**Question:** Neck nodes are commonly seen with occult primary in -

A. Head and Neck Squamous Cell Carcinoma
B. Nasopharyngeal Carcinoma
C. Thyroid Cancer
D. Lung Cancer

**Core Concept:**
The term "occult primary" refers to a situation where a malignant tumor is initially diagnosed as a regional lymph node metastasis without the identification of a primary tumor site. In such cases, the most common primary sites are lungs, head and neck, nasopharynx, and thyroid gland.

**Why the Correct Answer is Right:**
In the context of neck nodes being commonly seen with occult primary, option D (Lung Cancer) is the correct answer because lung cancer is a common primary site for occult primary malignancies. The tumor cells can spread to regional lymph nodes via the lymphatic system before the primary tumor is identified.

**Why Each Wrong Option is Incorrect:**
A. Head and Neck Squamous Cell Carcinoma (Head and Neck SCC) is also a possible primary site for occult primary, but it is less common compared to lung cancer.
B. Nasopharyngeal Carcinoma (NPC) is a rare primary site for occult primary, and while it can present with neck lymphadenopathy, it is less prevalent than lung cancer.
C. Thyroid Cancer is a relatively rare primary site for occult primary, and while it can present with neck lymphadenopathy, it is less common compared to lung cancer.

**Clinical Pearl:**
A thorough clinical examination and appropriate investigations, including imaging studies, are essential in such cases to identify the primary tumor site and plan the appropriate management strategy. This may involve a combination of diagnostic workup, including imaging studies, biopsy, and possibly fine-needle aspiration cytology (FNAC) to establish the primary site.

**Correct Answer:** D. Lung Cancer