. 7
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7-7. A. Penectomy specimen for multifocal carci-
noma in situ of the distal urethra (left). B. Transi-
tional cell carcinoma in situ of the penile urethra.

Diseases of the Male Genital System 431
7-8. Metastatic malignant melanoma in the penile urethra.

7-9. Spermatocele surgically resected from a hilar, paratesticular situa-
tion is derived from cystic dilatation of a portion of the efferent ducts
of the epididymis or the rete testis. Histology shows a cuboidal epithe-
lial lining and degenerating spermatozoa.

432 Diseases of the Male Genital System

7-10. A. Epididymal cysts usually develop in men
of about 40 years of age and may be multiple. They
present as a cystic lump in the head of the epi-
didymis (top right). The smooth, spherical cyst
indents the upper pole of the testis and gives a spu-
rious appearance of an intratesticular situation. B.
The lining of the cyst (left) consists of low cuboidal
epithelium, and a portion of the epididymis is pres-
ent (right). (continued on next page)


Diseases of the Male Genital System 433

7-10. (Continued) C. Testis is indented by this
white-colored, keratin-containing epididymal inclu-
sion cyst (*). D. Histology shows a squamous
epithelial lining to the cyst with inspissated keratin
in its lumen.


434 Diseases of the Male Genital System

7-11. A. Acute orchitis may be part of epididy-
moorchitis following ascending infection (as in this
patient), or it may occur as isolated orchitis sec-
ondary to bloodborne infection or autoimmune dis-
ease. Note the acutely in¬‚amed testis showing focal
hemorrhages and suppuration within the testis sec-
ondary to gram-negative bacterial infection of the
genitourinary tract. B. Histology shows acute sup-
purative in¬‚ammation within and around seminif-
erous tubules in the testis.

Diseases of the Male Genital System 435

7-12. A. Subacute epididymoorchitis showing a
large hydrocele (right) alongside distorted testis
with partial cystic transformation. Note the lipid-
rich postin¬‚ammatory deposits within the epi-
didymis (*). B. Neutrophils, lymphocytes, and
hemosiderin deposits in the ¬brous tissue enclosing
the hydrocele.


436 Diseases of the Male Genital System

7-13. Suture granuloma (*) of the testis following
orchiopexy (inguinal testis was surgically relocated
into the scrotum). Histology is needed to make the

7-14. Granulomatous orchitis showing pale white
solid tissue replacing most of the testis apart from
the brownish remnant (lower right). The condition
is a type IV (cell-mediated) noncaseating granulo-
matous response to the seminiferous tubules.

Diseases of the Male Genital System 437
7-15. Infarction of the testis. A. Hemorrhagic infarc-
tion of the testis following arterial occlusion. Simi-
lar lesion may follow torsion of the testis. B. Focal
infarction (arrow) of the upper pole of another testis.


438 Diseases of the Male Genital System
7-16. A. Organizing hematoma around the testis.
B. Histology shows festoons of histiocytes growing
into the hematoma.


Diseases of the Male Genital System 439
7-17. Traumatic injury to the testis (bottom center).
The testis and scrotum have been bisected, and
recent widespread hemorrhage is present within the

440 Diseases of the Male Genital System

7-18. A. Hemorrhagic nodule within the testis due
to polyarteritis nodosa. B. Whole mount section of
a testis replaced by hemorrhagic choriocarcinoma.
C. High-power view of the choriocarcinoma show-
ing malignant cyto- and syncytiotrophoblast.


Diseases of the Male Genital System 441

7-19. A. Bisected small, dysplastic testis of a patient
with cryptorchidism that showed intratubular germ
cell neoplasia (ITGCN). This change is a preinvasive
form of germ cell tumor. B. Histology of ITGCN
shows atypical germ cells lining seminiferous
tubules having thickened basement membranes. No
spermatogenesis is evident. C. Two intraabdominal
testes removed after puberty from a phenotypically
normal female with complete androgen insensitivity
syndrome (previously termed “testicular feminiza-
tion syndrome”) and X and Y chromosomes. The
gene mutation is on the X chromosome in band
Xq11-q12. The subjects have no uterus, are infertile,
and never menstruate.

