Skin tumor

Skin Pathology Overview

  • Molluscum contagiosum

    • Viral skin disease caused by a Poxvirus.

    • Common in healthy children; in adults, transmitted via abrasions or sexual contact.

    • Reservoirs include swimming pools.

    • Incubation: 14 to 50 days.

Presentation

  • Papules are skin-colored to erythematous, smooth, umbilicated, up to 1 cm.

  • Histology:

    • Contains a central keratinous core.

    • Crater-like appearance with hyperplastic squamous epithelium.

    • Lesions may be solitary or multiple, compressed nuclei appear basophilic in staining.

    • Eczematous dermatitis may co-occur in children.

Prognosis and Treatment

  • Lesions resolve spontaneously, especially in children; observation is an option.

  • Treatment includes cryotherapy, topical retinoids, imiquimod, and oral antivirals for immunocompromised individuals.

Seborrheic Keratosis

  • Definition: Benign epithelial skin tumors, often removed for cosmetic reasons.

  • Epidemiology: Common in elderly, especially white populations; 11-60% in older adults.

Presentation

  • Appearance: Waxy, rough, variably pigmented papules or plaques with "stuck-on" look.

  • Size: Millimeters to several centimeters; more frequent with aging.

  • Histology:

    • Showcases acanthosis, hyperorthokeratosis, and horn pseudocysts.

    • Leser-Trélat sign indicates underlying malignancy.

Keratoacanthoma

  • Definition: Rapidly growing tumor from sun-exposed skin, considered a variant of squamous cell carcinoma.

  • Epidemiology: Mostly affects older males.

Presentation

  • Lesions: Cup-shaped, varying from 1-2 cm with a keratin plug.

  • Evolution: Develops rapidly, typically involutes in 5-6 months, leaving a scar.

  • Histology reveals a symmetrical tumor with neutrophilic microabscesses.

Pilomatricoma

  • Definition: Common adnexal neoplasm seen in children and middle-aged adults.

  • Epidemiology: More common in females, can be familial.

Presentation

  • Lesions: Firm, hard nodules from 2mm to 3cm, often asymptomatic.

  • Most common on the head and neck; shows multifaceted angulation when stretched.

  • Histology features basaloid and ghost cells, frequent calcifications.

Basal Cell Carcinoma (BCC)

  • Definition: The most common malignant skin neoplasm associated with sun exposure.

  • Epidemiology: Fair-skinned individuals at higher risk; equal sex distribution with increased age association.

Presentation

  • Types:

    • Pearly telangiectatic papules, pigmented variants, and "rodent ulcer".

  • Histology: Basaloid nests with peripheral palisading, notable mitotic activity.

Melanocytic Compound Nevus

  • Definition: Benign growth of melanocytes, common in childhood.

  • Epidemiology: Arises from sun exposure; diminishes incidence into adulthood.

Presentation

  • Characteristics: Macules or plaques, uniformly pigmented, all body sites affected.

  • Histology: Nested melanocytes in epidermis and dermis, symmetrical and circumscribed.

Melanoma

  • Definition: Malignant skin tumor arising from melanocytes, linked to high UV radiation exposure.

  • Epidemiology: Common in older adults, but young people too, predominantly affecting those with fair skin.

Risk Factors

  • Family history of dysplastic nevi, immunosuppression conditions.

Presentation (ABCDE)

  • Asymmetry, Border irregularity, Color variation, Diameter >6 mm, Evolution over time.

Types

  • Traditional subtypes include superficial spreading, nodular, and acral lentiginous melanoma.

Prognostic Factors

  • Features such as mitotic rate, lymphocytic response, tumor thickness, and levels of invasion are critical.

Keloid

  • Definition: Benign fibrous tissue growth due to abnormal healing.

  • Prevalence higher in Afro-Americans; genetic predisposition noted.

Characteristics

  • Raised firm nodules, extending beyond wound limits, usually appearing from 10-30 years of age.

  • Predilection for chest, earlobes, cheeks, and deltoid regions.

Histology

  • Characterized by dense, hyalinized collagen bands, diagnosed often requiring multiple sections.

Dermatofibroma

  • Definition: A benign skin tumor, often visible under the dermis, typically found on young women.

Histology

  • Composed of a mixture of collagenous blastic cells and histiocytes with melanin.

Skin Pathology Overview (additional)

Molluscum contagiosum

  • Definition: A viral skin disease caused by the molluscum contagiosum virus, a member of the Poxvirus family.

  • Epidemiology: Commonly found in healthy children, with a prevalence rate of approximately 1-5% among pediatric populations; in adults, it often results from skin abrasions or sexual contact.

  • Reservoirs: Swimming pools, communal baths, and contact sports are common environments for transmission.

  • Incubation Period: Ranges from 14 to 50 days, making early diagnosis challenging.

Presentation

  • Lesions: Characterized by smooth, dome-shaped papules that are skin-colored to erythematous, typically measuring up to 1 cm in diameter. Lesions can occur singularly or in clusters, and may have a central dimple (umbilication).

  • Histology: Key features include a central keratinous core within the lesion, a crater-like appearance, hyperplastic squamous epithelium, and compressed nuclei that are basophilic when stained. Eczematous dermatitis frequently co-occurs in children, complicating the clinical picture.

