ABSTRACT
Hyperkeratosis: Thickened stratum corneum which appears delicately layered or dense and compact (pink), often with prominent granular layer ( Figure 2.1)
Parakeratosis: Thickened stratum corneum with retained nuclei of the keratinocytes (incomplete keratinization). Note this is normal on mucous membranes (Figure 2.2)
Erosion: Partial loss of epidermis (compare to ulceration, which is complete loss of epidermis/and portion of the dermis)
Acanthosis: Thickening (hyperplasia) of the epidermis
1. Psoriasiform – elongated rete ridges of uniform thickness with suprapapillary thinning (Figure 2.3)
2. Pseudoepitheliomatous hyperplasia (PEH) – extreme hyperplasia of the epidermis and adnexal epithelium, closely simulating squamous cell carcinoma due to pushing bulbously expanded rete ridges, mitoses, and squamous eddies (Figure 2.4)
3. Papillomatosis – acanthosis with irregular undulated projections above the surface of the skin (Figure 2.5)
Atrophy: Decreased thickness of the epidermis (or/and dermis)
Spongiosis: Intercellular edema by stretching the intercellular bridges and separation of the keratinocytes, which appear rhomboid; spongiotic vesicles (blisters) form by coalescing of edematous spaces (see Figure 2.2)
Acantholysis: Complete detachment of keratinocytes which results in intraepidermal clefts, blisters, and
bullae; keratinocytes appear round due to loss of intercellular cohesion (desmosomes) (see Figure 2.1)
Dyskeratosis: Abnormal premature/faulty keratinization of individual keratinocytes (or less often group of keratinocytes) which show pycnotic (shrunken) nucleus and pink cytoplasm (Figure 2.6)
• Corps ronds – “swollen” round cells with normal cytoplasm and perinuclear halo, look like “owl’s eye” (in stratum spinosum and stratum granulosum)
• Corps grains – “shrunken” oval cells with condensed cytoplasm, look like “plump parakeratosis” (in stratum granulosum and stratum corneum)
Apoptosis: A normal (programmed)/abnormal (premature or faulty) cell death resulting in shrunken keratinocytes with dense and pink (eosinophilic) cytoplasm and condensed nucleus which can be fragmented; they are shed in the dermis as colloid bodies/Civatte bodies (eosinophilic deposits in the lower epidermis or upper dermis formed from the intracellular filaments of apoptotic keratinocytes; may entrap immunoglobulin or fibrin)
NB In a 6 mm punch biopsy a normal epidermis has one or two apoptotic cells.