442 Diseases of the Male Genital System

7-20. Atrophy of the testis may follow orchitis of
any cause, cryptorchidism, ischemia, irradiation,
and prolonged administration of female hormones,
along with other causes. A. Atrophic testis follow-
ing mumps orchitis. B. Whole mount section of
testis and epididymis showing generalized atrophy
of seminiferous tubules in testis. C. Hyalinized,
atrophic seminiferous tubules are more easily
appreciated at this higher power.

Diseases of the Male Genital System 443


7-21. Seminoma of the testis. A. Large, homoge-
neous, light tan-colored tumor mass (X) has
replaced much of the testicular tissue. Necrosis is
uncommon in seminoma. B. Close-up view of
another seminoma shows focal areas of necrosis
(yellow) within the tumor. (continued on next page)

444 Diseases of the Male Genital System

7-21. (Continued) C. Low-power histology of the
seminoma shows a pink-colored area of necrosis
within the cellular, blue-colored tumor. D. High-
power view of seminoma shows the cells to have
pale-staining nuclei with prominent nucleoli, well-
de¬ned cell borders, and scanty interstitial lym-
phocytes. (continued on next page)


Diseases of the Male Genital System 445


7-21. (Continued) E. Retroperitoneal lymph nodes
post chemotherapy contain metastatic, partially
necrotic, seminoma. F. Secondary spread of anaplas-
tic seminoma to almost totally replace the kidney.

446 Diseases of the Male Genital System


7-22. A. Combined seminoma (yellow, homoge-
neous areas) (*) and nonseminomatous (teratoma-
tous) germ cell tumor (cystic areas with hemorrhage
and necrosis) (arrow). B. Histology shows semi-
noma (left) and portion of teratoma (top and right).


Diseases of the Male Genital System 447
7-23. Teratocarcinoma (malignant transformation of
a teratoma with the development of mucin-secret-
ing adenocarcinoma in this case) has totally
replaced the testis and extended beyond its original
boundaries. The solid white tumor shows extensive
necrosis and hemorrhage.

7-24. A. Embryonal carcinoma is poorly delineated
and occupies the mid- and inferior portion of the
testis. B. Histology of embryonal carcinoma shows
sheets of primitive cells giving rise to glands.


448 Diseases of the Male Genital System

7-25. A. Solid white tumor in testis comprises
embryonal carcinoma with yolk sac elements. Yolk
sac tumor is the most common testicular tumor in
infants (in whom it has a good prognosis). In adults,
yolk sac tumor usually occurs in combination with
embryonal carcinoma, as in this patient. B. Histol-
ogy of embryonal carcinoma with yolk sac elements
(arrows) comprising papillary projections covered
by a double cell layer simulating a developing yolk

Diseases of the Male Genital System 449

7-26. A. Malignant lymphoma of the testis showing
an overgrowth by a solid, ¬‚eshy, yellow-white
tumor tissue with extensive areas of necrosis. The
lymphoma may arise in the testis (it is the most
common testicular neoplasm in men older than
60 years), or it may spread there from elsewhere in
the body. B. In¬ltrating lymphomatous cells sepa-
rate the seminiferous tubules.


450 Diseases of the Male Genital System
7-27. A variety of malignant tumors may spread to
the testis. A few examples are illustrated here.
A. Diffuse myelomatous in¬ltration of the testis.
B. Histology of the same testis shows sheets of neo-
plastic plasma cells surrounding a surviving semi-
niferous tubule. (continued on next page)


Diseases of the Male Genital System 451

7-27. (Continued) C. Leukemic in¬ltration of the
testis with partial necrosis of the malignant in¬l-
trate. D. Metastatic neuroblastoma in the testis of an
infant. Tumor nodules are also present on the sper-
matic cord. E. Histology of the same testis shows
small, dark blue tumor cells of metastatic neurob-


452 Diseases of the Male Genital System
7-28. Partly macerated fetus showing the intraab-
dominal situation of both testes (arrows) approach-
ing the inguinal canals.

