bb5_28.qxd 13.9.2006 14:16 Page 337
CHAPTER 20
Tumours of Undefined Neoplastic Nature
There are many conditions of bone that are generally consi-
dered non-neoplastic, but often constitute important lesions to
be considered in the differential diagnosis of bone tumours.
Some feature the appearance and cytogenetic characteristics of
neoplasms, although the clinical behaviour rather supports a
non-neoplastic nature. Only the most important conditions are
included in this chapter.
bb5_28.qxd 13.9.2006 14:16 Page 338
A.E. Rosenberg
Aneurysmal bone cyst
G.P. Nielsen
J.A. Fletcher
Definition Epidemiology Primary ABC is well circumscribed and
Aneurysmal bone cyst (ABC) is a benign ABC affects all age groups, but is most composed of blood filled cystic spaces
cystic lesion of bone composed of blood common during the first two decades of separated by fibrous septa. The fibrous
filled spaces separated by connective life (median age approximately 13 years) septa are composed of a moderately
tissue septa containing fibroblasts, and has no sex predilection {1345, dense cellular proliferation of bland
osteoclast-type giant cells and reactive 2200}. The estimated annual incidence is fibroblasts, with scattered multinucleated
woven bone. ABC may arise de novo 0.15 per million individuals {1239}. osteoclast-type giant cells and reactive
(primary ABC), or secondarily compli- woven bone rimmed by osteoblasts. The
cate other benign and malignant bone Sites of involvement woven bone frequently follows the con-
tumours (secondary ABC) that have ABC can affect any bone but usually aris- tours of the fibrous septa. In approxi-
undergone haemorrhagic cystic change. es in the metaphysis of long bones espe- mately 1/3 of cases the bone is
cially the femur, tibia and humerus, and basophilic and has been termed "blue
Synonyms the posterior elements of vertebral bodies. bone", however, its presence is not diag-
Multilocular haematic cyst, giant cell Rare tumours whose morphology is iden- nostic as it can be seen in other entities.
reparative granuloma. tical to primary ABC of bone have also Mitoses are commonly present and can
been described in the soft tissues {53}. be numerous, however, atypical forms
are absent. Necrosis is rare unless there
Clinical features / Imaging has been a pathological fracture. The
The most common signs and symptoms solid variant of ABC has the same
are pain and swelling, which are rarely components as the septa and is very
secondary to fracture. In the vertebrae it similar, if not identical, to giant cell repar-
can compress nerves or the spinal cord ative granuloma. Primary ABC accounts
and cause neurological symptoms. for approximately 70% of all cases
Radiographically, ABC presents as a lytic, {177,1859}.
eccentric, expansile mass with well The majority of secondary ABC develop
defined margins. Most tumours contain a in association with benign neoplasms,
thin shell of subperiosteal reactive bone. most commonly giant cell tumour of
Computed tomography and magnetic bone, osteoblastoma, chondroblastoma
resonance imaging studies show internal and fibrous dysplasia {1173,1345, 2200}.
septa and characteristic fluid-fluid levels However, ABC-like changes may also
created by the different densities of the omplicate sarcomas, especially
cyst fluid caused by the settling of red osteosarcoma.
blood cells {1173,2200}. In secondary
ABC, CT and MRI may show evidence of
an underlying primary lesion.
Macroscopy
ABC is a well defined and multiloculated
mass of blood filled cystic spaces
separated by tan white gritty septa. More
solid areas can be seen which may rep-
A
resent either a solid portion of the ABC or
a component of a primary tumour that has
undergone secondary ABC-like changes.
Histopathology
ABC may arise de novo (primary ABC),
or secondarily complicate other benign
B
and malignant bone tumours (secondary
Fig. 20.01 Aneurysmal bone cyst. A Plain X-ray of
ABC) that have undergone haemorrhagic
an eccentric lytic mass of the proximal fibula. Note Fig. 20.02 Aneurysmal bone cyst. MRI of large
cystic change {1281,1557,1699,1849,
the peripheral shell of reactive bone. B CT of the destructive lesion of distal femur. Note numerous
same lesion (arrow). 1926}. fluid-fluid levels.
338 Tumours of undefined neoplastic nature
bb5_28.qxd 13.9.2006 14:16 Page 339
A B
Fig. 20.03 Aneurysmal bone cyst. A Septa composed of reactive woven bone, fibroblasts, and scattered osteoclast-like giant cells. B So-called 'blue bone" in wall of
the lesion.
