#dermpathjc January 2019:

Thursday, January 24, 9pm EST

Article discussed: Pigmented Lesions of the Nail Unit

Authors: Nevares-Pomales O, Sarriera-Lazaro C, Barrera-Llaurador J, Santiago-Vazquez M, Lugo-Fagundo N, Sanchez JE, Sanchez JL.

Temporary open access at: https://journals.lww.com/amjdermatopathology/Abstract/2018/11000/Pigmented_Lesions_of_the_Nail_Unit.1.aspx

Summary prepared by Patrick Rush, DO (@DrPatrickRush)

Journal Club summary:

This month’s journal club article discussed a topic that gives many of us much consternation, pigmented lesions of the nail unit. The article was a good overall review in many regards; there was discussion (with images) of the clinical features of melanocytic lesions and the concerning signs, as well as a review of the epidemiology, histology, and molecular findings. The learning objectives for the article were very well laid out, and there are accompanying CME questions for obtaining AMA PRA Category 1 credits.

It was a lively discussion, and those active in the discussion overall agreed with the author’s summary and findings.

There were a few take home points from the paper and subsequent discussion, which touched on all aspects:

Embryology:

Proximal nail matrix = predominantly dormant melanocytes
Distal nail matrix = active and dormant melanocytes (more likely for a melanocytic lesion to arise within this zone)

Epidemiology:

Melanocytic macule more common in adults
Nevi more common in children

Clinical:

Longitudinal melanonychia not always due to a melanocytic lesion (Fungus, drugs, trauma, infection, etc can be causative)
Amelanotic subungual melanoma has been reported at rates between 15-50% (while they only comprise 2-8% of melanomas at other sites)

Sampling:

Many seem to groan with nail clippings to evaluate for a melanocytic lesion
If clippings are sent, if negative they will usually be emblazoned with a caveat in an comment

Histology:

Most peoples malignant lesions have been composed of melanoma in situ with invasive melanoma making up the minority.

Immunohistochemistry:

SOX10 not as useful in the nail unit as in other parts of the body
Mart-1 / Melan A are preferred, and felt to work better
Some also order a Fontana Mason in addition

Molecular:

Subungual melanoma more commonly harbor KIT mutations
Predictions through immunohistochemistry has thus failed to be predictive of molecular aberrations
Gold standard for interrogation of KIT mutations remains molecular analysis

Some Highlights from the Evening:

jan1