Congenital Intraspinal Lipomas:Histological Analysis of 234 Casesand Review of the Literature

ARIELLE LELLOUCH-TUBIANA,1* MICHEL ZERAH,2 MARTIN CATALA,3NICOLE BROUSSE,1 AND ALAIN-PIERRE KAHN2

1Laboratoire d’Anatomie Pathologique, Hopital Necker-Enfants Malades, 149 rue de Sevres, 75015 Paris, France2Service de Neurochirurgie Pediatrique, Hopital Necker-Enfants Malades, 149 rue de Sevres, 75015 Paris, France3Laboratoire d’Histologie-Embryologie, Hopital Pitie-Salpetriere, Paris, URA CNRS 2115, 75013 Paris, France

Received November 28, 1997; accepted September 4, 1998.

ABSTRACTThe clinical, radiologic, and pathologic data from aseries of 234 patients hospitalized in the Pediatric Neuro-surgical Department of the Necker–Enfants MaladesHospital, Paris, for congenital intraspinal lipomas andoperated on from 1976 to 1995 were examined. Histologi-cal studies showed that these lesions may be simplelipomas, similar to those developing elsewhere in thebody, or they may be more complex forms including inaddition to the lipomatous component a variety ofunusual ectopic tissues of ectodermal, mesodermal,and/or endodermal origin. These complex forms indicate the malformative nature of these tumors. When theycontain elements that are truly foreign to the region,the possibility of teratoma with a tumoral potentialshould be considered. Data found in the literatureand from Necker–Enfants Malades Hospital are dis-cussed.

Key words: congenital intraspinal lipoma, dysraphia,teratoma

INTRODUCTIONCongenital intraspinal lipomas are a rare form ofspinal dysraphism in children. They can be definedas a mass of adiposal tissue coming in contact withthe medullary nervous tissue. Intraspinal lipomas

involve mainly the lower extremity of the spinal

canal: they may involve the filum or, more often,

the conus. Lipomas of the cord are exceptional, and

are mostly thoracic.

The incidence of the malformation, calcu-

lated from two French regional registers, was found

to be 4 to 8.5/100,000. This estimate, however, is

certainly low, because the number of symptomless

intraspinal lipomas is unknown. In all series, the

two main clinical features leading to diagnosis

were cutaneous stigmata on the lower back and

neurological disturbances that are mainly neuro-

orthopedic and sphincter-related. These presum-

ably stable lesions can grow in some cases. Surgical

indications are controversial in asymptomatic pa-

tients and pathogenesis is still a matter of debate.

Using the series of 234 intraspinal lipomas oper-

ated on in the Pediatric Neurosurgical Department

of the Hopital des Enfants Malades in Paris, we

describe here the histological findings of these rare

lesions and discuss their anatomic, clinical, embryo-

logic, and pathologic features.

METHODSThe study was carried out retrospectively, using

data from 234 patients who had congenital intraspi-*Corresponding author

Pediatric and Developmental Pathology 2, 346–352, 1999 Pediatric and Developmental Pathology

r1999 Society for Pediatric Pathology

nal lipomas and were operated on at the Necker–Enfants Malades Hospital in Paris from 1976 to1995.

The mean age of the patients at the time ofsurgery was 6 years, 4 months. The lipomas in-volved almost exclusively the conus. Rare cases of

lipomas of the filum were included in this study. Allsurgical specimens were examined histologically.The samples were fixed by immersion in 10%formaldehyde, dehydrated, and embedded in paraf-fin, then sectioned and stained with hematoxylin-eosin-safranin and Masson’s trichrome.

Figure 1. Macroscopy of a spinal lipoma, showing agreasy surface.

Figure 2. Photomicrograph of the lipoma. The tumor iscomposed of well-differentiated adipose tissue. Fibroussepta divide the fatty mass into a multilobular pattern.Hematoxylin-eosin, 3100.

Figure 3. Intralipomatous Vater-Pacini neurosensorialcorpuscle. Hematoxylin-eosin, 3400.

Figure 4. Intralipomatous glial tissue surrounded bydense fibrosis. Hematoxylin-eosin, 3200.