Diseases of the Male Genital System 453

7-29. Benign prostatic hyperplasia (BPH). A. Macro-
scopic appearance of hyperplasia of the prostate
gland showing the characteristic multinodular cut
surface due to multifocal hyperplasia that led to
overall glandular enlargement. B. Whole mount of
BPH showing nodules composed of proliferating
glands surrounded by stromal proliferation. Cystic
dilatation of some glandular spaces is also evident.
C. Higher-power view of BPH.



454 Diseases of the Male Genital System


7-30. Adenocarcinoma of the prostate gland.
A. Entire prostate gland that was excised by radical
prostatectomy. B. Transverse section of prostate
gland showing lipid-rich (yellow-colored) prostatic
cancer that has arisen toward the periphery of the
gland and has in¬ltrated inward. The resection line
(prostate has no capsule) has been marked with
black ink. (continued on next page)

Diseases of the Male Genital System 455



7-30. (Continued) C. Multiple slices of an advanced
prostatic cancer that has replaced most of the gland.
D. Whole mount section of prostate gland showing
benign prostatic hyperplasia on the left and inva-
sive cancer (solid tissue) on the right (*). (contin-
ued on next page)

456 Diseases of the Male Genital System

7-30. (Continued) E. Intermediate-power histology
shows massive crowding of the malignant glandu-
lar acini. F. High-power view of prostatic cancer
showing clear cells containing prominent nucleoli
within large, clear nuclei. (continued on next page)


Diseases of the Male Genital System 457

7-30. (Continued) G. Perineural invasion by cancer
of the prostate gland. H. Thrombosed veins of the
periprostatic venous plexus “ this plexus bears pro-
static cancer to the vertebral column.

458 Diseases of the Male Genital System
7-31. Malignant ¬brous histiocytoma of the prostate
gland grossly mimics cancer of the prostate gland.

7-32. In¬‚ammatory ¬brous pseudotumor of the
scrotum. Without histology, the mass could be mis-
taken for a true tumor.

Diseases of the Male Genital System 459
8 Bones and Joints

8-1. Head of femur shows a line of irregular ¬bro-
cartilaginous callus (arrows) consistent with a
nonunited fracture of the head.

460 Bones and Joints
8-2. A. Nonunited fracture of the tibia that allowed
movement at this site (i.e., a pseudoarthrosis is
present). B. Appearance of ¬brous tissue separating
the fractured ends of the bone.


Bones and Joints 461
8-3. Osteoporosis of the vertebrae. A jet of water
has been used to drive out most of the bone mar-
row, revealing a paucity of bony spicules.

8-4. Compression fractures of two vertebral bodies
in a patient with osteoporosis.

462 Bones and Joints
8-5. Orthopedic repair of vertebral fractures.

Bones and Joints 463

8-6. A. Osteitis of the lower lumbar vertebrae has
produced a greenish discoloration of the affected
bones, which have been transected obliquely. The
greenish-colored material on the left of the picture
is pus within a psoas abscess. B. Histology of
osteitis shows necrotic bone (the sequestrum) lying
within a sea of neutrophils. C. Dense new cortical
bone has been laid down over the area of osteitis.
(continued on next page)


464 Bones and Joints
8-6. (Continued) D. Appearance of the psoas
abscess prior to sectioning of the vertebral osteitis
that gave rise to the abscess. E. Histology of the
psoas abscess shows destruction of skeletal muscle
with a cavity in the muscle that is ¬lled with poly-
morphonuclear leukocytes (neutrophils).


Bones and Joints 465

8-7. A. Tuberculous osteitis has produced a patho-
logical fracture of a vertebra. The tuberculous infec-
tion is spreading as a “cold abscess” (due to absence
of signs of acute in¬‚ammation) in the psoas muscle
sheath to the left of the vertebrae in the picture.
B. Histology shows active tuberculosis with bony
fragments lying within the chronic in¬‚ammation. A
single Langhans giant cell is present in the center
of the ¬eld.

