KEY NOTES CHAPTER 2: SKIN AND SOFT TISSUE LESIONS - Benign Non-pigmented Skin Lesions. Flashcards
(16 cards)
What skin lesions are of epidermal origin?
Seborrhoeic keratosis Squamous papilloma Viral wart Actinic keratosis Keratin horn Bowen's disease Keratoacanthoma
How do you classify benign non-pigmented skin lesions?
Benign non-pigmented skin lesions can derive from:
Epidermis:
∘ Keratinocytes
∘ Melanocytes
∘ Merkel cells
Dermis: ∘ Hair follicles ∘ Sebaceous glands ∘ Apocrine glands ∘ Eccrine sweat glands ∘ Neural tissue
Miscellaneous: ∘ Epidermoid cysts ∘ Pilar cysts ∘ Milia ∘ Xanthelasma.
Tell me about the different lesions and their treatments.
Seborrhoeic keratosis
• Common; aka basal cell papilloma.
• Greasy plaque-like lesion
• Treated by curettage.
Squamous papilloma
• Common; aka ‘skin tag’ or ‘acrochordon’.
• Treated by excision.
Viral wart
• Caused by HPV epidermal infection
• Treated by cryotherapy, curettage or laser.
Actinic (solar) keratosis (AK)
• Scaly, crusted area; typically on sun-exposed areas in the elderly.
• Recent evidence suggests AK is part of a spectrum from sun-damaged skin to SCC in situ.
∘ 0.1% per year progress to SCCs
∘ 15-25% per year spontaneously regress.
• Treatment: monitor, cryotherapy, PDT, or topical imiquimod, diclofenac or 5-fluorouracil (5-FU).
Keratin horn
• Hard, protruding lump of cornified proliferation of keratin.
• Base is benign in 50%, malignant in 20% (usually SCC) and AK in 30%.
What is Bowen’s disease?
- John T Bowen (1912): American dermatologist.
- Red scaly lesion, usually elderly.
- Histologically resembles SCC limited to epidermis (in situ SCC).
- 3-5% develop into invasive SCCs.
- Treatment options: cryotherapy, curettage, excision, topical 5-FU, imiquimod, PDT.
What is a keratoacanthoma?
• Benign epithelial tumour of pilosebaceous origin composed of keratinising squamous cells.
• Characterised by rapid evolution (weeks or months) into a nodule with a central keratotic core.
• Followed by spontaneous involution to a depressed scar ~ 4-6 months.
• Histologically difficult to differentiate from SCCs.
• Some maintain they are well-differentiated SCCs rather than a distinct entity.
• Familial forms of KA include:
∘ Ferguson-Smith syndrome
∘ Muir-Torre syndrome.
What syndromes are associated with keratoacanthomas?
Ferguson-Smith syndrome
Muir-Torre syndrome
What is Ferguson-Smith syndrome?
• Linked to a single gene mutation on chromosome 9, characterised by:
∘ Autosomal dominant inheritance
∘ Multiple self-healing epitheliomas, which look and behave like KAs.
• Most patients can trace their ancestry to an 18th century family in Western Scotland.
What is Muir-Torre syndrome?
• Described by Muir (1967), then Torre (1968).
• Autosomal dominant in 2/3 cases: mutation in one of the DNA mismatch repair genes hMLH1 or hMSH2.
• Characterised by:
∘ One or more sebaceous neoplasms (sebaceous adenoma, sebaceous epithelioma, sebaceous carcinoma) or KAs
∘ One or more visceral malignancies (usually gastrointestinal or genitourinary carcinomas).
How are dermal skin lesions classified histologically?
Hair follicles (pilar) differentiation
- Trichoepithelioma
- Trichofolliculoma
- Trichoblastoma
- Tricholemmoma
- Pilomatrixoma
Sebaceous glands
- Sebaceous naevus
- Sebaceous gland hyperplasia
- Sebaceous adenoma
Sweat glands
- Poroma
- Syringoma
- Syringocystadenoma papilliferum (SCAP)
- Hidrocystoma
Neural tissue
- Neurofibroma
- Neurilemmoma
What are the hair follicle derived skin lesions?
Trichoepithelioma
• Translucent pinky-white nodules (Diff dx BCC)
• Often located around nose and mouth; may run in families.
Trichofolliculoma
• Nodules and central pore often containing white hairs.
• Histologically like BCC with additional keratin-filled macrocysts.
Trichoblastoma
• Slow-growing solitary nodule in H&N.
• Clinically and histologically similar to trichoepithelioma and BCC.
Trichilemmoma
• Small, skin-coloured, warty papules usually on face.
• Cowden’s disease
- AD
- Characterised by multiple hamartomas and high risk of breast, endometrial and thyroid carcinoma.
- Mucocutaneous lesions (90%)
∘ Facial trichilemmomas
∘ Acral keratoses
∘ Oral papillomatous papules and mucosal cobblestoning.
- Hamartomatous polyps of intestinal tract (40-60%).
Pilomatrixoma
• Calcifying epithelioma of Malherbe.
• Arises from outer root sheath cells of hair follicles.
• Solitary rock-hard subcutaneous nodule (children).
∘ 40% in first decade of life; another 20% second.
