Impact of the 2009 AJCC staging guidelines for melanoma on the number of mitotic figures reported by dermatopathologists at one institution.
BACKGROUND
In 2009 the revised seventh staging system for melanoma recommended the use of mitotic count to separate stage T1a from T1b. However, careful scrutiny of cases may lead to an inadvertent selection effect, with consequent increased reporting of mitotic counts.


METHODS
We investigated whether there is a significant increase in mitotic counts reported since 2009 for melanomas with a Breslow thickness of 1.0 mm or less. We conducted a retrospective, case-controlled study examining invasive melanoma cases at a large academic center. Mitotic counts were compared between pathology reports before 2009 (n = 61) and after 2009 (n = 125), with a subset of slides re-examined in a blinded fashion.


RESULTS
Before the 2009 staging guidelines, 51% of cases had one or more mitosis reported compared to 38% after 2009 (p = 0.113). Blinded re-counting did not yield a significant difference when compared with the original pathology reports in either group.


CONCLUSIONS
There was not a significant difference in the number of mitoses reported after the implementation of the new guidelines.
Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA.|Department of Dermatology, Boston Medical Center, Boston, MA, USA.
Allison R
AR
Larson
Department of Dermatology, Colorado Permanente Medical Group, Denver, CO, USA.|Harvard Combined Dermatology Residency Program, Boston, MA, USA.
Brian
B
Rothschild
Harvard Combined Dermatology Residency Program, Boston, MA, USA.
Andrew C
AC
Walls
Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA.
Scott R
SR
Granter
Department of Dermatology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
Abrar A
AA
Qureshi
Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA.
George F
GF
Murphy
Division of Dermatopathology, Department of Pathology, Brigham and Women's, Hospital, Harvard Medical School, Boston, MA, USA.
Alvaro C
AC
Laga
D016022:Case-Control Studies; D000066491:Clinical Decision-Making; D003880:Dermatology / Q000592:standards; D006801:Humans; D008495:Medical Oncology / Q000592:standards; D008545:Melanoma / Q000145:classification / Q000473:pathology*; D008940:Mitotic Index; D009367:Neoplasm Staging / Q000379:methods / Q000592:standards*; D017410:Practice Guidelines as Topic; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000145:classification / Q000473:pathology*; D000096142:Cutaneous Malignant Melanoma
melanoma; mitotic count; selection effect; staging