The document provides details on several cases of bone cysts, including unicameral bone cysts and aneurysmal bone cysts. It describes the typical presentation, characteristics, treatment approaches, and outcomes for each type of cyst. Radiographic images and histological photomicrographs are included to illustrate features of the cysts.

1. Contents for Volume 9
Bone cysts
Unicameral bone cyst-------------Case 190-97 & 984-96
Aneurysmal bone cyst------------Case 198-204 & 997-1039
Epidermoid cyst-------------------Case 205-6

2. Bone Cysts

3. Unicameral Bone
Cysts

4. Unicameral Bone Cysts
The unicameral or solitary bone cyst is a very common pseudo-
tumor seen in bone in children and is the most common cause for
pathological fracture in that age group. The bone cyst is considered
to be a hamartomatous developmental process with an unknown
etiology. It may be a degenerative process seen in a pre-existing
fibrous lesion of bone, such as monostotic fibrous dysplasia, that
occurs between the ages of 5 and 15 years, more common in boys
than girls, with half the cases in the proximal humerus and half in
the proximal femur. These patients are usually asymptomatic until
the time of fracture. The cysts are usually located in the metaphyseal
portion of long bones, immediately adjacent to the growth plate
during the early years when the lesions are considered active. As
the patient approaches maturity, the cyst will start to migrate away
from the growth plate and go into what is referred to as the inactive
stage. Radiographically, the lesions are well marginated with a thin
sclerotic edge at the periphery. They are centrally located in the

5. metaphysis with thinning and slight dilatation of the surrounding
cortex and no matrix calcification.
The cysts are filled with a clear serous fluid with increased
pressure during the active phase that some experts feel may cause
the cyst to enlarge by a hydraulic dynamic mechanism. The cyst is
lined by a fibrous membrane studded with macrophages and,
occasionally, foam cells. In some cases, tissue similar to fibrous
dysplasia can be found at either end of the lesion. The periosteal
covering over the cyst is normal and for this reason, the pathological
fractures go on to heal without difficulty. Because of the potential
for repeated pathological fractures, surgeons are tempted to carry
out some type of bone grafting procedure during the early, active
phase of the disease but become frustrated with a recurrence rate of
30-50 per cent. For this reason, the more common and current way
to handle bone cysts in the early age group, before bone maturity,
is by simple aspiration with a double needle technique with the
instillation of methylprednisolone into the cyst cavity that inhibits

6. the macrophage activity and reduces the chance of local recurrence.
It slows down the active lytic process of the disease. This injection is
usually required on multiple occasions, every 3 to 6 months until
the patient reaches maturity, at which time the disease tends to
become inactive. 3 to 8 injections over this period of time may be
required to avoid the necessity of a bone grafting procedure at a later
date. The success rate is approximately 85%. In patients over the age
15 years, steroid injections in the inactive phase of the disease are not
beneficial because the macrophage activity has disappeared. At this
point, the only acceptable treatment would be a classic bone grafting
procedure to strengthen the bone and reduce the chance of patho-
logical fracture in the future. Physicians must be aware of the
possibility that an apparent bone cyst on radiographic examination
may masquerade as a malignant tumor such as an osteosarcoma. If
one is unable to obtain fluid at time of aspiration, a biopsy should
be performed to rule out this possibility.

