Dark skin focalities

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Author: Mikael Häggström [notes 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.

Fixation

Generally 10% neutral buffered formalin.

See also: General notes on fixation

Gross processing of skin excisions

Gross pathologic processing of skin excisions[1][notes 2]
Lesion size
<4 mm 4 - 8 mm 9 - 15 mm
Benign appearance

Tissue selection from skin excision with lesion less than 4 mm with benign appearance.png

Tissue selection from skin excision with lesion 4-8 mm with benign appearance.png

Tissue selection from skin excision with lesion 9-15 mm with benign appearance.png

Suspected malignancy 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

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

Evaluation is largely based on the relative incidence and malignancy of various differential diagnoses (see pie chart). Main approaches are:

  • Direct pattern recognition
  • Systematic

Either way can be done by scrolling through the epidermis at intermediate magnification and then through the dermis at a lower magnification.

Pattern recognition

Systematic

One approach for the most common conditions are:

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

Notes

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

References

  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.