466 Bones and Joints


8-8. A. Aseptic necrosis of the femoral head. Most
of the head is necrotic, but the necrosis is best
appreciated in the local yellow area (arrow).
B. Another level of the same head shows a wider
area of recognizable necrosis just under the carti-
lage layer.

Bones and Joints 467
8-9. Infarction of the bone marrow in the lower end
of the femur due to steroid therapy in an organ
transplant recipient.

468 Bones and Joints
8-10. Osteopetrosis is an inherited defect in bone
resorption due to inadequate osteoclastic function.
This leads to abnormally dense but fragile bones
that easily fracture. A. Osteopetrosis of the skull
bone showing thickened, extremely dense bone
devoid of any marrow cavity. Focal vascularization
of the subperiosteal bone due to extramedullary
hematopoiesis is noted. B. Close-up view of the
hyperdense bone. (continued on next page)


Bones and Joints 469

8-10. (Continued) C. Histology shows the full thick-
ness of the bone to be comprised of dense, cancel-
lous bone, only with no bone marrow. D. The ribs
show similar features in cross-section.

470 Bones and Joints
8-11. Craniofacial dysostosis (Crouzon syndrome)
leads to premature closure of sutures between the
skull bones. Note the protruding eyes due to unusu-
ally shallow eye sockets. The ears are also low

Bones and Joints 471


8-12. Hypertrophic osteoarthropathy associated
with lung cancer. A. Proximal shaft of femur (top),
proximal ulna bone (middle), and proximal radius
bone all show additive subperiosteal ossi¬cation.
B. The subperiosteal new bone is clearly evident as
an additional layer of bone surrounding the origi-
nal cortical bone of the shaft of this femur. (contin-
ued on next page)

472 Bones and Joints

8-12. (Continued) C. Histology shows the outer new
bone (arrows) to have a darker color than the under-
lying original cortical bone. This contrast is more
evident in the left-hand side of the picture.
D. Close-up histology shows the outer new bone
(top) to be darker staining and to have thinner bony


Bones and Joints 473

8-13. A. Expanded and distorted outline of a rib
due to ¬brous dysplasia. B. Histology of ¬brous dys-
plasia shows irregularly shaped, acutely angled tra-
beculae (so-called Chinese letters) of woven bone
lying in a ¬brous stroma without any osteoblastic


474 Bones and Joints


8-14. Osteoma is a benign tumor of bone that occurs
most often on the skull and facial bones. A. This
osteoma is arising as a sessile, semicircular-shaped,
bony mass on the surface of this skull bone. Multi-
ple osteomas occur in Gardner syndrome. B. Osteoid
osteoma is a small, often painful, osteoma that usu-
ally arises within one of the leg bones. X-ray of the
tibia shows a central radiolucent zone surrounded
by denser, less radiolucent bone. (continued on next

Bones and Joints 475

8-14. (Continued) C. Macroscopic appearance of an
osteoid osteoma shows a central bony nidus within
a small cavity. D. Histology shows the central
osteoid osteoma (X) to be composed of more deli-
cate, densely arranged bony lamellae than the sur-
rounding bone, which shows reactive thickening
around the lesion. The lesion is painful due to the
constraint on its growth expansion.


476 Bones and Joints
8-15. A. Enchondroma of the ¬bula is seen as con-
tiguous islands of clearly recognizable cartilage
within the substance of the bone. B. Histology
shows the enchondroma to be composed of well-
differentiated, mature-looking cartilage.


Bones and Joints 477

8-16. A. Osteochondroma (cartilage-capped exosto-
sis) is a hamartoma that develops at the ring of Ran-
vier of the growth plate. The new bone growth
occurs laterally instead of toward the metaphysis.
B. Histology shows endochondral ossi¬cation is
occurring under the cartilage cap.


