RESUMO
Epidermal naevi (EN) are considered mosaic disorders. Postzygotic mutations are thought to occur during early embryogenesis. They are usually arranged along Blaschko's lines and tend to be noted either at birth or shortly thereafter. Skin tumours arising on EN are occasionally reported, with ongoing discussion as to whether these are collision tumours or a malignant transformation of the EN. We describe a 76-year-old woman with segmentally arranged seborrhoeic keratoses that showed impending atypia and, in one lesion, even overt malignant transformation. In biopsies from various lesions we found FGFR3 and PIK3CA hotspot mutations but there was no consistent pattern of mutations explaining the premalignant or malignant growth. So far it is unclear whether the precancerous changes as noted in this elderly patient can be taken as an unusual manifestation of one of the established types of EN, or whether this may represent a separate disorder that could be called 'SASKIA naevus'. The acronym would stand for segmentally arranged seborrhoeic keratoses with impending atypia.
Assuntos
Carcinoma de Células Escamosas/genética , Ceratose Seborreica/genética , Mutação/genética , Fosfatidilinositol 3-Quinases/genética , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos/genética , Neoplasias Cutâneas/genética , Idoso , Carcinoma de Células Escamosas/patologia , Classe I de Fosfatidilinositol 3-Quinases , Feminino , Humanos , Ceratose Seborreica/patologia , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/patologia , Neoplasias Cutâneas/patologiaRESUMO
Seborrheic keratosis (SK) and epidermal nevi (EN) represent benign skin tumors and congenital lesions, respectively. Oncogenic mutations are fundamentally involved in their pathogenesis and SK is characterized by a broad spectrum of somatic mutations in the FGFR3, PIK3CA, RAS, AKT1 and EGFR genes. In contrast to malignant tumors, SK is genetically stable without alterations of tumor suppressor genes. The ENs are caused by postzygotic activating hot spot mutations in FGFR3, PIK3CA and particularly HRAS, resulting in a genetic mosaicism. The size of the lesions and the differentiation potential of the mutated cell into various tissue types depends on the time point of the mutation during embryogenesis. The genetic mosaic may predispose to a later growth of benign and malignant (adnexal) tumors.
Assuntos
Ceratose Seborreica/genética , Neoplasias Cutâneas/genética , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Análise Mutacional de DNA , Predisposição Genética para Doença/genética , Humanos , Ceratose Seborreica/classificação , Mosaicismo , Nevo/classificação , Nevo/genética , Oncogenes/genética , Mutação Puntual/genética , Pele/patologia , Neoplasias Cutâneas/classificaçãoRESUMO
BACKGROUND: Benign lichenoid keratoses (BLKs) are solitary skin lesions which have been proposed to represent a regressive form of pre-existent epidermal tumours such as solar lentigo or seborrhoeic keratosis. However, the genetic basis of BLK is unknown. OBJECTIVES: FGFR3, PIK3CA and RAS mutations have been shown to be involved in the pathogenesis of seborrhoeic keratosis and solar lentigo. We thus investigated whether these mutations are also present in BLK. METHODS: After manual microdissection and DNA isolation, 52 BLKs were screened for FGFR3, PIK3CA and RAS hotspot mutations using SNaPshot(®) multiplex assays. RESULTS: We identified 6/52 (12%) FGFR3 mutations, 10/52 (19%) PIK3CA mutations, 6/52 (12%) HRAS mutations and 2/52 (4%) KRAS mutations. FGFR3 and RAS mutations were mutually exclusive. One BLK showed a simultaneous PIK3CA and HRAS mutation. In nine BLKs with a mutation, nonlesional control tissue from the epidermal margin and the dermal lymphocytic infiltrate were wild-type, indicating that these mutations are somatic. To demonstrate that these findings are specific, 10 samples of lichen planus were analysed without evidence for FGFR3, PIK3CA or RAS mutations. CONCLUSIONS: Our results indicate that FGFR3, PIK3CA and RAS mutations are present in approximately 50% of BLKs. These findings support the concept on the molecular genetic level that at least a proportion of BLKs represents regressive variants resulting from former benign epidermal tumours such as seborrhoeic keratosis and solar lentigo.
