dermatology and cancer Flashcards
How many layers are present in the epidermis of a layer of thick skin and what are these?
5 stratum basale/germinativum stratum spinosum stratum granulosum stratum lucidum stratum corneum
What cells/ structures are present in the stratum basale?
stem cells/basal cells that continually replicate to replenish the loss of keratinocytes from the outer layers. Melanocytes are also most commonly present here where they produce melanin and transfer it to the nuclei of the basal cells. Merkel cells are also present- slowly adapting mechanoreceptors stimulated by deformation of the epidermis
What cells/structures are present in the stratum spinosum?
desmosomally connected keratinocytes giving a spiny appearance
What cells/structures are present in the stratum granulosum?
many staining granules of keratohyalin (form cross links between the developing keratin and help to dehydrate the cells (death of cells) in addition lamellar bodies help to provide the lipid rich covering to the cells which improves water proofing. Melanocytes.
What cells/structures are present in the stratum lucidum?
Cells form clear layers as they lose their nuclei and organelles, contain an intermediate form of keratin (eleidin). Melanocytes
What cells/structures are present in the stratum corneum?
Terminal differentiation step in the keratinocytes (stratified squamous). Cells shrink and leave behind the strongly linked keratin strands/lipid-rich lamellar bodies/ceramide.
What inflammatory/immune cells are present in the skin?
Langerhans cells are present in the epidermis and are APCs, lymphocytes are present in both the epidermis and dermis, histiocytes are wandering macrophages in the dermis that collec pigments and inflammatory debris, mast cells are found in the papillary dermis.
What is contained within the papillary dermis?
This is the dermal layer that comes into contact with the rete ridges of the epidermis and contains a rich blood, lymphatic and nerve supply for the stratum basale. Hair traverses it from the reticular dermis. It contains looser collagen fibres and elastin compared to the more fibrous and tough reticular layer.
Give some examples of genes/proteins involved in carcinogenesis.
P53- this is a gatekeeper gene that is able to reduce activation of a protein that enhances cyclin-CDK complexes and produce a protein that inhibits these directly. Hence the cell is inhibited from entering the cell cycle.
BRCA1/2- these genes code for caretaker proteins that repair damage in DNA in response to the detection of these mistakes by ATM proteins and hence can initiate DNA repair processes
KRAS- these genes are forms of proto-oncogenes that affect G-proteins and can hence mutate and become constitutively activated even in the absence of growth factors etc.
MYC- these are genes that code for transcription factors and may become aberrant causing excess or powerful transcription of genes needed to enter the cell cycle.
Rb- this protein inhibits a transcription factor E2F in its inactivated form. When phosphorylated however this induces a conformational change and allows release of the E2F leading to transcription of proteins needed to enter the cell cycle.
What subtypes of lung cancer exist and what are their relative proportions?
squamous cell (25-40%) adenocarcinoma (25-40%) large cell (10-15%) small cell (<20%)
What distinguishes a squamous cell carcinoma?
if well enough differentiated, there will be signs of intercellular bridges and keratinisation. Normally near the hila.
What distinguishes an adenocarcinoma?
signs of glandular differentiation, alveolar hyperplasia is a an early warning sign, mucin production. Often in the lung peripheries.
What distinguishes a small cell carcinoma?
poorly differentiated neuroendocrine cells- major cause of paraneoplastic syndromes.
name 5 signs/symptoms seemingly unrelated to the lungs that a patent may present with.
pancoast’s- Horner’s syndrome, brachial plexus damage
SVC syndrome
rib involvement and destruction
damage to recurrent laryngeal nerve (hoarseness)
damage to phrenic nerve (diaphragm paralysis)
paraneoplastic- hyponatraemia, hyper/hypocalcaemia, carcinoid, cushing’s
name some known carcinogens/irritants in cigarette smoke.
polycyclic aromatic hydrocarbons (benzene)- squamous cell
nitrosamine- adenocarcinoma
hydrogen cyanide- cilia paralysis
