ARTICLE
Auteur(s) : María
del Carmen Boente, Raúl A Asial
Centro de Investigaciones Dermatológicas, Tucumán, Argentina
accepté le 24 Août 2005
Giant congenital melanocytic nevi (GCMN) are rare congenital
pigmented tumours present in 1:20,000 live births. They are usually
dark brown or black hairy lesions measuring ≥ 20 cm in
diameter with a consistency similar to the adjacent skin [1-3]. In
general they show a patchy distribution without midline demarcation
[4].Diverse cutaneous changes within the nevus (hypoplasia of the
subcutaneous fat, neuroid proliferations, halo phenomenon, etc.),
as well as the rare spontaneous regression of the lesion have been
described [5, 6].Ruiz-Maldonado et al. [7] reported a new type of
GCMN showing a sclerodermoid reaction that progressively destroys
the melanocytic cells. He gave this nevus the name: “Desmoplastic
Hairless Hypopigmented Naevus (DHHN)”.We report a new case of this
type of nevus with unusual clinical features.
Case report
A 6-year-old boy was first seen at birth with a GCMN involving the
lumbosacral area, buttocks, perineum and scrotum. At birth, the
lesion was hairless, dark red-brown in colour with irregular
mottled borders, and of a hard ligneous consistency ( (figure 1) ). A punch
biopsy showed an increased number of melanocytes in the basal
layer. The deep dermis showed an increased number of nevus cells of
epithelioid configuration and melanophages intermingled with thick
collagen bundles. Adnexal structures were absent ( (figure 2) ).
During his first year of life a progressive reduction in colour,
size and consistency of the nevus was noted. Intense pruritus and
xerosis were the only constant complaints.
This progressive improvement continued until the age of four
when a small, hard, well-demarcated dermal tumour appeared on the
right buttock ( (figure
3A) ). The tumour became exophytic in few weeks, reaching
the size of 2 × 2 cm in diameter. It was pedunculated and
showed a granular surface (( (figure 3B) ). Resection of
this outgrowth was performed. Histopathological examination showed
nevus cells of spindle and epitheliod appearance, without atypia,
between thick collagen bundles ( (figure 4A and 4B) ).
Immunostaining results showed S100 +, Vim +, HMB45 (–), and CD34
(–).
During the 2 year follow up, no other tumours appeared. A
progressive loss of pigment and induration was observed, and areas
of normal-appearing skin became evident within the tumour ( (figure 5) ).
Discussion
Giant congenital melanocytic nevi (GCMN) are important congenital
tumours due to their significant cosmetic disfigurement as well as
their potential malignant transformation [3]. Although spontaneous
regression of GCMN has rarely been described, the involution is
usually not associated with sclerosis or hair loss [7, 8].
Ruiz-Maldonado et al. [7] described a unusual type of congenital
hairless melanocytic nevus showing a peculiar form of spontaneous
regression and named it “Desmoplastic Hairless Hypopigmented Naevus
(DHHN)”.
Among the clinical features of this particular type of GCMN are
the hard indurate texture, the absence of hair, the progressive
loss of pigment, an irregular mottled erythematous border and
pruritus (table 1)( Table 1 )[7].
Histological features are dermal fibrosis, desmoplasia, paucity of
melanocytes, atrophic or absent hair follicles and atrophic or
absent sebaceous glands (table 2)( Table
2 )[7].
A nodular growth in a GCMN usually raises suspicion of malignant
transformation. Melanomas inside GMCN develop as deep focal nodules
of rapid growth. Many have already metastasized at the diagnosis
[3].
In DHHN the progressive desmoplasia with melanocyte depletion
resulting in pigment loss may indeed imply a reduced risk of
malignant transformation. Patee et al. [5] reported a case of giant
congenital nevus with a progressive sclerodermoid reaction and
considered that an immune reaction against melanocytes of the nevus
may explain this phenomenon. We assume that in this type of nevus,
a tumour growth within the nevus may represent another type of
immunologic reaction without malignant probability.
So far, the number of reported cases of DHHN is rather limited.
Future reports may show whether the emergence of a pedunculated
benign tumor within DHHN, as noted in the present case, is an
exceptional feature or not during the evolution of this type of
nevus.
Table 1 DHHN: clinical features
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• Giant congenital melanocytic naevus
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• Hard indurate texture
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• Alopecia
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• Progressive loss of pigment
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• Irregular mottled border
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• Pruritus
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Table 2 DHHN: histopathological features
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• Dermal fibrosis – Desmoplasia
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• Paucity of melanocytes
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• Atrophic or absent hair follicles
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•Atrophic or absent sweat and sebaceous glands
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References
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Epidemiology of congenital pigmented naevi. Incidence and relative
frequencies. Br J Dermatol 1981; 104: 307-15.
2 Kopf AW, Bart RS, Hemnessey P. Congenital
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123-30.
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4 Happle R. Mosaicism in human skin: Understanding the
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Regression d’un naevus pigmenté géant congénital du cuir chevelu
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