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Giant congenital naevus of the scalp and cranium: case report and review of the literature
Journal of Plastic Surgery (1997), 50, 20-25 0 1997 The British Association of Plastic Surgeons
British
Giant congenital naevusof the scalp and cranium: case report and review of the literature A. Madaree*, P. IL Ramdial? and M. Du Trevouf Departments of *Plastic and Reconstructive Surgery, fAnatomica1 Pathology and JNeurosurgery, Wentworth Hospital, University of Natal, Durban, Natal, South Africa SUMMARY. Congenital pigmented naevi are lesions that are usually confined to skin. We report a giant congenital naevus of the scalp which involved skin, galea, full thickness cranial bone, dura and the intracranial venous sinuses. The literature on giant congenital naevi with direct involvement of underlying bone is reviewed.
Case report
logical variation in different areas. At the centre of the lesion the tumour had a biphasic population of plump, spindled, dendritic cells and epithelioid cells that were arranged in compact nests and sheets. There was abundant cytoplasmic melanin pigment which in most cells had the appearance of fine granules while in other cells it exhibited coarse granularity. The nuclei were visible in most cells and they were small, central and normochromatic, with small nucleoli. None of the cells contained macronucleoli. Although these cells were present in the papillary dermis, their density was greatest in the reticular dermis and subcutaneous tissue. The lesional cells were present in the adventitial dermis around pilosebaceous and eccrine units but were not seen within the epithelia of these structures. These cells were also seen within the walls of blood vessels and in the endoneurium and perineurium of cutaneous nerves. In some sections, nests of nonpigmented spindled cells were seen surrounded by the biphasic lesional pigmented cells, creating an alveolar pattern. There were areas of cystic degeneration. An MRI scan, performed at the age of 2 years, confirmed involvement of the underlying meninges in the region of the occiput centrally. There was no evidence of involvement of the brain parenchyma (Fig. 4).
A neonate, the second of a twin delivery, was referred to our hospital with a large congenital naevus occupying approximately 35% of the scalp in the parieto-occipital region. The naevus was raised and had an area of necrosis and central ulceration with incipient sepsis(Fig. 1). A CT scan, performed at the age of 1 week, revealed underlying destruction of bone with a calvarial defect (Fig. 2). The patient was taken to theatre and the necrotic area was excised. The naevus was found to consist of soft massesof melanic pigment with little evidence of cellular architecture. The tissue was very friable and impossible to stitch. The bone was invaded by the melanin tissue and dural extension at the suture lines was noted. It was decided to allow the wound to granulate. The histological features were in keeping with those of a combined naevus in which a junctional naevocellular melanocytic naevus was present, in addition to a dermal cellular blue naevus (Fig. 3). The epidermis contained nests of naevus cellsat the dermo-epidermal junction. These naevoid cells had small central nuclei without any cellular pleomorphism and contained abundant fine melanin granules. The reticular dermis contained a pigmented lesion which extended transdermally into the subcutis and showed histo-
Figure
Congenital pigmented naevi may transform to a malignant melanoma. The risk factor is controversial and has been reported to vary from 1.8% to 45%. Quaba and Wallace’, after reviewing the literature, calculated the risk to be 8.52% within naevi larger than 2% of total body surface area during the initial 15 years of life. In the absence of malignant transformation, congenital pigmented naevi are usually confined to the skin. Bauer and Vicar? reviewed 180 patients with congenital pigmented naevi. Although 78 of these lesions were classified as giant congenital pigmented naevi (greater than 2% of body surface area), none had invaded bone. On reviewing the literature, there have been only four previous reports of congenital pigmented naevi having invaded bone.3-6 All four cases were scalp lesions with erosion of the bone down to dura. This paper presents a fifth such case and reviews the literature on this subject.
Fig. 1
20
l-Preoperative
view.
Giant coneenital naevus
21
Fig. 3 Fig. 2 Figure
Figure 3-Combined naevuswith junctional (arrow) and intradermal components.
2-CT scan.Arrow indicatesbone defect in calvarium.
