This document provides an overview of the approach to cystic bone lesions. It begins with definitions and classifications of benign and malignant cystic bone lesions. Key aspects to consider in the approach include the age of the patient, location of the lesion, characteristics of the transitional zone, presence of a matrix, status of the bone cortex, periosteal reaction, and soft tissue swelling. Specific cystic lesions discussed individually include aneurysmal bone cyst, solitary bone cyst, fibrous dysplasia, and enchondroma. Treatment approaches are also summarized for some of the lesions.

1. APPROACH TO CYSTIC
LESIONS OF BONE
PRESENTER:DR.ARGHA BARUAH
MODERATOR:DR.TN SURESH
DR.SIDDARAM.N PATIL

2. Outline
 1.Definition
 2.Classification
 3.Approach to cystic lesions
 4.Cystic lesions(individually)
 5.Cases
 6.Summary

3. Case1 :20 year female presented with progressive pain in the
clavicular region since 4 months
Anastomosing trabeculae of osteoid.Rimmed by
single layer of benign activated
osteoblasts.Numerous osteoclasts

4. CASE 2: 20 YEAR F PRESENTED WITH PAIN AND SWELLING IN THE KNEE
JOINT SINCE 2 MONTHS.
well-defined, expansile osteolytic lesion with thin peripheral bone shell

6. What is a cystic lesion of bone?
 Cysts are closed capsule or sac-like structures, typically filled with liquid, semisolid
or gaseous material .
 Cysts lesions of bone develop when one or several factors that affect bone
remodelling cause a focally increased rate of resorption relative to the formation

7. Numerous influences may produce this net
effect:
 1)tumor
 2)vascular disturbances(ABC)
 3)intraosseous enzymatic effect(Unicameral bone cyst)
 4)hormonal influences such as parathormone linked osteoclastic resorption
 4)external factors-trauma, infection (osteomyelitis),inflammation(rheumatoid
arthritis),degenerative joint disease

8. Benign cystic lesions classification:

9. Malignant cystic lesions of bone:
 Giant cell tumor
 Osteosarcoma
 Chondrosarcoma
 Multiple myeloma
 Ewings sarcoma
 Metastasis-lung,renal ,thyroid

10. Osteolytic lesion of bone:

12. A L T - M C P S
Age
Location
Transitional zone
Matrix
Cortex
Periosteal reaction
Soft tissue swelling

13. According to the age:

16. According to location:
Epiphysis:
 In young patients it is likely to be either a chondroblastoma or an infection.
 In patients over 20, a giant cell tumor has to be included in the differential
diagnosis.
 In older patients a geode, i.e. degenerative subchondral bone cyst must be added
to the differential diagnosis.
Metaphysis:
 NOF, SBC, Osteosarcoma, Chondrosarcoma, Enchondroma and infections.
Diaphysis:
 Ewing's sarcoma, SBC, ABC, Enchondroma, Fibrous dysplasia

17. Location:
Centric in long bone:
SBC, eosinophilic granuloma, fibrous dysplasia, ABC and enchondroma are lesions that
are located centrally within long bones.
Eccentric in long bone:
Osteosarcoma, NOF, chondroblastoma,, GCT and osteoblastoma are located
eccentrically in long bones.

18. Zone of transition:
In order to classify osteolytic lesions as well-defined or ill-defined, we need to look at
the zone of transition between the lesion and the adjacent normal bone.
Wide zone of transition: An ill-defined border with a broad zone of transition is a
sign of aggressive growth
Small zone of transition:A small zone of transition results in a sharp, well-defined
border and is a sign of slow growth.

