What the report is saying

ASP means the specimen contains atypical squamous epithelium, but the pathologist cannot make a more definitive diagnosis from the sampled tissue.
It is not synonymous with invasive SCC, but it is also not a reassuring benign diagnosis.
Common reasons include superficial shave biopsy, transection at the base, tangential sectioning, ulceration, heavy inflammation, cautery artefact or a keratinising crateriform lesion with incomplete architecture.
The differential includes reactive squamous hyperplasia, hypertrophic actinic keratosis, Bowen disease, keratoacanthoma-type lesion, verruca/verrucous carcinoma and invasive well-differentiated cSCC.
The report comment is important: wording such as “cannot exclude invasive SCC” should trigger active resolution rather than observation by default.

Clinical risk stratification

Higher-risk clinical settings include lip, ear, scalp, hand, genital skin, chronically inflamed skin, scars, radiation field and immunosuppression.
Clinical features that increase concern are rapid growth, tenderness, bleeding, ulceration, induration, fixation, recurrence after treatment or a thick keratinising nodule.
Histology features that increase concern are transection at the base, deep margin involvement, marked atypia, infiltrative architecture, perineural concern or a pathology comment favouring SCC.
A small, flat, fully represented lesion with pathology favouring actinic keratosis/reactive change may be managed less aggressively if the clinical picture is concordant.
Risk assessment should combine patient, site, lesion behaviour and pathology adequacy; the diagnosis label alone is not enough.

If the lesion persists or invasive SCC cannot be excluded, obtain deeper/wider biopsy or excise the residual lesion.
For high-risk sites or patients, consider referral into the local skin cancer pathway or MDT discussion rather than repeated small superficial biopsies.
If the first biopsy was transected, sample the base or remove the lesion so architecture and invasion can be assessed.
If infection, hypertrophic lichen planus, prurigo or pseudoepitheliomatous hyperplasia is plausible, tell the pathologist and investigate/treat the underlying condition while maintaining cancer safety-netting.
Photographs, lesion size, duration, immune status and precise site improve the diagnostic value of dermatopathology review.

Ask whether the sample is adequate to exclude invasive SCC and whether the base is present.
Ask what diagnosis is favoured if the report is ambiguous: reactive PEH, actinic keratosis, SCC in situ, keratoacanthoma-type SCC or invasive SCC.
Request deeper levels or additional review if the clinical lesion and report are discordant.
Provide immune status, prior radiotherapy, transplant history and previous SCC history because these change clinical threshold.
Use the final excision or repeat-biopsy diagnosis, not the initial ASP label, for staging and follow-up decisions.

Treating ASP as a benign diagnosis without checking the pathology comment can miss invasive cSCC.
Treating ASP as proven SCC in every case can over-treat reactive/inflammatory lesions.
Repeated partial biopsies can prolong uncertainty; one adequate diagnostic procedure is usually preferable.
Destructive treatment before histological clarification removes the chance to assess invasion and margins.
Do not stage or code the lesion as invasive SCC until adequate tissue confirms invasion, unless local pathology guidance states otherwise.