478 Bones and Joints

8-17. A. Surgically excised chondromyxoid ¬broma
comprises a ¬rm, lobulated, yellow-gray tumor.
B. Histology shows a cellular tumor composed of
mononuclear and multinucleated giant cells in a
myxoid and/or chondroid stroma.

Bones and Joints 479

8-18. A. Nonossifying ¬broma (metaphyseal ¬brous
defect) of bone is one of the more common benign
tumors of children and adolescents. It comprises
mainly ¬brous tissue and occurs in the metaphysis
of a long bone (e.g., the tibia), as in this patient. In
the transverse section of bone (top), the lesion has
penetrated the cortical bone. The usual treatment is
curettage and bone grafting. The lesion may resolve
spontaneously at skeletal maturity, but it may pre-
dispose to bone fracture. B. Histology shows that
cortical bone has been replaced by mature ¬brous
tissue containing ¬broblasts. Osteoclasts may also
be present in some cases.

480 Bones and Joints
8-19. Aneurysmal bone cyst. A. Aneurysmal bone
cyst has led to eccentric expansion of the ¬bula by
a clotted, blood-¬lled cavity that also includes areas
of solid tissue. The expanded bony cortex on the
right has been reduced to a thin, brittle bony struc-
ture covering the lesion. The cause of the lesion is
unknown but is believed to be related to a distur-
bance of the bony capillary network. In about 50%
of cases, a preexisting tumor or other bone pathol-
ogy may be present. B. Histology shows blood-¬lled
spaces surrounded by ¬broblasts and osteoclastic
giant cells.


Bones and Joints 481
8-20. Giant cell tumor. A. Giant cell tumor (osteo-
clastoma) of the humerus has destroyed the epiph-
ysis and the adjacent metaphysis, resulting in a
pathological fracture. The tumor is invading the
surrounding soft tissues. The tumor occurs after the
age of 20 years and is more common in Asian
women. B. Histology of giant cell tumor shows
multinucleated giant cells of osteoclastic type,
which are reactive in nature (i.e., not neoplastic),
and the neoplastic stromal cells that have a plump,
¬broblastic appearance.


482 Bones and Joints


8-21. Conventional osteosarcoma. A. High-grade
osteosarcoma of the upper femur has spread locally
outside the bone. B. Osteosarcoma of the lower
femur in a young child is invading through the epi-
physeal plate (left). (continued on next page)

Bones and Joints 483


8-21. (Continued) C. A wedge-shaped tumor mass
in Codman™s triangle has elevated the periosteum,
and new (nonneoplastic) bone is being laid down
(*). D. Histology of the tumor shows a poorly dif-
ferentiated osteosarcoma. (continued on next page)

484 Bones and Joints

8-21. (Continued) E. Osteosarcoma of the tibia has
undergone a therapy-induced regression, leaving
only necrotic tumor. F. Histology of a postcytotoxic
osteosarcoma shows no recognizable tumor tissue,
only ¬brosis and scanty residual tumor-derived
osteoid (right).

Bones and Joints 485


8-22. Juxtacortical (parosteal) osteosarcoma is a
rare, slowly growing variant of osteosarcoma that
often arises alongside the lower femur and may
encircle the bone. A. Lobulated parosteal sarcoma
that arose posterior to the lower femur in a young
adult. B. Parosteal osteosarcoma is arising from the
outer surface of the bone.

486 Bones and Joints

8-23. A. Well-differentiated, low-grade, intrame-
dullary (intraosseous) osteosarcoma in head of
femur. B. The lesion has a deceptively bland histo-
logic appearance, but it does show both atypia and
an in¬ltrative growth pattern with destruction of
cortical bone.


Bones and Joints 487

8-24. A. Telangiectatic osteosarcoma is destroying
the lower end of the femur and shows a prominent
degree of vascularity and hemorrhage throughout
much of the tumor. B. Unlike an aneurysmal bone
cyst, this osteosarcoma shows malignant osteoblasts
lining the blood-¬lled spaces.


