Conjunctival Melanocytic Tumors

Key Points at a Glance

Key Points of This Disease

• Conjunctival melanocytic tumors are broadly classified into three categories: benign nevi, precancerous primary acquired melanosis, and malignant melanoma.
• Conjunctival melanoma accounts for approximately 2% of all ocular tumors, and its incidence is increasing.
• About 60–75% of melanomas arise from primary acquired melanosis (PAM).
• The basic treatment is a combination of complete surgical excision using the “no-touch technique” and cryotherapy.
• Tumor thickness, lesion location, and AJCC staging strongly influence prognosis; caruncular lesions have the worst prognosis with a 3-year mortality rate of 50%.
• Genetically, conjunctival melanoma resembles cutaneous melanoma, with BRAF, NF1, NRAS, and ATRX mutations as major drivers.
• Primary acquired melanosis shows a “wax and wane” pattern, so disappearance of pigment does not indicate cure; regular histological confirmation is necessary.

1. What Are Conjunctival Melanocytic Tumors?

Conjunctival melanocytic tumors are a collective term for benign and malignant neoplasms arising from melanocytes of the conjunctiva. They are mainly classified into three categories.

• Nevus: A congenital benign tumor. It is the most common conjunctival melanocytic tumor, with an overall risk of malignant transformation of about 1%.
• Primary acquired melanosis: An acquired pigmented lesion that develops after middle age. It is divided into those without atypia (benign) and those with atypia (precancerous). Recently, it is also called conjunctival melanocytic intraepithelial lesion (C-MIL)⁴⁾, and a C-MIN score of 5 or higher is considered melanoma in situ⁸⁾.
• Conjunctival melanoma (malignant melanoma): A malignant tumor accounting for approximately 2% of all ocular tumors and 5–7% of all ocular melanomas ^{1, 4, 5, 6)}.

Epidemiology

The global incidence of conjunctival melanoma is approximately 0.3–0.8 per million per year, with the highest rates in Northern Europe and North America. Incidence has been increasing over the past 50 years. An estimated 130 new cases occur annually in the United States and about 320 in Europe. The age-adjusted incidence in Asians is low at 0.15 per million per year ²⁾, with the highest occurrence in Whites (91.2%) and only 2.4% in Afro-Caribbean populations.

The mean age at onset is 55–65 years, and cases under 20 years of age are extremely rare ⁵⁾. Pediatric cases account for only 1% of all conjunctival melanomas ⁹⁾. Primary acquired melanosis accounts for 11% of all conjunctival lesions ⁸⁾ and is the most common origin of melanoma (approximately 60–75%).

Breakdown by origin of melanoma:

• From primary acquired melanosis: approximately 60–75% (most common)
• De novo: approximately 19%
• From nevus: 7–20%

Conjunctival melanoma is the only mucosal melanoma for which an association with ultraviolet exposure has been suggested, because the bulbar conjunctiva is directly exposed to UV radiation ⁶⁾. The fact that melanin filters UVB radiation by about twofold is thought to explain the lower incidence in people of color.

Q How common are conjunctival melanocytic tumors?

A

The incidence of conjunctival melanoma is 0.3–0.8 per million per year, making it a relatively rare disease, but it has been increasing over the past 50 years. On the other hand, nevi are the most common conjunctival melanocytic tumors and are almost always benign.

2. Main symptoms and clinical findings

Diffuse PAM of the lower palpebral conjunctiva and pigmentation of the corneal limbus

Koç İ, et al. Current Management of Conjunctival Melanoma Part 1: Clinical Features, Diagnosis and Histopathology. Turk J Ophthalmol. 2020. Figure 2. PMCID: PMC7610047. License: CC BY.

When the lower eyelid is everted, diffuse PAM is observed especially in the tarsal conjunctiva, and pigmentation of the corneal limbus is also visible. This corresponds to primary acquired melanosis discussed in the section “2. Main symptoms and clinical findings.”

