B111 Non-melanocytic skin tumors

Question 1

List the non-melanocytic skin tumors

Answer 1

a) Benign and premalignant epithelial lesions
i. Seborrheic keratosis
ii. Sebaceous adenoma
iii. Actinic keratosis

b) Malignant epidermal tumors
i. Squamous cell carcinoma
ii. Basal cell carcinoma

Question 2

Bening epithelial neoplasms

Answer 2

They are common and insignificant

Derived from epidermal stem cells and hair follicle stem cells, and differentiate into epidermal adnexa structures:

hair, errector pilli muscle, sebaceous glands, sweat glands, nails

They have limited growth and do not transform.

Question 3

Seborrheic keratosis

morphology, histology

associated mutations

risk, pathogenesis

Answer 3

Common epidermal tumors in middle age and elderly caused by localized basaloid keratinocyte proliferation.

Morphology

• raised, round, warty lesion.
• Brown of black coloration, which may have multicolored areas
• Has a fissured, variegated surface.

Histology:

• Most imporantly, they remain in the epidermal layer, there is no penetration of the dermis
• This makes them described as having the appearance of being “stuck on” or “pasted on” to the skin
• Form kartin filled microcysts
• The epithelium is predominantly dark staining, large basaloid keratinocytes, and the normal pale staining epithelium may appear to form nests or islands within these darker cells.

Mutations:

• FGF3 receptor activating mutations

Significance:

• Basically just cosmetic
• Except when they suddenly appear in very large numbers.
  
  • This is a paraneoplastic syndrome, called the Lesser-Trelat sign
  • Indicates internal malignancy, usually GI cancers.

Question 4

Actinic Keratosis

Answer 4

A pre-malignant state to melanoma. All have potential to transform. Common in light skinned people, increase with age and sun exposure. If seen should be checked histologically, and removed by local cryotherapy or topical agents

Morphology:

• are flat, red lesions.
• rough, sandpaper textures
• less than 1 cm in diameter
• appear on sun exposed areas, face, arms, hands

Histology

• overall atrophy and thinning of the epidermis
• lower epidermal regions show atypia, which in some cases may extend through all the layers, being squamous cell carcinoma in situ.
• stratum corneum is thickened and contains nuclei
• hyperplasia of basal cells
• blue-gray elastic fibers are seen in the dermis, result from chronic sun damage solar elastosis

Question 5

Squamous cell cacinoma of the skin

mophology, histology

Answer 5

Morphology:

• Appear first as carcinoma in situ, as
  
  • defined, red, scaling plaque
  • May arise out of previous actinic keratosis.
• Advanced, invasive lesions
  
  • Nodular, raised lesion
  • May be scaly
  • Can look like large ulcerative lesions

Histology:

• Full thickness cellular atypia in the epidermis
• Dense, crowded, pleomorphic cells
• Invades through the basement membrane.
• Can be variable differentiated
  
  • well differentiated: orderly clumps of cells with extensive keratinization
  • poorly: disorganized, highly anaplastic cells. foci of necrosis and minimal or abortive keratinization.
    *

Question 6

Presentation and progression of Squamous cell carcinoma

Answer 6

Arises in sun exposed sites in old people.

Higher incidence in males.

Ionizing radiation, industrial carcinogen exposure, chronic ulcers, old burn scars.

It is usually discovered as an isolated lesion. Only 5% have metastasized to lymph nodes by diagnosis, and are easily treatable by resection.

Lesion thickness and invasion to the subcutaneous tissue predicts likelihood of metastasis.

Can also arise in the mucosa surfaces, and these are generally more aggressive.

Question 7

Basal cell carcinoma,

patient population, morphology, histology, associated mutation

Answer 7

Presentation

• Slow growing, rarely metastatic cancer
• Occurs at sun exposed sites, in light skinned elderly people

Morphology:

• Smooth papules that can be pearly and translucent, or pigmented and mimicing nevi
• Prominently dilated subepidermal blood vessels are often visible in the tumors.
• They only arise from skin epidermal basal cell layer or follicular epithelium, can not arise in mucosa
• Can become quite large, several cm, and ulcerated.

Histology:

• Dense cellular tumor,
• Pleomorphic cells composed of almost entirely nuclei and little cytoplasm
• Pallisading arrangement of cells around its periphery
• Tall, columnar basal cells with very little cytoplasm
• Contains multifocal growths located in the epidermis, and nodular lesions; Nests of basal cells penetrating downward into the dermis and subcutaneous layer.

Mutaion:

• Mutations in the PTCH tumor suppressor gene.
• Causes excessive sonic hedgehog pathway signaling.