shows keratinocyte nuclei retained within cells in the stratum corneum. Which of the following descriptive terms best applies to this microscopic finding?
Dermatopathology Indian Medical PG Practice Questions and MCQs
Question 61: Parakeratosis most frequently occurs in which of the following conditions?
A. Actinic keratosis (Correct Answer)
B. Seborrheic keratosis
C. Molluscum contagiosum
D. Basal cell carcinoma
Explanation: ***Actinic keratosis***
- **Actinic keratosis** is a precancerous lesion caused by chronic sun exposure, characterized microscopically by **parakeratosis** (retained nuclei in the stratum corneum) and epidermal dysplasia [1], [2].
- The abnormal maturation of keratinocytes due to **UV damage** leads to the incomplete differentiation seen as parakeratosis [1].
*Seborrheic keratosis*
- This is a benign epidermal tumor characterized by **keratinocyte proliferation**, often appearing as "stuck-on" lesions.
- Microscopically, it typically shows **hyperkeratosis (orthokeratosis)** and acanthosis, **not parakeratosis** as a feature.
*Molluscum contagiosum*
- This is a viral skin infection caused by a **poxvirus**, presenting as umbilicated papules [3].
- Histologically, it is characterized by large, eosinophilic **Molluscum bodies** within keratinocytes, without prominent parakeratosis [3].
*Basal cell carcinoma*
- This is a common **skin cancer** originating from basal cells of the epidermis.
- Histological features include nests of basaloid cells with peripheral palisading and retraction artifact, generally **lacking parakeratosis** unless there is secondary inflammation or ulceration.
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1156.
[2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 644-645.
[3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1177-1178.
Question 62: Acantholytic cells in pemphigus are derived from:
A. Stratum spinosum (Correct Answer)
B. Stratum basale
C. Stratum granulosum
D. Langerhans cells
Explanation: Acantholytic cells in pemphigus are keratinocytes that have lost their desmosomal attachments due to autoimmune destruction, primarily affecting the integrity of the stratum spinosum [1]. This layer is characterized by abundant desmosomes, and their disruption leads to the characteristic intraepidermal blistering seen in pemphigus [2]. While pemphigus can affect the basal layer in some forms (like pemphigus vegetans), the primary acantholytic process occurs above this layer, leading to suprabasal cleavage [1]. The stratum granulosum lies above the stratum spinosum and contains keratohyalin granules and lamellar granules, which are essential for skin barrier function. While cells from all epidermal layers can eventually slough off, acantholysis itself primarily originates from the more adhesive cells of the stratum spinosum. Langerhans cells are dendritic antigen-presenting cells found predominantly in the stratum spinosum but are not keratinocytes. While they play a role in immune surveillance, they are not the cells that undergo acantholysis or form the bulk of the epidermal layers [3].
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1170-1172.
[2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 645-646.
[3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.
Question 63: Pautrier's microabscess is a histological feature of which disease?
A. Sarcoidosis
B. Tuberculosis
C. Mycosis fungoides (Correct Answer)
D. Pityriasis lichenoides chronica
Explanation: ***Mycosis fungoides***
- **Pautrier's microabscesses** (intraepidermal collections of neoplastic T-lymphocytes) are a characteristic histological hallmark of **mycosis fungoides**, a cutaneous T-cell lymphoma [1].
- These collections are typically seen in the **epidermis**, especially in the patch and plaque stages of the disease, reflecting the **epidermotropism** of the malignant T-cells [1].
*Sarcoidosis*
- Characterized by **non-caseating granulomas** in various organs, including the skin.
- **Pautrier's microabscesses** are not a feature of sarcoidosis.
*Tuberculosis*
- Identified by the presence of **caseating granulomas** composed of epithelioid cells, lymphocytes, and Langerhans giant cells.
- It does not involve the formation of **intraepidermal microabscesses** of lymphocytes.
*Pityriasis lichenoides chronica*
- A benign inflammatory skin condition characterized by a **lymphocytic vasculitis** and interface dermatitis.
- Histology shows a **wedge-shaped inflammatory infiltrate** in the dermis with interface changes, but not Pautrier's microabscesses.
**References:**
[1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 564-565.
Question 64: Birbeck granules in the cytoplasm are characteristic of which cells?
A. Neutrophils
B. Natural killer cells
C. Eosinophils
D. Langerhans cells (Correct Answer)
Explanation: ***Langerhans cells***
- Characterized by the presence of **Birbeck granules**, which are unique to these dendritic cells [1].
- These granules can be identified via **electron microscopy** and play a role in antigen presentation [1].
*Natural killer cells*
- Primarily involved in the **innate immune response** against viral infections and tumors.
- Do not contain **Birbeck granules**; instead, they have different cytoplasmic granules containing **perforin and granzymes**.
*Neutrophil*
- Part of the **acute inflammatory response** and primarily involved in **phagocytosis** of pathogens.
- Neutrophils contain **azurophilic granules** but lack Birbeck granules entirely.
*Eosinophil*
- Involved in the response to **parasitic infections** and **allergic reactions**, characterized by **bilobed nuclei** and granules containing major basic protein.
- Eosinophils do not possess **Birbeck granules**; their granules are specific to their function against allergens and parasites.
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 630.
Question 65: A 27-year-old woman has developed areas of scaling skin over the past month. On physical examination, there are 1- to 3-cm light pink plaques covered with silvery scale on her arms and torso. A punch biopsy of one lesion, examined microscopically, shows keratinocyte nuclei retained within cells in the stratum corneum. Which of the following descriptive terms best applies to this microscopic finding?
A. Acanthosis (thickened epidermis)
B. Dyskeratosis (abnormal keratinization below stratum granulosum)
C. Hyperkeratosis (thickened stratum corneum without nuclei)
D. Parakeratosis (nuclear retention in stratum corneum) (Correct Answer)
Explanation: ***Parakeratosis***
- The finding of **retained keratinocyte nuclei** in the stratum corneum indicates parakeratosis, typically seen in conditions like psoriasis [1].
- This reflects **impaired maturation of keratinocytes**, leading to an abnormality in the shedding process.
*Hyperkeratosis*
- Refers to **thickening of the stratum corneum** without the presence of retained nuclei.
- Commonly found in chronic skin conditions but doesn't capture the **nuclear retention** seen here.
*Acanthosis*
- Describes **thickening of the epidermis** due to increased cell proliferation, primarily in the basal layer.
- It does not relate to the presence of nuclei in the stratum corneum, which is specific to parakeratosis.
*Dyskeratosis*
- Refers to **abnormal keratinization** that occurs within the confines of the epidermis, not at the surface.
- This term does not accurately describe the finding of retained nuclei in the **stratum corneum**.
**References:**
[1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 640-641.
