4. Stratum basale/germinativum (“basal or “forming”
layer)
One layer thick mitotic cells
10-25% melanocytes with processes into next layer
Merkel cells with sensory neurons
Stratum spinosum (“prickly” layer)
Cells appear spiny due to numerous desmosomes
Many Langerhans cells
Stratum granulosum (“grainy” layer)
Cells flatten
Organelles/nuclei begin to disintegrate
Keratin precursor granules begin to form
Stratum corneum + Lucidum(“horny” layer)
Cells are dead—too far from underlying capillaries to live
20-30 cells thick up to ¾ of dermal thickness
5.
6. Definitions
Hyperkeratosis
Thickening of the stratum corneum, often associated
with a qualitative abnormality of the keratin.
Parakeratosis
Modes of keratinization characterized by the retention
of the nuclei in the stratum corneum.
Dyskeratosis
Abnormal keratinization occurring prematurely within
individual cells or groups of cells below the stratum
granulosum
7. Acanthosis
Diffuse epidermal hyperplasia
Acantholysis
Loss of intercellular connections resulting in loss of
cohesion between keratinocytes.
8. keratocanthoma
Dome-shaped
nodule with central
keratin plug; 1-5 cm.
diameter
Cup-shaped lesion with
central crater of keratin;
downward pushing rounded
border
Higher power
keratoacanthomalarge, glassy
squamous cells with
islands of
eosinophilic keratin.
10. Histology - SCC
Irregular masses of epidermal cells proliferating
into dermis
Keratinization in well-differentiated tumors
Range in degree of anaplasia
11. In Situ SCC
In situ SCC-type II (moderate) with atypical
keratinocytes extending to the lower two thirds of the
epidermis
12. In situ SCC
In situ SCC-type III (severe) with atypical
keratinocytes extending more than two thirds to full
thickness
of the epidermis
13. SCC
Irregular tongues of dysplastic
squamous epithelium invading the
dermis
Epithelial cells exhibit glassy
eosinophilic cytoplasm. Dyskeratotic
cells, parakeratosis and horn pearl
formation are also observed.
17. Basal Cell Carcinoma
HISTOLOGY
•Large oval
nuclei with
little cytoplasm
•Nuclei are
uniform
•Connective
tissue stroma
causes
palisading
Nests of basaloid cells within the dermis
21. Baso Squamous
Shows feature of both basal
cell and squamous cell carcinomas
More aggressive clinically
Undifferentiated cells in
combination with
parakeratotic cells and
horn cysts
22. Evolution of dysplastic nevus into malignant melanoma over time
(not inevitable, but the potential always exists)
Lentigo
Junctional
Nevus
Advanced MM:
vertical growth
into dermis
Dysplastic
compound
nevus
Early MM: radial
growth in
epidermis,
superficial dermis
28. Nests of small blue
cells, with minimal
cytoplasm
Electron Microscopy: membrane-bound dense
core neurosecretory granules (blue arrows) and
stacks of perinuclear cytokeratin filaments
(black arrows)
30. Staining for HHV-8 in KS
IHC for HHV-8- been shown
99% sensitive
100% specific
31. Densely cellular spindle cells in radially arranged fascicles,
invading into subcutis and muscle fibers.
Main portion shows a storiform arrangement with extension into
the subcutaneous fat, with fat entrapment creating a honeycomb
pattern