**Question:** Commonest manifestation of retinoblastoma is -

A. Intraocular mass
B. Proptosis
C. Infiltration of adjacent tissues
D. Systemic manifestations

**Correct Answer:** D. Systemic manifestations

**Core Concept:** Retinoblastoma is a rare and aggressive form of childhood cancer that originates in the retina of the eye. It arises due to mutations in the RB1 gene, which is responsible for regulating cell growth and division.

**Why the Correct Answer is Right:** Retinoblastoma can lead to systemic manifestations due to the fact that it is a highly malignant tumor that can invade surrounding tissues, invade the optic nerve, and spread to other parts of the body. When the tumor is not treated promptly, it can lead to the following systemic manifestations:

1. **Option A (Intraocular mass):** The primary manifestation of retinoblastoma is the presence of an intraocular mass in the affected eye. This mass can lead to vision loss, inflammation, and even rupture of the eye, which can result in severe pain and systemic complications.
2. **Option B (Proptosis):** Proptosis occurs when the tumor enlarges and pushes the eyeball forward, causing protrusion of the eye. Though proptosis can be a sign of retinoblastoma, it is not the primary manifestation and can be present concurrently with other symptoms.
3. **Option C (Infiltration of adjacent tissues):** Retinoblastoma can infiltrate adjacent tissues, causing inflammation and leading to glaucoma, cataract formation, and optic nerve compression, which may result in vision loss and blindness. However, this option also focuses on the consequences of the tumor rather than its primary manifestation.
4. **Option D (Systemic manifestations):** The primary manifestation of retinoblastoma includes the presence of an intraocular mass and the subsequent complications mentioned above. Systemic manifestations arise when the tumor spreads to other parts of the body, leading to:
- Liver and bone marrow involvement: Retinoblastoma can spread to the liver and bone marrow, causing anemia, thrombocytopenia, and leukopenia. These manifestations can be confused with other hematological disorders like leukemia, resulting in misdiagnosis.
- Skin, lung, and bone involvement: Retinoblastoma can also spread to the skin, lungs, and bones, causing pain, swelling, and bone deformities.

**Why Each Wrong Option is Incorrect:**

1. **Option A (Intraocular mass):** Although an intraocular mass is a primary manifestation, it is not a systemic manifestation.
2. **Option B (Proptosis):** Proptosis is a consequence of the tumor's mass effect on surrounding tissues, not a primary manifestation.
3. **Option C (Infiltration of adjacent tissues):** While infiltration of adjacent tissues is a consequence of the primary manifestation (intraocular mass), it is not a standalone manifestation.

**Why Option D is Right:** Systemic manifestations are critical for diagnosing retinoblastoma