Genetics ment, and as evidenced by the absence
The most notable genetic feature is the of 17p rearrangement in some cyto-
characteristic rearrangement of the genetically abnormal aneursymal bone
chromosome 17 short arm {1645}. The cysts {135,435,938,1645,1909,2281,
chromosome 17 rearrangements are 2311}. It is also striking that these
often in the form of balanced transloca- varied, but related, cytogenetic abnor-
tions, in which material is exchanged malities have been reported across the
with the long arm of chromosome 16. entire clinicopathological spectrum of
However, there are many variations on aneursymal bone cysts. Chromosome
this theme, and at least five different 16 rearrangement was identified in a
chromosomes can serve as transloca- solid variant aneursymal bone cyst,
tion partners with chromosome 17 whereas chromosome 17 rearrangement
{435,938,1645,1909,2281,2311}. The was found in an extra-osseous case
cytogenetic analyses invariably reveal {435}. Hence, it appears that there are
normal metaphases along with those generalisable transforming mecha-
bearing the translocations. Therefore, nisms, that are utilised irrespective of
the translocations can be assumed to histological subtype or site of origin.
result from acquired aberrations, arising
in cytogenetically normal precursor Prognostic factors
cells. The cytogenetic findings provide ABC is a benign potentially locally
compelling evidence that many aneursy- recurrent lesion. The recurrence rate fol-
mal bone cysts are clonal proliferations, lowing curettage is variable (20-70%).
with activation of a 17p oncogene play- Spon- taneous regression following
ing a key role in their tumourigenesis. incomplete removal is very unusual.
The mechanisms of oncogene activation Rare cases of apparent malignant trans-
Fig. 20.04 Aneurysmal bone cyst of proximal fibula.
appear to be heterogeneous, as shown formation of ABC have been reported
The well-defined haemorrhagic multicystic mass
by the different types of 17p rearrange- {1197}.
has a prominent solid component in the centre.
Aneurysmal bone cyst 339
bb5_28.qxd 13.9.2006 14:16 Page 340
R.K. Kalil
Simple bone cyst
E.S. Araujo
Definition Roentgenograms show a metaphysio- Prognostic factors
An intramedullary, usually unilocular, diaphyseal lucency, extending up to Recurrence is reported at 10-20% of
bone cyst (cavity) filled with serous or epiphyseal plate, with little or no expan- cases, especially in children. Growth
sero-sanguineous fluid. sion of bone; marginal sclerosis is arrest of the affected bone and avascular
absent or very thin. The cortex is usual- necrosis of the head of the femur after
Synonyms ly eroded and thin, but is intact unless pathological fracture can occur {2022}.
Solitary bone cyst; unicameral bone cyst; pathological fracture has occurred. Spontaneous healing after fracture has
juvenile bone cyst; essential bone cyst. There can be partial or complete septa- been described {52}.
tions of the cavity. MRI usually confirms
Epidemiology its fluid content, that can be bloody in
Males predominate in a ratio of 3:1. fractured lesions {1328}.
About 85% of patients are in the first two
decades of life. Aetiology
Growth defect at the epiphyseal plate
Sites of involvement has been postulated, or that a venous
There is a predilection for long bones, blood flow obstruction causes the sim-
proximal humerus, proximal femur and ple cyst {342}.
proximal tibia accounting for up to 90%
of cases. Pelvis and calcaneus are also Macroscopy
common locations in older patients. The cystic cavity is usually filled with
serous or sero-sanguineous fluid. The
Clinical features / Imaging inner surface of the cyst shows ridges
Fig. 20.06 Simple bone cyst of proximal ulna. A
Simple bone cyst can produce pain and separating depressed zones covered
unilocular cyst contains fibrin clot.
swelling but, more frequently, patients by a layer of thin membrane. Partial
present with a pathological fracture. septae may be seen.
The occasionally curetted specimen
consists of fragments of a usually thin,
whitish membrane that may be
attached at one surface to bone
spicules.
Histopathology
The inner lining and septae of the cyst
consist of connective tissue that can,
occasionally, contain foci of reactive
new bone formation, haemosiderin pig-
ment and scattered giant cells.
Fibrinous deposits are often seen.
Some of these are mineralized, resem-
bling cementum. Occasionally, histo-
logical features of fracture callus may
be prominent. Rare "solidified" cases of
simple bone cyst have been described
in older subjects.