7. CLASSIC
Case #190
sclerosis
10 year female
unicameral cyst
proximal humerus

8. Photomic showing giant cells in cyst lining

9. X-ray following
curettement and
bone grafting

10. 6 months after bone
grafting with nearly
complete loss of graft

11. 1 year following surgery
and even further loss
of graft material

12. Case #191
9 year female
unicameral bone cyst
proximal humerus

13. Injection of cortisone into cyst

14. Healed 10 mos later

15. Case #192
9 year male with path fracture thru
monostotic fibrous dysplasia

16. One year later with cystic changes

17. 3 years later with
even more cystic
changes

18. Progressive cystic changes at 4 years

19. Age 16 and healed
path fracture thru
nearly pure cyst

20. Surgical window into large cystic lesion

21. Fibular strut taken from opposite leg

22. X-ray opposite leg
where graft was taken
reveals another
fibrous dysplastic lesion

23. Cyst packed with fibular strut & crest graft

24. Immediate post op
radiograph

25. 6 months post op

26. Case #193
15 year female
unicameral cyst
ilium

27. Post op x-ray
After bone grafting

28. Case #195
9 year female with unicameral cyst prox fem epiphysis

29. Case #196
15 year male with unicameral cyst os calcis

30. Case #196.1
18 year old female with incidental finding in foot

31. Sag gad
Axial T-1 T-1

32. Cor T-1 T-2
Gad

33. PO bone graft

34. Case 196.1
Pseudo UBC - rheumatoid synovial cyst
60 yr female with long history of stiff and painful ankle

35. Sag T-1
Sag T-2

36. Cor PD Axial T-2 FS

37. Case #197
16 year female with unicameral cyst os calcis

38. Sagittal T-2 MRI

39. Coronal T-2 MRI
showing fluid-fluid
level

40. Case #984
14 year male with
unicameral bone cyst
proximal humerus with
pathologic fracture

41. 2 months later with
healing of upper part
of cyst and now a new
fracture in lower part

42. 4 months after 1st
fracture and the two
parts have joined with
gradual healing in as
result of fracture