Figure 5. Photomicrograph of a lipoma showing afibrous nodule containing an ependymal-lined canalsurrounded by arachnoidal tissue. Hematoxylin-eosin,3180.

Figure 6. Photomicrograph of a squamous epithelialtissue.

CONGENITAL INTRASPINAL LIPOMAS 347

RESULTSClinically in our series there was a significantfemale preponderance (F/M: 1.6/1). The averageage at diagnosis was 6.4 years. The malformationwas diagnosed earlier in the presence of cutaneousstigma as well as more recently. From 1990 to 1994,the average age at diagnosis was 9 months, withpatients showing skin abnormality. Cutaneousanomalies were present in 89.4% of our patients.The most frequent of these skin anomalies was asubcutaneous lump located at the midline of thelower back. Neurological deficits affected 56.7% ofour patients; these were predominantly sphincterdisturbances (42%) and motor deficits (31%). In allseries, vesical sphincter dysfunctions were the mostfrequent deficit. They affected more than half ofour patients and included incontinence, dysuria/retention, and infection. Bowel dysfunction con-sisted of constipation, sometimes severe, and stoolleakage. A neuro-orthopedic syndrome was presentin 31% of our patients and affected the lower limbs:40% of our patients had a club foot, often with anequinovarus deformity with clawing of the toes,36% had muscular atrophia of the leg, 21% hadhypotrophia of the leg or foot, and 27.6% hadsuperficial hypoesthesia. At examination, 34% ofpatients had a central motor neuron syndrome.

Associated spinal malformations occurredmostly as spina bifida occulta, which was presentin 91% of our patients. Associated visceral malfor-mations were found in 27% of patients in our series(Table 1). Uroanogenital malformations were themost frequent. Eighty percent of intraspinal lipo-mas in this series involved the conus, and 20%, thefilum. In 23% of cases histological examinationshowed lipomas similar to subcutaneous lipomasdeveloping elsewhere in the body (Fig. 1). Theywere made of mature adiposal cells, arranged inlobules with a striking amount of fibrous tissue

interspersed between the adiposal lobules (Fig. 2).In 77% of cases lipomas appeared more complex,containing a wide variety of ectopic tissues ofectodermal, mesodermal, or endodermal origin(Tables 2 and 3). Indeed, careful examination of thelipomas showed associated tissues. In our series,the more frequent tissues encountered were stri-ated muscular tissue (37%), nerves (63%), andsensory nerve corpuscles, such as Vater-Pacini (Fig.3) or end-bulb of Krause (21%). All these tissueswere intralipomatous, surrounded by a dense fibro-sis, and were part of the lesion. In 18% of cases glialor neuroglial tissue, surrounded by fibrous tissue,was observed, without an association of myelome-ningocele (Fig. 4). In 7% of cases arachnoid tissuewas found associated with glial tissue or isolated ina fibrous strand. Ependymal structures, arrangedas ependymal cells lining canals of irregular out-lines, and sometimes surrounded by glial tissue,were present in 5% of cases (Fig. 5). Other tissueswere more rarely observed in association with thefatty cells of the lipoma. In our series we foundsquamous epithelial tissue (2%) (Fig. 6), often

Table 1. Visceral associated malformations

Malformations n %

Anorectal 15 6.4

Genital 9 3.8

Urinary 14 6

Cardiac 5 2.1

Other 21 8.9

Total 64 27

Table 2. Type of tissues found in lipomas

n %

Tissues normally presentin sacrococcygeal region

Skeletal muscle 87 37

Sensory nerve corpuscles 50 21

Neuroglial tissue 37 18

Ependymal tissue 10 5

Meningeal tissue 14 7

Skin 5 2

Bone 8 3

Cartilage 15 6

Smooth muscle 15 6

Autonomic ganglia 11 5

Ganglion cells 3 1

Lymph nodes 8 3

Tissues foreign to sacrococcygeal region

Homologous

Cerebellar tissue 1 ,1

Immature neural tissue 5 2

Heterologous

Renal 2 1

Respiratory 2 1

Digestive 2 1

348 A. LELLOUCH-TUBIANA ET AL.

lining dermoid or epidermoid cysts, cartilaginousnodules (6%), bone tissue (3%), lymph nodes (3%),and autonomic ganglia (5%), as well as capillaryangiomas included in the lipomatous mass (4%)(Fig. 7). Finally, other tissue patterns foreign to thelumbosacral region were present in our series:smooth muscular tissue (6%), and respiratory ordigestive epithelia lining cysts (2%). Some epithe-lial cysts were lined by ciliated cells and had asmooth muscle muscularis in their walls and con-tained seromucous glands, suggesting bronchialwalls. We also found renal corpuscles (1%) (Fig. 8)and cerebellar tissue (,1%) (Fig. 9).