Genetics
A highly complex clonal structural
rearrangement involving chromosomes
4, 6, 8, 16, 21 and both chomosomes
12 has been described in a surgically
Fig. 20.07 Simple bone cyst. The lining is usually
resected solitary bone cyst in an 11-
Fig. 20.05 Simple bone cyst of proximal femur. The inconspicuous and contains scattered spindle
lesion does not expand the bone. year-old boy {2195}. cells and giant cells.
340 Tumours of undefined neoplastic nature
bb5_28.qxd 14.9.2006 8:19 Page 341
G. Siegal
Fibrous dysplasia
P. Dal Cin
E.S. Araujo
Definition the skull are favoured sites in men circumscribed of blue-tinged translucent
Fibrous dysplasia (FD) is a benign {2154}. In the monostotic form, about material {2154}.
medullary fibro-osseous lesion which 35% of cases involve the head, a sec-
may involve one or more bones. ond 1/3 occur in the femur and tibia, and Histopathology
an additional 20% in the ribs. In the The lesion is generally well circum-
Synonyms polyostotic form, the femur, pelvis, and scribed and composed of fibrous and
Fibrocartilagenous dysplasia, general- tibia are involved in the majority of cases osseous components; which are present
ized fibrocystic disease of bone. {890}. in varying proportions from lesion to
lesion and also within the same lesion.
Epidemiology Clinical features / Imaging The fibrous component is composed of
Fibrous dysplasia occurs in children and Fibrous dysplasia may present in a cytologically bland spindle cells with a
adults world-wide and affects all racial monostotic or polyostotic form, and in low mitotic rate. The osseous component
groups with an equal sex distribution. the latter case, can be confined to one is comprised of irregular curvilinear tra-
The monostotic form is six times more extremity or one side of the body or be beculae of woven (or rarely lamellar)
common than polyostotic fibrous dys- diffuse. The polyostotic form often mani- bone. Occasionally, the osseous compo-
plasia. fests earlier in life than the monostotic nent may take the form of rounded
form {890}. The lesion is often asympto- psammomatous or cementum-like bone.
Sites of involvement matic but pain and fractures may be part Secondary changes such as foam cells,
The gnathic (jaw) bones are the most of the clinical spectrum {333}. Fibrous
common site of involvement in surgical dysplasia may also be associated with
series (because they are often sympto- oncogenic osteomalacia {1660}.
matic) {1596}. In women, long bones are The polyostotic form of fibrous dysplasia
more often involved, whereas ribs and is intimately associated with McCune-
Albright syndrome, in which there are
endocrine abnormalities and skin pig-
mentation. There is also a relationship
between fibrous dysplasia and intramus-
cular myxomas (Mazabraud syndrome)
{630}.
Rontgenographic studies often show a
non-aggressive geographic lesion with a
ground glass matrix. There is generally
no soft-tissue extension, and a
periosteal reaction is not seen unless
there is a complicating fracture. CT
scans and MRI further delineate these
features and better define the extent Fig. 20.09 CT of skull with fibrous dysplasia. In flat
bones the process is often expansile.
{422,1035,2118}.
Aetiology
Activating mutations of the G proteins
have been identified in both the mono-
stotic and polyostotic forms and may be
aetiologically important.
Macroscopy
The bone is often expanded and the
lesional tissue has a tan grey colour with
a firm-to-gritty consistency. There may
be cysts, which may contain some yel-
Fig. 20.08 X-ray of a polyostotic form of fibrous dys-
low-tinged fluid {1948}. When cartilage
Fig. 20.10 Fibrous dysplasia with gross cartilaginous
plasia. There is a well defined lucency with scle-
rotic margins. is present, it often stands out as sharply components.
Fibrous dysplasia 341
bb5_28.qxd 13.9.2006 14:16 Page 342
A B
Fig. 20.11 Fibrous dysplasia. A Characteristic C shaped bony spicules with hypocellular spindle cell stroma. B High power appearance showing the typical appear-
ance of bone which seems to be dissected by spindle cell proliferation. Note that there is no osteoblastic rimming.
multinucleate giant cells, a secondary ed in monostotic as well as polyostotic far are structural rearrangements in-
aneurysmal bone cyst or myxoid change fibrous dysplasia {382} (see also chap- volving 12p13 and trisomy 2 (three
may occur. ter on McCune-Albright syndrome). cases each).
