Case Number : Case 764 - 22nd May Posted By: Guest

Melanocytic lesion with high grade pleomorphism and atypical mitoses. Spindle cell/blue nevus-like melanoma

Melanoma.

? melanoma, ? atypical blue naevus.

It is difficult to diagnose based only in high power pictures, but i will try: spindle and heavily pigmented melanocytes with atypia and some mitotic figures. As we know, it is difficult to differentiate malignant blue nevus from atypical blue nevus and some cellular blue nevus. Many histologic and cytologic features are necessary for this differentiation, including size of the lesion, borders, mitotic count, atypia and others. Based only on these high power images it could be a Malignant blue nevus x Atypical blue nevus.

A pigmented lesion on a man’s back or on a woman’s calf always concerns me, mainly if there are atypical melanocytes and mitotic activity, like this case.
My first impression is malignant blue nevus (pictures #1 and #3) arising in a preexisting benign cellular blue nevus (picture #2).
On the other hand, there is only one discernible mitotic figure in the midst of blander cells, and cytologic atypia may be confined to the same microscopic field shown by both picture #1 and picture #3. Since I can’t access the features that I would take in count to distinguish the differential diagnosis, I can’t dispel doubt between malignant blue nevus X cellular blue nevus.
I prefer not to use controversial expressions like “melanocytic tumor of uncertain malignant potential (MELTUMP)” and “atypical cellular blue nevus” because they are not diagnosis at all, but a more sophisticated way for saying “I don’t know”!

I think it is blue nevus like melanoma

Blue nevus-like melanoma (malignant blue nevus)

Melanoma (blue nevus like), or metastatic melanoma.

[color=#1C2837][font=arial, verdana, tahoma, sans-serif][size=4]Melanoma[/size][/font][/color]

I ended up calling this melanoma (blue nevus like). At our consensus conference, the atypical blue nevus discussion was brought up.