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 the 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?

**Core Concept**
The underlying principle being tested is the histopathological hallmark of a specific skin condition characterized by abnormal keratinization and retention of nuclei within the stratum corneum. This condition is a form of psoriasis, a chronic inflammatory skin disease.

**Why the Correct Answer is Right**
The correct answer is related to the characteristic microscopic feature of psoriasis, which is the presence of nuclei within the stratum corneum. This is due to the abnormal keratinization process, where keratinocytes undergo premature differentiation and retain their nuclei within the stratum corneum. This is a result of the increased proliferation and turnover of keratinocytes in the epidermis, which is driven by the abnormal expression of pro-inflammatory cytokines and transcription factors.

**Why Each Wrong Option is Incorrect**
**Option A:** Parakeratosis is a term used to describe the retention of nuclei within the stratum corneum, but it is a more general term and not specific to psoriasis.

**Option B:** Hyperkeratosis refers to an increase in the thickness of the stratum corneum, which can be seen in various skin conditions, including psoriasis. However, it does not specifically describe the retention of nuclei within the stratum corneum.

**Option C:** Dyskeratosis is a term used to describe the abnormal maturation of keratinocytes, but it is not the correct term to describe the retention of nuclei within the stratum corneum.

**Option D:** Orthokeratosis is a term used to describe the normal maturation of keratinocytes, where nuclei are lost within the stratum corneum.

**Clinical Pearl / High-Yield Fact**
A mnemonic to remember the histopathological features of psoriasis is "KOPP": Keratinocyte proliferation, Orthohypergranulosis (thickening of the granular layer), Parakeratosis (retention of nuclei within the stratum corneum), and Pustules (in some cases).

**Correct Answer: C. Dyskeratosis**

✓ Correct Answer: D. Parakeratosis