Clonal chromosome aberrations have
Genetics been reported in eight of eleven in- Prognostic factors
Activating mutations in the GNAS1 vestigated cases, suggesting that this The prognosis of patients with FD is
gene, encoding the alfa subunit of stim- entity is neoplastic in nature {439}. The good. Malignant transformation occurs,
ulatory G protein, has been demonstrat- only recurrent changes described so but rarely.
342 Tumours of undefined neoplastic nature
bb5_28.qxd 13.9.2006 14:16 Page 343
V.J. Vigorita
Osteofibrous dysplasia
B. Ghelman
P.C.W. Hogendoorn
Definition lateral or contralateral involvement of the blending into the surrounding host
Osteofibrous dysplasia (OFD) is a self- fibula. Other sites include the ulna and bone. The periosteum often appears
limited benign fibro-osseous lesion of radius {1055}. Multifocal or large conflu- intact but the cortex is thin or absent.
bone characteristically involving cortical ent lesions oriented longitudinally along The medullary extension is usually
bone of the anterior mid-shaft of the tibia the cortical axis are not unusual. demarcated by a sclerotic rim.
during infancy and childhood.
Clinical features / Imaging Histopathology
Synonyms The lesion is rare after the age of 15. The The histopathologic findings in OFD
Kempson-Campanacci lesion, cortical most common presenting symptoms are are irregular fragments of woven bone
fibrous dysplasia. swelling or a painless deforming bowing often rimmed by lamellar layers of bone
of the involved segment of the limb. OFD laid down by well defined osteoblasts.
Epidemiology is typically epicentered in the cortical Osteoclasts may be present. The fibrous
The lesion is more commonly seen in bone but may involve the medullary cavi- component consists of bland spindle
boys during the first two decades of life ty by extension. Although slow growth is cells with collagen production and a
with a precipitous drop-off thereafter, characteristic of OFD, some lesions are matrix that varies from a myxoid com-
OFD has been reported in neonates, but aggressive and may involve the entire ponent to one that is moderately fibrous.
is extremely rare after skeletal matura- bone with significant bowing deformity. Mitoses are extremely rare. A zonal
tion. Often well demarcated, it is associated architecture has been delineated with
with a thinning, expanding or even miss- thin spicules and woven bone or even
Sites of involvement ing cortex. The expanding cortex is often fibrous tissue predominating in the cen-
The proximal or middle-third of the tibia is sclerotically rimmed near the medullary tre of the lesion with more abun-
the most frequent site of involvement bone. Separate or confluent oval-shaped, dant anastomosing and lamellar bone
{301}. Lesions can be bilateral with ipsi- scalloped, saw-toothed or bubbly multi- peripherally, the latter often blending
loculated lytic lesions are often noted.
Perilesional sclerosis may be consider-
able. The radiodensity of the interior of
the lytic foci are typically more radio-
dense than soft tissue. Periosteal reac-
tions and soft tissue extensions are
unusual. Bone scans are typically hot. CT
scans classically delineate a cortical epi-
centre to the lesion not breaking through
into the soft tissue and demarcated from
medullary bone by sclerosis. MRI find-
ings show high intensity lesions on T2
weighted images and mixed signals on
T1 and fat suppressed images.
Aetiology
The occurrence of so-called OFD-like
adamantinoma, to be distinguished from
classic epithelium-rich adamantinoma
but differentiated from OFD with difficulty,
raises the possibility of an association
between OFD and adamantinoma {112,
918,1188}. Some cases of OFD may
arise de novo and are not related to
adamantinoma.
Fig. 20.13 Osteofibrous dysplasia. Low power
Fig. 20.12 Osteofibrous dysplasia. Expansile
lucent, longitudinally-oriented tibial lesion sur- magnification of the lesion featuring hypocellular
Macroscopy
rounded by sclerosis and thinning of the anterior spindle cell proliferation and spicules of bone. The
bony spicules display prominent osteoblastic
cortex of the diaphysis of the tibia. Note the ante- OFD is solid with a whitish, yellowish or
rior bowing of the tibia. reddish colour and soft or gritty texture rimming.
Osteofibrous dysplasia 343
bb5_28.qxd 13.9.2006 14:16 Page 344
Table 20.01
demonstrated {256, 267}, as well as
Chromosomal abnormalities in osteofibrous dysplasia.
FOS and JUN proto-oncogene prod-
ucts.