20. Matrix
Ground Glass – Fib.Dys.
Calcification -
Chondrosarcoma

21. Matrix
“Cloud” like Ossific densities in Bone
= Osteosarcoma

22. Wide Zone of
Transition and
Broken Cortex
could be signs of
Aggressiveness /
Malignancy
Cortex:
Intact or
Broken

24. Soft Tissue
Enormous soft tissue seen in Ewing’s Sarcoma

25. According to symptoms(if no pain):
 Fibrous Dysplasia
 Enchondroma
 NOF
 Solitary Bone Cyst

26. Multiple Lesions????
 Mnemonic: FEEMHI
 Fibrous dysplasia
 EG
 Enchondroma
 Mets, Myeloma
 Hyperparathyroidism
 Infection

27. ANEURYSMAL BONE CYST
Solitary expansile Blood filled reactive lesion of bone .
Locally destructive.
Age :- usually in 1st ,2nd & 3rd decade of life .
Sex :- slight female predominance.
Location :- any bone may be involved.
-Most common is proximal humerus
,distal femur,proximal tibia & spine.
Types :-
Primary :apears de novo following intraosseous
A-V fistula.
Secondary :-results of cystic changes in GCT
,OSTEOBLASTOMA etc.

28. ANEURYSMAL BONE CYST
Clinical feature :-
-Pt complain of mild to moderate pain.
-Swelling
-Limitation of joint movements.
-Neurological deficit or radicular pain.
-Rapid growth may occur which clinically
presents as a malignancy.
X ray findings :-
Affected bone is expanded, cystic & ballooned
outward.
Eccentrically placed.
Cortex is breached.
Surrounded by a faint outline representing new
periosteal bone.

29. ANEURYSMAL BONE CYST
Other investigation:-
Bone scan :- shows diffuse or peripheral tracer uptake
with decreased uptake in center.
Ct scan :- helpful in delineating the cyst in complex
area ex. Spine ,pelvis .
MRI :- shows multi loculated cavities & fluid level.

30. ANEURYSMAL BONE CYST
PATHOLOGY :-
GROSS :-
-Large mass is attached by a broad base to the shaft of
long bone .
-Growing outwards & displacing the soft tissue.
-Thin shell of bone enclosing the blood filled spaces.
Spongy honeycombed blood filled mass with cystic
spaces
Microscopic :-
-Bone & marrow are replaced by the large pool of blood
enclosed in fibro osseous septae.
-Connective tissue bordering the vascular space contain
multinucleated giant cells, new bone formation &
calcium deposits.

33. Treatment :-
 Curettage & bone grafting.
 Marginal resection Is indicated in expendable bone
 Low dose radiation has been used effectively ,associated with rapid ossification.

34. SOLITARY BONE CYST
Is a common lesion
Age :- most commonly in 5-15 yrs
rarely after 20 yrs
Sex :- male predominant (2:1)
Location :- long tubular bones particularly humerus & femur
-metaphyseal region is the preferred site.
2 types :-
Active cystic lesion :- develops under 10yrs age . Within 1cm of epiphysis
Benign latent cyst :- develops after 20 yrs age. Towards diaphysis
- seperated from epiphysis

36. SOLITARY BONE CYST
Physical findings :-
- Usually asymptomatic.
-Cyst lying adjacent to growth plate can
lead to growth disturbances.
X ray findings :- centrally located,lytic lesion.
-Expansion of the bone.
-Well marginated outline.
-Thinning of the cortex( scalloping).
- Fallen fragment sign
--loculated appearance is due to presence of
ridges over inner surface of cyst.

38. SOLITARY BONE CYST
Pathology :-
Gross :-
- Bone displays an area of fusiform
expansion.
- Underlying bone is egg-shell thin.
- Cavity contain yellow fluid.
-
Microscopic :-
- Connective tissue composed of fibroblast
contaning multinucleated giant cells , foam
cell.
- Cortical wall consist of loosely trabeculated
osseous tissue & many thin walled vessels.

40. Unicameral bone cyst is filled with straw colored fluid rich in
prostaglandins, GAGs, mucopolysaccharides and lysosomal enzymes. This
fluid contributes to bone resorption.

