A scalp biopsy is a diagnostic procedure where a small tissue sample, often including hair follicles, is removed from the scalp for microscopic examination. This analysis helps dermatologists identify specific conditions affecting the scalp and hair, particularly when a diagnosis is unclear from a clinical examination alone. It provides information to pinpoint the underlying cause of scalp issues and guide appropriate treatment.
Diagnosing Hair Loss Conditions
A scalp biopsy is used to diagnose various forms of hair loss, known as alopecia. It helps distinguish between scarring (cicatricial) and non-scarring alopecias, which is important for determining treatment. In scarring alopecias, inflammation destroys hair follicles, replacing them with scar tissue, leading to permanent hair loss.
For conditions like androgenetic alopecia (male or female pattern hair loss), a biopsy can reveal miniaturization of hair follicles, where thick terminal hairs are replaced by thinner, shorter vellus hairs. A biopsy can confirm miniaturized hairs and a mildly increased telogen-to-anagen ratio. In alopecia areata, an autoimmune condition causing patchy hair loss, the biopsy typically shows characteristic inflammatory infiltrates around hair follicles.
Telogen effluvium, characterized by excessive hair shedding, is identified by an increased percentage of hair follicles in the resting (telogen) phase. The overall hair follicle density usually remains normal in this non-scarring condition. Scarring alopecias, such as lichen planopilaris, discoid lupus erythematosus, and frontal fibrosing alopecia, demonstrate the destruction of hair follicles and their replacement with fibrous scar tissue. For instance, lichen planopilaris biopsies show inflammatory infiltrates around hair follicles and evidence of follicular destruction. Frontal fibrosing alopecia, a variant of lichen planopilaris, exhibits similar histopathological features.
Identifying Inflammatory Conditions
Scalp biopsies help diagnose inflammatory skin conditions affecting the scalp. The microscopic examination reveals specific patterns of inflammation, cellular changes, and tissue damage. For instance, scalp psoriasis biopsies show characteristic epidermal thickening, parakeratosis, and specific inflammatory cell patterns.
Seborrheic dermatitis may require a biopsy in atypical cases. Biopsy findings can include parakeratosis around follicular openings, spongiosis, and inflammatory infiltrates. Eczematous dermatitis, including contact dermatitis or atopic dermatitis, presents with spongiosis and inflammatory cell infiltration in the biopsy sample. These findings help differentiate between various inflammatory conditions that may present with similar clinical appearances.
Detecting Infections and Other Lesions
A scalp biopsy can detect microbial infections and various abnormal growths, including cancerous lesions. For fungal infections like tinea capitis, the biopsy identifies fungal elements within hair shafts or follicles. Similarly, bacterial infections, such as folliculitis or cellulitis, can be confirmed by the presence of bacteria and an associated inflammatory response in the tissue sample.
The procedure is important for diagnosing skin cancers on the scalp, including basal cell carcinoma, squamous cell carcinoma, and melanoma. The biopsy enables pathologists to detect malignant cells and observe their characteristic growth patterns, aiding early diagnosis and treatment planning. Benign tumors or cysts, such as pilar cysts or lipomas, can also be confirmed through biopsy, differentiating them from more concerning lesions. A scalp biopsy can sometimes reveal microscopic changes indicative of underlying systemic diseases, providing clues for broader medical evaluation.