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Chapter49: Lungs, Pleura and Mediastinum 297
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Pneumothorax
Clinical features
The clinical picture is determined by the age of the
patient, the size of the pneumothorax, the presence or
absence of tension and the nature of any underlying
pulmonary disease [Box49.2]. Symptoms include pain
in the chest and dyspnoea.
Signs include displacement of the trachea to the contralateral site and displacement of the apex beat. There is
diminished movement of the chest wall, a hyper- resonant
percussion note and diminished air entry on the side of the
pneumothorax. In the typical spontaneous pneumothorax of
adolescence, there is sudden onset of symptoms, usually in
a tall, athletic boy with no pre-existing illness.
Box 49.2 Causes of pneumothorax
1 Spontaneous, often in teenagers, from apical bleb
2 Rupture of subpleural abscess in staphylococcal
pneumonia
3 Neonatal pulmonary disease (e.g. hyaline membrane
disease)
4 Rupture of subpleural emphysematous bulla
(e.g.asthma, cystic fibrosis)
5 Traumatic, following chest wall injury (Chapter38)
6 Perforation of oesophagus by ingested foreign body
or during oesophagoscopy
7 Iatrogenic (e.g. after paracentesis)
8 Rupture of hydatid cyst
9
Post-operative, after thoracotomy
Chest x-rays are usually diagnostic [Fig. 49.2], but
occasionally, a huge cyst or unusual types of diaphragmatic hernia may look similar radiologically.
Treatment
Urgent relief of tension by needle thoracocentesis or
intercostal drainage with an intercostal chest tube is
required. The underlying cause may require further
investigation (usually a CT scan of the chest). In
spontaneous pneumothorax, the scan will often reveal
apical cysts. If this is the first episode, the patient is
managed with chest drainage as required and no further
intervention. If the pneumothorax persists and recurs
on the same side or apical cysts are seen on imaging,
most surgeons perform a thoracoscopic apical blebectomy
± an apical pleurectomy.
Pleural effusion
The accumulation of fluids (pus, serofibrinous exudate,
blood, chyle or transudate) in the pleural cavity occurs
in a variety of conditions [Box49.3].
The physical signs are usually unmistakable, but
radiographs are necessary and may require careful
interpretation to distinguish a pleural collection from
such conditions as hydatid cyst or neuroblastoma.
Paracentesis may provide information on the nature
of the fluid and material for cytological and bacteriologic
examination, and indicates the necessity for further
drainage.
Figure 49.2 Neonatal pneumothorax. Tension pneumothorax
has caused displacement of the mediastinum to the right with
collapse of the right lung.
Chylothorax
Chylothorax may occur spontaneously or after cardiothoracic operations where the thoracic duct has been
injured. Some cases require aspiration, while some
patients require thoracoscopy or thoracotomy to ligate
the leaking thoracic duct. Replacing the fat content of
Box 49.3 Causes of pleural effusions
1 Pulmonary infection: acute (staphylococcal
pneumonia) and chronic (TB)
2 Disturbed haemodynamics: cardiac failure and
hypoproteinaemia
3 Malignancy: lung, pleura and mediastinum
4 Chylothorax: damaged and/or obstructed thoracic duct
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the diet with medium-chain triglycerides that are
absorbed via the portal vascular system may control, or
even cure, the condition, as only the long-chain fats
enter the lacteals and travel via the thoracic duct.
Bronchiectasis
Recurrent or chronic bronchitis is the most common
precursor of bronchiectasis. This type of bronchiectasis
tends to be widespread, although the disease is usually
most marked in one area.
Infection associated with permanent collapse of one
or more lobes of one lung may be the cause. However,
the bronchiectasis may remain dry, that is, structural
changes may be demonstrated by bronchography, but
symptoms and signs are minimal or absent if the affected
area remains free of infection.
Other causes include pulmonary tuberculosis, hydatid
disease, congenital weakness of the bronchial wall
(bronchomalacia), cystic fibrosis and the inhalation of a
foreign body. In healed tuberculosis, the bronchiectasis
is usually dry, while in bronchomalacia and cystic
fibrosis, dilatation of the bronchi is usually widespread
and associated with copious sputum.
Clinical features
Physical signs may be diffuse, localised or even absent,
according to the aetiology and the extent of the disease.
