<unk> , left upper paraspinal back Physicians usually diagnose<unk>  by doing a thorough physical examination, through a combination of visual observation and touch. However a biopsy may be necessary when the keratosis is large in diameter, thick, or bleeding, in order to make sure that the lesion is not a skin cancer.<unk>  may progress to invasive squamous cell carcinoma (SCC) but both diseases can present similarly upon physical exam and can be difficult to distinguish clinically. Histological examination of the lesion from a biopsy or excision may be necessary to definitively distinguish<unk>  from in situ or invasive SCC. In addition to SCCs,<unk> s can be mistaken for other cutaneous lesions including seborrheic keratoses, basal cell carcinoma, lichenoid keratosis, porokeratosis, viral warts, erosive pustular dermatosis of the scalp, pemphigus foliaceus, inflammatory dermatoses like psoriasis, or melanoma. Biopsy A lesion biopsy is performed if the diagnosis remains uncertain after a clinical physical exam, or if there is suspicion that the<unk>  might have progressed to squamous cell carcinoma. The most common tissue sampling techniques include shave or punch biopsy. When only a portion of the lesion can be removed due to its size or location, the biopsy should sample tissue from the thickest area of the lesion, as SCCs are most likely to be detected in that area. If a shave biopsy is performed, it should extend through to the level of the dermis in order to provide sufficient tissue for diagnosis; ideally, it would extend to the mid-reticular dermis. Punch biopsy usually extends to the subcutaneous fat when the entire length of the punch blade is utilized. Histopathology Normal skin (left) and<unk>  (right) with the defining characteristic of atypical basal keratinocytes that do not involve the full thickness of the epidermis.<unk> , atrophic form On histologic examination,<unk>  usually show a collection of atypical keratinocytes with hyperpigmented or pleomorphic nuclei, extending to the basal layer of the epidermis. A "flag sign" is often described, referring to alternating areas of orthokeratosis and parakeratosis. Epidermal thickening and surrounding areas of sun-damaged skin are often seen. The normal ordered maturation of the keratinocytes is disordered to varying degrees: there may be widening of the intracellular spaces, cytologic atypia such as abnormally large nuclei, and a mild chronic inflammatory infiltrate. Specific findings depend on the clinical variant and particular lesion characteristics. The seven major histopathologic variants are all characterized by atypical keratinocytic proliferation beginning in the basal layer and confined to the epidermis; they include: *Hypertrophic: Notable for marked hyperkeratosis, often with evident parakeratosis. Keratinocytes in the stratum malphigii may show a loss of polarity, pleomorphism, and anaplasia. Some irregular downward proliferation into the uppermost dermis may be observed, but does not represent frank invasion. *Atrophic: With slight hyperkeratosis and overall atrophic changes to the epidermis; the basal layer shows cells with large, hyperchromatic nuclei in close proximity to each other. These cells have been observed to proliferate into the dermis as buds and duct-like structures. *Lichenoid: Demonstrate a band-like lymphocytic infiltrate in the papillary dermis, directly beneath the dermal-epidermal junction. *Achantholytic: Intercellular clefts or lacunae in the lowermost epidermal layer that result from anaplastic changes; these produce dyskeratotic cells with disrupted intercellular bridges. *Bowenoid: This term is controversial and usually refers to full-thickness atypia, microscopically indistinguishable from Bowen's Disease. However most dermatologists and pathologists will use it in reference to tissue samples that are notable for small foci of atypia that involve the full thickness of the epidermis, in the background of a lesion that is otherwise consistent with an<unk> . *Epidermolytic: With granular degeneration. *Pigmented: Show pigmentation in the basal layer of the epidermis, similar to a solar lentigo. Dermoscopy Dermoscopy is a noninvasive technique utilizing a handheld magnifying device coupled with a transilluminating lift. It is often used in the evaluation of cutaneous lesions but lacks the definitive diagnostic ability of biopsy-based tissue diagnosis. Histopathologic exam remains the gold standard. Polarized contact dermoscopy of<unk> s occasionally reveals a "rosette sign," described as four white points arranged in a clover pattern, often localized to within a follicular opening. It is hypothesized that the "rosette sign" corresponds histologically to the changes of orthokeratosis and parakeratosis known as the "flag sign." * Non-pigmented<unk> s: linear or wavy vascular patterning, or a "strawberry pattern," described as unfocused vessels between hair follicles, with white-haloed follicular openings. * Pigmented<unk> s: gray to brown dots or globules surrounding follicular openings, and annular-granular rhomboidal structures; often difficult to differentiate from lentigo maligna.
Actinic keratosis
Squamous cell skin cancer
Hydrocarbon keratosis
Arsenical keratosis
Reactional keratosis
Seborrheic keratosis
Smokeless tobacco keratosis
PUVA keratosis