No./Author Age/sex Tumour (type) Karyotype abnormality
Mutations of the alpha-subunit of sig-
1 Bridge {256} 11,M OFD (R) 47,XY,+12 (FISH: also +8,+20) nal transducing G-proteins with an
increase in cyclic AMP formation are
2 Bridge {256} 19,M OFD (R) 49,XY,+7,+8,+22
specifically absent {1845}.
3 Bridge {257} 18,F OFD (P/R) 52,XX,+5,+7,+7,+8,+21,+21
Prognostic factors
The natural history of osteofibrous
P, primary tumour; R, recurrence, FISH: fluorescence in situ hybridization. Cases 1/2:keratin-negative OFDs.
dysplasia is that of gradual growth dur-
ing the first decade of life with stabi-
lization at about 15 years of age
into the surrounding host bone {298}. and Leu7. Isolated cytokeratin positive followed by healing or spontaneous
Secondary changes of hyalinization, mast cells have been mentioned. resolution. The progression of OFD-like
haemorrhage, xanthomatous change, A tumour should be defined as OFD- adamantinoma (or  OFD with keratin
cyst formation and foci of giant cells are like adamantinoma when keratin-posi- positive cells ) to classic adamantino-
rare. Cartilage or clusters of epithelial tive epithelial cells are found ma has been shown in a few patients
cells are absent. {918,1534}. {562,918, 1041,2016}. In many others,
there is at least strong suggestion of a
Immunophenotype Genetics progression {381,2157, 2235}.
Osteofibrous dysplasia is positive for Numerical chromosomal abberations, OFD-like adam- antinoma seldom
vimentin and occasionally so for S100 especially trisomy 7 and 8 have been progresses to classic adamantinoma.
344 Tumours of undefined neoplastic nature
bb5_28.qxd 13.9.2006 14:16 Page 345
B.R. De Young
Langerhans cell histiocytosis
K.K. Unni
Definition wide age distribution ranging from the or loss of teeth can be encountered.
Langerhans cell histiocytosis is a neo- first months to the 8th decade of life with Vertebral body disease may result in
plastic proliferation of Langerhans cells. 80-85% of cases seen in patients under compression fracture and possible neu-
the age of 30, and 60% under the age of rological impairment. In adults, the lesion
ICD-O codes 10. Males are affected twice as often as can present as an incidental finding on
Langerhans cell histiocytosis, females {1026,1253,1259,2253}. imaging studies.
NOS 9751/1 Early lesions may appear very aggres-
Langerhans cell histiocytosis, Sites of involvement sive radiographically. Roentgenograms
unifocal 9752/1 Although any bone may be involved, generally show a purely lytic, well demar-
Langerhans cell histiocytosis, there is a predilection for LCH to involve cated lesion, usually associated with
multifocal 9753/1 the bones of the skull, notably the calvar- thick periosteal new bone formation.
Langerhans cell histiocytosis, ium. Other frequently involved sites Skull lesions are sometimes described
disseminated 9754/3 include the femur, the bones of the as representing a "hole in a hole" due to
pelvis, and the mandible {1259,2253}. In uneven involvement of the two osseous
Synonyms adults, the rib is the most frequent site of tables. In the vertebrae, the body is
Eosinophilic granuloma, Langerhans cell involvement {2253}. Monostotic disease involved producing collapse giving rise
granulomatosis, histiocytosis X. Clinical is much more common than polyostotic. to vertebra-plana.
variants have been referred to as Hand-
Schuller-Christian disease and Letterer- Clinical features / Imaging Macroscopy
Siwe disease. Pain and swelling of the affected area The involved tissue is soft and is red in
occur most commonly. Other findings are colour.
Incidence related to the bone involved. In cases of
Langerhans cell histiocytosis (LCH) is a temporal bone involvement, the present- Histopathology
relatively rare disorder, accounting for ing features can show significant clinical The diagnosis depends on the recogni-
less than 1% of all osseous lesions. LCH overlap with otitis media or mastoiditis. tion of Langerhans cells, which are inter-
involving bone has been reported in a With mandibular involvement, loosening mediate size with indistinct cytoplasmic
Fig. 20.14 Langerhans cell histiocytosis. Plain X- Fig. 20.15 Langerhans cell histiocytosis. Low power magnification shows loose aggregates of histiocytic
ray showing lucency in the shaft of the femur asso- appearing cells in a mixed inflammatory background with prominent eosinophilia and evidence of recent
ciated with thick periosteal new bone formation. haemorrhage.