Clinical assessment of the nature and amount of
sputum, any interference with normal life and school
attendance, and the frequency of acute toxic episodes of
pneumonitis, should precede any investigations.
Bronchoscopy aims to confirm the diagnosis and
determine the distribution and severity. A CT scan of the
chest confirms the extent of the disease process. Culture
of the sputum is a useful guide to antibacterial choices,
particularly during exacerbations of infection.
Treatment
Conservative treatment, with physiotherapy, postural
drainage and antibiotics, is usually effective.
Lobectomy and/or segmental resection is required
occasionally and, in localised disease, is curative. As a
general rule, resection should be deferred until late
childhood, in case progressive disease in the remaining
lobes of the lungs develops. When the bronchiectasis is
more widespread, resection of a particularly diseased
area may considerably improve the patient’s well-being
and reduce the amount of sputum produced, although
some coughing may persist.
Congenital malformations
Congenital lobar emphysema and congenital cystic lung
lesions (Chapter4) may present in older children, and
there is no typical clinical pattern. Often recurrent
respiratory infections lead to an x-ray examination of
the chest, with a subsequent diagnosis.
A CT scan will often provide additional information,
and fluoroscopy may demonstrate trapped air in the
lobeconcerned, that is, movement of the mediastinum
towards the affected side during inspiration and away
from it during expiration.
Treatment typically involves removal of the affected
portion of the lung.
Pulmonary sequestration
A sequestrated lobe is pulmonary tissue that does not
have a normal communication with the bronchial tree,
and it receives its blood supply from an anomalous
systemic artery, usually from the aorta. It does not participate in the normal function of the lung and is consequently prone to infection. Two types are recognised:
extralobar and intralobar.
In extralobar sequestration, there is complete anatomical and physiological separation from the normal lung,
and the sequestrated portion may be above or below the
diaphragm. This is sometimes seen in association with
congenital diaphragmatic hernia. The arterial supply is
from the aorta (above or below the diaphragm) or one of
its branches (Fig.4.3, Chapter4).
In intralobar sequestration, the abnormal tissue
is contiguous with the normal lung, which partially
surrounds it. This type is almost always in the postero-lateral portion of the right or left lower lobe. The
blood supply comes from large direct branches of
theaorta (75%) or from other thoracic or abdominal
vessels (25%), and the venous drainage is through the
pulmonary veins.
The sequestrated lobe may consist of a large cyst, multiple cysts, branching bronchi without cysts, or all three
of these.
Chapter49: Lungs, Pleura and Mediastinum 299
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Clinical features
The diagnosis is most often made on routine antenatal
ultrasonography. At birth, the neonate is often asymptomatic. In children presenting beyond the neonatal
period, the usual history is of repeated episodes of
pulmonary infection with signs confined to one area.
Although the infection commonly subsides, acute suppuration may supervene. Subsidence of the acute phase
often leaves in its wake chronic suppuration with poor
health, a persistent cough and sometimes low-grade
pleural pain. Haemoptysis occurs occasionally.
Chest x-rays show an opacity in the posteromedial
part of one of the lower lobes or cystic spaces, with or
without fluid levels, in a lower lobe. In the acute phase,
the opacity increases in size and may produce mediastinal displacement.
Ultrasonography and CT scanning demonstrates the
anomalous arterial supply, confirms the diagnosis and is
useful in planning the operative approach.
Treatment
Resection, usually by thoracoscopy, is indicated because
of the susceptibility to infection. Where acute infection
has occurred, it is treated with antibiotics, and the sequestration is subsequently resected during a quiescent phase.
The child with a mediastinal mass
A child may present with a mediastinal mass in one of
two ways:
1 A symptomless mass demonstrated in a chest x-ray
2 Symptoms caused by compression of mediastinal
structures
A symptomless mass
The thymus is large in infancy, and determining whether
its appearance on chest x-ray is normal requires experience. Some radiographic techniques cause apparent
enlargement.
A symptomless mediastinal mass may develop in
thecourse of a generalised disease, for example, from
enlarged hilar lymph nodes in leukaemia or Hodgkin’s
disease, or as metastases from a malignant disease.
Paravertebral and para-aortic masses of neuroblastoma
may involve the mediastinum, often as the primary site
but also as metastases from tumour elsewhere, for
example, in the abdomen (Chapter25).