Prognosis and Treatment

  • Prognosis: Lesions generally resolve spontaneously, particularly in pediatric cases, making observation a legitimate management option. However, lesions may take months to years to resolve completely.

  • Treatment Options: Include cryotherapy, topical retinoids (such as tretinoin), imiquimod (an immune response modulator), and empirical oral antivirals particularly for immunocompromised individuals.

Seborrheic Keratosis

  • Definition: Benign epithelial skin tumors characterized by a proliferation of keratinocytes, often removed for cosmetic reasons due to their appearance.

  • Epidemiology: Commonly seen in elderly populations, especially in Caucasians, with reported incidence rates of 11-60% in older adults. Gender prevalence has been observed but not consistently significant.

Presentation

  • Appearance: Lesions present as waxy, rough papules or plaques that can be variably pigmented, exhibiting a classic "stuck-on" appearance.

  • Size: Ranges from a few millimeters to several centimeters, with an increased frequency of occurrence associated with aging.

  • Histology: Exhibits acanthosis, hyperorthokeratosis, and horn pseudocyts; the Leser-Trélat sign may indicate possible underlying malignancy and necessitates further investigation.

Keratoacanthoma

  • Definition: A rapidly growing tumor originating from sun-exposed skin, categorized as a variant of squamous cell carcinoma.

  • Epidemiology: Predominantly affects older males and is commonly associated with significant sun exposure and immunosuppressive states.

Presentation

  • Lesions: Typically cup-shaped, growing from 1-2 cm with a central keratin plug that may be mistaken for a squamous cell carcinoma.

  • Evolution: Rapid growth characteristic, usually involutes within 5-6 months, often leaving a scar post-resolution.

  • Histology: Features a symmetrical tumor morphology with the presence of neutrophilic microabscesses that aid in differential diagnosis.

Pilomatricoma

  • Definition: A common adnexal neoplasm, particularly prevalent in children and young adults. It is often found in the context of familial syndromes such as myotonic dystrophy.

  • Epidemiology: More common in females, with a distinct predilection noted in certain ethnic groups.

Presentation

  • Lesions: Present as firm, hard nodules measuring from 2 mm to 3 cm, often asymptomatic. The lesions are most commonly found on the head, neck, and upper extremities and exhibit multifaceted angulation upon stretching.

  • Histology: Typically exhibits basaloid cells and ghost cells with frequent calcifications indicative of the tumor's mature stage.

Basal Cell Carcinoma (BCC)

  • Definition: The most common form of malignant skin neoplasm, strongly associated with cumulative sun exposure over a lifetime.

  • Epidemiology: Fair-skinned individuals are at significantly higher risk, with a more balanced gender distribution; incidence rises with age.

Presentation

  • Types: Includes pearly telangiectatic papules, pigmentation variants, and infiltrative forms referred to as "rodent ulcers."

  • Histology: Characterized by basaloid nests with peripheral palisading of nuclei, significant mitotic activity, and sometimes stromal retraction.

Melanocytic Compound Nevus

  • Definition: A benign proliferation of melanocytes that presents commonly during childhood and tends to evolve as individuals age.

  • Epidemiology: Associated with sun exposure, its incidence generally diminishes as individuals transition into adulthood.

Presentation

  • Characteristics: Appears as macules or plaques that are uniformly pigmented, possibly affecting all body sites depending on individual UV exposure history.

  • Histology: Exhibits nested melanocytes located both in the epidermis and dermis, ensuring features of symmetry and circumscription.

Melanoma

  • Definition: A malignant neoplasm arising from melanocytes, with significant associations to high UV radiation exposure and familial risk factors.

  • Epidemiology: Common in older adults but increasingly seen in younger demographics, particularly among those with fair skin types.

Risk Factors

  • Includes family history of dysplastic nevi, immunosuppressive conditions, and increased sun sensitivity.

Presentation (ABCDE Criteria)

  • Asymmetry: One half of the mole does not match the other half.

  • Border irregularity: Edges are ragged, notched, or blurred.

  • Color variation: Varied shades of brown, black, and sometimes red, white, or blue.

  • Diameter >6 mm: A mole that is larger than the size of a pencil eraser.

  • Evolution over time: Any change in size, shape, color, or elevation, or new symptoms such as bleeding, itching, or crusting.

Types

  • Traditional subtypes include superficial spreading melanoma, nodular melanoma, and acral lentiginous melanoma, each with distinct characteristics and risks.

Prognostic Factors

  • Features critical to prognosis include mitotic rate, immune response (lymphocytic infiltration), tumor thickness (Breslow depth), and levels of invasion, guiding treatment decisions and surveillance strategies.

Keloid

  • Definition: A benign growth of fibrous tissue resulting from abnormal healing processes, often leading to extensive scarring.

  • Epidemiology: More prevalent in individuals of Afro-American descent and shows a genetic predisposition.

Characteristics

  • Lesions: Raised, firm nodules that extend beyond the original wound edges, typically appearing between 10-30 years of age.

  • Common Locations: Chest, earlobes, cheeks, and deltoid regions are typical sites for keloid formation.

Histology

  • Characterized by dense, hyalinized collagen bands that may require multiple sections for accurate diagnosis due to heterogeneity in the tissue.