This document contains 53 cases of osteoid osteoma and osteoblastoma. Case 1-50 cover osteoid osteoma, with the typical presentation of a painful nidus most commonly in long bones visualized on CT or bone scan. Cases 51-94 cover osteoblastoma, a larger variant of osteoid osteoma most often in the spine. Later cases demonstrate recurrence, progression to aneurysmal bone cyst, and treatment with curettage or resection.

1. Contents for Volume 1
Osteoid osteoma--------------------------------Case 1-50
Osteoblastoma----------------------------------Case 51-94
Osteofibrous dysplasia-------------------------Case 95-101
Ossifying fibroma of jawbone----------------Case 102-107

2. Osteoid
Osteoma

3. Osteoid Osteoma
The osteoid osteoma is the most common osteoid-forming tu
seen in the skeletal system, accounting for 10% of all benign
bone tumors. It is more common in males than females with the
peak incidence in the second decade of life. The lesions produc
symptoms of dull, aching pain that is more severe at night. The
pain is relieved with anti-inflammatory medication such as
aspirin or non-steroidal anti-inflammatory drugs (NSAID)
that inhibit the high concentration of prostaglandins found in
the nidus of the osteoid osteoma. The lesions occur typically in
the cortical structures of long bones such as the femur or tibia
but can also be found in the small bones of the ankle, wrist or
vertebral column. The lesion is characteristic for its dense,
sclerotic response in the cortical bone resulting in a fusiform
enlargement on the surface of the cortex as a response to the
small inflammatory nidus or granuloma (measuring up to one

4. centimeter in diameter) in the central area of the sclerotic
response. If the lesion is located in a central medullary area,
such as the metaphysis or on the very superficial surface of a
bone, the sclerotic response is less severe. If the nidus is
located close to or within a joint structure, as in the femoral
neck area, there will be a significant inflammatory synovitis
in the adjacent joint that gives the clinical appearance of a
pyarthrosis. In the spine, the lesions are usually located in the
posterior elements of the spine such as the laminae or pedicles
The lumbar spine is the most common location followed second
by the dorsal spine. Atypical secondary painful scoliosis will
develop with the convexity seen on the side opposite the
inflammatory lesion.
The two most significant diagnostic imaging studies are a CT
scan through the nidus area to identify its anatomic location and
bone isotope scan which is invariably positive, especially in a
symptomatic lesion. It is the current feeling that the osteoid
.

5. osteoma is a true benign neoplasm of bone in which a com-
bination of osteoclastic and osteoblastic activity are seen.
There are no inflammatory cells such as lymphocytes or
plasma cells as would be seen in a Brodie’s abscess. Non-
steroidal anti-inflammatory medications such as prostaglandin
inhibitors can be very effective in controlling the disabling
symptoms and helping the patient get thru a period of one or
two years during which time the lesion will typically involute
into a painless lesion that does not require surgery. However,
if the patient is unable to live with the pain during this time,
a surgical approach is indicated. Following exposure of the
lesion, a high speed burr is used to burr into the inflammatory
bone that is characterized by a pinkish hyperemia. When the
nidus is found, a small curette is used to core the inflammatory
nidus for pathological diagnosis and the cavity of the nidus
is burred an additional 2 or 3 mm which usually results in a very
dramatic relief of symptoms and a permanent cure from the

6. disease process. It is not necessary to remove the large
dense sclerotic bone surrounding the nidus; doing so could
result in a pathologic fracture following surgery. In the spine,
a simple laminectomy is frequently carried out. If the lesion is
located in the pedicle a simple burring into the pedicle will
relieve the patient of the inflammatory pain.
More recently, relatively non-invasive techniques have been
tried to remove the nidus of the osteoid osteoma by means of a
CT guided burr placed through a protective trocar or by place-
ment of a heat-producing radio frequency probe that, when
properly positioned, can destroy the nidus through thermal
coagulation. These techniques are particularly valuable for dee
seated lesions located in the acetabulum. For lesions located in
the pedicle of a vertebra one must be careful not to damage an
adjacent spinal root or spinal cord.

