**Core Concept**
Pemphigus is a group of autoimmune skin diseases characterized by the formation of blisters (bullae) due to the breakdown of adhesion between epithelial cells. Acantholytic cells are a hallmark of pemphigus, where keratinocytes are detached from each other and from the underlying basement membrane.

**Why the Correct Answer is Right**
Acantholytic cells in pemphigus are derived from keratinocytes, which are a type of epithelial cell found in the epidermis. The autoantibodies in pemphigus target desmoglein proteins, which are essential for cell-to-cell adhesion. When these autoantibodies bind to desmoglein proteins, they disrupt the intercellular connections between keratinocytes, leading to acantholysis and the formation of blisters. The affected keratinocytes become detached from each other and from the basement membrane, resulting in the characteristic acantholytic cells seen in pemphigus.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because acantholytic cells are specifically derived from keratinocytes, not from melanocytes, which are a different type of epithelial cell responsible for producing melanin.

**Option B:** This option is incorrect because acantholytic cells are not derived from fibroblasts, which are a type of cell found in the dermis and are responsible for producing collagen and other extracellular matrix proteins.

**Option C:** This option is incorrect because acantholytic cells are not derived from dendritic cells, which are a type of immune cell involved in antigen presentation.

**Clinical Pearl / High-Yield Fact**
Acantholytic cells are a key diagnostic feature of pemphigus, and their presence can help distinguish pemphigus from other blistering skin diseases. In addition, the presence of autoantibodies against desmoglein proteins can provide further evidence of pemphigus.

**Correct Answer:** C. Keratinocytes