Squamous Cell Carcinoma (Eyelid)

Squamous cell carcinoma (SCC) of the eyelid is a malignant tumour arising from keratinocytes of the eyelid skin and lid margin epithelium. It represents the second most common periocular malignancy in Western populations (after basal cell carcinoma), accounting for approximately 5–10% of eyelid cancers. In Singapore and Southeast Asia, the epidemiology differs — sebaceous gland carcinoma is relatively more prevalent among Asian patients, but periocular SCC is still encountered, particularly in Caucasian expatriates and fair-skinned individuals with chronic sun exposure.

The lower eyelid (∼ 75%) and medial canthus are the most frequently affected sites. SCC may arise de novo or progress from precursor lesions such as actinic keratosis (AK) or Bowen disease (SCC in situ). Unlike basal cell carcinoma, periocular SCC carries a clinically meaningful risk of regional lymph node metastasis (3–10%) and occasional distant spread, particularly in high-risk cases.

• Chronic ultraviolet (UV-B) radiation: primary driver via cumulative actinic DNA damage; UV-induced pyrimidine dimers cause p53 tumour suppressor mutation.
• Actinic keratosis / Bowen disease progression: important precursor pathway — AK is premalignant field change; Bowen disease is full-thickness intraepidermal SCC (in situ).
• Immunosuppression: organ transplant recipients (65× higher cutaneous SCC risk), haematologic malignancy, chronic immunosuppressive therapy — increased incidence and aggressiveness.
• Oncogenic HPV: types 16, 18, 33 implicated, especially in immunosuppressed patients and periungual/anogenital but also periocular.
• Chronic scars/inflammation: Marjolin-like transformation within burn scars, chronic wounds, discoid lupus lesions.
• Carcinogenic exposures: ionising radiation, inorganic arsenic, polycyclic aromatic hydrocarbons, tar, PUVA phototherapy (in psoriasis patients).
• Genodermatoses: xeroderma pigmentosum (XP), epidermolysis bullosa, oculocutaneous albinism — greatly amplified UV susceptibility.

1. UV-induced p53 mutation: UV-B creates cyclobutane pyrimidine dimers; p53 inactivation removes the cell-cycle checkpoint → keratinocyte clonal expansion.
2. Intraepidermal dysplasia: progressive keratinocyte atypia → partial-thickness (actinic keratosis) → full-thickness atypia (Bowen disease / SCC in situ) without basement membrane breach.
3. Basement membrane invasion: matrix metalloproteinase activation degrades the BM → tumour cells enter the dermis; this defines surgically invasive SCC.
4. Perineural / lymphovascular invasion: high-risk tumours track along perineurial sheaths (trigeminal branches V1/V2) or invade lymphatics — enabling regional spread to preauricular, parotid, submandibular, and cervical nodes.
5. Immune evasion: in immunosuppressed hosts, reduced cytotoxic T-cell surveillance permits rapid tumour growth, multifocality, and higher metastatic rates.

• Cumulative UV exposure: outdoor workers, agricultural/maritime occupations; fair skin (Fitzpatrick types I–II), blue/green eyes, red/blonde hair.
• Older age and male sex: most patients are middle-aged to elderly men in Western cohorts; in Singapore, Caucasian expatriates are disproportionately affected.
• Immunosuppression: solid organ transplant recipients (up to 65× increased SCC risk); haematologic malignancies; chronic corticosteroid or biological therapy use.
• Precursor lesions: actinic keratosis (AK), Bowen disease, extensive field cancerisation of periocular skin.
• Prior skin cancer: personal history of SCC or BCC significantly increases lifetime risk of new primaries.
• Genodermatoses: xeroderma pigmentosum (XP), oculocutaneous albinism, Fanconi anaemia — markedly elevated UV sensitivity.
• Tobacco smoking: independent risk factor for head and neck SCC, including periocular sites.
• Chronic non-healing wounds / radiation fields: Marjolin ulcer transformation; prior radiotherapy to orbital/facial region.
• Carcinogen exposure: inorganic arsenic, PUVA therapy, polycyclic aromatic hydrocarbons.

• Painless non-healing sore, scaly patch, or rough lesion at eyelid margin or skin — most common presentation.
• Intermittent bleeding and recurrent crusting over the lesion (may mimic blepharitis).
• Foreign body sensation, ocular irritation, or mild tenderness on palpation.
• Cosmetic asymmetry from progressive enlargement of the eyelid mass.
• Advanced symptoms: tearing (lacrimal outflow obstruction), blurred vision, periocular pain, diplopia, or restricted eye movement — indicating deep orbital invasion.
• Facial numbness, tingling, or paraesthesia in V1/V2 distribution — hallmark of perineural spread; requires urgent MRI.

• Local recurrence: 4–23% depending on tumour size, margins, and histologic risk features — exceeds BCC recurrence rates.
• Local tissue destruction: progressive invasion of eyelid skin, tarsus, canthal tendons, lacrimal outflow system, and orbital rim.
• Perineural invasion: spreads along V1/V2 trigeminal branches; causes pain, numbness, and can track intracranially to cavernous sinus.
• Orbital extension: proptosis, globe displacement, diplopia, compressive optic neuropathy — potential evisceration/exenteration required.
• Regional nodal metastasis (3–10%): preauricular, parotid, submandibular, and cervical lymph node chains — higher rate than any other common periocular malignancy.
• Distant metastasis: rare but reported — lungs, liver, bone; almost exclusively in poorly differentiated or immunosuppressed patients.
• Post-surgical complications: lid malposition, lagophthalmos, epiphora, or corneal exposure following wide resection and reconstruction.

Unlike sebaceous gland carcinoma (associated with Muir-Torre syndrome), periocular SCC is not typically associated with a defined internal malignancy syndrome. However, several systemic contexts dramatically alter its behaviour.

• Solid organ transplant: 65-fold increased cutaneous SCC risk; more aggressive, multifocal, treatment-resistant disease. Prompt referral and streamlined oncology co-management are mandatory.
• Haematologic malignancy (CLL, lymphoma): SCC may be sentinel lesion or arise from immune dysregulation; often presents as multiple simultaneous lesions.
• HIV/AIDS: moderately elevated skin cancer risk; SCC may present insidiously.
• Xeroderma pigmentosum (XP): autosomal recessive NER pathway defect; multiple skin cancers (including SCC) in childhood/young adulthood; early periocular involvement.
• Regional nodal metastasis: parotid, preauricular, submandibular, and cervical chains — requires imaging staging and MDT review.
• Paraneoplastic effects: rare; in advanced metastatic SCC, hypercalcaemia (PTHrP-mediated) may occur.

• Good prognosis when: early detection, complete margin-negative excision; well-differentiated tumour; T1 disease; immunocompetent patient. 5-year recurrence-free survival >90% for localised T1.
• Adverse factor — perineural invasion: substantially worsens local control and increases risk of intracranial spread; necessitates adjuvant RT and close MRI surveillance.
• Adverse factor — poor differentiation (Grade III/IV): higher metastatic rate; more likely to require systemic therapy.
• Adverse factor — nodal metastasis: 5-year survival drops substantially; parotid node positivity carries worse prognosis than cervical-only disease.
• Adverse factor — immunosuppression: post-transplant SCC has higher recurrence, multifocality, and treatment resistance; requires expedited oncology co-management.
• Recurrence risk (>BCC): overall eyelid SCC recurrence 4–23% (significantly exceeds BCC recurrence at <5% with margin-controlled surgery). Delayed diagnosis substantially increases morbidity and metastatic risk.