Case Number : Case 2586 - 04 June 2020 Posted By: Saleem Taibjee

Tumoral melanosis

59 minutes ago, Cem Leblebici said:

Tumoral melanosis

Agree. 

A question: Was the previous bcc histologically assessed?

Tumoral melanosis + amyloid 

Some interim points/food for thought:

1. Yes, the BCC was histologically confirmed.

2. If tumoral melanosis, what are the implications / cause / management?

3. The significance of amyloid?

I studied that there is a correlation between BCC and amyloid reactive stroma, but I don’t know much about this. 

However, I’m not sure we can rule out melanoma. 

This is an interesting case to demonstrate the pitfall that impressive tumoral melanosis can also occasionally arise as a result of regression of pigmented epithelial lesions.

I reviewed the original clinical images of the BCC which was treated by radiotherapy the preceding year, and as you can see below, it was a pigmented variant of BCC. The histology was clearly BCC, with no evidence of any melanocytic lesion in the original biopsy prior to radiotherapy.

There is a pertinent publication in this regard.

Flax et al. Nodular melanosis due to epithelial neoplasms: A finding not restricted to regressed melanomas.  Am J Dermatopathol 1998;20:118-22

The table from the paper is shown below, showing the range of epithelial lesions which were described in their series.

This means that we do sometimes need to be wary of automatically inferring a regressed melanocytic lesion or melanoma when encountering tumoral melanosis, even though that remains the most likely cause.

As Vincenzo correctly points out, epithelial tumours, in particular BCC, not infrequently result in residual (keratin-derived) amyloid when regressing. The amyloid can be highlighted by a pankeratin stain if necessary. This is a further clue in this case as to the origin of the tumoral melanosis.

Thanks so much, for the many learning points. 

very informative case!