DISCUSSIONCongenital intraspinal lipomas are well-known le-sions that have been reported on numerous occa-sions, but only few reports have included histologi-cal study [1–6]. Anatomically, intraspinal lipomasare distributed on both sides of a spina bifida—onone side in the subcutaneous tissue, without de-fined outlines and along with the normal adiposetissue, and on the other side intradurally in thesubarachnoid spaces before terminating on theposterior face of the spinal cord (Fig. 10). Thespinal cord is exceptionally normal and its termina-tion is usually low lying, under the second lumbarvertebra, which is considered the normal inferiorlevel. Anomalies of the spinal cord include cavita-tion, torsion, duplication, and rarely, segmentar

agenesis. Hydromyelia is the anomaly most fre-quently observed; it is usually terminal, and rarelyextends to thoracic or cervical segments. The rootsgenerally show abnormal direction, conformation,or distribution.

Embryologically, the tail bud is formed afterthe end of primary or classic neurulation. Afterclosure of the posterior neuropore, all the tissueslying caudally to the already formed neural tubeaggregate to form a mass of cells, the so-called tailbud. This mass grows and yields a solid cellularcylinder, the medullary cord. This cavitates andcoalesces with all the cavities that ultimately form acentral canal, prolonging that which was formedduring primary neurulation. The tail bud is thusresponsible for development of the caudal part ofthe spinal cord. This type of neurulation proceed-ing cavitation has been termed secondary neurula-tion [7].

In our series, as in most others in the litera-ture, there was a significant female preponderance.The average age at diagnosis in our series was 6.4years, similar to that reported in the literature (7.1years). In all series, the two main clinical featuresleading to diagnosis were cutaneous stigmata onthe lower back and neurological disturbances, thatare mainly neuro-orthopedic and sphincter-related.The concept that intraspinal lipomas cause neuro-logical symptoms by ‘‘tethering’’ the spinal cord inthe growing child has gained wide acceptance [8,9],although this does not necessarily exclude thecompression effect that is restricted to a few caseswith larger lesions or with unstable lesions mani-festing growth.

In all series, 90.5% of the patients had skinstigmata and neurologic deficits affected .58% ofpatients, predominantly sphincter disturbances(61%) and motor deficits (39%). Overall, vesicalsphincter dysfunctions were the most frequentdeficit. They affected more than half of our pa-tients. Associated visceral malformations were re-ported in 16% of the published cases and 27% inour series.

The consensus in the literature on surgicalindications in symptomatic children is that earlysurgery is favored. Surgery for asymptomatic pa-tients, however, is still debated. There are very fewhistopathological studies of these congenital intra-spinal lipomas. Some of them report the histologi-

Table 3. Quantity of tissues present in lipomas

n %

Fat alone (pure lipomas) 54 23

Regional tissues other than fat

1 Tissue 56 24

2 Tissues 35 15

3 Tissues 10 4.27

4 Tissues 4 1.7

5 Tissues 1 ,1

Tissues not normally present in region

Renal only 1 ,1

Respiratory only 1 ,1

Digestive only 2 1

Cerebellar 1 ,1

Immature neural tissue 5 2

Renal 1 respiratory 1 ,1

CONGENITAL INTRASPINAL LIPOMAS 349

cal features of an adult adipose tissue, showing astriking amount of fibrous tissue scattered through-out the entire fatty mass; for this reason, someauthors called them fibrolipomas [3,10]. In ourseries, these lipomas represented 23% of the cases.

