Alles wat je moet weten over de blauwe nevus bij huidziekten

Abstract

Blue nevus is a benign melanocytic lesion whose most frequent variants are dendritic (common) blue nevus and cellular blue nevus. Atypical cellular blue nevus presents an intermediate histopathology between the typical and a rare variant of malignant blue nevus/melanoma arising in a cellular blue nevus. An 8-year-old child presented a pigmented lesion in the buttock since birth, but with progressive growth in the last two years. After surgical excision, histopathological examination revealed atypical cellular blue nevus. Presence of mitoses, ulceration, infiltration, cytological atypia or necrosis may occur in atypical cellular blue nevus, making it difficult to differentiate it from melanoma. The growth of blue nevus is unusual and considered of high-risk for malignancy, being an indicator for complete resection and periodic follow-up of these patients.

Discussion

Dermoscopy has revolutionised clinical diagnosis of ALM by enabling detailed morphologic analysis of pigmented patterns. In this study, we found that grey colour, PRP, and IDP were significantly less common in small ALMIS than in large ALMIS (P = 0.002, P = 0.035, and P = 0.001, respectively).

PRP is the cardinal dermoscopic feature of ALM 9,10,17,19 . It is defined as prominent band-like pigmentation on the ridges of the dermatoglyphic lines 10 . Although it is the most well-known important dermoscopic features of ALM, PRP was absent in four cases of the small group (36.4%) in our data. Upon further analysis of small ALMIS without PRP, they showed other malignant features: irregular dots and globules in three, irregular fibrillar pattern in two, and IDP in one. Therefore, careful investigation of melanoma-specific dermoscopic patterns in addition to PRP is important especially in small lesions. IDP with variable shades from tan and grey to black colour is also specific to ALM 10,17 . Thirteen cases (61.9%) had IDP. This pattern was more prevalent in large lesions.

Early detection is crucial in improving melanoma prognosis. Saida and Koga proposed that a cut-off of larger than 7 mm is a helpful clue for ALM and incorporated this criterion in the three-step algorithm for early ALM screening 20 . Nonetheless, as ALMs generally arise de novo 9,21 , recognising small evolving lesions is essential for adequate management. However, the current literature on this topic is scarce. Data from Mayo clinic suggested that 6-mm acral melanomas could be missed when using the three-step algorithm 22 . Moreover, we reported two exceptional cases of evolving small ALMIS (4.5 mm and 5 mm). The cases were initially difficult to diagnose because they showed non-typical patterns. However, follow-up dermoscopic examination revealed increase in size and changing dermoscopic patterns. These cases highlight the importance of detecting small evolving pigmented macules for optimising ALM management.

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Atypical cellular blue nevus or malignant blue nevus? *

1 Division of Dermatology, Internal Medicine Department - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

Lygia Bertalha Yaegashi

2 Department of Pathology - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

Rodrigo Abdalah Freitas

2 Department of Pathology - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

Bruno de Carvalho Fantini

1 Division of Dermatology, Internal Medicine Department - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

Cacilda da Silva Souza

1 Division of Dermatology, Internal Medicine Department - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

1 Division of Dermatology, Internal Medicine Department - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

2 Department of Pathology - Medical School of Ribeirão Preto - Universidade de São Paulo- Ribeirão Preto (SP) -Brazil.

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