7. CLASSIC
Case #1
19 yr old female painful
Osteoid osteoma nidus
femur

9. CT scan
nidus

10. Macro section of nidus

11. Photomic of nidus

12. Case #2
29 year male
osteoid osteoma
femur
nidus

13. CT scan
nidus

14. Case #3
11 yr male
osteoid osteoma
femur

15. Bon
e
sca
n

16. CT scan
nidus

17. Photomic

18. Case #4
nidus
5 yr male osteoid osteoma femur

19. Case #5
12 yr male
osteoid osteoma
femur
nidus

20. Case #6
10 yr male
osteoid osteoma
femur
nidus

21. nidus

22. nidus
CT scan

23. Case #7
30 yr female
osteoid osteoma
femur
nidus

24. nidus
Coronal T-1 MRI

25. nidus
edema
Axial PD MRI

26. nidus
Macrosection

27. Case #8
23 yr female
osteoid osteoma
femur
nidus

28. Bone Scan

29. Nidus
CT Scan

30. Case #9
12 yr male
osteoid osteoma
femur nidus

31. Macro sectionnidus

32. Photomic

33. Case #10
nidus
10 yr female with osteoid osteoma femoral neck

34. Photomic

35. One yr after curettement

36. Case #11
nidus
25 yr male with osteoid osteoma femoral neck

37. nidus
CT scan

38. Case #12
nidus
6 yr male osteoid osteoma acetabulum

39. nidus

40. Bone scan

41. Case #13
nidus
11 yr male
osteoid osteoma
distal femur

42. Bone scan

43. Case #14
nidus
16 yr male
osteoid osteoma
distal femur

44. Case #15
6 yr male
osteoid osteoma
tibia
nidus

45. Bone scan

46. Excessive
bone block
resection
nidus

47. nidus
Macro section of nidus

48. Photomic

49. Post op x-ray

50. Resultant fracture
one year later

51. Case # 16
10 yr male
osteoid osteoma
tibia

52. Shaving down with osteotome

53. Further shaving to find nidus

54. Burred out nidus defect

55. Case # 17
15 yr male
osteoid osteoma
tibia

56. Lateral view
nidus

57. Bone scan

58. Coronal T-2 MRI
nidus

59. Coronal Gad
contrast MRI edema
nidus

60. nidus
T-1 axial MRI

61. Photomic

62. Photomic

63. Case #17.1 Osteoid osteoma
52 year old male with ankle pain for 3 mos.

64. Sag T-1 T-2 Gad

65. Axial T-1 T-2
Gad

66. Case #18
nidus
17 yr male
osteoid osteoma
femur

67. Gross
specimen
nidus

68. Photomic

69. Case #19
18 yr male
Osteoid osteoma tibia

70. Case #20
18 yr female
osteoid osteoma nidus
tibia

71. Case #21
nidus
12 yr male with parosteal osteoid osteoma tibia

72. Case #22
nidus
17 yr male
osteoid osteoma
fibula

73. Lateral view

74. Case #23
nidus
26 year female with
epiphyseal osteoid
osteoma prox radius

75. Case #24
16 yr female
osteoid osteoma
ulna
nidus

76. Bone scan

77. Case #25
16 yr male
osteoid osteoma
humerus
nidus

78. Case # 26
nidus
14 yr male
osteoid osteoma
L-4

79. Bone scan

80. Photomic

81. Case # 27
nidus
15 yr male
osteoid osteoma
L-3

82. Case #28
nidus
46 yr male
osteoid osteoma
dorsal spine

83. Bone scan

84. Case #29
nidus
18 yr male with osteoid osteoma C-3

85. nidus
Laminogram

86. Bone scan

87. Case #30
nidus
12 yr male with osteoid osteoma C-3 spine

88. Case #31
nidus
25 yr male
osteoid osteoma
C-5

89. Case # 32
nidus
27 yr female with osteoid osteoma S-1

90. Case #33
nidus
22 yr male with osteoid osteoma sacrum

91. Case #34
nidus
18 yr male
osteoid osteoma
finger

92. nidus
X-ray

93. nidus
AP x-ray

94. Case #35
nidus
24 yr male with osteoid osteoma thumb

95. Bone scan

96. Case #36
nidus
19 yr female with osteoid osteoma finger

97. Case #37
nidus
20 yr male with osteoid osteoma thumb

98. Case #37.1
nidus
17 year female with dull aching pain index finger 1 yr

99. Case #38
nidus
23 yr male with osteoid osteoma capitate

100. Case #39
nidus
25 yr male with osteoid osteoma narvicular

101. Case # 40
nidus
34 yr female with osteoid osteoma 2nd metatarsal

102. double
nidus
CT scan

103. edema
Axial T-2 MRI

104. Case #41
nidus
24 yr female with osteoid osteoma big toe

105. nidus
Gross Specimen

106. Photomic

107. Photomic

108. Case #42
nidus
