Extensive Acanthosis Nigricans due to rectal carcinoma (5 of 7)

Suspicion for malignancy-associated acantosis nigricans
should arise when it occurs when resent onset in a
non-obese patient who does not have diabetes.

The malignant disease appears concomitantly in 61% of
patients, but in almost 20% the acanthosis nigricans may
precede the diagnosable tumor by years. In these patients,
frequent surveillance is necessary. In a patient known to
have had an abdominal adenocarcinoma who then develops
acanthosis nigricans, a vigorous search for recurrence or
metastatic disease should be undertaken. The mechanism
of malignant acanthosis nigricans is thought to be related to
peptide growth factors released by the tumor.