When the patient was two and a half years old, a croissant-shaped tissue expander was inserted subgaleally into the anterior scalp and expanded over a few weeks. The patient was taken to thkatre for definitive excision of the naevus. Total excision of the involved skin was performed. The underlying galea and periosteum were involved and were therefore excised.The bone in the parieto-occipital region was also found to be involved and was excised (Fig. 5). The naevus was found to be invading the dura and this was resected. The dura over the posterior part of the superior sagittal sinus and the confluence of venous sinuses was involved by the naevus. Resection of this area was not performed as it would have required a major reconstruction with a high risk of morbidity and mortality. This area was, however, thinned with a computerised ultrasonic aspirator. The defect in the dura was reconstructed with collagen sponge (Bicol, Codman & Shurtleff, Randolph, USA). The defect in the bone was reconstructed with methyl methacrylate. A large transposition flap of the expanded skin was raised based on the right temporal vesselsand used to cover the defect. Split skin graft was applied to the donor defect. Postoperatively the patient developed repeated effusions under the flap which did not respond to further surgical explorations. It was decided to remove the methyl methacrylate and the wounds subsequently healed. The histological features of the second biopsy were in keeping with those of a cellular blue naevus, confirming a biphasic population of heavily pigmented epithelioid and
dendritic spindle cells (Fig. 6). The cells appeared slightly larger than those in the initial biopsy and also exhibited a prominence of cells with coarsely granular melanin pigment. The nuclei were partially obscured by the cytoplasmic pigment but macronucleoli cellular pleomorphism or increased mitotic activity were not evident. Both cell types were seen extending into the adventitial dermis of skin appendages with sparing of the epithelial component. There was more conspicuous and extensive endoneural, perineural and vascular wall involvement. The cystic degenerative phenomenon which was prominent in the earlier biopsy was not seen in the second biopsy. An alveolar pattern could no longer be identified. Deeper in the dermis, subcutis and loose connective tissue, cellshaving a wavy, schwannoid appearance were seen dissecting collagen bundles. Four areas of necrosis were seen in which there was abundant central free melanin surrounded by a scattering of acute inflammatory cells (Fig. 7). In these areas as well as in the rest of the tumour, mitotic figures were not seen. Despite adequate sectioning, a junctional or intradermal naevocelluar melanocytic naevus component could not be identified. The cellular blue naevus extended through the scalp, periosteum, bone and outer half of the dura matter (Fig. 8). The sections of the bone showed heavily pigmented epithelioid and spindled cellsbetween bony trabeculae (Fig. 9). The patient was seen 2 years postoperatively (Fig. 10). There was no evidence of recurrence on the scalp. Split cranial bone grafting is planned to reconstruct the defect in the skull.
British
Journal
of Plastic Surgery
Fig. 4 Figure
4-MRI
scan. Axial and sagittal views.
Fig. 5
5-Intraoperative view showing involvement of bone and tissue expander in situ. Solid black arrows indicate areas of involved scalp and periosteum. White arrow indicates areas of bone involvement. Open arrows indicate tissue expander and overlying expanded skin in frontal region. Figure
Fig. 6
6-Heavily (encircled). Figure
pigmented spindle (arrow) and epithelioid cells
Fig. 7
Fignre7-Necrotic bracket).
area with free melanin (marked by square
Giant congenital naevus
23
Fig. 8 Figure mater
I-Pigmented naevus cells (marked by square bracket).
confined
Fig. 10 to outer
half
of dura
Fig. 9 Figure
9-Pigmented
melanocytes
in bone.
Discussion
Congenital pigmented naevi occur in 2-3% of neonates. The subgroup of giant congenital naevi (2% or greater of total body or face area) occurs in 1 in 20 000 infants. These are usually confined to the skin and rarely invade the fascia or muscle. In a review of 78 patients with giant congenital melanocytic naevi, Bauer and Vicari’ found that 19 involved the scalp. None involved the underlying bone.
Figure
lo-Two-year
postoperative
view.