41. SOLITARY BONE CYST
Treatment :-
Curettage
Aspiration
Steroid injection

42. FIBROUS DYSPLASIA
-Non inherited, sporadic developmental anomaly.
-Replacement of bony tissue with fibrous tissue.
Age :- begins in childhood(<10 yrs).
Sex :- M:F=1:1
Location :- base of the skull & long bones.
Clinical features:-
-Pain
-Limp
-Deformity
-Asymmetry of face
-Endocrine disorder
-Limb length discrepancy.
-Sexual precocity

43. It can be
 Monostotic form (85%)
 Polyostotic form (15%)
 Craniofacial form- Leontiasis Ossea
 Cherubism
 McCune McCune-Albright Syndrome (10%)
Polyostotic , café-au au-lait , endocrine dysfunction
(precocious female puberty (20%), hyperthyroidism)
 MAZABRAUD’s syndrome: ( polyostotic F.D + intramus. Myxomas)

46.  RIBS>FEMUR>TIBIA>MAXILLA>MANDIBLE>SKULL>HUMREUS .
INTRAMEDULLARY ,ECENTRIC OR CENTRAL LOCATION.

47. FIBROUS DYSPLASIA
Radiological findings :-
-intramedullary & predominantly diaphyseal.
-central or eccentric in location.
-Ground glass appearance.
-lesion is well defined with sclerotic margins
-Cortex thinning & expansion is seen.
-Pathological fractures .
-Bowing of bones.
-HARRISON’S GROOVE.

48. FIBROUS DYSPLASIA
Pathology :-
Gross :-
-Bone is irregular in shape & bent.
-Grey tough fibrous tissue that cut with a gritty resistance “SANDPAPER”
-Well circumscribed,
-Tan-white-yellow, gritty
-Cortical bone often thin and expanded
Micro :-
-composed of dense,mature collagenous tissue.
-fibroblast are oriented in linear /whorl pattern.
-Curvilinear trabeculae (Chinese letters) of metaplastic woven bone
in hypocellular, fibroblastic stroma

49. TREATMENT
- Conservative management includes bracing & modification of
activities.
Surgical management :-
-Pathological fracture usually heals but develops deformity.
-Fracture of long bone should be treated preferably with I.M
nails along with bone grafts.
Large lesion which jeopardize the integrity of bone should be
treated with curettage & bone grafting

50. Arthritis related cyst:
 Subchondral cyst: multiple,vary in size,occur in one or both sides of joint,central
location,more in weight bearing bones.
 Pyriform in shape and multilocular.
 Contiguous with the joint or may have fine bone plate.End of the bone shows
degenerative changes

53. INTRAOSSEOUS GANGLION CYST
-Lesion of uncertain pathogenesis.
Age :- can occur at any age.
-Most commonly seen in 20-60yrs age .
Location :- subchondral region of bone ,
acetabulum & carpel bones.
Clinical feature :-are usually clinically silent.
-Chronic mild pain
-Swelling if associated with soft tissue ganglion.
-Usually solitary

54. INTRAOSSEOUS GANGLION CYST
Radiographic findings :-
-Well demarcated ,sharply circumscribed
osteolytic lesion.
-Sclerotic margin is evident.
-In para articular location gas may be
evident.
Treatment :-
- Local excision of overlying soft tissue &
curettage of involved bone.
- Recurrence is rare.

57. EPIDERMOID CYST
 Uncommon.
 M >F
 Age :- usually in 2nd ,3rd & 4th decade of life.
 Location :- skull & phalanges of hand are commonly affected.
Clinically :-
 Pain & swelling
Microscopically :-
 They resemble epidermal cyst of skin.
 Cysts are filled with keratinous material & lined by squamous epithelium.

58. EPIDERMOID CYST
RADIOGRAPHIC :-
Well defined osteolytic lesion with
sclerotic margins .
CT & MRI are rarely required.
Treatment :-
Excision

61. Giant cell reparative granuloma:

64. CHONDROMA
•Benign lesions of hyaline cartilage.
•It can arise within a bone ( ENCHONDROMA)
or on the surface of bone ( PERIOSTEAL
/JUXTACORTICAL CHONDROMA).

