Suspected malignant skin excisions

Author: Mikael Häggström
Suspected malignant skin excisions:

Fixation

Generally 10% neutral buffered formalin.

  See also: General notes on fixation

Common targets

If directly suspected from the referral, see:

• Melanoma

• Melanoma in situ
• Invasive melanoma of the skin

• Basal-cell carcinoma
• Squamous-cell carcinoma of the skin

Gross processing

Gross examination

Note:

• Color
• Well-defined or diffuse border
• Size
• Any elevation

• 

  See separate article in case of dark skin focalities

Tissue selection

Tissue selection from suspected malignant skin lesions, by lesion size:

<4 mm	4 - 8 mm	9 - 15 mm

In table above, each top image shows recommended lines for cutting out slices to be submitted for further processing. Bottom image shows which side of the slice that should be put to microtomy. Dashed lines here mean that either side could be used. Further information: Gross processing of skin excisions

Microscopic evaluation

If the lesion was pigmented on gross examination, evaluate as a dark skin focality. If not:

Look for atypical cells, possibly by scrolling through the epidermis at intermediate magnification and then through the dermis at a lower magnification. If atypical cells are found, look for:

• Similarity to epidermal basal cells, evaluate as suspected basal-cell carcinoma

• 

  Basal-cell carcinoma

• Similarity to squamous cells: See below:

Squamous cell-like skin proliferations: Differential diagnosis

Main differential diagnoses and their characteristics:

• 

  Invasive squamous-cell carcinoma of the skin: Atypical and pleomorphic keratinocytes, involving the dermis and the sub-cutis with a potential metastatic spread.

• 

  Squamous-cell carcinoma in situ (Bowen’s disease): Atypical keratinocytes at every layer of epidermis.

• 

  Actinic keratosis: Atypical keratinocytes that do not span the full thickness of the epidermis (or, in Bowenoid variant, are less disordered with less nuclear atypia and crowding).

• 

  Keratoacanthoma: Symmetrical and circumscribed proliferation of keratinocytes, with central horn plug, with epidermis that extends over the tumor. It can be regarded as a highly differentiated SCC.

• 

  Crush artifacts: Needles used to orient the skin sample may create crush artifacts (black arrow) mimicking cellular atypia with mainly hypereosinophilia and nuclear pleomorphism. Image also shows folding artifacts (white arrows).

• 

  Adnexal carcinomas: Squamous differentiation, but does not show connection with the epidermis and highlights adnexal features.

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  Adenosquamous carcinoma: Mixed glandular and squamous differentiation.

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  Verruca vulgaris: Marked hyperkeratosis and papillomatosis. Rete ridges slope inward at the borders of the lesion.

• 

  Verrucous squamous cell carcinoma: Exophytic squamous proliferation with marked papillomatosis and low atypia and the presence of koilocyte-like changes. Found in head and neck locations, as well as in the genitalia and sole of the foot.

• 

  Inverted follicular keratosis:: Sharply circumscribed endophytic verrucous proliferation with prominent squamous features.

• 

  Seborrheic keratosis: Acanthosis, absence of atypia, pseudo-horn cysts, in inflamed lesions, mitoses may be present.

• 

  Bowenoid papulosis: Atypical keratinocytes and mitoses. Histology similar to Bowen’s disease.

• 

  A melanoma may have relatively plentiful eosinophilic cytoplasm, and be seemingly continuous with the squamous epithelium (at left in image), thus resembling a squamous cell carcinoma. However, the nesting of cells at right in the image is more characteristic of a melanoma.

• 

  Metastasis: Personal medical history of the patient, nodular proliferation without connection to epidermis, immunohistochemical evaluation. Squamous-cell carcinoma metastasis from lungs to the skin is pictured.

General benign imitators of skin malignancy

• 

  Granulomatous skin inflammation often contains giant cells that may appear atypical.

Further workup of malignant findings

In case of skin cancer, determine whether the peripheral/radial and deep margins are clear, close or continuous. A close margin has various definitions for different malignancies, but for basal-cell carcinoma and cutaneous squamous cell carcinoma it is defined as being closer than 1 mm from the edge (but yet non-continuous with it), but 2-3 mm for melanoma.

Previous biopsy

(At least if there is a known previous biopsy, look for changes that are consistent with a biopsy site, to confirm that it was taken from the excised area.) Such changes in the skin include:

• Granulation tissue in more fresh biopsies
• Dense collagen
• Fibrosis with vertical blood vessels
• Fibrosis that replaces solar elastosis

Reporting

Preferably see specific article on the condition at hand, if available.

• Optionally, the presence of a keratinized squamous epithelium.
• Any abnormalities, generally preceded by location in terms of epidermal, dermal or more specific layers thereof.
• If malignant:

• Degree of differentiation

• Radicality, mainly into either of the following:

• >___ mm (Definitions vary for the distance as per Further workup of malignant findings above): "Clear margins" (or: "Clear margins at over __ mm")((or the exact distance thereof)).))
• <___ mm but not continuous with edge: "Close margins at __ mm at (location). [[Locations are mainly the deep edge, or the (superior/inferior/medial/lateral) radial edge.]]." Numbers are generally given at an exactness of 0.1 mm.
• Continuous with margin: "Not radically excised at (location)."

For skin shave biopsies, non-radicality may be reported as: "Extending to base and peripheral edges of biopsy" (as they may not be regarded as "margins" on a biopsy).

• Perineural or vascular invasion if present.

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