∘ H&N, limbs, trunk. Periocular tissues involved in 10-17%; 5% of cases are multifocal.
• Malignant change rare.
• Treated by excision.
Sebaceous naevi are derived from sebaceous gland differentiation. How do you manage these lesions?
• Aka sebaceous naevus of Jadassohn / organoid naevus.
• Typically present at birth; may enlarge and become raised in puberty due to sebaceous gland hyperplasia.
• Scalp lesions often excised on aesthetic grounds because they cause a bald patch.
• Some excise because of ~15% chance of transformation into secondary tumour:
- Benign = 13.6% into syringocystadenoma papilliferum (SCAP), trichoblastoma or trichilemmoma.
- Malignant = 0.8% into BCC (SCC, malignant appendigeal tumour very rare).
BUT French paper (Cribier et al., Journal of the American Academy of Dermatology 2000):
- ~600 SN analysed.
- BCCs = 0.8% (mean age 40)
- Benign tumours = 13.6% (mean age 46)
- Age under 16: 232 cases, no malignancies, only 1.7% benign tumours.
• Clinical follow-up rather than excision especially children is sufficient.
What other lesions are derived from sebaceous gland differentiation?
Sebaceous gland hyperplasia
• Small yellowish papules; usually found on the face.
• Dermoscopy helps differentiate between this and BCC.
• Rhinophyma is severe sebaceous hyperplasia of the nose.
Sebaceous adenomas
• Small smooth papules; usually occur on the scalp of the elderly.
What lesions are derived from sweat gland differentiation?
Poroma
• Relatively common; small nodules on palms or soles of adults.
Cylindroma
• Pink lesions; usually on scalps of elderly.
• Large or multiple lesions = ‘turban tumours’.
Syringoma
• Small, skin-coloured dermal papules.
• Typically on eyelid and chest of women.
• A subtype of syringoma is associated with Down’s syndrome.
Syringocystadenoma papilliferum (SCAP)
• Solitary papule or smooth hairless plaque on scalp and forehead.
• De novo or in association with sebaceous naevus.
Hidrocystoma
• Cystic lesion; typically on face.
• Can differentiate into apocrine and eccrine subtypes.
What dermal skin lesions are derived from neural tissue?
Neurofibroma
• Skin-coloured nodule composed of neural tissue and keratin.
• Arises from non-myelinating Schwann cells +/- other cell types.
• Classified into dermal and plexiform subtypes:
∘ Dermal (cutaneous) NF: associated with a single peripheral nerve.
∘ Plexiform NF: associated with multiple nerve bundles. Large infiltrative lesions usually in head and neck. 2 types:
1. Nodular
2. Diffuse (aka elephantiasis neurofibromatosa).
∘ Characterised by wrinkled, pendulous appearance due to overgrowth of skin and subcutaneous tissue.
• Wound complications are common following excision.
• Neurofibromas can occur as solitary lesions or associated with neurofibromatosis (see Chapter 3, ‘Craniofacial)
Neurilemmoma
• Also known as schwannoma; composed solely of myelinating Schwann cells (more homogeneous than neurofibroma).
• Encapsulated tumours; can be separated from parent nerve, unlike neurofibroma.
• Multiple neurilemmomas should raise possibility of NF.
What other miscellaneous skin lesions are there (1)?
Inclusion cysts
• Implantation cysts result from trapping a segment of epidermis within dermis following trauma.
Dermoid cysts
• Occur following entrapment of embryonic epithelium at sites of fusion during facial development.
• Usually submuscular
- angular dermoids = outer corner of eye
- central dermoids = midline between forehead and nasal tip.
- more posteriorly, associated with anterior fontanelle.
• Central dermoids may have deep intracranial extensions: preoperative radiological assessment is recommended.
Epidermoid cysts
• Most common
• Firm subcutaneous swellings attached to skin.
• May have an overlying punctum
• Histologically, consist of stratified squamous epithelium surrounding keratinised material + sebum secreted by sebaceous glands.
• Treated by excision of cyst + overlying punctum.
Gardner syndrome
• Autosomal dominant, characterised by:
1. Familial polyposis coli with 100% risk of malignant transformation
2. Multiple skin and soft tissue tumours
- Epidermoid cysts, desmoid tumours, other benign tumours.
3. Jaw osteomas.
Pilar cysts
• aka trichilemmal cysts.
• Similar to epidermoid cysts but derive from outer root sheath of hair follicles.
• Typically occur on scalp.
• Most occur sporadically; some are autosomal dominant.
• Treated by surgical excision.
What other miscellaneous skin lesions are there (2)?
Milia
• Small, keratin-filled intraepidermal cysts.
• Usually occur on the cheeks.
• In children, they typically disappear on their own.
• In adults, they may require treatment by needle enucleation.
Xanthelasma
• Represent accumulation of lipid within the skin.
• Usually located around the eyes as thin, well-demarcated plaques.
• Xanthelasmata that become large or nodular are called xanthomas.
• Myocardial infarction, ischaemic cardiovascular disease and death are commoner in patients with xanthelasmata than in those without.
∘ Serum lipids should be checked: 50% will have hypercholesterolaemia.
• Removal is accomplished by excision, laser or topical trichloroacetic acid peel.