43. 3 years later and
nearly complete
healing without
treatment

44. Case #985
16 year male with
unicameral bone cyst
proximal humerus with
path fracture

45. Surgical exposure for placement of fibular bone graft

46. Scanning lens photomic of curetted lining of cyst showing
giant cell activity and recent hemorrhage from fracture

47. Café-au-laite noted at
site of fibular graft
harvesting

48. X-ray appearance 3 mos
following bone grafting

49. Case #986
11 year male with
unicameral bone cyst
proximal humerus with
path fracture

50. 18 months later

51. Post op x-ray after
curettment and packing
with plaster of Paris
pellets

52. 4 months later with
gradual resorption of
pellets

53. 18 months post op and
pellets have dissolved

54. The pellet treatment did
not prevent another fracture
seen healing here

55. Case #987
15 year female with
path fracture thru
unicameral bone cyst
proximal femur

56. 6 months post op
fibular strut and fibula
DHS fixation

57. 3 years post op

58. Case #988
44 year female with unicameral bone cyst femoral neck

59. Coronal T-1 MRI

60. Coronal T-2 MRI

61. Case #989
9 year male with unicameral bone cyst femoral neck

62. Photomic showing giant cell activity in cyst lining

63. 6 weeks post op packing with cancellous allograft

64. 3 months later with slight recurrence

65. 9 months post op and even more recurrence

66. Case #989.1
16 year female with
unicameral bone cyst
Proximal femur

67. Coronal T-1 MRI

68. Coronal T-2 MRI

69. Coronal gad contrast MRI

70. Case #989.2
21 year female with path fracture thru UBC distal femur

71. Photomic from bone cyst lining

72. 2 yrs post op curettement and cancellous bone grafting

73. Case #989.3
12 year female with
unicameral bone cyst
distal femur

74. Lateral view

75. Coronal T-1 MRI

76. Coronal T-2 MRI

77. Axial T-1 MRI

78. Axial T-2 MRI

79. Case #989.4
10 year male with unicameral bone cyst tibia

80. Post op curettement & cementation with cancellous allograft

81. Case #989.5
11 year male with
unicameral bone cyst
tibia

82. Coronal T-1 MRI
showing multiloculation

83. Coronal T-2 MRI

84. Axial T-2 MRI showing fluid-fluid level

85. Case #989.6
8 year female with
unicameral bone cyst
proximal tibia

86. Case #989.7
5 year female with
UBC prox tibia

87. Lateral view

88. CT scan

89. Case #989.8
11 year female with
unicameral bone cyst
distal fibula

90. Case #989.9
53 year male with
unicameral bone cyst
4th metacarpal

91. Bone scan

92. Coronal T-2 MRI

93. Case #989.91
6 year female with unicameral bone cyst 5th metacarpal

94. Case #990
25 year male with unicameral bone cyst thumb

95. Case #991
22 year male with UBC capitate

96. Case #992
18 year male with
unicameral bone
cyst distal ulna

97. Case #992.1
3 year male with
unicameral bone cyst
distal radius

98. Lateral view

99. Case #993
29 year female with
unicameral bone cyst
talus

100. Lateral view

101. Photomic with foam cells and giant cells

102. Case #994
16 year female with bilateral unicameral bone cysts

103. Case #995
36 year female with unicameral bone cyst ilium

104. Bone scan showing signal
Void in bone cyst

105. CT scan

106. Coronal T-1 MRI

107. Axial T-2 MRI with fluid-fluid level posterior

108. Case #996
12 year male with unicameral bone cyst ischium

109. Photomic showing giant cell activity

110. Post op x-ray after packing with cancellous bone graft

111. One year later

112. Aneurysmal Bone
Cysts

113. Aneurysmal Bone Cysts
The aneurysmal bone cyst is another clinical entity that presents
as a hemorrhagic pseudotumor in bones in the pediatric age group,
most typically in the femur, tibia, pelvis and spine. It has many of
the characteristic clinical features of the giant cell tumor, except in
a younger age group, and is frequently associated with other well
known neoplastic conditions such as giant cell tumor, chondro-
blastoma, osteoblastoma, fibrous dysplasia, or in some cases of
osteosarcoma, especially the hemorrhagic type. It is a very lytic,
destructive lesion of bone occurring in patients between the ages
of 10 and 20 years. Its characteristic feature is an aneurysmal
appearance seen on radiograph that, in the early stages, is extremely
destructive,osteolytic and permeative, taking on the radiographic
features of a malignant tumor such as a hemorrhagic osteosarcoma.
In two thirds of the cases in the spine, the aneurysmal bone cyst is
seen most commonly in the posterior elements, but in one third they
will be seen in the vertebral body. In the case of the giant cell tumor

114. in the spine, the lesions are almost always found in the vertebral body.
At the time of surgical biopsy, the surgeon will note a large amount
of hemorrhage in a cystic lesion that has a very friable, mossy lining
at the periphery and one sees reactive bone as it forms a shell around
the hemorrhagic cyst. Microscopically, the mossy tissue will be
loaded with large, reactive-type giant cells and the background
stromal tissue will be made up of benign-appearing spindle cells with
a large amount of interstitial hemorrhage and reactive bone formation,
and even a few mitotic figures will be noted similar to the situation
seen in hemorrhagic osteosarcoma. However, in hemorrhagic osteo-
sarcoma, the number of mitotic figures would be very large. One must
be very careful when sampling a biopsy of this type of lesion to
make sure that one obtains multiple specimens, especially from the
more fleshy portion of the tumor, looking for the possibility of an
adjacent osteosarcoma.
As far as treatment is concerned, this is a lesion that tends to in-
volute spontaneously as the child matures into the young adult age

115. group. However, because of early progressive destruction and pain
associated with these osteolytic lesions, surgeons will usually curette
the tumor and then repair the defect with bone graft or, in some cases,
bone cement and Steinman pins. In the case of large pelvic lesions or
large spinal lesions that are difficult to resect surgically, intra-arterial
embolization is a good technique to stimulate rapid involution of the
tumor. Radiation therapy is a very effective in controlling massive
lesions of the pelvis and spine, however, one runs the risk of a
secondary sarcoma arising 5 to 15 years later.

