What is pericanthal Squamous Cell Carcinoma (SCC)?

Pericanthal Squamous Cell Carcinoma (SCC)

Pericanthal squamous cell carcinoma (SCC) is a malignant tumor arising from the keratinizing cells of the epidermis or its appendages in the periocular region, specifically near the medial or lateral canthi of the eye, with potential for local invasion, perineural spread, and metastasis.

Definition and Clinical Presentation

• Pericanthal SCC is a variant of cutaneous squamous cell carcinoma that develops in the periocular region, specifically near the canthi (medial or lateral corners) of the eye 1
• It typically presents as an indurated nodular keratinizing or crusted tumor that may ulcerate, or as an ulcer without evidence of keratinization 2
• Due to its location near critical structures of the eye, pericanthal SCC requires special consideration for diagnosis and management 1

Risk Factors

• Chronic ultraviolet light exposure is the primary risk factor, making it common in sun-damaged skin of fair-skinned individuals 2
• Other risk factors include:
  • Previous exposure to ionizing radiation or arsenic 2
  • Development within chronic wounds, scars, burns, ulcers or sinus tracts 2
  • Pre-existing lesions such as Bowen's disease (intraepidermal SCC) 2
  • Immunosuppression (organ transplantation, lymphoma, leukemia) 2
  • Human papillomavirus infection 2

Diagnosis

• Definitive diagnosis is established histologically through biopsy 2
• A comprehensive histology report should include:
  • Pathological pattern (e.g., adenoid type) 2
  • Cell morphology (e.g., spindle cell SCC) 2
  • Degree of differentiation (well or poorly differentiated) 2
  • Histological grade (as described by Broders) 2
  • Depth (thickness in mm) 2
  • Level of dermal invasion (Clark's levels) 2
  • Presence or absence of perineural, vascular or lymphatic invasion 2

Prognostic Factors

• Size: Tumors greater than 2 cm in diameter are twice as likely to recur locally (15.2% vs. 7.4%) and three times as likely to metastasize (30.3% vs. 9.1%) compared to smaller tumors 2
• Depth: Tumors greater than 4 mm in depth or extending to subcutaneous tissue (Clark level V) have higher recurrence and metastasis rates (45.7%) compared to thinner tumors 2
• Location: Periocular region, including the canthi, is considered a high-risk location due to proximity to critical structures and potential for perineural invasion 2
• Histologic subtype: Aggressive subtypes include adenoid (acantholytic), desmoplastic, and poorly differentiated variants 3
• Perineural invasion: A particularly concerning feature in periocular SCC that significantly increases risk of recurrence, orbital invasion, and intracranial spread 1, 4

Treatment Considerations

• Surgical excision is the treatment of choice for the majority of pericanthal SCCs 2
• For low-risk, well-defined tumors less than 2 cm in diameter, surgical excision with a minimum 4-mm margin is appropriate 2
• For high-risk tumors (larger size, higher grade, deeper invasion) or those in the periocular region, wider margins (6 mm or more) with histological examination or Mohs micrographic surgery is recommended 2, 1
• Mohs micrographic surgery is particularly valuable for pericanthal SCC as it:
  • Provides the highest cure rates in this high-risk area 1
  • Allows for smaller margins of excision where tissue conservation is important 1
  • Enables immediate histological monitoring of surgical margins 1

Special Considerations for Pericanthal Location

• Due to the proximity to critical orbital structures, pericanthal SCCs require careful evaluation for:
  • Orbital invasion 4
  • Perineural spread, which may present with neurologic symptoms including pain, burning, stinging, anesthesia, paresthesia, facial paralysis, diplopia, or blurred vision 2
  • Potential for intracranial extension, particularly with perineural invasion 4

Follow-up and Monitoring

• Regular follow-up is essential as pericanthal SCCs can recur locally 5
• Patients with high-risk features should be monitored more closely for recurrence and metastasis 2
• Perineural invasion warrants particular vigilance as it carries a poor prognosis, with death resulting in over 50% of cases at 5 years 4

Common Pitfalls

• Misdiagnosis due to variable clinical presentation - all suspicious lesions warrant biopsy 1
• Inadequate surgical margins, particularly critical in the periocular region 1
• Failure to recognize perineural invasion, which requires a high degree of clinical suspicion 4
• Underestimating the aggressive potential of certain histologic subtypes 3