BENIGN SKIN LESIONS
Classification based on tissue of origin
1)
tumors of epidermis
2)
tumors of epidermal appendage(hair structures, sebaceous glands, apocrine
and eccrine glands)
3)
dermis
Tumors of Epidermis
seborrheic keratosis/basal cell papilloma
 common benign hereditary tumor in advanced and middle-aged persons.
 typically a raised papular lesion of variable color from light to dark brown.
 may be smooth or wartlike with visible pitting
Histology
 exophytic lesion
 increased number of basal cells form cords and/or sheets of cells with cysts of
keratin (horn cysts).
 varying degrees of acanthosis, papillomatosis, and hyperkeratosis.
Subtypes
 Irritated SK is one subtype, characterized by a predominance of basal cells but
with whorling sheets of squamous cells. This squamous metaplasia is a
consequence of irritation and requires careful discrimination from
basosquamous carcinoma.
 Inverted follicular keratosis is an endophytic variant associated with a
pilosebaceous follicle. Squamous metaplasia also is frequently present.
Dermoscopy
 Fissures/ridges
 Crypts
 Multiple milia-like cysts
 Globules
 Absent network
 keratin
Management
 Case reports of melanomas resembling basal cell papilloma
 Curettage, cryotherapy, shave excision
Skin tag/Acrochordon
 fibroepithelial polyp, fibroma molle, and fibroepithelial papilloma
 tend to be located in the intertriginous areas of the axilla, groin, and
inframammary regions as well as in the low cervical area along the collar line
 consist of a thin squamous epithelium surrounding a fibrovascular core.
 removed for bleeding, irritation, cosmesis, and discomfort - electrodesiccated,
shaved, or removed with cryoablation..
Keratoacanthoma
 benign cutaneous neoplasms, usually solitary
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occur in elderly patients who are frequently exposed to the sun
characterized by spontaneous involution and eventual disappearance of this
lesion within months
 rapidly increases in size within 6-8 weeks, with the eventual formation of a
central keratin plug.
 During the immunologically mediated regression phase, the central keratin
plug is extruded, and only a flat scar remains.
Histology
 domelike lesion
 proliferating squamous epithelial cells with no cytologic abnormalities and
have a normal nuclear-to-cytoplasmic ratio.
 Peripheral location of proliferating-cell nuclear antigen immunostaining
versus diffuse staining in SCC
Treatment
 surgical excision - difficulties in distinguishing between keratoacanthomas
and SCCs
 topical 5-fluorouracil therapy to accelerate the regression phase of the
keratoacanthoma without the need for diagnostic biopsy.
 Expect partial response within 3 weeks and complete resolution within 8
weeks.
Tumours of epidermal appendage
Hair follicles
1. pilomatrixoma
2. trichoepithelioma
3. trichofolliculoma
4. tricholemmoma
Sebaceous glands
1. Sebaceous hyperplasia
2. Benign sebaceous adenoma
3. Nevus sebaceus of Jadassohn
Apocrine glands
1. Hidradenoma papilliferum
Eccrine glands
1. Syringoma
2. Eccrine poroma
3. Cylindroma
Hair Follicle tumors
Pilomatrixoma
 calcifying epithelioma of Malherbe
 a benign skin neoplasm that arises from hair follicle matrix cells.
 commo in the pediatric population (most <11yo)
Clinical
 presents as a slow-growing dermal or subcutaneous mass, most often
located in the head and neck regions.
 May be associated with ulceration
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20-40% have pain, tenderness
mobile, cystic, or solid mass attached to the skin.
distinguished from epidermoid and dermoid cysts by the presence of
irregular nodules, which slide freely under the overlying skin.
malignancy has rarely been reported
Histology
 Histopathologically, pilomatrixoma is sharply demarcated and contains
basaloid cells and eosinophilic keratinized (shadow) cells.
 granulomatous inflammation in areas of keratinization.
