What is squamous carcinoma of the conjunctiva?

Squamous carcinoma of conjunctiva (cornea)
Definition: malignant neoplasm of conjunctiva characterized by invasion of the substantia propria and squamous differentiation
Incidence/Prevalence: squamous carcinoma is the most common conjunctival malignancy in adults. The conjoined incidence of dysplasia, carcinoma in situ, and invasive carcinoma of the cornea and conjunctiva was estimated to be 1.9 per 100,000 per year averaged for 10 years in a study from Brisbane, Australia. In a study from Queensland, Australia, 288 cases were identified : 155 dysplasia, 71 carcinoma in situ, and 62 squamous cell carcinoma. 78.5% of the cases occurred in males with an average age of 60.1 years.
Etiology: Squamous carcinoma is strongly correlated to overexposure of the conjunctiva to ultraviolet light. The appearance of dysplasia has also been found to result from human papillomavirus type 16 (HPV 16).
Clinical Findings: Most present in elderly people as a white vascularized lesion in the limbal and perilimbal areas of the interpalpebral fissure. Squamous carcinomas usually invade superficially. The lesions may be papillary and elevated and even protrude from the interpalpebral fissue in neglected cases. Squamous carcinomas often mimic pterygium, the most frequent misdiagnosis. If dendritic melanocytes are present, squamous carcinoma in situ or squamous carcinoma may even be misdiagnosed clinically as malignant melanoma. If the tumor infiltrates the eye, the reaction may masquerade as an anterior uveitis, glaucoma (as the trabecular meshwork is blocked) or as epithelial downgrowth.
Histopathology: In general one finds the presence of multiple areas of squamous carcinoma in situ and dysplasia (arrows 1 in the figure) that





















coexist with invasive nests of squamous cells that infiltrate through the basement membrane of the epithelium. Invasive nests (arrows 2) have a characteristic signature of groups of cells that form pointed extensions (arrows 4), isolated islands, strands or single cells in the collagen of the substantia propria. In these photographs there are numerous invasive nests as well a broad sheets of tumor that infiltrate the substantia propria. There may be associated fibrosis, desmoplasia and retraction artifact (arrow 3) associated with the tumor .





















Various degrees of squamous differentiation may be present as indicated by individual cell dyskeratosis (arrow 2), surface keratinization, squamous eddies, squamous pearls, and intercellular bridges.
Treatment: Complete excision is generally recommended. This has been successfully combined with adjunctive cryotherapy and topical chemotherapy with Mitomycin C and 5FU. Careful dissection to remove the tumor in one piece is helpful for evaluation of margins. A suture should be placed in the specimens at 12 o’clock for orientation and most important the specimen should be placed on filter paper in the operating room and fixed in the flat state so that tangential sectioning is avoided. It is best for the pathologist to examine and ink the margins under a dissecting microscope to ensure that the specimen remains flat. Embedding is best performed with the aid of a dissecting microscope as well.
Prognosis: Generally the tumors invade superficially in the conjunctiva and cornea but in longstanding or aggressive cases the carcinomas may invade locally into the eye and orbit. Regional lymph node metastases occur but are relatively uncommon. Several authors have noted that death from metastatic disease occurs but is quite rare from this tumor (1-2% of most series).