Case 17 Female, 39 years. Locally recurrent pigmented lesion, skin of breastShow diagnosis & comments
Locally recurrent superficial spreading melanoma
In the common acquired naevus slide set, many examples of recurrent naevi have been included. However, of course melanoma can recur locally as well; not just any architectural irregularity and cylogical variation can be accepted as part of the spectrum of recurrent naevus.
For obvious reasons, locally recurrent melanoma is most common after incomplete or narrow-margin excision of the initial melanoma, not followed by re-excision. This may be because the specimen was not submitted for histopathology, or the diagnosis of melanoma was missed by the pathologist. The latter mistake is of course more common in case of a 'naevoid melanoma' (melanoma resembling a naevus), so that on the whole, locally recurrent melanoma is more commonly of the naevoid type than is melanoma in general. This compounds the problem of its recognition, since the recurrent melanoma naevoid has to be distinguished from an irregular recurrent naevus. It goes without saying that revision of initial histology is mandatory.
This is an instance of recurrent naevoid melanoma. There is variable cytological atypia, rather extensive ascent of atypical melanomas, abrupt variations in cell type and architecture from area to area, focally dense cellularity of the lesion. These findings point to the diagnosis of melanoma. In this instance, the initial lesion had not been submitted for histopathology.
It is useful to bear in mind that recvurrent naevi generally manifest themselves within weeks to months after the first attempt at removal (usually by shave biopsy) whereas, paradoxially, recurrent melanoma usually takes years to become clinically apparent.