Epidermis – primarily cellular

•  Keratinocytes – main cell type in epidermis; originate from basal layer; provide mechanical barrier

•  Melanocytes – neuroectodermal origin (neural crest cells); in basal layer of epidermis

•  Have dendritic processes that transfer melanin to neighboring keratinocytes via melanosomes

•  Density of melanocytes is the same among races; difference is in melanin production

  Dermis – primarily structural proteins (collagen) for the epidermis

  Langerhans cells

•  Act as antigen-presenting cells (MHC class II)

•  Originate from bone marrow

•  Have a role in contact hypersensitivity reactions (type IV)

  Sensory nerves

•  Pacinian corpuscles – pressure

•  Ruffini’s endings – warmth

•  Krause’s end-bulbs – cold

•  Meissner’s corpuscles – tactile sense

  Eccrine sweat glands – aqueous sweat (thermal regulation, usually hypotonic)

  Apocrine sweat glands – milky sweat

•  Highest concentration of glands in palms and soles; most sweat is the result of sympathetic nervous system via acetylcholine

  Lipid-soluble drugs – ↑ skin absorption

  Type I collagen – predominant type in skin; 70% of dermis; gives tensile strength

  Tension – resistance to stretching (collagen)

  Elasticity – ability to regain shape (branching proteins that can stretch to 2× normal length)

  Cushing’s striae – caused by loss of tensile strength and elasticity

FLAPS

  MCC of pedicled or anastomosed free flap necrosis – venous thrombosis

  Tissue expansion occurs by local recruitment, thinning of the dermis and epidermis, mitosis

  TRAM flaps

•  Complications – flap necrosis, ventral hernia, bleeding, infection, abdominal wall weakness

•  Rely on superior epigastric vessels

•  Periumbilical perforators most important determinant of TRAM flap viability

UV RADIATION

  Damages DNA and repair mechanisms

  Both a promoter and initiator

  Melanin single best factor for protecting skin from UV radiation

  UV-B – responsible for chronic sun damage

MELANOMA

  Represents only 5% of skin CA but accounts for 65% of the deaths

  Risk factors for melanoma:

•  Dysplastic, atypical, or large congenital nevi – 10% lifetime risk for melanoma

•  Familial BK mole syndrome – almost 100% risk of melanoma

•  Xeroderma pigmentosum

•  Fair complexion, easy sunburn, intermittent sunburns, previous skin CA, previous XRT

•  10% of melanomas familial

  Most common melanoma site on skin – back in men, legs in women

  Prognosis worse for men, ulcerated lesions, ocular and mucosal lesions

  Signs of melanoma (ABCDE) – asymmetry (angulations, indentation, notching, ulceration, bleeding), borders that are irregular, color change (darkening), diameter increase, evolving over time

  Originates from neural crest cells (melanocytes) in basal layer epidermis

  Blue color → most ominous

  Lung – most common location for distant melanoma metastases

  Most common metastasis to small bowel – melanoma

  Dx:

•  < 2 cm lesion – excisional biopsy (tru-cut core needle biopsy) unless cosmetically sensitive area – need resection with margins if pathology comes back as melanoma

•  > 2 cm lesions or cosmetically sensitive area – incisional biopsy (or punch biopsy), will need to resect with margins if pathology shows melanoma

  Types:

•  Melanoma in situ or thin lentigo maligna (Hutchinson’s freckle) – just in the superficial papillary dermis; 0.5-cm margins OK

•  Lentigo maligna melanoma – least aggressive, minimal invasion, radial growth 1st usual; elevated nodules

•  Superficial spreading melanoma – most common, intermediate malignancy; originates from nevus/sun-exposed areas

•  Nodular – most aggressive; most likely to have metastasized at time of diagnosis; deepest growth at time of diagnosis; vertical growth 1st; bluish-black with smooth borders; occurs anywhere on the body

•  Acral lentiginous – very aggressive; palms/soles of African Americans

  Staging – chest/abd/pelvic CT, LFTs, and LDH for all melanoma ≥ 1 mm; examine all possible draining lymph nodes

  Tx for all stages → 1) resection of primary tumor with appropriate margins and; 2) management of lymph nodes

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