65. ENCHONDROMA
Age :- usually all age group are affected .
More commonly young individual in 2nd -4th decade.
Sex :- equally (M:F=1:1)
Location:- any bone can be affected but commonly phalanges of
hand & feet.
-solitary enchondromas involve humerus , tibia & femur.
Clinical findings :-
-Swelling
-Tenderness
-Pain

66. ENCHONDROMA
X RAYS FINDINGS :-
-well-defined lytic lesion in the hand is almost always
an enchondroma
-small loculated area with well defined margins.
-Cortex is thinned & expanded.
-Interlesional calcification :- calcification is irregular
Stippled ,punctate or popcorn.
-no reactive bone formation
CT scan :-
Evaluate endosteal erosion to rule out
chondrosarcoma.

67. ENCHONDROMA
Pathology :-
Gross :-
-Tumour is surrounded by a fibrous capsule.
-The neoplastic tissue is composed of bluish
white translucent cartilage
- Areas of calcification.
Microscopically :-
-Tumour shows stages of cartilage formation.
-Mesenchymal tissue is seen at periphery.
-Most mature cartilage is seen at center.

68.  Ollier’s Disease= multiple enchondromas which usually develop in childhood. The
growth of these enchondromas usually stops after skeletal maturation.The affected
extremity is shortened (asymmetric dwarfism) and sometimes bowed due to
epiphyseal fusion anomalies. Persons with Ollier disease are prone to breaking
bones and normally have swollen, aching limbs.
 Maffucci’s Syndrome =characterized by enchondromas and soft tissue
hemangiomas

70. TREATMENT
 Treatment of solitary enchondroma consist of observation with serial radiographs.
 If the lesion appears to be radiographically stable & asymptomatic then no further
investigation is required.
 If the lesion appears to be unstable , growing then extended curettage is done.

71. CHONDROMYXOID FIBROMA
-Least common cartilage tumour.
-Not known to metastasize.
-2% of all benign tumour.
-Seen in patients <30yrs specially in 2nd
& 3rd decade
-Tumour is more common in male
(M:F=2:1).
-Observed in long tubular bones
specially in lower extremity.

72. CHONDROMYXOID FIBROMA
Clinical features:-
-Pain near the joint without h/o trauma
-Occasionally swelling
-Pathological fractures ( rare)
-May presents with soft tissue swelling.
Radiographic findings :-
-Translucent mass located eccentrically.
-Fusiform expansion in small bones.
-Cortex is expanded & thinned.
-Margin’s are scalloped & sclerosis +.
-Periosteal reaction is uncommon.

73. CHONDROMYXOID FIBROMA
Pathology :-
Gross :-
-Cut surface reveals solid tumour mass
containing small cavities with mucoid tissue.
-Calcified areas are unusual.
-Surface is sharply demarcated ,lobulated &
surrounded by thin scalloped border of dense
bone.
Microscopic :-
-Composed of lobulated areas of stellate cells
with indistinct cytoplasmic borders.
-At the periphery ,the appearance is more
cellular & collagenous.

74. TREATMENT
-local excision & filling the cavity with autogenous bone.
-Curettage is not sufficient as tumour may recure especially
childrens.
-Wide en- bloc excision gives high rate of cure.
-If tumour recure even after en bloc excision then studies has to
be done to rule out the malignant transformation.

75. FIBROUS CORTICAL DEFECT
 Benign well circumscribed fibrous growth with in a small area of long bone.
 A/k/a nonossifying fibroma,fibroxanthoma
 Localised form of fibrous dysplasia.
 Age :- <30yrs
 Location :- metaphysis of long bone.-usually lower limb.
 Sex :-M:F=1:1
Clinical feature :-
 -usually asymptomatic
 -occasionally presents with pathological fracture.

76. FIBROUS CORTICAL DEFECT
X ray findings :-
-well defined lobulated lesion.
-Ecentrically placed.
-Cortex thinning & expansion
-Multilocular appearance or ridges in bony
wall.
-No periosteal reaction.
Treatment :-
Excision & curettage

77. FIBROUS CORTICAL DEFECT
Pathology :-
Gross :- thin cortex enclose soft /tough rubbery gray –yellow or reddish brown tissue.
Microscopic :-
 Spindle shaped cell distributed in a whorled pattern.
 Fibroblastic proliferation with high cellularity.
 Giant & foam cells are present.