There have been only four other reported cases of a congenital naevus of the scalp having invaded through to the dura. Menter et a1.3 reported on a 2-year-old child with a giant blue naevus of the scalp which eroded through to the dura. This was very similar to our patient. Silverberg et a1.4 reported on a 3-year-old child with a cellular blue naevus of the scalp which invaded the periosteum, bone and dura. In their report it is claimed that the parenchyma was infiltrated. However, Prolo in a commentary on the article by Marano et al6 refers to the autopsy finding of the child described by Silverberg which revealed that there was no involvement of the brain parenchyma. Findler et a1.5 reported on a 6-year-old patient with a giant pigmented naevus of the scalp with infiltration into the periosteum, bone and dura. There was no evidence of involvement of the leptomeninges and brain parenchyma. Marano et a1.6 reported on a giant pigmented naevus of the scalp in a newborn with an underlying absence of the bone. The tumour had infiltrated the dura but here again there was no involvement of the leptomeninges or brain parenchyma. In the initial biopsy specimen of our patient both the junctional and cellular blue naevus components were easily identified. In the resection specimen, however, the junctional component was not identified either as a junctional or an intradermal naevocellular
British Journal of Plastic Surgery
24
melanocytic component. The junctional component was a small component and was most probably fully excised in the first biopsy. The cellular blue naevus had a slight but notable change in its cellular constituents. Heavily dendritic and epithelioid cells were still seen but the number and islands of non-pigmented spindle cells were markedly decreased compared to the first biopsy. Although four previous cases of an invasive, giant cellular blue naevus of the scalp have been reported, only one case had a junctional component (Marano et a1.)6 and would, as in our case, be classified as a combined naevus. Histologically the worrisome feature in our specimen was, as in the case described by Silverberg et a1.4 the presence of necrosis in the lesion. The cause of this necrosis may be ischaemia due to tumour bulk outgrowing its blood supply or may represent intrinsic tumour necrosis that characterises aggressive tumours. In the previous case reports, the latter was implied, but in our case it is not possible to confirm histologically the exact cause of the necrosis. However, as in previous reports, the necrosis was the only feature to explain an aggressive behaviour in the total absence of other histological stigmata of malignancy. In the four previous cases and in our case, the naevus extended through the scalp into the deeper connective tissue, periosteum and outer dura. The pia-arachnoid and brain were not invaded by the lesion. This pattern of invasion adds to the slowly increasing number of aggressive cellular blue naevi extending into the outer dura mater but sparing the brain and pia-arachnoid and strengthens Prolo’s suggestion that the brain is a ‘privileged sanctuary’ in this type of lesion. 6 Leptomeningeal pigmentation is the result of an embryological aberration. Sites of leptomeningeal pigmentation are the convexities of the cerebral hemispheres, base of the brain and ventral surfaces of the pons, medulla and upper cervical and lumbosacral spinal cord.7 Such pigmentation is not seen in the dura mater because of its embryological derivation which differs from that of the pia-arachnoid and scalp. The entity of neurocutaneous melanosis (NCM) was considered. NCM refers to the presence of large (> 20 cm) or numerous (> 3) pigmented naevi in association with leptomeningeal melanosis or melanoma.’ Included in the definition is the absence of cutaneous melanoma, except in histologically benign meningeal lesions, and absence of meningeal melanoma, except in histologically benign cutaneous lesions. In our patient the pigmented dendritic and epithelioid cells were seen extending into the outer half of the dura only, as described in all the previous cases of aggressive cellular blue naevus, confirming that this is an invasive component, rather than co-existent leptomeningeal melanocytosis. Frieden et a1.7 describe the magnetic resonance abnormalities of leptomeningeal melanocytosis. In the case reported by us, none of these abnormalities were present. In the case reported by Menter et a1.3, there was an underlying bony defect and total excision was not possible due to involvement of the superior sagittal, transverse and sigmoid sinuses. The child made a good recovery. The case reported by Silverberg et a1.4
