Seasonal presentation of skin cancers has been previously described, b
ut the seasonal presentation of keratoacanthomas is less well document
ed, Pathology reports and dermatology clinic visits were examined from
the Roger Williams Medical Center, the major dermatopathology service
in Rhode Island, U.S.A., from 1990 to 1992. Seasonal presentation was
defined as the ratio of keratoacanthomas during the summer months (Ju
ne-September) to the number diagnosed during the winter months (Decemb
er-March). A peak incidence of keratoacanthomas was noted in the summe
r and early autumn months. The summer/winter ratio (1.38) was statisti
cally significant (P = 0.002). The summer/winter ratio of office visit
s was smaller at 1.12, but also significant (P < 0.001), There appears
to be a seasonal presentation of keratoacanthoma in southern New Engl
and. This suggests that ultraviolet radiation has an acute effect on t
he development of keratoacanthoma.