**Core Concept**
Lichen planus is a chronic inflammatory mucocutaneous condition characterized by a T-cell mediated immune response, leading to damage of the basal layer of the epidermis. The exact pathogenesis involves a complex interplay between immune cells, keratinocytes, and the release of various cytokines and chemokines.

**Why the Correct Answer is Right**
The most characteristic feature of lichen planus is the presence of **colloidal bodies**, also known as Civatte bodies or apoptotic bodies, which are seen in the basal layer of the epidermis. These are small, homogeneous, basophilic structures that represent the remnants of necrotic keratinocytes. The formation of colloidal bodies is thought to be a result of the immune-mediated damage to the basal layer, leading to apoptosis of keratinocytes. This is a hallmark feature of lichen planus and can be seen on histopathological examination.

**Why Each Wrong Option is Incorrect**
* **Option A:** While lichen planus can involve the oral mucosa, the presence of oral lesions is not the most characteristic feature of the condition.
* **Option B:** The presence of a lichenoid reaction pattern can be seen in various conditions, including contact dermatitis and graft-versus-host disease, but it is not specific to lichen planus.
* **Option C:** The presence of a hyperkeratotic scale is more characteristic of psoriasis than lichen planus.

**Clinical Pearl / High-Yield Fact**
Lichen planus is often associated with other autoimmune conditions, such as alopecia areata and vitiligo. A patient with lichen planus is more likely to have another autoimmune condition, making it essential to look for these associations in clinical practice.

**Correct Answer:** C. Colloidal bodies.