**Core Concept**
Postoperative radiotherapy is a treatment strategy used to eliminate residual cancer cells in the pelvis after surgery for endometrial carcinoma. The decision to use radiotherapy depends on various factors, including the depth of myometrial invasion, presence of lymph node metastasis, and involvement of the cervix.

**Why the Correct Answer is Right**
The presence of estrogen receptor (ER) positivity is not a direct indication for postoperative radiotherapy in endometrial carcinoma. ER positivity is actually a favorable prognostic factor, as it suggests that the tumor may respond well to hormonal therapy. However, the decision to use radiotherapy is based on the risk of local recurrence, which is influenced by factors such as myometrial invasion, lymph node status, and cervical involvement. ER status is not a critical factor in this decision.

**Why Each Wrong Option is Incorrect**
**Option A:** Myometrial invasion >1/2 thickness is a well-established indication for postoperative radiotherapy, as it increases the risk of local recurrence.

**Option B:** Positive lymph nodes are a strong indication for postoperative radiotherapy, as they indicate a higher risk of distant recurrence.

**Option C:** Endocervical involvement is a risk factor for local recurrence and is an indication for postoperative radiotherapy.

**Clinical Pearl / High-Yield Fact**
When considering postoperative radiotherapy for endometrial carcinoma, remember that the decision is based on the risk of local recurrence, which is influenced by factors such as myometrial invasion, lymph node status, and cervical involvement. ER status is a favorable prognostic factor, but not a direct indication for radiotherapy.

**Correct Answer:**
✓ Correct Answer: D. Tumor positive for estrogen receptors