Retinoblastoma in Adults - Recognizing and Treating a Rare Presentation

Introduction

Retinoblastoma is a rare retina tumor, a tissue located at the back of the eye, responsible for converting light signals into electrical signals. These signals are then sent to the brain, contributing to the sense of vision. This particular type of tumor is most commonly observed in children below the age of five. The occurrence of this tumor in adults is extremely rare. This tumor can develop due to a germline mutation of the RB1 (retinoblastoma protein 1) gene, or it can be a nonheritable condition. Heritable disorders can present early in life and affect both eyes, whereas nonheritable disorders manifest later in life and can affect only one eye.

What Are the Clinical Features Of Retinoblastoma in Adults?

The clinical features of retinoblastoma in adults include:

• Eye Discomfort: Adults affected by this condition may experience painful swelling in the affected eye. The swelling may gradually increase over time, accompanied by dull pain around the eye.

• Vision Changes: Affected individuals may experience blurriness or a decrease in vision. As the disease progresses, vision can become significantly impaired, potentially leading to blindness.

• Difficulty in Eye Movements: There can be challenges in moving the eye smoothly due to the presence of the tumor.

• Headaches: Some adults may experience headaches due to the pressure exerted by the tumor on surrounding structures.

What Is the Diagnosis of Retinoblastoma in Adults?

The diagnosis of retinoblastoma in adults includes:

1. Clinical Examination: A noticeable mass can be observed inside the affected eye. The eye may protrude more than usual, and the white part of the eye (sclera) becomes stretched. The blood vessels on the affected eye are dilated and swollen. The front part of the eye may be covered with red tissue. On palpation, the mass is soft and tender. The unaffected eye may not display any abnormality and may function normally.

2. Blood Examination: Blood tests such as hemoglobin levels, differential leukocyte count, total leukocyte count, and peripheral blood smear appear normal. Additionally, liver function tests, kidney function tests, serum calcium, and serum phosphorus levels appear normal.

3. Fine Needle Aspiration Cytology (FNAC): This technique is used to observe the affected cells under the microscope. A thin 22-gauge needle is used to collect the sample, which is spread on slides and stained with Giemsa stain and PAS (Periodic Acid Schiff's) stain. On microscopic examination, the Giemsa stained slides reveal small round cells grouped, forming rosette-like formations suggestive of retinoblastoma. The PAS-stained slides show the presence of granules in the cytoplasm of the tumor cells. These pinkish granules result from the staining process, suggesting features of retinoblastoma.

4. Noncontrast Computed Tomography (NCCT) Scan: This scan shows an enlarged affected eyeball due to the growing mass. The affected eye exhibits significant proptosis or bulging eyes. The mass appears denser (hyperdense) than the neighboring tissues, with some areas containing fluid-filled cystic components. The mass may extend into the front part of the skull, referred to as the anterior cranial fossa, leading to the destruction of the orbital walls. The growth may also affect the anterior ethmoidal and frontal sinuses. Additionally, the growth may destroy the great wing of the sphenoid bone, a bony area.

Apart from the CT scan of the head, the CT scans of the abdomen and chest are normal. Retinoblastoma affecting younger children showed calcification in the CT scans, and the amount of calcification was linked to the tumor size. The smaller the tumor, the less calcification was present. However, in the case of adults, calcification is absent even in advanced stages.

5. Immunohistochemistry (IHC): A laboratory technique that detects specific proteins and antigens in tissue samples. Retinoblastoma cells test positive for the following stains:

• NSE (Neuron-Specific Enolase): This stain indicates the presence of nerve-related cells.

• Synaptophysin: It is an integral membrane glycoprotein that serves as a neuronal marker.

• GFAP (Glial Fibrillary Acidic Protein): This marker identifies the presence of glial cells.

• S-100: This marker identifies Schwann cells, which play a role in nerve function

What Is the Treatment of Retinoblastoma in Adults?

The management of retinoblastoma should save lives, preserve eye anatomy, achieve favorable cosmetic results, and retain vision. The management includes:

1. Enucleation: This surgical procedure involves the removal of the entire eye except the eye muscles. The placement of an artificial eye follows it.

2. External Beam Radiotherapy (EBRT): EBRT is a treatment in which high doses of radiation are delivered to kill or shrink cancer cells. In EBRT, a machine generates high-energy X-rays that destroy the cancer cells. While EBRT can temporarily shrink cancer cells and show promising results shortly, eye removal remains necessary even after its usage.

3. Systemic Chemotherapy and Chemoreduction: This type of chemotherapy is administered after enucleation. Six cycles of carboplatin, vincristine, and etoposide are given as chemotherapeutic agents.

4. Focal Therapy: Focal therapy is localized to cancer cells, sparing healthy surrounding tissues. Techniques like plaque brachytherapy or transpupillary thermotherapy can be used, but patients affected should still undergo enucleation.

What Are the Differential Diagnosis of Retinoblastoma in Adults?

The differential diagnosis of retinoblastoma in adults includes:

• Primary Intraocular Tumor: These tumors originate within the eye and can develop from different eye structures such as the iris, choroid, retina, or ciliary body.

• Metastatic Carcinoma: This is a type of cancer that originates from other sites of the body called a primary tumor.

• Malignant Melanoma: It is a type of cancer that occurs from the cells that give color to the skin called melanocytes.

• Lymphoma: A type of cancer that occurs in the immune system, also called the lymphatic system.

• Adult Onset Coats Disease: It is a rare eye disorder that is non-hereditary and affects primarily adults. In this, there is abnormal development of blood vessels in the retina.

• Amelanotic Melanoma: A skin cancer that arises from mutated melanocytes that lack pigmentation

• Fungal Granuloma: It is a type of inflammatory response due to a fungal infection.

• Retinocytoma: It is a rare tumor that occurs from the retinal cells, and it is a benign condition.

Conclusion

Retinoblastoma in adults has transitioned from a deadly cancer to a curable one over many decades. Imaging modalities such as ultrasound and CT scans can aid in localizing and assessing the extent of the mass. In addition, FNAC (Fine Needle Aspiration Cytology) holds an advantage in identifying this condition. Early diagnosis and treatment can improve outcomes, and chemotherapy plays a crucial role. Long-term follow-up is necessary, along with careful observation of first-degree relatives, as it can be a heritable condition.