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Melanoma of the conjunctiva

Melanoma develops from cells called melanocytes. Melanocytes are the cells that produce melanin, the substance that gives colour to the eyes, skin and hair. Melanoma of the conjunctiva is an uncommon cancer. It accounts for only about 2%–3% of all eye cancers. Melanoma of the conjunctiva is also much less common than other types of melanoma, such as melanoma of the eye (intraocular melanoma) or melanoma of the skin.

Melanoma of the conjunctiva can develop with no known cause (referred to as de novo). Others develop from pre-existing conditions, such as primary acquired melanosis (PAM) or a mole (nevus) or melanoma in the eye.

Melanoma of the conjunctiva tends to occur in people in their 50s or 60s. It rarely occurs in people younger than 20 years of age.

Signs and symptoms

A conjunctival melanoma often appears as a raised coloured (pigmented) tumour. Some may contain little or no pigment. The colour of the conjunctival melanoma can range from light to dark brown. The most common location for a melanoma to occur in the conjunctiva is in the bulbar conjunctiva, which is the part of the conjunctiva that covers the outer surface of the eyeball.

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Grades

Grading is a way of classifying conjunctival melanoma cells based on their appearance and behaviour when viewed under a microscope. The grade of conjunctival melanoma represents where the melanoma started. Squamous cell carcinoma of the conjunctiva and lymphoma of the conjunctiva are graded differently.

GradeDescription

X

Origin of the primary tumour cannot be assessed

0

Primary acquired melanosis without atypical (not normal) cells

1

Conjunctival nevus (mole)

2

Primary acquired melanosis with atypical cells (epithelial disease only). Epithelial disease means that only the epithelial cells are affected. (Epithelial cells are specialized cells that make up the epithelium, which is a layer of cells that line the body’s hollow organs and glands and make up the outer layer of the skin.)

3

Primary acquired melanosis with atypical epithelial cells and invasive melanoma that grows into surrounding tissues

4

De novo malignant melanoma.

Grading plays an important part in planning treatment for conjunctival melanoma. It can also be used to help estimate the prognosis (future outcome).

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Stages

Staging is a way of describing or classifying a cancer based on the extent of cancer in the body. The most common staging system for malignant melanoma of the conjunctiva is the TNM system. The International Union Against Cancer (UICC) uses the TNM system to describe the extent of many solid tumour cancers.

Squamous cell carcinoma of the conjunctiva is staged differently.

TNM

TNM stands for tumour, nodes, metastasis. TNM staging describes:

  • the size of the primary tumour
  • the number and location of any regional lymph nodes that have cancer cells in them
  • whether the cancer has spread or metastasized to another part of the body

Primary tumour (T) – clinical staging

TX

Primary tumour cannot be assessed

T0

No evidence of primary tumour

Tis

Melanoma confined to the conjunctival epitheliumepitheliumA thin layer of epithelial cells that makes up the outer surfaces of the body (the skin) and lines hollow organs, glands and all passages of the respiratory, digestive, reproductive and urinary systems. (in situ). Includes primary acquired melanosis with atypical (not normal) cells.

T1

Melanoma of the bulbar conjunctiva

T1a – Tumour is in no more than one quadrant* of the conjunctiva.

T1b – Tumour is in more than one, but not more than 2 quadrants.

T1c – Tumour is in more than 2, but not more than 3 quadrants.

T1d – Tumour is in more than 3 quadrants.

T2

Melanoma of the non-bulbar conjunctiva involving the palpebral, forniceal or the caruncular conjunctiva.

T2a – Tumour is in the palpebral or forniceal conjunctiva and involves no more than one quadrant of the conjunctiva. There is no tumour in the caruncular conjunctiva.

T2b – Tumour is in the palpebral or forniceal conjunctiva and involves more than one quadrant of the conjunctiva. There is no tumour in the caruncular conjunctiva.

T2c – Tumour is in the caruncle, but does not involve more than one quadrant of the conjunctiva.

T2d – Tumour is in the caruncle and involves more than one quadrant of the conjunctiva.

T3

Tumour has spread into surrounding structures.

T3a – Tumour has spread into the globe.

T3b – Tumour has spread into the eyelid.

T3c – Tumour has spread into the orbit.

T3d – Tumour has spread into the sinus.

T4

Tumour has spread into the central nervous system (the brain and spinal cord).

Note: The conjunctiva is measured like a clock face. The conjunctiva is divided into 4 parts (quadrants) that correspond to 3, 6, 9 or 12 clock hours. The quadrants begin at the limbus (the part of the conjunctiva that starts at the edge of the cornea), extends from the central cornea, to and beyond the eyelid margins.