Management
 Complete surgical excision remains the treatment of choice
 In cases with tumor adherence to the dermis, the overlying skin might be
excised
 Recurrence rate 2-6%
Trichoepithelioma
 pink to flesh colored.
 frequently multiple and is not ulcerative
 may be transmitted AD
 more common in females
Histology
 characterized by collections of basal cells that are similar to the hair bulb. It is
also remarkable for the presence of numerous horn cysts.
 accompanied by an inflammatory stroma that is fibrous.
 abortive hair shafts and follicles are another characteristic sign
 may look like BCC on microscopy
Management
 Because of the multiplicity of the lesions, the treatment can be difficult
 Although extremely rare, some TEs may develop high-grade carcinomas with
aggressive behavior (including metastasis).
 A variant is the desmoplastic trichoepithelioma which is a solitary ring-shaped
shiny lesion and is usually excised because it can look like a basal cell
carcinoma.
Trichofolliculoma
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uncommon hamartoma of hair follicle tissue, typically occurring on the face
of adults
single, flesh-colored or whitish nodule or papule of varying duration, typically
on the face (most frequently around the nose).
Classic trichofolliculomas have a central pore or black dot filled with keratin
or fine white hair, possibly draining a sebaceouslike material.
Treatment by excision
Tricholemmoma
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smooth, asymptomatic papules or verrucoid growths
may occur as a solitary lesion or as multiple lesions, and they are usually
found on the face
arises from the outer root sheath of the hair follicle (mainly of the bulb
region).
may mimic BBC or wart
often reported in association with a nevus sebaceous of Jadassohn.
When many trichilemmomas are present, Cowden disease (multiple
hamartoma syndrome) should be suspected.
1. multiple facial tricholemmomas
2. keratoses on palms and soles
3. oral polyps
4. breast cancer in 50%
Sebaceous gland tumors
Sebaceous Hyperplasia
 common, benign condition of sebaceous glands in adults of middle age lesions
can be single or multiple and manifest as yellowish, soft, small papules on the
face (particularly nose, cheeks, and forehead) up to 3 mm in diameter. Close
inspection reveals a central hair follicle.
 benign, with no known potential for malignant transformation.
 caused by a decrease in the circulating levels of androgen associated with
aging.
 ultraviolet radiation and immunosuppression have been postulated as cofactors
 normal lobular patterns but hyperplastic
 can be difficult to clinically differentiate from basal cell carcinoma.
 Treatment with
o photodynamic therapy
o cryotherapy
o cauterization or electrodesiccation
o chemical peel treatments
o laser treatment (eg, with argon, carbon dioxide, or pulsed-dye laser)
o shave excision, and excision.
Sebaceous Adenoma
 Rare nodular and lobulated lesion with
peripheral generative cells and
variable sebaceous differentiations as
the center of the lesion is approached.
 Not as organized as the patterns of
sebaceous hyperplasia.
 distinct from the hamartomatous
variety encountered on the face of
patients with tuberous sclerosis
syndrome.
 Other associations between multiple sebaceous adenomas and GI/breast
adenocarcinomas recently have been described (Muir-Torre)
 contain lobular patterns that are irregular.
Nevus sebaceus of Jadassohn
 slightly raised yellow-brown plaque and is quiescent during childhood
 most common affected site is the scalp, although the face, the neck, and, more
rarely, the trunk and limbs may be involved.
 gradually enlarges, becoming more noticeable at puberty and taking on a
yellow, cobblestone appearance.
 May be pigmented
 Histology
i. Hamartomatous conglomerate of sebaceous glands associated with
heterotopic apocrine glands and hair follicles
 also called an organoid nevus because it involves the entire skin organ.
 In 10-20%of patients, nevus sebaceus evolves into basal cell carcinoma.
 Excision before puberty is recommended.
Apocrine tumors
Hidradenoma papilliferum
 benign adenoma of the apocrine gland that occurs in the vulva and perineum
of adult women.
 papillary tumor with cystic characteristics
Apocrine hidrocystomas
 benign cystic proliferations of the apocrine secretory glands.
 most commonly appear as solitary, soft, dome-shaped, translucent papules or
nodules and most frequently are located on the eyelids, especially the inner
canthus.
