In adults, conjunctival squamous papilloma usually appear as single and unilateral lesions, commonly arising close to the limbal area or bulbar conjunctiva. They are usually flat with a broad base, may be large and cover a large area of the conjunctiva, and may cover the cornea and interfere with vision. Sometimes it may be difficult to differentiate them clinically from squamous cell carcinoma.

Histologically, the squamous papilloma of childhood is composed of epithelial projections covered by nonkeratinized acanthotic stratified squamous epithelium, which may have goblet cells, and have a fibrovascular core in which acute and chronic inflammatory cells are often found (Fig. 15.1b). The basement membrane is always intact. Human papilloma virus has been demonstrated in these papillomas by various immunohistochemical and molecular techniques [5, 6].

In adults, the squamous papilloma usually has a broader base, and its acanthotic epithelium may show varying degree of epithelial pleomorphism, and even dysplasia can occur, albeit generally mild. Although the lesions are usually nonkeratinized, moderate keratinization may be present. The basement membrane is typically intact.

Small papilloma in children can be observed, as there usually is a slow spontaneous resolution. However, larger papillomas should be treated by complete surgical excision, preferably by the “no-touch technique” in order to avoid spreading the papilloma-related virus [3]. Cryotherapy is often used in conjunction with surgical excision, either to the conjunctiva around the excised lesion or to the lesion itself that is then excised in frozen state. Sometimes cryotherapy may be performed without excision, letting the lesion slough off the conjunctival surface later.

Conjunctival papillomas tend to recur often, usually when multiple lesions are caused by papillomavirus. Such lesions may be treated by adjuvant interferon alpha-2B locally or systemically [7, 8] or topical mitomycin C [9]. Others have used carbon dioxide laser vaporization [10], and there is one report of effective treatment of recurrent conjunctival papillomas with oral cimetidine [11].

The lesions derive their name from the propensity to invaginate inward into the underlying conjunctival substantia propria, instead of growing in an exophytic manner outward like the other conjunctival papillomas. Some of the lesions may show a mixed inverted-exophytic papilloma [12].

Seborrheic keratosis of the conjunctiva is extremely rare, and only a very few case reports are found in the medical literature [14]. They mostly appear as a pigmented conjunctival lesion and may be misdiagnosed clinically as conjunctival melanoma. The typical basaloid cell acanthosis and keratin-filled pseudocysts confirm the diagnosis.

This conjunctival lesion is secondary to irritation by concurrent or preexisting stromal inflammation [1–3].

This is a variant of conjunctival reactive epithelial hyperplasia that does not show spontaneous regression [1, 3, 15].

HBID is an autosomal dominant disorder with a high degree of penetrance occurring in descendants of an inbred isolate of European, African-American, and Native American (Haliwa Indian) origin in northeastern North Carolina. HBID has been subsequently detected in other parts of the United States. Using genetic linkage analysis, the HBID gene was localized to chromosome 4 (4q35) [16].

Dacryoadenoma is a rare conjunctival tumor that occurs in children and young adults. It appears as translucent pink lesion in the bulbar, forniceal, or palpebral conjunctiva [3]. It is uncertain whether the lesion is congenital or acquired. Histologically it is a benign epithelioid cell proliferation forming glandular lobules, similar to the lacrimal gland. In one reported case, scattered myoepithelial cells were associated with acinar-type epithelium, and goblet cells were intermixed [17]. The lesions are treated by simple excision.

Oncocytoma, known also as oxyphilic cell adenoma, is a rather common lesion of the lacrimal gland. It often arises in the caruncle or adjacent plica semilunaris and canthal conjunctiva as a slowly-growing benign yellow-tan or reddish lesion in older individuals, mostly women [2, 18]. Histologically, large cells with eosinophilic granular cytoplasm are arranged in nests, cords, or sheets and may form glandular or ductal structures. Ultrastructurally, the cytoplasm is laden with mitochondria. The lesion is treated by simple excision. Rarely, the tumor may undergo carcinomatous transformation.

Conjunctival cysts are common and may be congenital or acquired. The acquired cysts are more common and are mostly epithelial inclusion cysts that can occur spontaneously or following surgical or nonsurgical trauma [1, 3] (Fig. 15.4). Other common cysts are ductal cysts, usually of accessory lacrimal gland origin (Fig. 15.5).

This is a leukoplakic lesion that may develop in the limbal or bulbar conjunctiva, usually in the interpalpebral region [1, 2]. Histologically there is a focal thickening of keratin and epithelial layer, characterized mainly by acanthosis, hyperkeratosis, or parakeratosis. No dyskeratosis is seen. These lesions have little or no potential for carcinomatous changes.