Regional lymph nodes (N)

NX

Regional lymph nodes cannot be assessed

N0

No regional lymph node metastasis

N1

Regional lymph node metastasis

Note: The regional lymph nodes include those around the ear (preauricular nodes), lower jaw (submandibular nodes) and neck (cervical nodes).

Distant metastasis (M)

M0

No distant metastasis

M1

Distant metastasis

TNM pathological classification

The pathological classification (pTNM) is based on examination of the conjunctival melanoma by a pathologist (a doctor who specializes in the causes and nature of disease) after it has been removed by surgery.

Pathological primary tumour (pT)

pTX

Primary tumour cannot be assessed

pT0

No evidence of primary tumour

pTis

Melanoma is confined to the conjunctival epithelium (in situ). Also includes primary acquired melanosis with atypical (not normal) cells.

pT1

Melanoma of the bulbar conjunctiva

pT1a – Tumour is no more than 0.5 mm (0.02 inches) in thickness and has spread into the deeper, underlying layer called the substantia propria.

pT1b – Tumour is more than 0.5 mm, but not more than 1.5 mm (0.06 inches), in thickness and has spread into the substantia propria.

pT1c – Tumour is more than 1.5 mm in thickness and invades the substantia propria.

pT2

Melanoma of the palpebral, forniceal or the carunclular conjunctiva

pT2a – Tumour is not more than 0.5 mm in thickness and has spread into the substantia propria.

pT2b – Tumour is more than 0.5 mm, but not more than 1.5 mm, in thickness and has spread into the substantia propria.

pT2c – Tumour is more than 1.5 mm in thickness and has spread into the substantia propria.

pT3

Melanoma has spread to the eye, eyelid, nasolacrimal system, sinuses or orbit.

pT4

Melanoma has spread to the central nervous system (CNS).

Stage grouping for malignant melanoma of the conjunctiva

Unlike other cancers, there is no stage grouping for melanoma of the conjunctiva. The T and pT classifications can be grouped together as shown in the table below.

T and pT summary – malignant melanoma of the conjunctiva

T

Location

pT

T1

Bulbar conjunctiva

pT1 (includes pT1a, pT1b, pT1c)

T2

Non-bulbar conjunctiva (palpebral, forniceal, and caruncular conjunctiva)

pT2 (includes pT2a, pT2b, pT2c)

T3

Eyelid, globe, orbit or sinuses

pT3

T4

pT4

Recurrent conjunctival melanoma

Recurrent conjunctival melanoma means that the cancer has come back after it has been treated. It may recur in the same location as the original cancer or it may recur in another part of the body (metastatic conjunctival melanoma).

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Prognosis

Melanomas tend to spread to local tissues and structures and can metastasize to regional lymph nodes and distant parts of the body. Larger tumours and those that have spread into the eye, brain or other organs have a less favourable prognosis.

The survival rate for conjunctival melanoma ranges from 87%–95% after 5 years. About 20%–30% of people will develop metastatic disease, because melanoma tends to spread.

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Treatment

Treatment for conjunctival melanoma depends on the extent of the cancer. Treatment often includes surgery.

  • Surgery is the main treatment for conjunctival melanoma. It is done to remove the tumour and some (margin) of normal tissue around it.
  • Surgery may need to extend into the cornea.
  • The incision is stitched (sutured) and allowed to heal. A graft may be used if reconstruction of the conjunctiva is needed after extensive surgical resection. Grafts may be taken from the conjunctiva of the other eye, a piece of mucous membrane from the mouth or other suitable locations.
  • If the cancer is too large to preserve the eye or has spread into the orbit, then an exenteration may be done. About 20% of people with invasive conjunctival melanoma eventually need an orbital exenteration.

Additional (adjuvantadjuvantTreatment given in addition to the first-line therapy (the first or standard treatment) to help reduce the risk of a disease (such as cancer) coming back (recurring).) treatment after surgery is often required. More than 50% of people will develop a local recurrence after treatment of invasive conjunctival melanoma. The outcome improves with adjuvant therapy. Adjuvant therapies after surgery may include:

  • cryosurgery
  • radiation therapy – brachytherapy
  • topical chemotherapy
    • Topical chemotherapy may be used after surgery, especially if the cancer has spread into the epithelial tissues.
    • The drug often used is mitomycin (Mutamycin) eye drops. For more detailed information on specific drugs, go to sources of drug information.

If the melanoma cannot be removed by surgery (unresectable disease), then it may be treated with radiation therapy (including brachytherapy or external beam radiation therapy), cryosurgery or topical chemotherapy.

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