What is a pterygium?

Pterygium:
Definition: A pterygium is quite similar to a pinguecula in terms of location, and histologic features, but it encroaches onto the cornea in a winglike fashion.
Epidemiology/Incidence/Prevalence: Pterygia have been reported to occur in males twice as frequently as in females. It is the most common conjunctival specimen that we receive.
Etiology: Several surveys have shown that countries nearer the equator have higher rates of pterygia. UV (ultraviolet) B light may be a risk factor for the development of pterygia. UV B radiation may induce cellular changes in the exposed region of the cornea. Pterygia arise at the nasal or temporal limbus, almost invariably as an extension of a preceding conjunctival pinguecula. Pterygia are most likely initiated by prolonged solar exposure and appear to share many of the histologic features of solar degeneration seen in the skin.
Clinical Findings: Pterygia are usually confined to the exposed surface of the conjunctiva, and usually on the side closest to the nose. Less often, pterygium can also occur on the outer side of the cornea. One or both eyes may be involved. Pterygia may distort or obstruct vision if they grow into the visual axis or produce astigmatism.
Histopathology: Pterygia show the same consistent features as pinguecula but in addition show pannus undermining and destroying Bowman's layer. The destruction of Bowman’s layer (arrow 1 in the figure) by the advancing fibrovascular tissue results in a corneal scar. There is accompanying pannus formation (arrow 2) and chronic inflammation (arrow 3). So called recurrent pterygia lack the histopathologic features of elastotic degeneration and are more accurately classified as exuberant granulation tissue. Ultrastructurally, a case has been made for active elastogenesis in the form of elastic fiber precursors. Newly synthesized microfibrils and amorphous elastin appear to be secreted by fibroblasts as part of the repair process.
Treatment:Pterygia that interfere with vision can be removed surgically. Following surgical removal, it is not unusual for an elevated vascularized scar (“recurrent pterygium”) to form at the excision site. All specimens removed with the clinical diagnosis of pterygium should be examined histologically because squamous carcinoma are all too often thought clinically to be pterygia.

What is conjunctival hemangioma?

Hemangioma of the Conjunctiva
Definition: Proliferation of blood vessels within the substantia propria.
Incidence/ Prevalence: 3 cases of conjunctival hemangioma were reported from a series of 632 conjunctival biopsies, over 25 years so it is extremely rare in pathology material.
Etiology: Some consider the hemangioma of the conjunctiva as a benign neoplasm whereas others consider it an overgrowth of mature tissue that exist normally in the conjunctiva. In the latter instance it would then be considered the most common variety of hamartoma in the conjunctiva.
Clinical Findings: Although it may involve only the conjunctiva, typically the hemangioma is also present in the eyelid, face, and orbit. In the image shown the lesion involves the bulbar conjunctiva, plica and the caruncle. Congenital hemangiomas are detected at or shortly after birth as elevated, soft, red-purple nodules that may continue to grow in the first year of life before stabilizing. The majority of cases then begin a slow process of involution, resulting in complete regression.
Histopathology: The pathologic findings of conjunctival hemangioma change with age. In the early life of the lesion, biopsies reveal a cellular proliferation of plump endothelial cells forming solid nests and cords within the connective tissue stroma. Mitotic figures are often present. In more mature hemangiomas the endothelial cells flatten, forming easily recognizable capillary lumina.
The image above shows large thinned walled vessels filled with blood (arrow 1). In addition erythrocytes have extravasated from the vessels (arrow 2) that are lined by a single layer of endothelium (arrow 3). Click on the image to enlarge it. In the trichrome stained section below of the same case, small capillary size vessels are evident (arrow 4). In addition there are slightly larger vessels (arrow 5). The walls of the vessels contain only a thin layer of collagenous material (blue) (arrow 6). In the involutional phase the lobules of capillary proliferation are replaced by fibrous tissue.
Treatment: Removal is rarely needed and is indicated if vision is compromised. Conjunctival hemangiomas are known to involute without treatment.

What is a choristoma?

