Suspected malignant skin excisions

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Author: Mikael Häggström [note 1]
Suspected malignant skin excisions:


Generally 10% neutral buffered formalin.

  See also: General notes on fixation

Common targets

If directly suspected from the referral, see:

  • Melanoma

Gross processing

Gross examination


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

Tissue selection

Tissue selection from suspected malignant skin lesions, by lesion size:[1][note 2]
<4 mm 4 - 8 mm 9 - 15 mm
Tissue selection from skin excision with less than 4 mm suspected malignant lesion.png Tissue selection from skin excision with 4-8 mm suspected malignant lesion.png Tissue selection from skin excision with 9-15 mm 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

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 squamous cells: See below:

Squamous cell-like skin proliferations: Differential diagnosis

Main differential diagnoses and their characteristics:[2]

General benign imitators of skin malignancy

Further workup of malignant findings

In case of skin cancer, determine whether the peripheral/radial and deep margins are clear, close or continuous.[3][note 5] 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),[3][4] but 2-3 mm for melanoma.[5]

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


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: edit
  • >___ 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.[3]
  • 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.


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. The excision example shows a superficial basal cell carcinoma.
  3. - Buschke–Löwenstein tumor is an alternative name for verrucous squamous cell carcinoma in the ano-genital region.
    - Carcinoma cuniculatum is a characteristic form of verrucous squamous cell carcinoma on the sole.
  4. Inverted follicular keratosis is generally thought to be a rare variant of seborrheic keratosis, but this position is not universally accepted.
    - Karadag, AyseSerap; Ozlu, Emin; Uzuncakmak, TugbaKevser; Akdeniz, Necmettin; Cobanoglu, Bengu; Oman, Berkant (2016). "Inverted follicular keratosis successfully treated with imiquimod ". Indian Dermatology Online Journal 7 (3): 177. doi:10.4103/2229-5178.182354. ISSN 2229-5178. 
  5. "Peripheral" or "radial" margins are preferred rather than "lateral", since a "lateral" margin may be interpreted as opposite to the "medial margin".

Main page


  1. There are many variants for the processing of skin excisions. These examples use aspects from the following sources: ". Ochsner J 5 (2): 22–33. 2003. PMID 22826680. PMC: 3399331. Archived from the original. . 
    - With a "standard histologic examination" that, in addition to the lesion, only includes one section from each side along the longest diameter of the specimen.
    - It also shows an example of circular coverage, with equal coverage distance in all four directions.
    - The entire specimen may be submitted if the risk of malignancy is high.
  2. Initially copied from: Paolino, Giovanni; Donati, Michele; Didona, Dario; Mercuri, Santo; Cantisani, Carmen (2017). "Histology of Non-Melanoma Skin Cancers: An Update ". Biomedicines 5 (4): 71. doi:10.3390/biomedicines5040071. ISSN 2227-9059. 
    "This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ("
  3. 3.0 3.1 3.2 David Slater, Paul Barrett. Standards and datasets for reporting cancers - Dataset for histopathological reporting of primary cutaneous basal cell carcinoma. The Royal College of Pathologists. February 2019
  4. 1 mm as cutoff for close margin: Brodie M Elliott, Benjamin R Douglass, Daniel McConnell, Blair Johnson, Christopher Harmston (2018-12-14). New Zealand Medical Journal.
  5. Page 406 in: Klaus J. Busam, Richard A Scolyer, Pedram Gerami (2018). Pathology of Melanocytic Tumors . Elsevier Health Sciences. ISBN 9780323508681. 

Image sources