Incidental chest x-ray presentation
Sometimes, a mass is found incidentally on chest x-ray.
Initial investigations should include:
1 Examination of the peripheral blood for evidence of
leukaemia
2 Examination of the bone marrow for metastatic
neuroblastoma
3 Examination of the urine to determine the excretion
of methyl hydroxyl mandelic acid (MHMA) in a 24
specimen
4 A complete radiological assessment of the mediastinal
mass, including oblique views, computerised tomog-
raphy and magnetic resonance imaging, as indicated
In many instances, these investigations will give a good
indication of the diagnosis, but depending on discussions
with the oncology service, surgical exploration may still
be required to obtain material for a histological diagnosis
or to determine whether the mass is removable.
Surgical excision is generally curative in conditions
such as teratomas, duplication (enterogenous cysts), bronchogenic cysts and ganglioneuromas. In the latter, both
thoracotomy and laminectomy, combined or in stages,
may be required to remove both the components of a
dumb-bell tumour.
Total removal of infiltrating primary neoplasms or
extensive metastases in para-aortic lymph nodes is often
impossible, but there is evidence that even incomplete
removal may be of benefit in neuroblastoma, in which
maturation to benign ganglioneuroma may occur, particularly in those arising in the posterior mediastinum.
The operative findings, the histology and the results
of the preliminary examinations will determine the
need for chemotherapy and radiotherapy.
h
Compression of mediastinal structures
In childhood, this is nearly always the result of a malignant mass, of which lymphosarcoma is the most
common. Congestion of the veins of the head, neck and
upper limbs from obstruction of the superior vena cava,
wheezing, an unproductive or reverberating brassy
cough and increasing dyspnoea are all ominous signs.
Lymphosarcomas usually arise in the anterior mediastinum in the region of the thymus, and x-rays usually
show a large mass that extends laterally. The edges may
be irregular, rounded or ill defined; the tumour may
extend into the pleura and cause a pleural effusion. The
histological diagnosis may be made from cytology of the
cells in the pleural effusion.
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Figure 49.3 A mediastinal mass: in this case a neuroblastoma
with calcification in the posterior mediastinum.
A neural crest tumour (neuroblastoma or ganglioneuroma) is the usual cause of a paravertebral mass: areas
of both neuroblastoma and ganglioneuroma may be
present in a single tumour [Fig. 49.3]. Erosion of the
ribs and extension into a vertebral foramen causing
spinal symptoms are seen with infiltrating mediastinal
neuroblastomas.
A ganglioneuroma is a benign tumour arising in a
paravertebral gutter. It often grows through a vertebral
foramen into the spinal canal, resulting in two solid
elements connected by a narrow isthmus in the intervertebral foramen, a dumb-bell tumour.
Thymomas are much less common and are difficult to
distinguish from lymphosarcomas. They tend to grow
slowly, to reach an even larger size and to have a more
distinct margin in the x-rays of the chest.
Teratomas in the anterior mediastinum are very rare.
They are cystic or solid, only occasionally malignant,
and may extend laterally into one or other pleural
cavity.
Bronchogenic cysts arise close to the trachea or the
hilum of the lung; they usually contain air and many
show a fluid level in x-rays. There may be a history, suggestive of intermittent partial obstruction of one of the
larger bronchi, and operative excision is curative. This is
now often performed through a thoracoscopic approach.
Management
Compression of the trachea and/or bronchi may cause
severe respiratory distress, sometimes precipitated by
a supervening virus infection. When a chest x-ray
shows a mediastinal mass, tracheostomy is usually of no
assistance, for the obstruction is below the level of the
suprasternal notch. Nasotracheal intubation may be
necessary as an emergency. This situation is most commonly caused by a lymphosarcoma, and this presumptive
diagnosis should be confirmed quickly by examination of
the peripheral blood, the bone marrow or an accessible
enlarged lymph node (or occasionally the mass itself). As
with other malignancies, the stage of the disease will
determine the treatment. However, use of steroids and
cytotoxic agents, even without a histological diagnosis, is
justified in an emergency and brings dramatic relief. The
prognosis for most types of lymphosarcoma is good.
KEY POINTS
• Staphylococcal pneumonia may rapidly lead to empyema,
lung abscess and/or air leak.
• Children with parapneumonic pleural effusion should be
admitted to a tertiary paediatric centre.