Other tissues can be associated with adiposetissue. These complex forms represent 10% to 25%of the cases in the literature, but this percentagewas much more higher in our series (77%). Oneexplanation for this discrepancy could be that theresection of lipoma is incomplete and thereforesome tissue components cannot be included in thesample. Moreover, histological reports concern onlya few patients. In our series, we were able toobserve various tissue components of ectodermal,mesodermal, or endodermal origin. The tissuesmost commonly found were nerves, striated muscle,sensory nerve corpuscles, and glial tissue. Less

often we were able to identify epidermoid or der-moid cysts, cartilage, bone tissue, ependymal-linedcanals, arachnoidal tissue, lymph nodes, or angio-matous formations. These tissues have been dis-cussed in the literature [1,4–6,11–16]. All of theseelements are normally present in this region butare abnormally located within the lipoma. Theyindicate a defect in embryogenesis during second-ary neurulation. These intraspinal lipomas can beconsidered a malformation. The presence of epen-dymal, glial, or neuroglial and arachnoidal tissue inan intraspinal lipoma, if there are no other ectopictissues, suggests an association with a myelocysto-cele or meningocele [6], but this can be excluded byneurological imaging. In the same way, cartilage,bone, and muscle exist in the region and can beinfiltrated by the lipoma if there is spina bifida [1].Under the microscope they constitute cartilaginous

Figure 7. Intralipomatous capillary angioma. Hematoxy-lin-eosin, 3200.

Figure 8. Photomicrograph of a lipoma showing numer-ous renal corpuscles. Hematoxylin-eosin, 3200.

Figure 9. Nodule of cerebellar tissue attached to aspinal lipoma. Hematoxylin-eosin, 3400.

Figure 10. Schematic drawing showing a typical formof lumbar intraspinal lipoma. The subcutaneous compo-nent of the lesion extends intradurally before terminat-ing on the posterior wall of the spinal cord.

350 A. LELLOUCH-TUBIANA ET AL.

or bony nodules and muscular fascicles included

within the lipoma, far from the surrounding tissue.

Small intralipomatous angiomatous formations

were found in our series. These lesions have

been reported in the literature as angiolipomas

[17–21].

Much more rarely, ectopic tissues that are

never encountered in the region have been ob-

served in the lipoma. We have identified renal

corpuscles, cysts lined by a respiratory or digestive

epithelium, and even a nodule of cerebellar paren-

chyma attached to the lipoma. Occasionally one

finds bits of cerebellum free in the spinal subarach-

noid space because of herniation, but usually they

are necrotic. Endometrial tissue has been reported

in the literature in two observations [8,9], and

occasional lipomas have been associated with het-

erotopic thyroid tissue [10]. The presence of only

one ectopic mature tissue can be considered a

malformative heterotopia (choristoma). However,

if more than one heterotopic tissue type that is

totally foreign to the region, of ectodermal, endoder-

mal, and mesodermal origin, and at different stages

of maturation—from the embryonal stage to adult

tissue—is present within the lipoma, the possibility

of teratoma with a tumoral potential should be

considered. These are mostly benign teratomas,

and are pluritissular and mature. Individual cases

of malignant degeneration of these teratomas have

been described [22,23]. Delayed malignant transfor-

mation took the form of anaplastic carcinoma. The

presence of embryonal tissue components in the

teratoma, generally immature nervous tissue, sug-

gests an immature teratoma, which classically has

a bad prognosis. For Lemire and Beckwith [6], the

immaturity of a teratoma must be correlated with

the patient’s age and in a very young child, doesn’t

necessarily indicate a bad prognosis, in contrast to

an adult. For these authors, malignancy rarely

occurs in the form of a yolk sac tumor. This raises

the question as to whether these complex lipomas

can behave like a tumor. It is widely accepted that

congenital intraspinal lipomas are anatomically

stable lesions [24]. Nevertheless, growth has been

reported when obesity occurs [13,25]. Rarely,

growth of complex teratomas may result from

malignant degeneration [22,23].

In conclusion, congenital lumbosacral lipo-

mas are often complex lesions in which adiposal

tissue is associated with a variety of tissue patterns.

In most cases, they are malformative lesions or

hamartomas. But when they contain tissues totally

foreign to the region, the possibility of teratoma

with a tumoral potential should be considered, and

may explain their behavior.

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