Papillary thyroid cancer in childhood: is parental screening helpful?

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Excerpt

Thyroid cancer accounts for less than 3% of all malignancy in childhood,1 the vast majority being papillary thyroid carcinoma (PTC).2 The most common subgroup (90–95%) of thyroid carcinoma are those derived from epithelial cells, known as non‐medullary thyroid cancer (NMTC). This group encompasses, from the most to the least common, PTC, follicular (FTC), poorly differentiated or insular and undifferentiated or anaplastic thyroid cancer. PTC and FTC are commonly grouped together as differentiated thyroid cancers. Around 95% of NMTC are sporadic, with the remainder being familial non‐medullary thyroid cancer (FNMTC).2
PTC in children is often more advanced than the adult disease equivalent and an inverse relationship exists between age and how advanced the disease is at presentation.3 PTC in children frequently presents late at an advanced stage, exhibiting angioinvasion, large tumour size and extra‐thyroidal extension. In addition, these cancers more commonly display multifocality and/or a diffuse sclerosing histological pattern with respect to adult patients.4 FNMTC is an established subcategory of epithelial thyroid cancer with specific management and prognostic implications.2 By definition, the diagnosis of FNMTC requires the demonstration of thyroid cancer in three or more first‐degree relatives.6 The familial predisposition often translates into a clinical picture of early age at onset, aggressive characteristics such as local and angiolymphatic invasion, more frequent multifocal disease and increased risk of recurrence.6
Because the clinical features of FNMTC are similar to those seen in paediatric presentations of PTC, such a diagnosis in a child raises the question of screening of parents for the presence of an underlying familial disorder. The possibility that FNMTC and paediatric PTC may overlap is well recognized, with childhood thyroid cancer often being precluded from being classified as familial on the basis of insufficient diagnostic criteria.9 Current accepted clinical practice in cases of FNMTC is annual screening of first‐degree relatives with neck ultrasound.5 Recent genetic studies have shown that FNMTC exhibits ‘genetic anticipation’.5 Genetic anticipation is the tendency for a disease to exhibit a more aggressive course at an earlier age in subsequent generations, hence the rationale of screening asymptomatic parents of children with aggressive PTC. Unfortunately, there are, to date, no available genetic screening tests for FNMTC.12
The aim of this study is to determine if ultrasound screening of parents of children presenting with PTC but no known family history of thyroid cancer is of value in identifying the presence of FNMTC.

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