Description
Orbital Basal Cell Carcinoma (BCC) is a malignant skin cancer that arises from the basal cells of the skin, typically in the periocular region, which includes the eyelids and surrounding tissues. BCC is the most common malignancy of the eyelid.
Pathogenesis
BCC develops as a result of DNA damage in basal keratinocytes, which are cells found in the lowermost layer of the epidermis. The majority of this damage is caused by exposure to ultraviolet (UV) radiation from the sun or artificial sources.
Subtype
- Nodular BCC: The most common subtype, presents as a nodular lesion with telangiectasias on the surface.
- Infiltrative BCC: More aggressive form, demonstrates an ill-defined margin and often invades deeper tissues.
Epidemiology, Risk Factors & Associations
- Common in individuals with light skin types (Fitzpatrick skin types I and II)
- Associated with chronic sun exposure
- Increased incidence in immunosuppressed individuals
Clinical Features
- Slow-growing nodular lesion, often with a central ulceration (“rodent ulcer”)
- Presence of telangiectasias on the lesion surface
- May cause local destruction of tissues, including the eyelid and orbit
Complications
- Local invasion can lead to destruction of the eyelid and surrounding tissues.
- Although rare, distant metastases can occur in aggressive cases.
Pathological Features
Histopathology
- Macroscopic: Presents as a nodular or ulcerative lesion on the eyelid or surrounding tissues.
- Microscopic: Characterised by nests of basaloid cells with palisading nuclei at the periphery of the nests.
Serology
No specific serological markers.
Biochemistry
No specific biochemical markers.
Radiological Features
General Features
- Appears as a soft tissue mass in the eyelid or periocular region.
CT
- Non-contrast: May show an enhancing mass in the periocular region.
- Contrast-enhanced: Enhancing mass with the potential to invade adjacent structures such as the orbit, especially in aggressive cases.
MRI
- T1WI: Tumour is isointense to hypointense compared to muscle.
- T2WI: Tumour is isointense to hypointense compared to muscle.
- T1 C+: Enhances intensely following contrast administration.
- DWI/ADC: No specific characteristics noted.
US
- B-mode: Presents as a hypoechoic soft tissue mass in the eyelid or periocular region.
Grading and Staging
BCC is not typically graded or staged due to its low propensity for metastasis.
Diagnosis
The diagnosis of BCC is confirmed through histopathological examination of a biopsy specimen.
Differential Diagnosis
- Squamous Cell Carcinoma: Presents similarly but typically has a more rapid growth rate and greater propensity for metastasis.
- Sebaceous Gland Carcinoma: May mimic BCC but is more commonly found in the upper eyelid and often associated with loss of eyelashes.
Management
Management includes local excision, which is the first-line treatment for BCC. Mohs micrographic surgery may be considered in cases where tissue preservation is crucial, such as periocular BCC. Radiation therapy may be considered for unresectable tumours or in patients unfit for surgery.