Subjective symptoms

• Many patients visit a doctor after noticing the appearance of a new pigmented lesion or an increase in size of an existing lesion.
• Sensation of a spot or lump, irritation, pain⁴⁾
• Itching, blurred vision, decreased visual acuity (in cases of corneal invasion)⁴⁾
• May be accompanied by bleeding upon contact⁶⁾
• May remain asymptomatic and be discovered incidentally during health checkups or routine examinations⁵⁾

Clinical Findings

Nevus, primary acquired melanosis, and melanoma each present with different clinical features.

Nevus

Location: Most commonly on the bulbar conjunctiva near the limbus in the interpalpebral fissure.

Cysts: Usually accompanied by conjunctival inclusion cysts (detectable by slit lamp, ultrasound, or anterior segment optical coherence tomography). The presence of cysts is an important finding suggestive of benignity.

Course: Long-standing (congenital). May change in color and size during puberty due to hormonal changes. Rapid changes in adulthood raise suspicion of malignancy.

Corneal invasion: Rare.

Primary Acquired Melanosis

Patient background: Middle-aged to elderly, predominantly Caucasian, almost always unilateral.

Appearance: Flat pigmented lesion ranging from light brown to dark brown. May exhibit various shades of color.

Distribution: Can occur in any part of the conjunctiva. Continuous or discontinuous. May be hidden in the fornix or palpebral conjunctiva, so eyelid eversion is important for evaluation.

Course: May show wax and wane. Loss of pigmentation does not indicate regression of primary acquired melanosis ⁸⁾.

Conjunctival Melanoma

Predilection site: About 90% occur on the bulbar conjunctiva, with 63% localized in the temporal quadrant ^{4, 6)}.

Appearance: Pigmented (70%) or non-pigmented (30%) ⁵⁾. Non-pigmented lesions are pink to red masses and may be misdiagnosed as squamous cell carcinoma.

Characteristic findings: Nodular or flat. Often accompanied by feeder vessels. Adhesion to the sclera. The average distance from the tumor to the corneal limbus is 2 mm, and 61% reach the limbus ⁴⁾.

Imaging evaluation: Anterior segment optical coherence tomography (AS-OCT) shows hyperreflective lesions and allows assessment of Bowman’s membrane ⁴⁾. Ultrasound biomicroscopy (UBM) can confirm tumor thickness and scleral invasion ⁵⁾.

Q Are all pigmented conjunctival lesions malignant?

A

No. Among pigmented conjunctival lesions, benign nevi are the most common, and the overall risk of malignant transformation is only about 1%. The location of the lesion, presence of cysts, time of onset, and pattern of change are important for differentiating benign from malignant, and if suspicious changes occur, consultation with a specialist is recommended.

3. Causes and Risk Factors

Poor Prognostic Factors

The following factors are associated with increased risk of metastasis and death ^{1, 4, 5, 6, 8)}.

• Tumor thickness >2 mm: HR 1.20 per 1 mm increase
• Deep invasion: HR 2.35
• Lymphatic invasion: HR 7.49
• Ulceration: HR 7.01
• T3 tumor: HR 17.44
• Nodular melanoma: Metastasis risk RR 6.00–8.44, death risk RR 25.49–35.49
• Lesion site: Fornix/palpebral conjunctiva > bulbar conjunctiva. Caruncle lesions have the worst prognosis with a 3-year mortality rate of 50%
• Orbital invasion
• Incomplete resection: Approximately 49.3% of incomplete resections recur
• Hypopigmented/amelanotic melanoma
• Tumor-associated lymphangiogenesis⁵⁾

AJCC (American Joint Committee on Cancer) Stage Classification and Mortality

AJCC stage classification strongly correlates with prognosis¹⁾.

Stage	5-Year Cumulative Mortality
cT1	2.5%
cT2	28.6%
cT3	31.6%
cT3c (orbital invasion)	100%

The estimated 5-year distant metastasis rate for T3 tumors is 42%, and the 5-year mortality rate is 23%¹⁾.