79. BROWN TUMOR OF HYPERPARATHYROIDISM
-Hyperparathyroidism results in disorder of bone & mineral
metabolism.
-Diffuse & focal lesion may arise in multiple bones.
-These lesion are K/as brown tumours due to the presence of
hemorrhage in the lesion.
Location :-
Any bone can be affected.
Mainly diaphysis of long bone.
Clinical features :-
Stones
Bones
Groans

80. BROWN TUMOR OF HYPERPARATHYROIDISM
Radiological features :-
Salt & pepper skull
Multiple osteolytic lesions
Laboratory findings :-
↑ed levels of PTH
Hypercalcemia
↑ed serum phosphate & urate.
TREATMENT :- treatment of the primary cause
will cause the healing of lesion.

82. Eosinophilic granuloma:
 EG is like osteomyelitis a great mimicker of benign and malignant bone tumors.
 Must be included in the differential diagnosis of almost any ill-defined osteolytic
bone lesion in patients under the age of 30.
 May also present as a well-defined lesion.
 EG can be excluded in patients > 30 years.
 Either solitary bone involvement, multiple bone involvement (variable skin
involvement) or multiple organ involvement (bone, liver, spleen, other sites)

84. Microscopy:
 Infiltration by Langerhans cells (polygonal cells with eosinophilic cytoplasm,
nuclei with longitudinal grooves resembling coffee beans)
 Eosinophils, giant cells, neutrophils, foam cells, lymphocytes, plasma cells,
fibrosis, necrosis; may have typical and atypical mitotic figures

85. Giant cell tumor:
 Giant cell tumor is a benign lesion
 Most commonly seen in age 20-40 years.
 A well-defined margin is associated with a locally less aggressive biologic behavior.
 In many cases the margin is ill-defined
 These tumors often thin the cortex and may expand into the soft tissues
surrounding the bone.

88. Stromal cells are mononuclear, resemble macrophages
Giant cells are large, multinucleated (10 - 50 nuclei) with similar nuclei as stromal cells

89. Treatment
Surgical curettage (34% recur) or en bloc excision (7% recur); may implant into
adjacent soft tissue
Radiation therapy only if surgical excision impossible since it may promote
transformation

90. Osteosarcoma
 Most common primary bone tumor after myeloma
 60% male; usually ages 10 - 25 years or ages 40+ with other diseases
 Sites: metaphysis of long bones (distal femur, proximal tibia, proximal humerus;
sites of peak mitotic activity for bone cells); occasionally diaphysis, rarely epiphysis;
less common in flat bones or short bones; usually arises within medullary cavity
and extends to cortex

91. Osteosarcoma:
 Hallmark of osteosarcoma is the production of bony matrix, which is reflected by the sclerosis
 Usually typical malignant features including permeative-motheaten pattern of destruction, irregular
cortical destruction and aggressive (interrupted) periosteal reaction.
 Radio: Large, destructive, lytic or blastic mass with permeative margins.May break through cortex
and elevate periosteum.Sunburst pattern due to new bone formation in soft tissue
 Occasionally an osteosarcoma may present as a lytic or mixed lytic-sclerotic lesion.
 Completely lytic osteosarcoma may represent telangiectatic subtype, composed of multiple
cavities filled with blood (may resemble aneurysmal bone cyst!).

92. mixed osteolytic and sclerotic lesion in the proximal humerus with irregular cortical
destruction.
There is an aggressive periosteal reaction and a soft tissue mass.

93. Gross:
 Big, bulky, gritty, hemorrhagic with cystic degeneration
 Spreads within medullary cavity, destroys cortical bone, elevates periosteum and
invades soft tissue
 May form satellite nodules (“skip metastases”)
 Usually has well defined proximal and distal margins

96. Chondrosarcoma:
 Third most common bone malignancy after myeloma and osteosarcoma
 Usually ages 30 - 60 years, 75% males
 Most commonly presents as a well-defined lesion, but uncommonly it can be
encountered as an ill-defined lytic lesion.