Choristomas
Definition: Choristomas are defined as mature tissue elements not normally present at the site of occurrence. Examples include limbal dermoid, dermolipoma, ectopic lacrimal gland, and episcleral osseous choristoma. Teratomas require the presence of all 3 germ layers.
Incidence/Prevalence: Choristomas make up about 3% of conjunctival and corneal tumors in some series.
Etiology: Choristomas are congenital proliferations. Choristomas are occasionally familial.
Clinical Findings: Choristomas are the most common epibulbar and orbital tumors in children. Epibulbar choristomas may arise from the cornea, limbus or subconjunctival space, and range in appearance from a small, flat lesion to a large mass filling most of the epibulbar region. In the photograph the limbal choristoma has extended on to the cornea. Astigmatism is often present. Choristomas may be associated with coloboma, Goldenhar syndrome or epidermal nevus syndromes; those associated with the latter are often bilateral and extensive. Although choristomas most commonly involve the epibulbar area, they can affect many areas of the eye and orbit, and often affect more than one area. Clinically, complex choristomas usually are indistinguishable from dermoids or dermolipomas.
Histopathology: Complex choristomas, in addition to having the features of a dermoid or dermolipoma, include other tissues such as cartilage, bone, and lacrimal gland. In the image above there is cartilage (arrow 1), adipose tissue (arrow 2) and lacrimal gland tissue (arrow 3). A limbal dermoid generally shows a keratinized stratified squamous epithelium covering the surface of the lesion (4) with hair shafts and adnexal structures in the substantia propria. Here sebacaceous glands are prominently displayed (5). In addition the loose collagen of the substantia propria is replaced with dense collagen in thick bundles (6). Compare the limbal dermoid with the dermolipoma (below). The dermolipoma features dense collagen bundles, similar to what is seen in the dermis of skin (7), and adipose tissue (8). However, no adnexal structures are seen. Specifically, neither sebaceous glands nor hair follicles are present in this process. These are the criteria by which this categorical separation is made.
Treatment: Surgery is generally performed to improve vision or cosmesis, or to impede growth.

What is a pinguecula?

Pinguecula
Definition: A pinguecula is a vascularized growth of tissue, often bilateral, situated at the nasal or temporal limbus.
Incidence/Prevalence: Pingueculae occur more commonly in older patients but certainly occur frequently in individuals with prolonged exposure to sunlight at a younger age.
Etiology: Related to ultraviolet light exposure. More common in those living in sunny areas.
Clinical Findings: Wing shaped elevated grey vascular lesions that appear in the interpalpebral fissure (solar related) usually at 3 and 9 o’clock (see clinical photo below arrows labeled 1). They may be yellow particularly if there is accompanying spheroidal degeneration. In the clinical photo there are clearly dilated tortuous vessels (labeled 2).
Histopathology: There are 3 consistent characteristic findings:
1. basophilic degeneration of collagen (solar elastosis). These changes manifest as a nodule of fragmented basophilic degeneration (unlabeled arrows in the low mag photomicrograph below and arrow #1 in hi mag photomicrograph). Also called elastotic degeneration because the degenerated collagen will stain black with the Verhoeff-van Gieson stain and give the appearance of elastic fibers. Controversy arises as some believe pre-existing elastic fibers are involved while others point out that elastase does not eliminate the staining. There also may be a fibrillar degeneration of collagen that is not basophilic.













2. chronic inflammation in the substantia propria. The inflammation is usually mediated by lymphocytes and mononuclear inflammatory cells (arrow #2 in high magnification).
3. Enhanced vascularization (arrow #2 at low mag and arrow number 3 at high magnification). None of these findings are specific but they are virtually immutable. In addition the overlying epithelium is said to be thinned, but alas may be normal, hyperplastic or dysplastic (in which case the main diagnosis is dysplasia). There may be focal keratinization.
Treatment: Pinguecula are usually not removed unless there is concern for dysplasia, cosmesis or prolonged bouts of inflammation. However, with encroachment on the cornea, pinguecula become pterygia and may produce visual symptoms.