Histologic criteria for the diagnosis of mycosis fungoides: proposal for a grading system to standardize pathology reporting.
BACKGROUND
The histological diagnosis of early lesions of mycosis fungoides (MF) is often difficult for dermatopathologists and prior studies have shown a low agreement rate among pathologists. An important reason for such difficulty may be the lack of specific histological criteria.


METHODS
We tested a new method to interpret and report biopsies suspicious for MF. The method is based on a grading system reflecting the pathologist's degree of diagnostic certainty. A panel of four pathologists independently assessed a set of 50 biopsies suspicious for MF first without (Phase I) and subsequently with specific histological criteria (Phase II). A third Phase was carried out after a training session, using a new set of cases with corresponding immunophenotyping and gene rearrangement analysis. Weighted and unweighted kappa statistics were used to assess inter- and intra-pathologist variation.


RESULTS
The consensus rate among pathologists improved from 48% in Phase I to 76% in Phase III. Overall precision weighted kappas increased from 0.630 in Phase I to 0.854 in Phase III, indicating excellent inter-pathologist agreement by Phase III. There was a significant association between the presence of an abnormal phenotype and/or T-cell clonality and a higher diagnostic score.


CONCLUSIONS
The use of uniform criteria and training sessions can substantially improve the consensus rate among pathologists in the diagnosis of MF.
Guitart
J
J
Department of Dermatology, Northwestern University Medical School, Chicago, Illinois 60611, USA. j-guitart@nwu.edu
Kennedy
J
J
Ronan
S
S
Chmiel
J S
JS
Hsiegh
Y C
YC
Variakojis
D
D
D001706:Biopsy / Q000592:standards* / Q000706:statistics & numerical data; D004817:Epidermis / Q000473:pathology; D015329:Gene Rearrangement, T-Lymphocyte; D006801:Humans; D016130:Immunophenotyping; D009182:Mycosis Fungoides / Q000473:pathology*; D015588:Observer Variation; D015203:Reproducibility of Results; D012878:Skin Neoplasms / Q000473:pathology*