Osteoid osteoma talus

109. Photomic

110. Case #43
Osteoid osteoma
pseudotumor
Brodie’s abscess
13 yr female
tibia
nidus

111. tunnel
Gopher’s sign

112. Case # 44
Osteoid osteoma
pseudotumor
Brodie’s abscess nidus
tibia
38 yr male

113. nidus
Axial T-2 MRI

114. Case #45
pseudo-nidus fracture
line
Osteoid osteoma pseudotumor
stress fracture femoral neck 38 yr male

115. Bone scan

116. Case #46
Osteoid osteoma
pseudotumor
33 year female
Early stress
fracture femoral
neck with pain
for 3 mos

117. Bone scan

118. One month later

119. Case #47
pseudonidus
Osteoid osteoma pseudotumor
stress fracture femoral neck 50 yr female

120. pseudonidus
Axial T-2 MRI

121. fracture line
Coronal T-2 MRI

122. Case #48 OO pseudotumor Stress fracture
20 year old male with pre-tibial pain for 3 months

123. Sag T-1 PD Gad

124. Case #49
Pseudo osteoid
osteoma femur
Chronic stress
periostitis from
adductor pull
14 yr male

125. pseudonidus
CT scan

126. Bone scan

127. Case #50
Pseudo osteoid
osteoma femur
38 yr male
Bone island

128. Bone scan

129. Coronal
T-1 MRI
pseudonidus

130. Osteoblastoma

131. Osteoblastoma
The so-called osteoblastoma is considered by most to be a la
or giant form of the similar clinical entity known as the osteoid
osteoma. As with the osteoid osteoma, it is found in children and
young adults, more often in males than females. It is less comm
than the osteoid osteoma, representing approximately 1% of all
bone tumors. It is found mostly in metaphyseal areas of long bo
and in the posterolateral elements of the axial skeleton where
nearly 50% of the lesions are identified. Radiographically these
lesions are more osteolytic than the osteoid osteoma and have
central nidus that measures more than 1.5 cm in diameter with
less reactive sclerosis seen at the periphery than an osteoid
osteoma. It is not unusual for an aneurysmal component to be
associated with the osteoblastoma, similar to the reaction seen
adjacent to chondroblastomas and giant cell tumors. The micro-
scopic appearance of the nidus material is almost identical to

132. that of the osteoid osteoma and under higher power cannot be
differentiated by even the most competent pathologists. The
major concern is a microscopic appearance similar to an osteo-
sarcoma and, for this reason, multiple samples must be evaluate
in order to establish the correct diagnosis in cases where these
lesions arise from the metaphyseal areas of long bone.
In the spinal area, the osteoblastoma is typically located in th
posterolateral elements where it can cause problems with spinal
cord or nerve root compression that may require aggressive
surgical decompression and even spinal stabilization. On occasi
an osteoblastoma will spontaneously convert into an osteo-
sacoma, especially if it has been treated with radiation therapy.
The primary treatment for the osteoblastoma is a surgical one w
a fairly aggressive curettement of the lesion. There is no particul
reason to take wide margins because the recurrence rate is quite
low and in some cases the lesions resolve spontaneously with o
any surgery at all, similar to what occurs with osteoid osteomas.

133. A variant of the osteoblastoma, the so-called aggressive or
“malignant” osteoblastoma, is a clinical entity halfway between th
classic benign osteoblastoma and a full blown malignant osteo-
sarcoma. This “malignant” osteoblastoma appears and behaves
clinically at the local site like an osteosarcoma but has no potenti
to metastasize to distant parts. In this situation, local treatment
must be more aggressive and probably would require a wide loca
resection to avoid a local recurrence because radiation therapy o
even systemic chemotherapy is not effective for this aggressive b
benign entity.

