Figure 13-1 Cross section of a normal eyelid. Proceeding from top (anterior) to bottom (posterior), note the epidermis; the dermis, resting on the orbicularis; the tarsus, surrounding the meibomian glands; and the palpebral (tarsal) conjunctiva.
Following are several terms used commonly in dermatopathology:
acanthosis: increased thickness (hyperplasia) of the stratum malpighii (consisting of the strata basale, spinosum, and granulosum) of the epidermis
hyperkeratosis: increased thickness of the stratum corneum of the epidermis
parakeratosis: retention of nuclei within the stratum corneum with corresponding absence of the stratum granulosum
papillomatosis: formation of fingerlike upward projections of epidermis lining fibrovascular cores
dyskeratosis: premature individual cell keratinization within the stratum malpighii
acantholysis: loss of cohesion (dissolution of intercellular bridges) between adjacent epithelial cells
spongiosis: widening of intercellular spaces between cells in the stratum malpighii due to edema
Table 13-1
Congenital Anomalies
See also BCSC Section 7, Orbit, Eyelids, and Lacrimal System.
Distichiasis
Distichiasis is the aberrant formation within the tarsus of cilia that exit the eyelid margin through the orifices of the meibomian glands. The pathogenesis of distichiasis is thought to be an anomalous formation within the tarsus of a complete pilosebaceous unit rather than the normal sebaceous (meibomian) gland. Histologically, hair follicles can be seen within the tarsal plate. The tarsus may be rudimentary, and the glands of Moll are often hypertrophic. See BCSC Section 6, Pediatric Ophthalmology and Strabismus, and Section 8, External Disease and Cornea, for additional discussion.
Phakomatous Choristoma
A rare congenital tumor, phakomatous choristoma (Zimmerman tumor) is formed from the aberrant location of lens epithelium within the inferonasal portion of the lower eyelid. These cells may undergo cytoplasmic enlargement, identical to the “bladder” cell in a cataractous lens. PAS-positive