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Pathology - Benign Cutaneous Lumps
This summarizes common benign cutaneous lumps, focusing on their clinical presentation and key histological features for effective study and understanding.
I. Epithelial Tumors
A. Fibroepithelial Polyps:
A. Melanocytic Naevi (Moles):
A. Lipoma:
This summarizes common benign cutaneous lumps, focusing on their clinical presentation and key histological features for effective study and understanding.
I. Epithelial Tumors
A. Fibroepithelial Polyps:
- Clinical: Multiple small, pedunculated papules around neck, axillae, and groin. Often removed for cosmetic reasons.
- Histology: Core of fibrovascular tissue covered by normal or hyperplastic epidermis.
- Clinical: Common cysts on face, neck, upper trunk, vulva, or scrotum.
- Histology: Cyst filled with laminated keratin; lined by squamous epithelium with a granular layer.
- Clinical: Common cysts, almost always on the scalp.
- Histology: Lined by pale squamous epithelial cells; abrupt keratinization without a granular layer (key differentiating feature from epidermoid cysts).
- Clinical: Very common in middle-aged/elderly; brown-black, greasy, warty nodules; often multiple; occur anywhere except palms and soles.
- Histology: Proliferation of basaloid keratinocytes with variable squamous differentiation; hyperkeratosis and horn cyst formation.
- Clinical: Brown to black, well-circumscribed macules; can occur anywhere.
- Histology: Elongated epidermal rete ridges; increased basal melanocytes; increased pigmentation in epidermis and papillary dermis.
A. Melanocytic Naevi (Moles):
- Clinical: Extremely common; virtually universal in white individuals; found anywhere on the body; evolve temporally (junctional → compound → intradermal).
- Histology:
- Junctional: Melanocyte nests at rete ridge tips.
- Compound: Dermal melanocytes in addition to junctional nests.
- Intradermal: Dermal melanocytes only.
- Clinical: Relatively common dermal naevus; dark blue papule; wide age range; more common on hands, feet, buttocks, scalp, and face.
- Histology: Heavily pigmented spindled and dendritic dermal melanocytes.
- Clinical: Benign; typically in children/young adults; pink or red/brown papule or nodule; usually on head, neck, and extremities.
- Histology: Compound melanocytic lesion; large epithelioid and/or spindled cells with abundant eosinophilic cytoplasm and conspicuous nucleolus. (Important: Large melanocytes can mimic melanoma – crucial for differential diagnosis).
A. Lipoma:
- Clinical: Very common benign fatty tumor; slow-growing, mobile, painless subcutaneous lump.
- Histology: Lobules of mature adipocytes.
- Clinical: Common benign fibrous tumor; reddish-brown papule on trunk or lower legs.
- Histology: Ill-defined dermal lesion; short interlacing spindle cells; variable collagen, foamy macrophages, blood vessels, and inflammatory cells.
- Clinical: Benign vascular tumor; red papules or nodules; often ulcerate and bleed; mostly on head/neck or extremities.
- Histology: Polypoid dermal lesion; lobules of small capillaries.
- Clinical: Common benign nerve sheath tumor; mostly sporadic, but multiple neurofibromas and café-au-lait spots are associated with neurofibromatosis type 1; soft, flesh-colored papule or nodule.
- Histology: Dermal or subcutaneous lesion; Schwann cells and fibroblasts in a fibrillar background.
- Clinical: Common benign skin tumor; hair matrix differentiation; firm papule or nodule in children/young adults; often on the cheek.
- Histology: Nodules of basaloid cells transforming into anucleate eosinophilic ("ghost") cells; calcification is common.
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