116. CLASSIC
Case #198
9 year female
ABC proximal fibula

117. growth
plate
Resection specimen cut in path lab

118. blood
osteoid
Photomic showing giant cells

119. Case #199
9 year male with ABC proximal humerus

120. Rapid destruction 3 months later

121. Surgical photo of outer reactive bone shell

122. Photomic showing large giant cells

123. Immediate post op x-ray with bone graft struts

124. 7 years later

125. Case #200
9 year female
ABC distal tibia

126. Lateral view

127. 18 months following simple curettement

128. Case #200.1
ABC
14 year old male with ankle pain for 3 months

129. Sag T-1 Cor STIR Sag Gad

130. Axial T-2 Gad

131. Surgical curettments

132. Case #201
12 year male with ABC proximal tibia

133. Coronal T-2 MRI

134. X-ray following
cementation procedure
cement

135. Case #202
17 year male with ABC mid lumbar vertebra

136. Ct scan

137. Coronal T-1 MRI

138. Axial T-2 MRI with fluid-fluid levels

139. Case #203
17 year female
ABC ilium

140. Increased size
6 months later

141. Axial T-1 MRI

142. Coronal T-2 MRI

143. Reconstruction with large bone allograft and recon plates

144. Case #204
17 year female with ABC ilium

145. CT scan

146. 2 years after curettement, embolization and radiation

147. reactive shell
CT scan 2 years post treatment

148. X-ray at 5 years showing proximal hip migration

149. Radiation ulceration of skin over lesion

150. 2 months after myocutaneous flap coverage

151. 6.5 yrs post radiation with radiation OGS in SI area

152. Photomic of radiation sarcoma

153. Case #997
25 year male with ABC pelvis

154. R
Bone scan

155. Photomic

156. 2 months later with progressive lysis

157. CT scan

158. ABC
CT scan lower level

159. ABC
CT scan thru pubic area

160. ABC
Coronal T-1 MRI

161. Axial T-2 MRI

162. Arteriogram at time of embolization therapy

163. 8 months after external beam RT

164. Post op hemipelvectomy

165. Case #998
15 year male with ABC acetabulum

166. Photomic from biopsy specimen

167. 5 months post op curettement and bone grafting

168. CT scan 5 mos post curettage

169. CT at a higher level

170. Extensive peripheral calcification several mos post RT

171. CT at a higher level after RT

172. CT scan of chest reveals multiple metastatic nodules

173. Photomic of pulmonary lesion biopsy showing OGS

174. Case #999
19 year female with ABC pelvis

175. 8 months post RT

176. Case #1000
17 year female with asymptomatic ABC sacrum

177. 2 years later
without treatment

178. Another 9 months later

179. 1.5 years later with burned out inactive lesion without pain

180. Case #1001
42 year male with burned out ABC ilium

181. CT scan

182. Case #1002
11 year male with active ABC pelvis

183. 4 years later and nearly inactive without treatment

184. Case #1003
14 year male with ABC ischium

185. Case #1004
14 year female with ABC pubic area

186. Case #1005
8 year male with
ABC C-2

187. Bone scan

188. CT scan with fluid-fluid level

189. Photomic

190. 3 years post op posterior fusion

191. Case #1006
17 year male with
ABC T-12

192. Lateral view

193. CT scan

194. Sagittal T-2 MRI

195. Axial T-2 MRI

196. Case #1007
21 year female with
ABC L-2

197. Oblique view

198. Coronal T-2 MRI

199. Sagittal T-2 MRI

200. Axial T-2 MRI showing fluid-fluid levels

201. Case #1008
4 year male with
ABC L-5

202. 3 months post op
curettement alone

203. Case #1009 CT scan
25 year female with ABC lumbar spine

204. 5 months post op simple curettement

205. Case #1010
13 year male with
ABC C-4

206. Case #1011
25 year female with ABC C-7

207. Case #1012
33 year female with ABC clavicle

208. Bone scan

209. Sagittal T-1 MRI

210. Axial T-2 MRI

211. Case #l013
12 year female with ABC clavicle

212. CT scan

213. Case #1014
11 year male with ABC clavicle

214. Case #1015
11 year male with
ABC distal femur

215. Lateral view

216. Coronal T-1 MRI

217. Axial T-1 MRI

218. Axial T-2 MRI

219. 18 months later
without treatment

220. Lateral view

221. osteoid
Biopsy photomic

222. 3 years after simple
curettement

223. Lateral view

224. Case #1016
47 year female with
ABC arising from a
small focus of monostotic
fibrous dysplasia seen at ABC
upper pole of lytic area

225. fibrous
dysplasia
Lateral view ABC

226. Sagittal T-1 MRI

227. Coronal T-2 MRI

228. Photomic from curettement specimen

229. Case #1017
17 year female with
ABC proximal femur

230. Bone scan

231. Coronal Gad
Contrast MRI

232. Coronal T-2 MRI

233. Axial gad contrast MRI

234. Case #1018
27 year male with ABC distal femur

235. Lateral view

236. Sagittal PD MRI

237. Axial T-2 MRI

238. Sagittal T-2 MRI

239. Biopsy photomic

240. Case #1018.1 ABC
56 year female with anterior knee pain for 2 years

241. Sag T-2 PD FS

242. Axial PD FS Cor PD FS

243. Case #1019
5 year female with
ABC proximal femur

244. 3 months later with enlargement

245. Lateral view

246. CT scan

247. Case #1020
12 year female with
ABC proximal tibia

248. Lateral view

249. Coronal T-1 MRI

250. Sagittal PD MRI

251. Coronal T-2 MRI

252. Sagittal T-2 MRI

253. Scanning lens photomic

254. Higher power photomic

255. Case #1021
14 year male with
early ABC distal
tibia

256. 18 months later

257. Lateral view

258. Sagittal T-2 MRI

259. Coronal T-1 MRI

260. Axial T-2 MRI

261. Case #1021.1 Bone abscess - ABC pseudo tumor
04 07 04 07
16 yr male with 3 yr history of intermittent pain and swelling at knee

