KEY NOTES CHAPTER 2: SKIN AND SOFT TISSUE LESIONS - Benign Non-pigmented Skin Lesions. Flashcards
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.