demonstrated full thickness involvement of scalp, galea, pericranium, bone, dura and apparent infiltration of the occipital lobe. Because of extensive involvement of the major dural sinuses, total excision was not performed and the patient was reported to have made an uneventful recovery. However, Prolo in his commentary on the article by Marano et a1.6 states that the patient described by Silverberg died in May 1972 and, at autopsy, diffuse metastases were found in the pleura, lungs, heart, mediastinum, peritoneum, liver, oesophagus, stomach, small and large intestine, kidneys, adrenals, ureter, pancreas, thyroid gland, bone marrow and leptomeninges but not the brain. Findler et al.’ reported on a 6-year-old child with a giant naevus in the right temporal region. This had infiltrated the temporal fascia and muscle, pericranium, full thickness calvarium and outer layer of the dura. The brain and pia arachnoid were normal. Excision included removal of the involved dura. Repair was effected using freeze-dried cadaver dura, tantalum mesh-methyl methacrylate and a rotation flap. The recovery was uneventful. The case reported by Marano et a1.6 revealed a bony defect and involvement of full thickness scalp, muscle, bone and dura mater over the transverse sinus. This was excised and closure obtained with a rotation flap and skin graft. A cranioplasty was performed at 7 months using titanium wire mesh and methyl methacrylate. At age 7 years the patient had a normal neurological examination and had achieved appropriate developmental milestones with no further internal or external manifestation of the naevus at the site of surgery. Our excision of the soft tissue and underlying bone was complete. However, the dural resection was incomplete. The involvement of the posterior aspect of the superior sagittal sinus and confluence of the venous sinuses precluded complete resection in this area. Acknowledgements We would like to thank our secretaries, Mrs B. Possolo and Mrs A. Walker, and the Medical Illustration Unit, Medical School, University of Natal for their kind assistance in the preparation of this manuscript.
References 1. Quaba AA, Wallace AF. The incidence of malignant melanoma (0 to 15 years of age) arising in “large” congenital nevocellular nevi. Plast Reconstr Surg 1986; 78: 174-81. 2. Bauer BS, Vicari FA. An approach to excision of congenital giant pigmented naevi in infancy and early childhood. Plast and Reconstr Surg 1988; 82: 1612-21. 3. Menter MA. Griessel PJC. de Klerk DJ. Giant blue naevus of the scalp with underlying skull defect. Br J Dermatol 1971; 85 (Suppl7): 73-5. 4. Silverberg GD, Kadin ME, Dorfman RF, Hanbery JW, Prolo DJ. Invasion of the brain by a cellular blue nevus of the scalp: a case report with light and electron microscopic studies. Cancer 1971; 27: 349-55. 5. Findler G, Hoffman JH, Thompson HG, Becker L. Giant nevus of the scalp associated with intracranial pigmentation: case report. J Neurosurg 1981; 54: 108-12. 6. Marano SR, Brooks RA, Spetzler RF, Rekate HL. Giant congenital cellular blue nevus of the scalp of a newborn with an underlying skull defect and invasion of the dura mater. Neurosurgery 1986; 18: 85-9.
Giant
congenital
2.5
naevus
7. Kadonaga JN, Frieden IJ. Neurocutaneous melanosis: definition and review of the literature. J Am Acad Dermatol 1991; 24: 747-55. 8. Frieden IJ, Williams ML, Barkovich AJ. Giant congenital melanocytic nevi: brain magnetic resonance findings in neurologically asymptomatic children. J Am Acad Dermatol 1994; 31: 423-9.
The Authors Anil Madaree MBChB, MMed, FCS(SA), Professor and Head of Department of Plastic and Reconstructive Surgery Pratistadevi K. Ramdial MBCHB, FCPath(Anat)(SA), Lecturer, Department of Anatomical Pathology Michael Du Trevou MBChB, MMed, FCS(SA), Consultant Neurosurgeon, Department of Neurosurgery, University of Natal, Durban, Natal, South Africa. Correspondence to Professor A. Madaree, and Reconstructive Surgery, Wentworth JACOBS 4026, South Africa. Paper received 4 January 1996. Accepted 12 August 1996, after
revision.