Metastasis Patterns

Lymphatic spread is the main route of metastasis. Temporal conjunctival lesions tend to metastasize to the preauricular lymph nodes, while nasal conjunctival lesions tend to metastasize to the submandibular lymph nodes. Distant metastases (hematogenous) occur in the brain, lungs, liver, skin, adrenal glands, heart, peritoneum, pancreas, intestines, kidneys, bones, spleen, etc.^{6, 1)} Lymph node metastases are found in 15–41% of cases at a mean of 2.3 years after diagnosis, and systemic metastases occur in 9–25% at 3 years. Even when lymph node metastases are not detected, distant hematogenous organ metastases occur in 38% of cases⁸⁾.

Q What is the most important factor determining the prognosis of conjunctival melanoma?

A

Major poor prognostic factors include tumor thickness (especially >2 mm), lesion location (caruncle has the worst prognosis), AJCC stage, nodular morphology, lymphatic invasion, and orbital invasion. Completeness of resection also greatly affects prognosis; approximately 49.3% of cases with incomplete resection recur.

4. Diagnosis and Examination Methods

Clinical Examination

• Slit-lamp microscopy: Evaluates lesion morphology, color, borders, and presence of cysts
• Anterior segment optical coherence tomography (AS-OCT): Assesses lesion depth and Bowman’s membrane. Depicted as a hyperreflective lesion⁴⁾
• Ultrasound biomicroscopy (UBM): Measures tumor thickness and checks for scleral invasion⁵⁾
• Ultrasound: Detects cysts in nevi
• Eyelid eversion: Essential because primary acquired melanosis may be hidden in the fornix or palpebral conjunctiva
• Photographic documentation: Objective assessment of changes during follow-up

Systemic evaluation

For confirmed melanoma, a systematic systemic evaluation is necessary.

• PET/CT: To search for systemic metastases^{1, 9)}
• Brain and orbital MRI^{1, 4)}
• Abdominal ultrasound, chest X-ray^{6, 4)}
• Lymph node palpation (preauricular, submandibular, cervical): at every outpatient visit
• Cervical lymph node ultrasound (annually for severe primary acquired melanosis/melanoma cases)⁸⁾

Histological diagnosis

Biopsy is required for definitive diagnosis.

Histological findings of nevus:

• Nevus cell nests at the junction or in the subepithelial area
• Conjunctival inclusion cysts are characteristic

Histological findings of primary acquired melanosis:

• No atypia: minimal melanocyte proliferation in the epithelial basal layer
• Atypia present: isolated/confluent nests of atypical melanocytes, pagetoid spread, large abnormal cells, prominent nucleoli, high nuclear-to-cytoplasmic ratio, mitotic figures

Histological findings of melanoma:

• Infiltration of melanoma cells into the subepithelial layer
• Pleomorphic nuclei, large nuclei, prominent nucleoli, mitotic activity, abundant cytoplasm⁵⁾
• Pagetoid growth, radial intraepithelial spread, band-like inflammation of the basal layer⁵⁾

Immunohistochemical markers

Immunohistochemistry is essential for definitive diagnosis and differentiation between benign and malignant lesions. The WHO 5th edition has adopted immunohistochemistry of melanocytic markers as the preferred diagnostic criterion⁸⁾.

Marker	Nevus	Melanoma	Notes
S100	+	+	Common to melanocytic lineage1)
SOX10	+	+	Common melanocytic marker1, 4)
HMB45	+	+	Common melanocytic marker1, 3, 9)
Melan-A/MART-1	+	+	Common melanocytic marker3, 5, 6)
Ki-67	Low	10–15% or higher	Proliferation index3, 4)
p16	Retained	Lost	Tumor suppressor7)
PRAME	−	+	Most useful differential marker7)
bcl2	−	Moderate to strong positive	Apoptosis inhibition3)

Special categories of indeterminate melanocytic proliferation

There are lesions that cannot be clearly classified as benign or malignant⁷⁾.