Langerhans cell histiocytosis 345
bb5_28.qxd 13.9.2006 14:16 Page 346
A B
Fig. 20.16 Langerhans cell histiocytosis. A High power photomicrograph depicting Langerhans cells with ovoid to reniform nuclei with irregular notches and grooves.
B Langerhans cells show distinct membrane based immunoreactivity for CD1a.
borders, eosinophilic to clear cytoplasm ed osteoclast-like giant cells and occas- sions known as Birbeck granules which
with oval nuclei which frequently are sionally lipid laden histiocytes may be are thought to arise from the cell mem-
indented, irregular in outline, and typical- present. The cells of LCH can exhibit a brane.
ly possess nuclear grooves. Chromatin is relatively brisk mitotic rate, with up to 5-6
either diffusely dispersed or condensed mitoses per 10 high power fields. Genetics
along the nuclear membrane. In osseous Studies of X-chromosome inactivation
LCH, the Langerhans cells are found in Immunohistochemistry demonstrated that LCH is clonal {2275}.
nests or clusters. Diffuse sheet-like archi- Langerhans cells have a characteristic
tecture is rare, and, if present, should immunophenotype which includes Prognostic factors
raise the suspicion of haematolymphoid expression of membrane based CD1a The prognosis for patients with either
malignancy. The Langerhans cells are {584} and S100 protein in both a nuclear monostotic or limited polyostotic disease
frequently admixed with inflammatory and cytoplasmic pattern {1530}. These is good. Death can result from LCH, but
cells including large numbers of cells typically fail to express CD45. this is a rare event and is associated only
eosinophils, as well as lymphocytes, with the disseminated forms of the dis-
neutrophils and plasma cells. Necrosis is Ultrastructure ease and usually occurs in younger indi-
common and does not portend an Langerhans cells contain unique intracy- viduals less than three years at diagnosis
aggressive clinical course. Multinucleat- toplasmic "tennis racket" shaped inclu- and with visceral involvement.
346 Tumours of undefined neoplastic nature
bb5_28.qxd 13.9.2006 14:16 Page 347
T.N. Vinh
Erdheim-Chester disease
D.E. Sweet
Definition weakness. Other manifestations include abundant intracytoplasmic lipid vacuoles
Erdheim-Chester disease (ECD) is a rare exophthalmos, diabetes insipidus, kid- and sparse mitochondria, lysosomes,
histiocytosis characterized by infiltration ney failure, cardiac, pulmonary, or neuro- and endoplasmic reticulum. Birbeck
of skeleton and viscera by lipid laden his- logical symptoms, eyelid xanthomas, granules are absent {664}.
tiocytes leading to fibrosis and osteo- and hepatosplenomegaly {627,1091,
sclerosis. 1218,2045,2203}. Despite the impressive Prognostic factors
lipid laden histiocytic infiltration, the The majority of patients eventually die
Synonyms serum lipid profile is relatively normal. within 3 years of renal, cardiovascular,
Lipogranulomatosis, lipoidgranulomato- The radiographic picture of ECD is pulmonary, or CNS complications {2203}.
sis, lipid (cholesterol) granulomatosis, unique and includes bilateral, symmetric,
polyostotic sclerosing histiocytosis. patchy or diffuse sclerosis of the
medullary cavity of major long bones,
Epidemiology with relative epiphyseal sparing {1785}.
The disease demonstrates a slight male One third of cases have a mixed oste-
predominance with a peak incidence in olytic and sclerotic pattern {276,1463,
the 5th through the 7th decades (age 2045}. The sclerotic lesions show
range is 7 to 84 years; mean age 53) increased uptake on bone scan. CT scan
{2203}. serves to detect orbital, dural, and
retroperitoneal lesions. On MRI the lesion
Sites of involvement is of low signal intensity on T1-weighted
ECD predominantly affects the major sequences, enhances intensely after
long bones of the extremities; but flat gadolinium injection {2299}, and gives
bones can also be involved {306,664, mixed signal intensity on T2-weighted
1138}. Extraskeletal manifestations occur sequences {118,2045}.
in more than 50% of cases, e.g.
kidney/retroperitoneum, heart/pericardi- Macroscopy
um, and lung. On gross examination, the lesions
appear as sulphur-yellow and variably
Clinical features / Imaging firm.