Department Hospital,
of Plastic Private Bag
British
Giant congenital naevusof the scalp and cranium: case report and review of the literature A. Madaree*, P. IL Ramdial? and M. Du Trevouf Departments of *Plastic and Reconstructive Surgery, fAnatomica1 Pathology and JNeurosurgery, Wentworth Hospital, University of Natal, Durban, Natal, South Africa SUMMARY. Congenital pigmented naevi are lesions that are usually confined to skin. We report a giant congenital naevus of the scalp which involved skin, galea, full thickness cranial bone, dura and the intracranial venous sinuses. The literature on giant congenital naevi with direct involvement of underlying bone is reviewed.
Case report
logical variation in different areas. At the centre of the lesion the tumour had a biphasic population of plump, spindled, dendritic cells and epithelioid cells that were arranged in compact nests and sheets. There was abundant cytoplasmic melanin pigment which in most cells had the appearance of fine granules while in other cells it exhibited coarse granularity. The nuclei were visible in most cells and they were small, central and normochromatic, with small nucleoli. None of the cells contained macronucleoli. Although these cells were present in the papillary dermis, their density was greatest in the reticular dermis and subcutaneous tissue. The lesional cells were present in the adventitial dermis around pilosebaceous and eccrine units but were not seen within the epithelia of these structures. These cells were also seen within the walls of blood vessels and in the endoneurium and perineurium of cutaneous nerves. In some sections, nests of nonpigmented spindled cells were seen surrounded by the biphasic lesional pigmented cells, creating an alveolar pattern. There were areas of cystic degeneration. An MRI scan, performed at the age of 2 years, confirmed involvement of the underlying meninges in the region of the occiput centrally. There was no evidence of involvement of the brain parenchyma (Fig. 4).
A neonate, the second of a twin delivery, was referred to our hospital with a large congenital naevus occupying approximately 35% of the scalp in the parieto-occipital region. The naevus was raised and had an area of necrosis and central ulceration with incipient sepsis(Fig. 1). A CT scan, performed at the age of 1 week, revealed underlying destruction of bone with a calvarial defect (Fig. 2). The patient was taken to theatre and the necrotic area was excised. The naevus was found to consist of soft massesof melanic pigment with little evidence of cellular architecture. The tissue was very friable and impossible to stitch. The bone was invaded by the melanin tissue and dural extension at the suture lines was noted. It was decided to allow the wound to granulate. The histological features were in keeping with those of a combined naevus in which a junctional naevocellular melanocytic naevus was present, in addition to a dermal cellular blue naevus (Fig. 3). The epidermis contained nests of naevus cellsat the dermo-epidermal junction. These naevoid cells had small central nuclei without any cellular pleomorphism and contained abundant fine melanin granules. The reticular dermis contained a pigmented lesion which extended transdermally into the subcutis and showed histo-
Figure
Congenital pigmented naevi may transform to a malignant melanoma. The risk factor is controversial and has been reported to vary from 1.8% to 45%. Quaba and Wallace’, after reviewing the literature, calculated the risk to be 8.52% within naevi larger than 2% of total body surface area during the initial 15 years of life. In the absence of malignant transformation, congenital pigmented naevi are usually confined to the skin. Bauer and Vicar? reviewed 180 patients with congenital pigmented naevi. Although 78 of these lesions were classified as giant congenital pigmented naevi (greater than 2% of body surface area), none had invaded bone. On reviewing the literature, there have been only four previous reports of congenital pigmented naevi having invaded bone.3-6 All four cases were scalp lesions with erosion of the bone down to dura. This paper presents a fifth such case and reviews the literature on this subject.
Fig. 1
20
l-Preoperative
view.
Giant coneenital naevus
21
Fig. 3 Fig. 2 Figure
Figure 3-Combined naevuswith junctional (arrow) and intradermal components.
2-CT scan.Arrow indicatesbone defect in calvarium.
