Familial melanoma by histology and age: joint data from five Nordic countries.
BACKGROUND
We aimed to estimate lifetime cumulative risk of melanoma (CRM) in relatives of patients with melanoma by histology and age at diagnosis in patients and relatives.


METHODS
A population-based cohort of 238724 first-degree relatives of 46091 melanoma patients diagnosed in 1955-2010 in Nordic countries was followed for cancer incidence.


RESULTS
The CRM (0-79 years) in first-degree relatives of a patient with superficial spreading (SSM), nodular (NM), or lentigo maligna melanoma was quite similar, ranging from 2.5% to about 3%, which represents about 2-fold increase over the general population risk. When one melanoma patient in the family was diagnosed before age 30, the CRM was about 3%. When there were > or =2 melanoma patients diagnosed before age 30 in a family, CRM for relatives was about 14%, 6% for diagnoses at age 30-59, and 5% for diagnoses at age 60 or older. Depending on age at diagnosis of same-sex twins (not known whether monozygotic/dizygotic), their CRM was about 7-21%. Although no familial case of concordant histological types of acral lentiginous/desmoplastic/compound nevus/spindle cell melanomas or malignant blue nevus was found, familial risks of discordant histological types of melanoma were interchangeably high for most of the types, e.g. higher risk of SSM when a first-degree relative had NM [standardized incidence ratios (SIR)=2.6, 95% confidence interval (CI)=2.1-3.3, n=72] or acral lentiginous (4.0, 95% CI=1.5-8.8, n=6) and vice versa. There was a tendency toward concordant age at diagnosis of melanoma among relatives of melanoma patients.


CONCLUSIONS
Findings of this study may help clinicians to find subjects at high melanoma risk for the genetic counseling. The risk was highest when melanoma occurred in a same-sex twin, one first-degree relative diagnosed at young age (<30), or > or =2 first-degree relatives. Histological type of melanoma does not seem to play an important role in familial melanoma.


BACKGROUND
This work was supported by the Nordic Cancer Union, Swedish Council for Working Life and Social Research, and German Cancer Aid.
Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany. Electronic address: M.Fallah@dkfz.de.
Mahdi
M
Fallah
Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland; School of Health Sciences, University of Tampere, Tampere, Finland.
Eero
E
Pukkala
Center for Primary Health Care Research, Lund University, Malmö, Sweden.
Kristina
K
Sundquist
Norwegian Cancer Registry, Oslo, Norway.
Steinar
S
Tretli
Institute of Cancer Epidemiology, Copenhagen, Denmark.
Jörgen H
JH
Olsen
Center for Primary Health Care Research, Lund University, Malmö, Sweden; Norwegian Cancer Registry, Oslo, Norway.
Laufey
L
Tryggvadottir
Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany; Center for Primary Health Care Research, Lund University, Malmö, Sweden.
Kari
K
Hemminki
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D005190:Family; D005192:Family Health; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008545:Melanoma / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D018570:Risk Assessment / Q000706:statistics & numerical data; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
Familial risk; Histology-specific; Melanoma; Nordic countries; Skin cancer; Standardized incidence ratio