134. CLASSIC
Case #51
26 yr male
osteoblastoma L-4

135. Lateral view

136. Bone scan

137. CT scan

138. Sagittal T-2 MRI

139. Photomic

140. Photomic

141. 5 yrs post op with spontaneous fusion

142. AP x-ray 5 yrs post op

143. Sagittal gad contrast MRI 5 yrs post op

144. Axial gad contrast MRI 5 yrs post op

145. Case #52
nidus
23 yr male with osteoid osteoma L-5

146. nidus
CT scan

147. Photomic

148. Photomic

149. Recurrence
Recurrence 8 mos post op laminectomy

150. CT
Recurrence as an osteoblastoma

151. Secondary ABC
behind osteoblastoma
Sagittal T-2 MRI
ABC
osteoblastoma

152. fluid-fluid
level
Axial T-2 MRI

153. ABC histology

154. ABC histology

155. Osteoblastoma histology

156. Osteoblastoma histology

157. Post op posterior
resection and fusion

158. AP x-ray
post op fusion

159. CT scan later shows anterior recurrence

160. Post op anterior
resection and bone
cement reconstruction

161. Lateral x-ray showing
anterior reconstruction
with cement
cement

162. cement
bone
graft
CD rods
Post op CT scan showing cement reconstruction

163. cement
graft
Post op CT

164. Case #53
surgical
towel clip
26 yr male with osteoblastoma L-4 following a laminectom
curettement three years previous for an osteoid osteom