When the patient was two and a half years old, a croissant-shaped tissue expander was inserted subgaleally into the anterior scalp and expanded over a few weeks. The patient was taken to thkatre for definitive excision of the naevus. Total excision of the involved skin was performed. The underlying galea and periosteum were involved and were therefore excised.The bone in the parieto-occipital region was also found to be involved and was excised (Fig. 5). The naevus was found to be invading the dura and this was resected. The dura over the posterior part of the superior sagittal sinus and the confluence of venous sinuses was involved by the naevus. Resection of this area was not performed as it would have required a major reconstruction with a high risk of morbidity and mortality. This area was, however, thinned with a computerised ultrasonic aspirator. The defect in the dura was reconstructed with collagen sponge (Bicol, Codman & Shurtleff, Randolph, USA). The defect in the bone was reconstructed with methyl methacrylate. A large transposition flap of the expanded skin was raised based on the right temporal vesselsand used to cover the defect. Split skin graft was applied to the donor defect. Postoperatively the patient developed repeated effusions under the flap which did not respond to further surgical explorations. It was decided to remove the methyl methacrylate and the wounds subsequently healed. The histological features of the second biopsy were in keeping with those of a cellular blue naevus, confirming a biphasic population of heavily pigmented epithelioid and
dendritic spindle cells (Fig. 6). The cells appeared slightly larger than those in the initial biopsy and also exhibited a prominence of cells with coarsely granular melanin pigment. The nuclei were partially obscured by the cytoplasmic pigment but macronucleoli cellular pleomorphism or increased mitotic activity were not evident. Both cell types were seen extending into the adventitial dermis of skin appendages with sparing of the epithelial component. There was more conspicuous and extensive endoneural, perineural and vascular wall involvement. The cystic degenerative phenomenon which was prominent in the earlier biopsy was not seen in the second biopsy. An alveolar pattern could no longer be identified. Deeper in the dermis, subcutis and loose connective tissue, cellshaving a wavy, schwannoid appearance were seen dissecting collagen bundles. Four areas of necrosis were seen in which there was abundant central free melanin surrounded by a scattering of acute inflammatory cells (Fig. 7). In these areas as well as in the rest of the tumour, mitotic figures were not seen. Despite adequate sectioning, a junctional or intradermal naevocelluar melanocytic naevus component could not be identified. The cellular blue naevus extended through the scalp, periosteum, bone and outer half of the dura matter (Fig. 8). The sections of the bone showed heavily pigmented epithelioid and spindled cellsbetween bony trabeculae (Fig. 9). The patient was seen 2 years postoperatively (Fig. 10). There was no evidence of recurrence on the scalp. Split cranial bone grafting is planned to reconstruct the defect in the skull.
British
Journal
of Plastic Surgery
Fig. 4 Figure
4-MRI
scan. Axial and sagittal views.
Fig. 5
5-Intraoperative view showing involvement of bone and tissue expander in situ. Solid black arrows indicate areas of involved scalp and periosteum. White arrow indicates areas of bone involvement. Open arrows indicate tissue expander and overlying expanded skin in frontal region. Figure
Fig. 6
6-Heavily (encircled). Figure
pigmented spindle (arrow) and epithelioid cells
Fig. 7
Fignre7-Necrotic bracket).
area with free melanin (marked by square
Giant congenital naevus
23
Fig. 8 Figure mater
I-Pigmented naevus cells (marked by square bracket).
confined
Fig. 10 to outer
half
of dura
Fig. 9 Figure
9-Pigmented
melanocytes
in bone.
Discussion
Congenital pigmented naevi occur in 2-3% of neonates. The subgroup of giant congenital naevi (2% or greater of total body or face area) occurs in 1 in 20 000 infants. These are usually confined to the skin and rarely invade the fascia or muscle. In a review of 78 patients with giant congenital melanocytic naevi, Bauer and Vicari’ found that 19 involved the scalp. None involved the underlying bone.
Figure
lo-Two-year
postoperative
view.
