Suspected malignant skin excisions

Author: Mikael Häggström
Suspected malignant skin excisions:

Fixation

• Generally: Buffered 4% formaldehyde.

Common targets

If directly suspected from the referral, see:

• Melanoma
• 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
File:Tissue selection from skin excision less than 4 mm with suspected malignant lesion.png	File:Tissue selection from skin excision 4-8 mm with suspected malignant lesion.png	File:Tissue selection from skin excision 9-15 mm with suspected malignant lesion.png

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

Look for atypical cells. If found, look for:

• Any pigmentation: Evaluate as dark skin focalities.

File:High-magnification micrograph of basal-cell carcinoma.jpg

Basal-cell carcinoma

• Similarity to epidermal basal cells, evaluate as suspected 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.
  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.
  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).
  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.
  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).
  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.
  Adnexal carcinomas: Squamous differentiation, but does not show connection with the epidermis and highlights adnexal features.
• Adenosquamous carcinoma: Mixed glandular and squamous differentiation.
  Adenosquamous carcinoma: Mixed glandular and squamous differentiation.
• Verruca vulgaris: Marked hyperkeratosis and papillomatosis. Rete ridges slope inward at the borders of the lesion.
  Verruca vulgaris: Marked hyperkeratosis and papillomatosis. Rete ridges slope inward at the borders of the lesion.
• Verrucous squamous cell carcinoma[note 3]: 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.
  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:[note 4]: Sharply circumscribed endophytic verrucous proliferation with prominent squamous features.
  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.
  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.
  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.
  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.
  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.

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