**Core Concept**
Endocervical sampling is a diagnostic procedure used during colposcopy to collect cells from the cervical canal, which can help in the early detection of cervical cancer or its precursors. This procedure is particularly useful in cases where the colposcopy findings are inconclusive or when there is a high suspicion of cancer.

**Why the Correct Answer is Right**
The correct answer involves a situation where endocervical sampling is recommended during colposcopy. This typically occurs when the colposcopy findings are **atypical squamous cells of undetermined significance (ASC-US)** or **low-grade squamous intraepithelial lesions (LSIL)**, but the endocervical canal appears abnormal, such as having a **glandular cell abnormality** or **cervical glandular neoplasia**. In such cases, the endocervical sampling can help in obtaining a more definitive diagnosis by examining the cells from the cervical canal.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, so we cannot provide a reason why it is incorrect.
* **Option B:** Endocervical sampling may not be recommended in cases where the colposcopy findings are **negative for intraepithelial lesions or malignancy (NILM)**, as the risk of cancer is low in these cases.
* **Option C:** While endocervical sampling can be performed in cases of **high-grade squamous intraepithelial lesions (HSIL)**, it may not be necessary in all cases, and other diagnostic procedures may be more appropriate.

**Clinical Pearl / High-Yield Fact**
When performing endocervical sampling, it is essential to use a **Cotton swab or a cytobrush** to collect cells from the cervical canal, taking care not to push the swab too far into the canal to avoid causing bleeding or other complications.

**Correct Answer: C.**