• Deep penetrating nevus (DPN): Activation of WNT/β-catenin pathway, BRAF V600E mutation positive in all cases, NRAS mutation negative, PRAME negative, low Ki-67. Female:male = 1.3:1, mean age 25 years. No reports of recurrence or metastasis after excision.
• Nevoid melanoma: Morphologically resembles a nevus but exhibits malignant behavior. Shows loss of p16, PRAME positivity, high Ki-67. Associated with BAP1 inactivation. Management follows melanoma guidelines.

Differential Diagnosis

• Complexion-associated melanosis
• Pigmented Axenfeld loop
• Conjunctival squamous cell carcinoma → Differentiation from amelanotic melanoma is particularly important⁵⁾
• Secondary pigmentation (exogenous pigmentation such as mascara)
• Subconjunctival extension of pigmented intraocular tumors

5. Standard Treatment

Management of Nevi

Usually only observation with photographic documentation. If enlargement or color change occurs, consider excision. However, changes during puberty are often due to hormonal changes, inflammation, or cyst enlargement; rapid changes in adulthood are indicators of malignancy.

Management of Primary Acquired Melanosis

• Biopsy: Carefully perform incisional/excisional/map biopsy for suspicious lesions
• Surgery: Add cryotherapy to the excision margins depending on the clinically suspicious area
• Topical chemotherapy: Consider topical administration of mitomycin C or interferon alpha-2b for histologically proven primary acquired melanosis with atypia
  • Mitomycin C 0.02%: Multiple sessions of 5 times/day for 1 week⁸⁾
  • Only intraepithelial lesions are eligible (inappropriate for invasive melanoma)
• Follow-up management note: Even if pigmentation disappears due to the “wax and wane” of primary acquired melanosis, the lesion may not have resolved. After mitomycin C treatment, mapping biopsy should confirm eradication of primary acquired melanosis⁸⁾.

Surgical treatment of conjunctival melanoma

Complete surgical excision is the first choice. The following principles are important:

• Resection margin: Total tumor excision with a 3–5 mm safety margin (some literature suggests 2–4 mm⁵⁾)
• No-touch technique: Avoid direct contact with the tumor using instruments to prevent tumor cell seeding^{5, 9)}
• Dry technique: Resect without using irrigation fluid (BSS)
• Scleral invasion: Perform scleroconjunctivectomy
• Corneal invasion: Alcohol corneal epithelial debridement is recommended, and the corneal portion is excised en bloc with a hockey knife⁴⁾

Adjuvant therapy

Cryotherapy: Apply to the base and margins of the excision using a double freeze-thaw technique. Elevate the conjunctiva to avoid scleral damage⁵⁾.

Mitomycin C topical chemotherapy:

• Intraoperative: 0.02% mitomycin C microsponge applied for 180 seconds⁴⁾
• Postoperative: 0.02% mitomycin C eye drops 4 times/day × 7 days, with 1 week off, for 3 cycles⁴⁾
• Dosage varies from 0.002% to 0.04% depending on the report⁵⁾
• Recurrence rate with primary mitomycin C treatment is 33–100%; as adjuvant therapy, recurrence rate is 0–66%⁵⁾

Interferon alfa-2b: Because it does not cause limbal stem cell deficiency, it is considered an alternative to mitomycin C⁵⁾.

Radiation therapy: Brachytherapy or external beam irradiation⁵⁾.

Surface Reconstruction

The following are used for conjunctival reconstruction after wide excision^{4, 5)}:

• Amniotic membrane transplantation: Has anti-inflammatory, anti-fibrotic, and anti-angiogenic effects
• Oral mucosal graft
• Contralateral conjunctival graft

Treatment of Advanced Cases

• Orbital exenteration: Indicated for extensive/recurrent cases. For reconstruction after resection, free radial forearm flap, temporoparietal fascial flap, anterolateral thigh flap, etc. are used²⁾.
• Enucleation: Indicated for cases with intraocular extension.

Sentinel Lymph Node Biopsy

In cases with tumor thickness >2 mm, sentinel lymph node biopsy should be considered⁹⁾.

