Are You Confident of the Diagnosis?
The term ’recurrent nevus’ is used when there is evidence that a benign melanocytic nevus has recurred at a site, typically after incomplete removal from a prior biopsy (Figure 1, Figure 2). Some authors distinguish between a ’persistent nevus’, which is one where there was clinical evidence (ie, residual pigmentation) that the lesion had never been completely removed, and ’recurrent nevus’, in which the lesion appeared to have been completely eradicated but returned.
What you should be alert for in the history
The main concern regarding recurrent nevi is whether the phenomenon truly is recurrent nevus vs melanoma. Extension of the pigmentation beyond the scar indicates that there is active growth of the entity, which raises the possibility that this could represent melanoma. A biopsy should be considered in that circumstance.
Expected results of diagnostic studies
Microscopically, recurrent nevi may show melanocytes encased within the scar (Figure 3, Figure 4). These melanocytes may be atypical in their microscopic appearance and may resemble fibroblasts, although they should still stain with typical immunohistochemical stains for melanocytes. The melanocytes may also have cytologic atypia in some but not all cases.
The microscopic differential diagnosis includes a partially regressed melanoma, and it can be difficult for a dermatopathologist to state with certainty in some cases whether the lesion is in fact a recurrent nevus or a partially regressed melanoma.
Who is at Risk for Developing this Disease?
Recurrent nevi classically occur with lesions that have not been completely removed by a biopsy, but could potentially occur with other types of trauma as well.
What is the Cause of the Disease?
Prior surgical removal of the lesion or trauma to a nevus.
Systemic Implications and Complications
A recurrent nevus, assuming that is the correct diagnosis, is a benign lesion and does not have any systemic implications.
The principal reason for any kind of intervention is to ensure that the lesion is in fact benign and not a melanoma. A recurrent nevus in itself is still a benign lesion.
Optimal Therapeutic Approach for this Disease
If indicated, a re-excision of the lesion to assure its complete removal, accompanied by histologic confirmation.
The level of concern that an incompletely removed pigmented lesion is clinically returning rests on two issues: what the original diagnosis was and whether the recurrence is actually a melanoma rather than a benign entity.
If the lesion was originally a nevus with higher levels of cytologic atypia or the clinical scenario is atypical, an additional surgical procedure to confirm the benignity of the process could be considered.
Unusual Clinical Scenarios to Consider in Patient Management
It may be prudent, on occasion, to get the original slides for review, to be assured that the original lesion was not misinterpreted.
What is the Evidence?
Arrese Estrada, J, Pierard-Franchimont, C, Pierard, GE. “Histogenesis of recurrent nevus”. American Journal of Dermatopathology. vol. 12. 1990. pp. 370-2. (An examination of 8 cases microscopically.)
King, R, Hayzen, BA, Page, RN, Googe, PB, Zeagler, D, Mihm, MC. “Recurrent nevus phenomenon: a clinicopathologic study of 357 cases and histologic comparison with melanoma with regression”. Modern Pathology. vol. 22. 2009. pp. 611-617. (An overview of the microscopic features.)
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