Treatment
 can be incised and drained; however, electrosurgical destruction of the cyst
wall often is recommended to prevent recurrence.
 Punch, scissors, or elliptical excision also can remove tumors.
 Multiple apocrine hidrocystomas can be treated with carbon dioxide laser
vaporization.
Eccrine
 distinctive feature of sweat duct (eccrine) tumors is a the double layer of
epithelium
Syringoma
 occur around the eyes, axilla, or anogenital region
 benign hamartomatous lesion formed by well-differentiated ductal elements.
 Enzyme immunohistochemical tests demonstrate the presence of eccrine
enzymes such as leucine aminopeptidase, succinic dehydrogenase, and
phosphorylase.
 skin-colored or yellowish, small, dermal papules
 treatment – dermabrasion, resurfacing with CO2 laser, curettage
Cylindroma
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most commonly occur on the head, the neck, and the scalp in solitary and
multiple patterns.
 When nodules enlarge and coalesce on the scalp, they form the distinctive
turban tumor feature
 Malignant cylindromas may develop within these lesions very rarely
 dermal tumor without attachment to the epidermis.
Histology
 Tumor islands are composed of 2 cell types. Peripheral cells are small and
highly basophilic; palisading is suggested. Larger, more pale-staining cells are
seen centrally.
Treatment
 For solitary lesions, treatment is by excision or electrosurgery.
 For small cylindromas, the carbon dioxide laser may be used.
 Multiple cylindromas usually require extensive surgery that may be obviated
by progressively excising a group of nodules in multiple procedures.
Eccrine poroma
 benign tumor that typically occurs on the palms and soles
 recent analyses by many investigators suggest that poromas can be of either
eccrine or apocrine lineage.
 typically are asymptomatic, slow-growing, or stable fleshy nodular lesions.
 Poromas are not clinically distinctive and usually cannot be diagnosed
clinically
Benign Dermal Tumors
Keratinous cyst
 2 types
1. inclusion/epidermal cyst – can be found anywhere
2. pilar/ trichilemmal cyst
 occurs almost exclusively on the scalp
 70% multiple
Histology
 Inclusion cyst
i. Cornified epithelium, a very well-demarcated granular layer, and multiple
lamellae of keratin without calcification
 Pilar cyst
ii. contain keratin and its breakdown products, lined by a wall resembling the
external (outer) hair root sheath
iii. hallmark is a trichilemmal keratinization pattern - pale keratinocytes,
which increase in height as they mature and transform abruptly into solid
eosinophilic-staining keratin without forming a granular cell layer. This
pattern is different from the lamellated form because the well-defined
granular layer is lacking.
Dermoid cysts
 true hamartomas - result of the sequestration of skin along the lines of
embryonic closure.
 In contrast to epidermal cysts, dermoid cysts in the skin are lined by an
epidermis that possesses various epidermal appendages. As a rule, these
appendages are fully mature.
Dermatofibroma
 common cutaneous nodule of unknown etiology that occurs more often in
women
 requently develops on the extremities (mostly the lower legs)
 usually asymptomatic, may be itchy or tender
 most common painful benign skin lesion
 Cells show clonal proliferation – probably a neoplasm
 Cell of origin – dermal dendrocyte or histiocyte
 Immunohistochemical testing with antibodies to factor XIIIa is frequently
positive in DF which diffenrentiates this from DFSP (CD34 +)
 clinical appearance is a solitary, 0.5- to 1-cm nodule.
 fixed to the skin surface and is freely movable over the subcutis.
 characteristic tethering of the overlying epidermis to the underlying lesion
with lateral compression – dimple sign
 dermoscopy not useful but may show central white patch
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treatment is surgical excision - superficially shaving the lesion or
cryosurgery can be attempted for cosmesis or to decrease the symptoms;
however, recurrences are more likely.