• Spontaneous pneumothorax is most common in
adolescentboys.
• Chronic/recurrent bronchitis may lead to bronchiectasis.
• Chest x-ray should be done in recurrent respiratory
infections to exclude underlying cause (congenital cystic
lung, foreign body, tumour).
Further reading
Adzick NS, Farmer DL (2012) Cysts of the lungs and medias-
tinum. In: Coran AG, Adzick NS, Krummel TM, Laberge J-M,
Shamberger RC, Caldamone AA (eds) Pediatric Surgery, 7th
Edn. Elsevier Saunders, Philadelphia, pp. 825–836.
Balfour-Lynn IM, Abrahamson E, Cohen G et al. (2005) BTS
guidelines for the management of pleural infection in children. Thorax 60(Suppl 1): i1–121. doi: 10.1136/ thx
2004.030676.
Puligandla PS, Laberge J-M (2012) Infections and diseases of
the lungs, pleura and mediastinum. In: Coran AG, Adzick
NS, Krummel TM, Laberge J-M, Shamberger RC, Caldamone
AA (eds) Pediatric Surgery, 7th Edn. Elsevier Saunders,
Philadelphia, pp. 855–880.
PART IX
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Skin and Soft Tissues
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CHAPTER50
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Vascular and Pigmented Naevi
CASE 1
The mother of an 11-year-old is concerned about a few small
brown at moles that are slowly enlarging and becoming slightly
nodular.
Q 1.1 Is it possible that any of these could be a melanoma?
Q 1.2
How should they be managed?
Vascular lesions
Cutaneous vascular malformations are common. Both
haemangiomas and vascular malformations may occur
as isolated lesions or as part of a syndrome with multisystem involvement.
Haemangiomas
Haemangiomas are the most common tumours of
infancy and childhood. They have increased endothelial
cell turnover and many mast cells, with relatively predictable behaviour and life cycle. They occur in 12% of
all 1-year-olds.
Haemangioma of infancy (strawberry naevus)
These usually appear shortly after birth as a pale, pink or
bright red spot or patch on the skin, the so-called herald
spot. The hallmark of these tumours is their rapid growth
in infancy, which continues for anywhere from 4 to 12
months, but typically ends around 9 months [Fig.50.1].
Gradual involution often begins at about 1 year of age,
with a grey patch appearing centrally, and is usually
complete by 6–8 years. A small amount of redundant
atrophic telangiectatic skin and subcutaneous tissue may
remain, requiring cosmetic correction. This is especially
true on the lip. Multiple skin lesions may be associated
with visceral involvement.
CASE 2
A 2-month-old was born with a red spot on the left upper eyelid.
This has progressively grown into a large red nodular lesion, and
partial ptosis is now present.
Q 2.1 What are the possible functional and cosmetic consequences?
Q 2.2
How should this be managed?
Haemangiomas on the skin surface have the typical red,
strawberry appearance. When haemangiomas are under
the skin, they are more blue in colour, but histologically,
they are the same. Apart from presenting later, their behaviour is identical. Often, haemangiomas have super ficial and
deep components.
Congenital haemangioma
A subgroup of haemangiomas is present fully formed at
birth. The haemangiomas of this subgroup either regress
rapidly in the first few months of life (rapidly involuting
congenital haemangioma or RICH), or they persist into
adolescence (non-involuting congenital haemangioma or
NICH). Congenital haemangiomas have a blue colour and
a pale periphery. They can be differentiated from infantile
haemangiomas on histology as they do not stain for
markers of immature endothelium, in particular Glut-1,
for which haemangiomas of infancy are uniformly positive.
Management of haemangiomas consists of accurate
diagnosis and careful observation. The parents need
reassurance during the normal rapid growth phase of
the lesion and must be warned that the haemangioma
may increase significantly in size. Failure to give this
warning leads to a loss of confidence in the treating doctor if alarming growth occurs. Problems of ulceration,
bleeding and rarely infection occur secondary to minor
trauma, especially in the nappy area. These are usually
Jones’ Clinical Paediatric Surgery, Seventh Edition. Edited by John M. Hutson, Michael O’Brien, Spencer W. Beasley,
Warwick J. Teague and Sebastian K. King.
© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.