There have been only four other reported cases of a congenital naevus of the scalp having invaded through to the dura. Menter et a1.3 reported on a 2-year-old child with a giant blue naevus of the scalp which eroded through to the dura. This was very similar to our patient. Silverberg et a1.4 reported on a 3-year-old child with a cellular blue naevus of the scalp which invaded the periosteum, bone and dura. In their report it is claimed that the parenchyma was infiltrated. However, Prolo in a commentary on the article by Marano et al6 refers to the autopsy finding of the child described by Silverberg which revealed that there was no involvement of the brain parenchyma. Findler et a1.5 reported on a 6-year-old patient with a giant pigmented naevus of the scalp with infiltration into the periosteum, bone and dura. There was no evidence of involvement of the leptomeninges and brain parenchyma. Marano et a1.6 reported on a giant pigmented naevus of the scalp in a newborn with an underlying absence of the bone. The tumour had infiltrated the dura but here again there was no involvement of the leptomeninges or brain parenchyma. In the initial biopsy specimen of our patient both the junctional and cellular blue naevus components were easily identified. In the resection specimen, however, the junctional component was not identified either as a junctional or an intradermal naevocellular
British Journal of Plastic Surgery
24
melanocytic component. The junctional component was a small component and was most probably fully excised in the first biopsy. The cellular blue naevus had a slight but notable change in its cellular constituents. Heavily dendritic and epithelioid cells were still seen but the number and islands of non-pigmented spindle cells were markedly decreased compared to the first biopsy. Although four previous cases of an invasive, giant cellular blue naevus of the scalp have been reported, only one case had a junctional component (Marano et a1.)6 and would, as in our case, be classified as a combined naevus. Histologically the worrisome feature in our specimen was, as in the case described by Silverberg et a1.4 the presence of necrosis in the lesion. The cause of this necrosis may be ischaemia due to tumour bulk outgrowing its blood supply or may represent intrinsic tumour necrosis that characterises aggressive tumours. In the previous case reports, the latter was implied, but in our case it is not possible to confirm histologically the exact cause of the necrosis. However, as in previous reports, the necrosis was the only feature to explain an aggressive behaviour in the total absence of other histological stigmata of malignancy. In the four previous cases and in our case, the naevus extended through the scalp into the deeper connective tissue, periosteum and outer dura. The pia-arachnoid and brain were not invaded by the lesion. This pattern of invasion adds to the slowly increasing number of aggressive cellular blue naevi extending into the outer dura mater but sparing the brain and pia-arachnoid and strengthens Prolo’s suggestion that the brain is a ‘privileged sanctuary’ in this type of lesion. 6 Leptomeningeal pigmentation is the result of an embryological aberration. Sites of leptomeningeal pigmentation are the convexities of the cerebral hemispheres, base of the brain and ventral surfaces of the pons, medulla and upper cervical and lumbosacral spinal cord.7 Such pigmentation is not seen in the dura mater because of its embryological derivation which differs from that of the pia-arachnoid and scalp. The entity of neurocutaneous melanosis (NCM) was considered. NCM refers to the presence of large (> 20 cm) or numerous (> 3) pigmented naevi in association with leptomeningeal melanosis or melanoma.’ Included in the definition is the absence of cutaneous melanoma, except in histologically benign meningeal lesions, and absence of meningeal melanoma, except in histologically benign cutaneous lesions. In our patient the pigmented dendritic and epithelioid cells were seen extending into the outer half of the dura only, as described in all the previous cases of aggressive cellular blue naevus, confirming that this is an invasive component, rather than co-existent leptomeningeal melanocytosis. Frieden et a1.7 describe the magnetic resonance abnormalities of leptomeningeal melanocytosis. In the case reported by us, none of these abnormalities were present. In the case reported by Menter et a1.3, there was an underlying bony defect and total excision was not possible due to involvement of the superior sagittal, transverse and sigmoid sinuses. The child made a good recovery. The case reported by Silverberg et a1.4
