Dark skin focalities

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Author: Mikael Häggström [note 1]

Dark skin focalities (in this case, from top left and clockwise: Spitz nevus, seborrheic keratosis, elevated melanocytic nevus and melanoma)

Skin with one or more areas that are darker than the surroundings. They are part of suspected malignant skin excisions.



Generally 10% neutral buffered formalin.

  See also: General notes on fixation

Gross processing of skin excisions

Gross pathologic processing of skin excisions[1][notes 1]
Lesion size
<4 mm 4 - 8 mm 9 - 15 mm
Benign appearance




Suspected malignancy      

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

Various diagnoses of pigmented skin lesions, by relative incidence upon biopsy, and malignancy potential.

Melanocytic lesions

Scrolling through the epidermis at intermediate magnification and then through the dermis at a lower magnification.

Melanocytic lesions (including nevus) are the most common, and can be classified as follows:

Atypia and/or dysplasia
Low High
and dermis
Junctional nevus Melanoma in situ
Dermis Dermal nevus Invasive melanoma

A compound nevus consists of both junctional and dermal melanocytic nevus nests.



  1. The excision examples show a normal mole (upper row, benign appearance) and a superficial basal cell carcinoma (lower row, suspected malignancy).
  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.

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.

Image sources