303
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best dealt with non-operatively. Bleeding is controlled
with pressure. Ulcerated haemangiomas are painful and
can be very slow to heal. Excision of an ulcerated haemangioma may be indicated if the defect can be directly
closed, particularly in the nappy area where recurrent
ulceration may occur. Haemangiomas of the eyelid are
of particular concern as pressure on the globe can distort the shape of the cornea, causing strabismus, and
this, or the occlusion of the visual axis, for even a few
weeks, can produce an amblyopic eye [Fig.50.1]. Early
referral to a paediatric ophthalmologist is mandatory for
haemangiomas of the eyelid.
Systemic steroids used to be the first-line treatment for
haemangiomas not amenable to surgery, but most centres now use oral propranolol as the first-line treatment.
Response to propranolol is generally rapid and occurs in
around 90% of cases. Steroids, alpha interferon and
vincristine are alternative treatments. Topical Timoptol
eye drops can be effective on superficial lesions.
Large haemangiomas of the liver can be associated
with high-output cardiac failure and can also deplete
thyroxine, causing unrecognised hypothyroidism. These
lesions may be fatal.
Consumptive coagulopathy (Kasabach–Merritt syndrome) with a very low platelet count is associated
with two rarer lesions, kaposiform haemangioendothelioma (KHE) and tufted angioma, but is not caused by
true infantile or congenital haemangioma. KHE and
tufted angioma (along with congenital haemangiomas)
do not respond to propranolol. Steroids and vincristine
are the preferred treatments, and rapamycin is sometimes used.
Pyogenic granuloma
Pyogenic granuloma is the other common cellularly
dynamic lesion. It may follow minor trauma to the face
and grows rapidly, becomes ulcerated and friable, and
bleeds readily. It is characterised by a central feeding
vessel supplying a mass of new capillaries and an
associated inflammatory infiltrate. The appearance is
often similar to haemangioma of infancy, but the age
of appearance differentiates it. Pyogenic granuloma is
(a)
(c)
(b)
Figure 50.1 a,b,c The common haemangioma of infancy
(strawberry naevus) on the lower eyelid, shortly after birth
(a), 6 months (b) and then at 2–3 years of age (c). The lesion
required frequent assessment, as obstruction of the visual axis,
for even a few weeks, will result in an amblyopic eye.
Table 50.1
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Chapter50: Vascular and Pigmented Naevi 305
Haemangioma of infancy Vascular malformation
Growth pattern Appears just before or just after birth and grows
rapidly
Involution Starts to involute between 6 and 18 months Does not involute
Endothelial characteristics Plump endothelial cells showing rapid turnover Stable flat endothelium
Pharmacological treatment Most respond to propronolol, backup treatment
of steroids, interferon or vincristine
Grows in proportion with child
No pharmacological treatment available
at present
treated by excision, which should include the feeding
vessel to prevent recurrence.
Vascular malformations
Regional vascular malformations, in contrast to haemangiomas, are composed of mature vascular elements and
do not regress [Table50.1]. They may be capillary, venous,
arteriovenous, lymphatic, or a combination of these.
Capillary malformations
Naevus flammeus medialis is the salmon patch or stork’s beak
mark seen on the nape of the neck in infancy. This lesion
does not change with time. The port wine stain is a cutaneous capillary malformation. There is gradual darkening
and hypertrophy of the lesion over a patient’s lifetime. This
lesion may be part of a syndrome, for example, the
Klippel–Trenaunay syndrome (limb overgrowth with lymphatic and venous anomalies) or the Sturge–Weber
syndrome (lesions involving the upper face with intracerebral involvement and epilepsy). Any capillary malformation around the eye requires assessment for glaucoma.
Current therapy centres on the use of lasers, with
wavelengths selective for haemoglobin and rapid, shortduration target heating times. This coagulates the lesion
while producing the least scarring in the skin. The results
of the treatment in children are better than those in adults.
Figure 50.2 A venous malformation affecting the pelvis and thigh.
Venous malformations
These compressible lesions occur anywhere on the body
and may occasionally undergo thrombosis. The presence of phleboliths (small, smooth, hard and mobile)
for specific problems but complete excision is rarely
possible. Compression garments and low-dose aspirin
therapy may be helpful.
is diagnostic of venous malformation [Fig. 50.2].