97. Partially ill-defined osteolytic lesion
There are cloud-like calcifications
indicating a chondroid matrix.

98. Pearly white or light blue, often with focal calcification
May have small cysts or myxoid change

99. Micro:
 Tumor cells produce cartilaginous matrix
 Either well, moderate or poorly differentiated
 May have only minor or focal atypia, but consider malignant if malignant radiologic
features
 Intracytoplasmic hyaline globules common in low grade tumors
 Grading: based on cellularity and nuclear changes in chondrocytes; well, moderate
or poorly differentiated correspond to grades 1 - 3; grade 4 is spindled tumor
representing either chondroblastic osteosarcoma or dedifferentiated
chondrosarcoma

101. Mutiple myeloma:
 Multiple myeloma must be included in the differential diagnosis of any lytic
bone lesion, either well-defined or ill-defined in age > 40.
 Most common presentation: multiple lytic 'punched out' lesions. A solitary
presentation is referred to as plasmacytoma.
 Usually no increased uptake on bone scan.
 The most common location is in the axial skeleton (spine, skull, pelvis and ribs)
and in the diaphysis of long bones (femur and humerus).

103. Round lesions filled with a soft reddish material are indicative of foci of
myeloma in this section of vertebral bone. Larger lesions may weaken the
bone to cause fracture with back pain.

104. Micro:

105. Ewings sarcoma
 Most common presentation: ill-defined osteolytic lesion with multiple small holes
in the diaphysis of a long bone in a child with a large soft tissue mass.
 Presentation with pain, mass, fever, anemia and leukocytosis.
 Most common location: femur, iliac bone, fibula, rib, tibia.
 Frequently aggressive type of periosteal reaction, but never a benign type.

108. Gross description
 White, fleshy, ill defined tumor with extensive involvement of medulla and cortex
with periosteal elevation
 May be necrotic or resemble pus
 Excised specimen show fibrosis, hemorrhage and necrosis
 Necrosis can be used as a predictor of long term outcome

110. Micro:
At lower power, is undifferentiated and densely cellular with "light" cell and "dark" cell appearance.Sheets of small,
round, uniform cells with scant clear cytoplasm, divided into irregular lobules by fibrous strands.Indistinct cell
membranes
Minimal amounts of stroma

111. Metastasis :
 Must be considered in the differential diagnosis of any bone lesion in a patient > 40
years.
 May present as well-defined osteolytic, ill-defined osteolytic and also as sclerotic bone
lesion.
 Majority of osteolytic metastases originate from lung, kidney, colon, melanoma.
 Cancer most commonly spreads to these sites in the skeleton:
Vertebra,Pelvis, Ribs, Skull,Upper arm and Long bones of the leg

115. Case3 :
30 YEAR F PRESENTED WITH PAIN AND SWELLING IN THE KNEE JOINT SINCE 1 WEEK
.PATIENT ALSO HAS FEVER SINCE 1 WEEK

116. Osteomyelitis :
 Osteomyelitis is the great mimicker of bone tumors.
 It has a broad spectrum of radiographic features and occurs at any age and has no
typical location.
 In the chronic stage it can mimic a benign bone tumor (Brodies abscess).
 In the acute stage it can mimic a malignant bone tumor with ill-defined margins,
cortical destruction and an aggressive type of periostitis.
 Only when there is a thick solid periosteal reaction we can recognize the non-malignant
underlying process

117. Case4:

118. Spotter:

119. “If I were you, I will run
to the Radiology
department
and get the x-ray films
and make them
available before the
Histology slides are
studied”
Prof. Peter G Bullough
Professor of Orthopedic Pathology
Hospital for Special Surgery,
Cornell University,
NEW YORK

120. Diagnosis of Cystic Tumours
Final Diagnosis
CLINICAL
PATHOLOGY
IMAGEOLOGY
(Radiology)

121. Take home message:
Following points to be kept in mind while reporting :
 History
 Age
 Location
 Multiple/single
 Radiological findings

122. References:
 1.Orthopaedic pathology Vincent J Vigorita
 2.Dahlin’s bone tumors
 3. The Radiology Assistant : Bone tumor - well-defined osteolytic tumors and
tumor-like lesions
 4.https://radiopaedia.org
 5.www.pathologyoutlines.com