[Collision tumor]

Area of Science:

• Dermatology
• Oncology
• Ophthalmology

Background:

• Periocular tumors require careful diagnosis due to the sensitive location.
• Collision tumors, where two distinct neoplasms arise at the same site, are uncommon.

Observation:

• A 65-year-old woman presented with a painless, lower eyelid lesion exhibiting both pigmented and hyperkeratotic features.
• The lesion was surgically resected for definitive diagnosis.

Findings:

• Histopathology revealed a collision tumor comprising a highly differentiated squamous cell carcinoma and a fibrosing basal cell carcinoma.
• The coexistence of these specific tumor types in a single lesion is exceptionally rare.

Implications:

• This case underscores the diagnostic challenges and rarity of combined squamous and basal cell carcinomas in the periocular region.
• Accurate histopathologic evaluation is crucial for identifying complex neoplastic presentations and guiding appropriate treatment strategies.