262. Bone scan

263. 07
Cor T-1 T-2 Gad

264. Sag T-1 T-2

265. Axial T-2 Gad

266. Case #1021.2 Bone abscess - ABC pseudotumor
25 yr Indian male with 3 yr history of intermittent aching pain R leg

267. CT Scan

268. Sag T-1 PD FS Gad

269. Axial T-1 T-2
Gad

270. Case #1022
15 year female with
ABC proximal tibia
oblique view

271. AP view

272. Case #1023
18 year female with ABC proximal tibia

273. Surgical specimen at
time of excisional
arthrodesis

274. Macro section

275. Scanning lens photomic

276. Case #1024
AP Lat
4 year male with ABC proximal tibia

277. Case #1025
17 year female with
ABC proximal fibula

278. Resected specimen cut in path lab

279. Macro section

280. Case #1026
13 year male with
ABC distal fibula

281. 5 months post op
simple curettement

282. Case # 1026.1
19 year female with
ankle pain 4 mos

283. Axial T-1 T-2
Gad

284. Sag T-1 PD FS Gad

285. Case #1027
7 year female with
ABC proximal humerus

286. Biopsy photomic

287. Rapid progression 6 weeks later

288. Another 6 weeks and rapid enlargement

289. Photo just prior to forequarter amputation

290. Surgical specimen cut open in path lab

291. Photomic shows features of hemorrhagic OGS

292. Post op chest x-ray shows pulmonary mets

293. Case #1028
17 year female with ABC distal humerus

294. Lateral view

295. Curettement photomic

296. Case #1029
54 year male with
burned out inactive
ABC proximal humerus

297. Case #1030
2 year female with ABC distal radius

298. Lateral view

299. Case #1031
11 year female with
ABC distal radius
Coronal T-1 MRI

300. Coronal T-2 MRI

301. Axial T-2 MRI with fluid-fluid level

302. blood
Photomic

303. Case #1032
5 year male with ABC distal ulna

304. Lateral view

305. Case #1033
17 year male with ABC ulna

306. Surgical appearance

307. Photomic

308. X-ray 1 month following simple curettement

309. 3 more months and further healing in

310. 3.5 years later and completely healed

311. Case #1034
51 year male with
ABC 2nd metacarpal

312. Case #1035
20 year male with ABC 1st metacarpal

313. AP view

314. Photomic

315. Case #1036
21 year male with ABC 1st metacarpal

316. Case #1037
10 year female with ABC distal phalanx

317. Biopsy photomic

318. Case #1038
16 year male with
ABC 3rd metatarsal

319. CT scan

320. Photomic

321. Case #1039
8 year female with
ABC 2nd metatarsal

322. Case #1039.1
CT scan
16 yr male with painful foot for 4 months

323. Axial T-1 T-2 FS
Gad

324. Cor T-1 T-2 FS
Gad

325. Sag STIR Gad

326. Epidermoid Cysts

327. Epidermoid Cyst
The least common cyst in bone is the epidermoid cyst. It is
usually seen in the distal phalanx or in the skull. In the case of the
distal phalanx, the lesion usually occurs as the result of a crushing
trauma to the distal phalanx that drives nail bed epithelium down
into the subadjacent bone where it implants and produces an ectopic,
squamous epithelial cystic lesion formed by a keratinized outer
shell. It is filled with clear fluid and creates a surface erosion of the
adjacent distal tuft of the phalanx that shows a very characteristic
radiographic appearance. The lesions will transluminate with a
flashlight. Other lesions that have a similar radiographic appearance
include enchondroma, glomus tumors of the distal phalanx and
perhaps a neurofibroma. Treatment consists of a simple curettement
and packing of the defect with autologous bone graft.

328. CLASSIC Case #205
35 year female with epidermoid cyst distal phalanx

329. keratin cyst lining
bone
Photomic

330. Case #206
40 year female with epidermoid cyst distal phalanx

331. Lateral view