Precautions and Side Effects in Treatment

Main side effects of mitomycin C eye drops: Mild: local irritation, hyperemia, tearing, allergy, keratoconjunctivitis, corneal erosion. Severe: punctal stenosis, cataract, persistent keratoconjunctivitis, limbal stem cell deficiency (up to 12%) have been reported⁵⁾. Recurrence rates: 26–60% at 5 years, 31–66.4% at 10 years, still high⁵⁾, long-term follow-up is essential.

Q What is the "no-touch technique" in conjunctival melanoma surgery?

A

To prevent tumor cell seeding (local recurrence or metastasis due to seeding), this technique involves resecting the tumor without directly touching it with instruments during surgery, and in a dry environment without using irrigation fluid (BSS). By ensuring a 3–5 mm safety margin and resecting the entire tumor en bloc, the risk of recurrence due to incomplete resection is reduced.

6. Pathophysiology and Detailed Pathogenesis

Genetic Similarity to Cutaneous Melanoma

Conjunctival melanoma is genetically similar to cutaneous melanoma rather than uveal melanoma. The major UV-related driver mutations are BRAF, NF1, and RAS. Markers of uveal melanoma (BAP1, GNAQ, GNA11, SF3B1) have been confirmed to be negative in conjunctival melanoma¹⁾.

Major Molecular Mutations

In a study of 101 cases by Lally et al. (2022), four high-frequency mutations were identified¹⁾.

NF1 mutation (39%)

Frequency: Most common mutation.

Prognosis: NF1 mutation alone is associated with low metastasis rates at 2 and 5 years.

Feature: No mutual exclusivity with BRAF mutation (can coexist).

BRAF mutation (31%)

Frequency: Second most common mutation. V600E mutation accounts for 80–90%.

Distribution: More common in bulbar conjunctival melanoma (sun-exposed sites)⁶⁾.

Prognosis: No significant association with metastasis or death. It is a therapeutic target for targeted therapy (BRAF inhibitors).

NRAS mutation (26%)

Frequency: Third most common mutation.

Prognosis: Increased risk of metastasis and death, especially death risk about 5 times higher.

Characteristics: Mutually exclusive with BRAF mutation.

ATRX mutation (25%)

Frequency: Fourth most common mutation.

Prognosis: Similar to NF1 mutation, associated with low metastasis rates at 2 and 5 years.

TERT promoter mutation

The TERT c.-124C>T mutation affects telomerase reverse transcriptase and has been reported to be associated with metastatic conjunctival melanoma^{1, 8, 6)}. It is also detected in moderate to severe atypia of primary acquired melanosis, suggesting a nature of melanoma in situ⁸⁾. It has also been shown to be associated with high tumor mutational burden⁶⁾.

Chou et al. (2023) analyzed the molecular profile of a T3c conjunctival melanoma case in a 94-year-old male. They identified NF1 mutations (c.4339C>T, VAF 31.5%; c.5606T>A, VAF 32.0%) and a TERT promoter mutation (c.-124C>T, VAF 31.4%), while BRAF, NRAS, and cKIT were all negative. The combination of NF1 mutation and NRAS negativity is considered a contributing factor to the relatively favorable course without metastasis¹⁾.

Immune tumor microenvironment

High PD-L1 expression and the presence of a transcriptional subtype rich in immune-related genes have been confirmed, providing a rationale for the use of immune checkpoint inhibitors. Data on BRAF inhibitors, MEK inhibitors, and PD-L1 inhibitors are promising but currently limited.

7. Latest research and future perspectives (research-stage reports)

For patients: Please read

The following content is currently at the research stage or under clinical trial and is not standard treatment available at general hospitals. It is reference information for experts regarding future medical developments.

Immune checkpoint inhibitors

PD-1 inhibitors (pembrolizumab, nivolumab) are being tested for metastatic conjunctival melanoma ⁵⁾. Reports of neoadjuvant (preoperative) immune checkpoint inhibitors also exist ⁴⁾.