Venous malformations tend to slowly expand over
time. MRI and ultrasound are the most useful investigations: venous malformations are not visualised
onconventional angiography. The most effective treat
ment is usually injection sclerotherapy performed by
the interventional radiologist. Surgery can be useful
Arteriovenous malformations
Arteriovenous malformations are high-flow lesions that
tend to have a more malignant course than low-flow
-
malformations. They often have an overlying capillary
stain. They tend to gradually increase in size over time,
especially around puberty and in pregnancy, and can
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ultimately develop skin ulceration and infection. Large
lesions become at risk of catastrophic bleeding. Ligation
of feeding vessels, either surgically or by angiographic
embolisation, is not curative and complicates future
treatment. Treatment is either surgical excision or intraarterial ethanol infusion under radiological control.
Recurrence is common.
Lymphatic malformations
Malformations of the lymphatic system range from
the small nodular lesions of lymphangioma simplex
tolarge cervical cystic hygromas. They can consist of large
cysts (macrocystic), multiple small cysts (microcystic) and
some times contain areas of solid fibrous tissue. Lymphatic
malformations have a propensity to infection, which must
be treated with prolonged antibiotic therapy. Well-defined
lesions should be excised if possible, although recurrence
is common and may occur inthe scar. Cystic hygromas are
usually located deep in the cervical and upper thoracic
area and may be associatedwith inflammatory and infectious complications. Macrocystic lesions are amenable to
injection sclerotherapy under radiological control, which
can be performed with a variety of agents. Microcystic
lesions and those not responding to injection, if causing
problems, require operative treatment. Surgery is technically difficult as the lesions are not confined by tissue
planes (see Fig16.2, Chapter16) and nerves frequently
pass through the centre of the lesion.
Telangiectasia and spider naevi
Telangiectasias may also be congenital and may be isolated or appear as part of a syndrome, for example,
Rendu–Osler–Weber syndrome. Spider naevi are common
and are distinguished by a central feeding vessel and
radial filling following careful occlusion of this vessel.
Treatment is by laser.
Pigmented naevi
True pigmented naevi are melanocytic in origin.
Junctional naevi
Histologically, these naevi show clusters of melanocytes
in the basal layers of the skin. They are flat brown or
black spots clinically and normally persist throughout
childhood. Junctional activity after puberty is a very
slight risk for malignant melanoma. Malignant change is
so rare that excision of these in childhood should be
avoided unless they have particularly worrying features
or if they are a significant cosmetic blemish.
Compound and intradermal naevi
A compound naevus has both junctional and
intradermal components. Naevus cells bud off into the
dermis where they proliferate and form a cluster of
cells, resulting in a raised palpable lesion. In later years,
the junctional activity ceases and the lesions become
mature intradermal naevi. They are felt to be benign
with no risk of malignant transformation. Surgical excision is for cosmetic reasons.
Spitz naevi
The juvenile or Spitz naevus is usually reddish in colour,
as melanin is less prominent. There is considerable junctional activity and spindle cells are present in the dermis.
The presence of mitotic figures and atypical cells sometimes leads to confusion with malignant melanoma.
Congenital naevi
Congenital naevi are found in 1% of babies. They may be
small (<1.5 cm), medium or large (>20 cm). These are
histologically similar to acquired compound naevi, and
the cells form nests deep within the dermis in association
with hair follicles and sebaceous glands. The giant naevus
occurs in 1:20,000 babies and covers a major segment of
the body, for example, bathing-trunk naevus [Fig.50.3a].
Multiple smaller naevi may also be present in other areas,
and there may be meningeal involvement. The giant naevus is largely intradermal, but may have a junctional
component. The risk of malignant melanoma, mainly
after puberty, is about 4% over a lifetime in large naevi
and may be higher in giant naevi. With adolescents, the
lesions tend to become more nodular and hairy.
Treatment is performed mainly for cosmetic reasons
by excision and direct closure where possible, or reconstruction with flaps, with or without tissue expansion.
In many instances, complete removal is impossible. In
giant naevi, extensive skin grafting is best avoided. Early
referral is essential, as many giant naevi can be improved
by curettage in the first few months of life [Fig.50.3b].
Occasionally, melanocytic naevi respond to laser treat
ment, but generally, results are disappointing.
-
Halo naevi
A halo naevus occurs when melanocytes disappear
from the periphery of a pigmented naevus. This is felt to
be an immunological phenomenon, and lymphocytes
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