demonstrated full thickness involvement of scalp, galea, pericranium, bone, dura and apparent infiltration of the occipital lobe. Because of extensive involvement of the major dural sinuses, total excision was not performed and the patient was reported to have made an uneventful recovery. However, Prolo in his commentary on the article by Marano et a1.6 states that the patient described by Silverberg died in May 1972 and, at autopsy, diffuse metastases were found in the pleura, lungs, heart, mediastinum, peritoneum, liver, oesophagus, stomach, small and large intestine, kidneys, adrenals, ureter, pancreas, thyroid gland, bone marrow and leptomeninges but not the brain. Findler et al.’ reported on a 6-year-old child with a giant naevus in the right temporal region. This had infiltrated the temporal fascia and muscle, pericranium, full thickness calvarium and outer layer of the dura. The brain and pia arachnoid were normal. Excision included removal of the involved dura. Repair was effected using freeze-dried cadaver dura, tantalum mesh-methyl methacrylate and a rotation flap. The recovery was uneventful. The case reported by Marano et a1.6 revealed a bony defect and involvement of full thickness scalp, muscle, bone and dura mater over the transverse sinus. This was excised and closure obtained with a rotation flap and skin graft. A cranioplasty was performed at 7 months using titanium wire mesh and methyl methacrylate. At age 7 years the patient had a normal neurological examination and had achieved appropriate developmental milestones with no further internal or external manifestation of the naevus at the site of surgery. Our excision of the soft tissue and underlying bone was complete. However, the dural resection was incomplete. The involvement of the posterior aspect of the superior sagittal sinus and confluence of the venous sinuses precluded complete resection in this area. Acknowledgements We would like to thank our secretaries, Mrs B. Possolo and Mrs A. Walker, and the Medical Illustration Unit, Medical School, University of Natal for their kind assistance in the preparation of this manuscript.
References 1. Quaba AA, Wallace AF. The incidence of malignant melanoma (0 to 15 years of age) arising in “large” congenital nevocellular nevi. Plast Reconstr Surg 1986; 78: 174-81. 2. Bauer BS, Vicari FA. An approach to excision of congenital giant pigmented naevi in infancy and early childhood. Plast and Reconstr Surg 1988; 82: 1612-21. 3. Menter MA. Griessel PJC. de Klerk DJ. Giant blue naevus of the scalp with underlying skull defect. Br J Dermatol 1971; 85 (Suppl7): 73-5. 4. Silverberg GD, Kadin ME, Dorfman RF, Hanbery JW, Prolo DJ. Invasion of the brain by a cellular blue nevus of the scalp: a case report with light and electron microscopic studies. Cancer 1971; 27: 349-55. 5. Findler G, Hoffman JH, Thompson HG, Becker L. Giant nevus of the scalp associated with intracranial pigmentation: case report. J Neurosurg 1981; 54: 108-12. 6. Marano SR, Brooks RA, Spetzler RF, Rekate HL. Giant congenital cellular blue nevus of the scalp of a newborn with an underlying skull defect and invasion of the dura mater. Neurosurgery 1986; 18: 85-9.
Giant
congenital
2.5
naevus
7. Kadonaga JN, Frieden IJ. Neurocutaneous melanosis: definition and review of the literature. J Am Acad Dermatol 1991; 24: 747-55. 8. Frieden IJ, Williams ML, Barkovich AJ. Giant congenital melanocytic nevi: brain magnetic resonance findings in neurologically asymptomatic children. J Am Acad Dermatol 1994; 31: 423-9.
The Authors Anil Madaree MBChB, MMed, FCS(SA), Professor and Head of Department of Plastic and Reconstructive Surgery Pratistadevi K. Ramdial MBCHB, FCPath(Anat)(SA), Lecturer, Department of Anatomical Pathology Michael Du Trevou MBChB, MMed, FCS(SA), Consultant Neurosurgeon, Department of Neurosurgery, University of Natal, Durban, Natal, South Africa. Correspondence to Professor A. Madaree, and Reconstructive Surgery, Wentworth JACOBS 4026, South Africa. Paper received 4 January 1996. Accepted 12 August 1996, after
revision.
Department Hospital,
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