General symptoms consist of mild bone
pain, occasionally associated with soft Histopathology
tissue swelling, fever, weight loss, and The histology consists of a diffuse infiltra-
tion of marrow by foamy histiocytes asso-
ciated with dense fibrosis, lymphocytes,
plasma cells and Touton giant cells.
Fig. 20.18 Erdheim-Chester disease. Macrosection
There is massive reactive sclerosis of
of tibia showing medullary sclerosis, which abruptly
cortical and cancellous bone with irregu-
ends at the physis.
lar cement lines.
Immunophenotype
Immunohistochemistry confirms the
monocyte/macrophage lineage of the
lipid laden foamy histiocytes and giant
cells by their expression for lysozyme,
Mac387, CD68 (Kp-1), CD4 {2168},
alpha-1-antichymotrypsin, alpha-1-antit-
rypsin and S100 protein (variable)
{1615}. They are negative for CD1a.
Ultrastructure
Fig. 20.17 Erdheim-Chester disease. Bone scan Fig. 20.19 Erdheim-Chester disease. Marrow infil-
Electron microscopy shows a predomi-
highlights the increased uptake throughout the entire tration by numerous foamy histiocytes associated
length of the bones involved. nance of histiocytes with indented nuclei,
with dense fibrosis.
Erdheim-Chester disease 347
bb5_28.qxd 13.9.2006 14:16 Page 348
E.F. McCarthy
Chest wall hamartoma
H. Dorfman
Definition Rarely, the lesion may be multifocal or ossification. Areas with fibroblast-like
Chest wall hamartoma is a non-neoplas- bilateral in the chest cavity {2132}. cells are also present. Cystic areas show
tic proliferation of mesenchymal tissue, features typical of aneurysmal bone cyst:
predominantly cartilage, admixed with Clinical features blood-filled lakes are bounded by fibrous
aneurysmal bone cyst elements. The Chest wall hamartoma presents as a septae which contain reactive bone and
lesion develops during fetal life and pres- mass or fullness of the rib cage. Most osteoclast-like giant cells.
ents at or shortly after birth with an often, the bulk of the mass is intratho-
extrapleural mass arising from the rib racic. As a result, infants frequently Prognostic factors
cage. develop respiratory distress. Complete surgical removal of the affect-
Radiographically, chest wall hamartoma ed ribs results in cure. Scoliosis is an
Synonyms is a partially mineralized mass arising occasional complication of surgery.
Vascular hamartoma of infancy, mes- from the inside of the rib cage and Rarely untreated patients may die of res-
enchymal hamartoma of the chest wall, extending into the chest cavity. The piratory insufficiency {1379}. However,
mesenchymoma. involved rib is partially destroyed, and most unoperated lesions remain stable.
adjacent ribs are deformed. CT images Spontaneous regression has also been
Epidemiology show an expansile mass and partial rib reported {721}.
The lesion is rare. To date only 59 cases destruction. Magnetic resonance images
have been documented. In approximate- shows alternating areas of high and low
ly 40% of cases, the mass is apparent at signal on T1 and T2 sequences, reflect-
birth. However, most cases present ing both solid and cystic components
between ages one month to one year {1886}.
{97}. Less frequently, lesions may pres-
ent in children up to age eight. One adult Macroscopy
aged 26 was diagnosed with a chest wall Lesions range from 3 to 7 cm in maxi-
hamartoma {531}. The lesion has also mum dimension. Cut surface reveals
been diagnosed in utero with CT scans grey to white solid areas adjacent to cys-
A
or ultrasound {1351,1807}. tic cavities filled with blood.
Sites of involvement Histopathology
The lesion is an intrathoracic and Solid areas consist primarily of mature
extraplural mass and arises from one or hyaline cartilage, although areas resem-
more ribs. Almost always, the posterior or bling chondroblastoma may be present.
lateral portions of the rib are affected. The cartilage often shows enchondral
B
C
Fig. 20.22 Chest wall hamartoma (A) showing the
typical chondroid matrix. B Histology similar to that
of a conventional aneurysmal bone cyst with blood-
Fig. 20.20 Chest wall hamartoma. X-ray of a newborn Fig. 20.21 CT scan of a chest wall hamartoma in a filled lakes separated by septae composed of stromal
showing a lesion in the right lower rib cage, involving three-day-old infant involving the inner aspect of a rib.
cells and multinucleated giant cells. C Immature
several ribs and projecting into the chest cavity. The lesion has a radiodense component.
chondroblastoma-like cells.
348 Tumours of undefined neoplastic nature