165. CT scan
Appearance 4 months later with a 1.5 cm nidus

166. A curettement at this time revealed an osteoblastoma

167. Myelogram 4 yrs
later

168. burned-out
lesion
CT scan at same time and no pain

169. Another CT cut

170. Burnt out
lesion
Sagittal T-1 MRI at same time

171. Sagittal T-2 MRI same time

172. T-2 MRI with residual ABC in inactive lesion

173. Axial T-1 MRI same time

174. Axial T-2 MRI with residual ABC component

175. Case #54
7 yr female
osteoblastoma L-2

176. Bone scan

177. T-2 MRI shows
high signal ABC
posterior to low signal
osteoblastoma
osteoblastoma
ABC

178. osteoblastoma
Sagittal ABC
T-2 MRI

179. Osteoblastoma Photomic

180. AP x-ray
post op posterior
spinal fusion

181. Lateral X-ray
post op

182. Case #55
14 yr female
osteoblastoma L-5

183. Oblique X-ray

184. Bone scan

185. CT scan

186. CT scan

187. Case #56
24 yr male with osteoblastoma L-3

188. Lateral view

189. Oblique view

190. Opposite oblique

191. Case #57
22 year male with osteoblastoma L-1 vertebra

192. Oblique view

193. Case #58
23yr male with burned out obteoblastoma L-4

194. Case #59
14 yr male
osteoblastoma C-3

195. Oblique view

196. Opposite oblique

197. One year
post op posterior
fusion and recurrent
tumor anterior

198. Anterior view
with recurrence

199. Post op anterior
debriedment and
fusion

200. Case #60
18 yr male
osteoblastoma
C-7

201. Oblique view

202. Lateral view
2 mo later

203. AP view
1 mo later

204. Resected nidus

205. Photomic

206. Photomic

207. Case #61
CT scan
55 yr female with osteoblastoma C-6

208. Bone scan

209. Sagittal T-1 MRI

210. Sagittal T-2 MRI

211. Axial T-2 MRI

212. Case #62
25 yr female with osteoblastoma C-6

213. AP x-ray

214. 10 yrs later

215. Lateral view 10 yrs later

216. Photomic

217. Photomic

218. Case #63
CT scan
40 yr male with osteoblastoma C 5-6

219. CT scan

220. Sagittal T-2 MRI

221. Sagittal
T-2 MRI showing
bulge in floor of
vertebral canal

222. Case #64
13 yr female with osteoblastoma C-6

223. Lateral view

224. Post op X-ray
After anterior
interbody fusion

225. Case #65
AP X-ray
14 yr female with osteoblastoma C-7

226. AP myelogram

227. Arteriogram showing
pressure on vertebral
artery

228. Post op debriedment

229. Case #66
CT scan
43 yr female with osteoblastoma T-8

230. Axial T-2 MRI

231. Sagittal T-1 MRI

232. Post op posterior
spine fusion

233. Case #67
28 yr male with osteoblastoma thoracic spine

234. CT scan

235. Post op resection

236. CT scan post op resection

237. Case #68
21 yr male
osteoblastoma S-1

238. 2 years later

239. 5 years later

240. Lateral view 5 years later

241. Photomic

242. Photomic

243. Case #69
8 yr male with ostoblastoma sacrum

244. Case #70
26 yr female with osteoblastoma acetabulum

245. Close up AP

246. Photomic

247. Photomic

248. X-ray 3 mos
following THA

249. Case #71
19 yr male with aggressive osteoblastoma acetabulum

250. Bone scan

251. Gross specimen from curettement

252. Photomic

253. Photomic

254. Post op internal
hemipelvectomy

255. Recurrence 4 months later

256. tumor
Ablative hemipelvectomy specimen

257. tumor
Hemipelvectomy specimen

258. Several years later with recurrent tumor on sacrum

259. Lateral view of recurrence

260. Case #72
38 yr male
osteoblastoma
pelvis

261. Frog lateral

262. Post op x-ray following curettage and cementation

263. Case #73
33 yr female with osteoblastoma acetabulum

264. Axial T-1 MRI

265. Coronal T-2 MRI

266. Case #74
26 yr male with osteoblastoma acetabulum

267. Frog lateral

268. Case #75
24 yr male with osteoblastoma pelvis

269. 18 mos later

270. Case #76
22 yr male with osteoblastoma ischium

271. nidus
X-ray of resected specimen

272. Case #77
26 yr male with osteoblastoma ilium

273. CT scan

274. Post op x-ray appearance after resection and cementa

275. Case #78
23 yr male
osteoblastoma
femur

276. CT scan

277. T-2 MRI

278. Sagittal T-2 MRI

279. Photomic

280. Case #78.1
19 year male with
tibial pain for 6 mos

281. T-1 T-2
Gad +
Axial

282. Coronal T-1 T-2 Gad

283. X-ray 3 months post op

284. Case #79
15 yr male
osteoblastoma
femur

285. Bone scan

286. CT scan

287. Axial T-2 MRI

288. Coronal T-1
MRI

289. X-ray at time of
surgery with marker
in tumor defect

290. Photomic of nidus

291. Case #79.1 CT scan Sclerosing
osteomyelitis
of Garre
14 yr male with dull aching thigh pain for 1 year

292. Coronal T-1 Coronal T-2

293. Sagittal T-2 Axial T-2

294. Case #80
13 yr male with osteoblastoma femoral neck
frog lateral view

295. AP view

296. Bone scan

297. Case #81
22 yr male with osteoblastoma talus

298. Sagittal T-1 MRI

299. Coronal T-2 MRI

300. Coronal T-2 MRI

301. Photomic

302. Case #82
25 yr male
osteoblastoma
talus

303. Lateral view

304. Close up lateral

305. Photomic

306. Case #83
18 yr female with osteoblastoma talus

307. Mortise view

308. X-ray 1 yr after curettage

309. Case #84
23 yr male with osteoblastoma talus

310. Case #85
25 yr female with osteoblastoma os calcis

311. Os calcis view

312. X-ray several months with progression of disease

313. Case #86
29 yr male with osteoblastoma os calcis

314. Case #87
53 yr male with osteoblastoma distal humerus

315. X-ray 3 years later

316. tumor
edema