In a case of bone metastasis from primary acquired melanosis reported by Goemaere et al. (2023), nivolumab and spinal radiation therapy were administered, followed by paclitaxel + carboplatin, and eventually transitioned to palliative care ⁸⁾. A standard systemic therapy regimen for metastatic conjunctival melanoma has not yet been established.

Targeted therapy

The use of BRAF inhibitors for BRAF mutation-positive cases is being attempted. The possibility of synergistic effects by simultaneously targeting the MAPK and AKT pathways is also under investigation ⁵⁾.

Advances in diagnostic techniques

The use of immunohistochemical panels (PRAME, p16, HMB45, Ki-67, beta-catenin, Cyclin D1) is enabling reclassification of lesions previously considered “indeterminate” ⁷⁾.

Eder et al. (2024) confirmed BRAF V600E positivity in all 34 DPN cases and NRAS Q61R negativity in all cases by FISH analysis. Additionally, the potential of microRNA profiling for differentiating benign from malignant lesions has been suggested ^{7, 8)}. FISH analysis evaluates RREB1 (6p25), CCND1 (11q13), MYB (6q23), and MYC (8q24).

Management of pediatric cases

Vishnevskia-Dai et al. (2023) reported a case of amelanotic de novo melanoma (8 mm × 2.5 mm) arising from the nasal bulbar conjunctiva in a 7-year-old boy. No-touch technique with 4 mm margins, cryocoagulation, and amniotic membrane transplantation were performed, resulting in a recurrence-free period of 73 months ⁹⁾. In pediatric cases, histological differentiation from Spitz nevus is particularly important.

Long-term outcomes of amniotic membrane transplantation

Amniotic membrane transplantation after extensive resection provides good epithelialization, but mild limbal stem cell deficiency, cicatricial keratoconjunctivitis, and rare local recurrence have been reported ⁵⁾.

Q Can immunotherapy be used for conjunctival melanoma?

A

Based on genetic similarities with cutaneous melanoma (BRAF, NF1, NRAS mutations, high PD-L1 expression), PD-1 inhibitors (pembrolizumab, nivolumab, etc.) and BRAF inhibitors are being attempted in metastatic cases. However, large-scale clinical trials have not been conducted, and evidence is currently limited; a standard regimen has not been established.

8. References

1. Chou LT, Lozeau DF, Boyle NS. A rare case of a long-standing, extensive and invasive conjunctival melanoma without systemic metastasis. Am J Ophthalmol Case Rep. 2023; PMC10121375.
2. Tan JA, Khoo ET, Al-Chalabi MM, et al. Orbital exenteration and reconstruction using a free radial forearm flap in conjunctival melanoma. Cureus. 2023; PMC10460132.
3. Montazer F, Heshmati SM, Asgari S, et al. Conjunctival melanoma: a case presentation. Iran J Pathol. 2023; PMC10646746.
4. Englisch CN, Berger T, Flockerzi F, et al. Conjunctival melanoma with pronounced central corneal invasion: one-year relapse free follow-up. Am J Ophthalmol Case Rep. 2024; PMC11403272.
5. Menna F, Tschopp M, Meyer P, et al. A case of conjunctival melanoma presenting as a squamous cell carcinoma. Case Rep Ophthalmol. 2024; PMC11509494.
6. Okongwu CC, Adewara BA, Olaofe OO, et al. Malignant melanoma of the conjunctiva metastasizing to the submandibular gland. BMC Ophthalmol. 2025; PMC11905526.
7. Eder A, Milman T, Mudhar HS, et al. Unusual conjunctival melanocytic proliferations: report of five cases and review of the literature. Surv Ophthalmol. 2024; PMC12208716.
8. Goemaere J, Lauwers N, de Keizer ROB, et al. Bone metastasis in a case of primary acquired melanosis with atypia resulting from conjunctival melanoma. Am J Ophthalmol Case Rep. 2023; PMC9763362.
9. Vishnevskia-Dai V, Davidy T, Zloto O. Amelanotic conjunctival melanoma in a child. Am J Ophthalmol Case Rep. 2023; PMC9792290.