Diagnosis:

Recurrent naevus after incomplete excision (Case 56A)

Comments:

RECURRENT NAEVUS

• History of removal of banal naevus
• Interval usually weeks to months (in contrast to recurent melanoma: local recurrence usually after years)
• Scar tissue in upper dermis, with slightly enlarged and usually pigmented melanocytes, in compact nests
• Irregular distribution of similar pigmented naevoid melanocytes in overlying neoepidermis
• Very often an entirely banal looking naevus remnant in the pre-existent dermis bordering the scar
• Re-examination of histology of previously removed naevus, if available, is important to confirm the diagnosis
• Some of these benign lesions are macroscopically irregular and therefore suspicious: 'pseudomelanoma' of Ackerman.

Reference:

Fox et al., Arch Pathol Lab Med 2011; 135: 842-6