Axial T-2 MRI

317. edema nidus
Coronal T-2 MRI

318. Post op x-ray
following distal
humeral resection
and allograft
reconstruction

319. Case #88
9 yr female
osteoblastoma
distal humerus

320. Coronal T-1 MRI
edema

321. tumor
edema
Axial T-2 MRI

322. Case #88.1
nidus
11 yr male with ABC response to osteoblastoma humeru

323. Sag T-1
Sag T-2

324. Axial T-2 MRI shows the multiloculated aneurysmal cys

325. Case #89
21 yr male with osteoblastoma ring finger

326. AP and Lateral radiographs

327. Gross specimen

328. Photomic

329. Case #90
18 yr male with osteoblastoma finger

330. Case #91
21 yr male with osteoblastoma thumb

331. Case #92
10 yr female with osteoblastoma finger tip

332. AP X-ray

333. Case #93
9 yr female
osteoblastoma tibia

334. AP x-ray

335. Case #94
24 yr male with osteoblastoma fibula

336. Lateral view

337. Osteofibrous
Dysplasia

338. Osteofibrous Dysplasia
Osteofibrous dysplasia is a rare condition occurring
in children less than 10 years of age. This benign lesion
has radiographic and microscopic features similar to fibrous
dysplasia of the tibia, the main difference being the presence
of more heavily ossified tissue at the periphery of the lesion
giving it a soap-bubbly appearance on x-ray. Microscopically
it has a similar “alphabet-soup” metablastic bone appearance
in a benign fibrous tissue stroma but with the additional feature
of heavy osteoblastic rimming of the trabeculae not seen in
fibrous dysplasia. It typically arises from the anterior cortex of
the tibia at mid shaft and causes a progressive anterior bowing
of the tibia over time, creating a cosmetic deformity associated
with pain of a dull, aching nature. The radiographic appearance
Is very similar to and impossible to separate from that of the
Malignant adamantinoma that also affects the tibia in children

339. and, for this reason, a biopsy must be performed to rule out the
malignant possibility. Occasionally osteofibrous dysplasia of the
tibia can progress gradually into a well-differentiated form
of the adamantinoma, which will have the microscopic
features of both osteofibrous dysplasia and adamantinoma
in the same lesion. As far as treatment is concerned, early
surgical debriedment and bone grafting before age 15 years
results in a high local recurrence rate and thus should be
discouraged until the child reaches full bone maturity at which
time a definitive debriedment and bone grafting procedure
can be performed without significant risk of recurrence. This
lesion occurs bilaterally in a very small percentage of cases
and can also involve the fibula on the same side. This process
in newborns appears to be more osteolytic and destructive in
nature.

340. CLASSIC
Case #95
9 yr male
osteofibrous dysplasia
tibia

341. AP and lateral x-ray

342. Photomic

343. Case #96
6 year female
osteofibrous dysplasia
tibia

344. Same case

345. Case #97
16 year female
osteofibrous dysplasia
tibia

346. Case #98
8 yr male
osteofibrous dysplasia
tibia

347. X-ray appearance
3 yrs later

348. 8 yrs later with
spontaneous healing

349. Case #98.1 Burnt out osteofibrous dysplasia
61 year old male with incidental finding in tibia for years

350. Bone scan

351. Sag T-1 PD FS Gad

352. Cor STIR Gad

353. Axial T-1 T-2 FS
Gad

354. Case #99
15 yr female
osteofibrous dysplasia
tibia
AP x-ray

355. Lateral x-ray

356. Case #100
Newborn with osteofibrous dysplasia tibia

357. edema
T-2 axial MRI

358. Photomic

359. Photomic

360. X-ray 1 yr later

361. Case #101
Another newborn
osteofibrous dysplasia
tibia

362. Another view

363. Ossifying Fibroma
of Jawbone

364. Ossifying Fibroma of Jawbone
Ossifying fibroma of jawbone is a benign condition similar to
osteofibrous dysplasia of the tibia in that histologically they are
almost identical. It is also a condition that is related to fibrous
dysplasia, which can have a very similar radiographic appearan
but in the case of fibrous dysplasia of jawbone osteoblastic
rimming of the trabecular bone is not seen under microscopic
evaluation. As with fibrous dysplasia, this condition is found in
children and is almost always an asymptomatic process resultin
in cosmetic deformation of the maxilla or mandible, usually on
one side but can be bilateral. The condition can result in
significant malocclusion of the teeth because of deformation
of the subadjacent alveolar ridge or maxillary structures. It also
can create problems with normal drainage from the air sinuses i
the maxilla that can lead to infection requiring surgical drainage
Most of the surgical treatment for this condition is for cosmetic
deformity.

365. Case #102
5 yr female
ossifying fibroma
maxilla

366. tumor
Maxillary view

367. tumor
Tomogram cut

368. tumor
CT scan

369. tumor
Another cut

370. Another cut

371. Photomic

372. Case #103
18 yr female with ossifying fibroma mandible

373. Oblique view

374. Photomic

375. Closeup of alphabet-soup metaplastic bone

376. Case #104
tumor
12 yr female with ossifying fibroma mandible

377. Opposite ramus

378. Case #105
14 yr female with ossifying fibroma mandible

379. Case #106
Young adult tumor
osteoma skull

380. tumor
Occipital view

381. Lateral view

382. Case #107
Cementoma mandible

383. Oblique view