488 Bones and Joints
8-25. Recurrent osteosarcoma at the site of an
implanted prosthesis that replaced the resected por-
tion of the femur in a patient previously treated for
an osteosarcoma.

Bones and Joints 489
8-26. Chondrosarcoma. The cartilaginous nature of
this malignant tumor of cartilage origin is clearly
indicated in the macrophotographs. A. Low-grade
chondrosarcoma within the head of humerus.
B. This chondrosarcoma is extensively destroying
the shaft of the humerus. C. Histologic appearance
of a low-grade chondrosarcoma.



490 Bones and Joints

8-27. Fibrosarcoma of bone. A. This advanced
¬brosarcoma of the humerus has extended into the
soft tissues around the upper end of the bone. B. Typ-
ical histologic appearance of a ¬brosarcoma.


Bones and Joints 491

8-28. Ewing™s sarcoma (primitive neuroectodermal
tumor). A. This tumor has arisen within the marrow
zone of the ¬bula and has spread through the cortex
in areas. B. This tumor is arising in the lower femur,
and the characteristic elevation of the periosteum is
again evident (arrow). C. Histology of Ewing™s sar-
coma shows a neoplasm made up of small, dark-
staining tumor cells having a very uniform appear-
ance and ¬lling the bone marrow space between
bony trabeculae.


492 Bones and Joints
8-29. Malignant ¬brous histiocytoma (MFH) has no
distinguishing naked eye features but does not pro-
duce either bone or cartilage. This MFH is con¬ned
to within the femur but is eroding the cortical bone
from within.

Bones and Joints 493

8-30. A. Angiosarcoma within bones of the ankle is
seen as multiple highly vascularized, lytic lesions.
B. Histology shows irregular vascular spaces lined
by atypical-looking, hobnail-shaped endothelial
cells. The lining cells will stain positively for CD31.


494 Bones and Joints
8-31. Multiple myeloma. A. X-ray shows multiple
punched-out lytic lesions in the shaft of the femur.
B. Plasmacytoma (arrow) in the head of the femur
lies just under the articular cartilage, and adjacent
hemorrhage is present. C. Multiple, rounded lytic
lesions are discernible on the inner aspect of the
skull bones. (continued on next page)


Bones and Joints 495
8-31. (Continued) D. Vertebral bodies contain
metastatic myeloma. E. Histology of a well differ-
entiated myeloma shows a proliferation of atypical-
looking plasma cells, some of which are much
larger than normal.


496 Bones and Joints

8-32. Langerhans cell histiocytosis (histiocytosis
X). The lesion illustrated corresponds to so-called
eosinophilic granuloma of bone. A. Transected rib
shows an expansile, ¬‚eshy, yellow mass that has
destroyed the bone at this site. B. Histology shows
prominent eosinophils against a background of pro-
liferating mononuclear cells (Langerhans cells). On
electron microscopy, the latter cells contain the
characteristic Birbeck granules.

8-33. Chordoma of the sacrum that is spreading
into adjacent soft tissue shows the characteristic
mucoid, gelatinous appearance of this tumor. Chor-
doma is believed to be derived from remnants of the
primitive notochord.

Bones and Joints 497

8-34. Extragnathic adamantinoma is a rare primary
biphasic long bone tumor. Older patients (in the
third decade) usually show the classic histology,
whereas younger patients (younger than 15 years)
usually show an osteo¬brous dysplasia-like
adamantinoma. A. Adamantinoma of the ¬bula and
the tibia is seen in both longitudinal and transverse
sections. The tumor has extended beyond the con-
¬nes of the ¬bula. B. Histology shows a classical
type of adamantinoma with positive staining for
cytokeratin of the epithelial cellular component
within the ¬brous component.

498 Bones and Joints
8-35. Acute myeloid leukemic in¬ltration occupies
the entire femoral bone marrow. No adipose tissue
is noted in the marrow, and solid aggregates of tis-
sue are focally present. In a normal middle-age
adult, the hemopoietic tissue only occupies the
proximal one-third of the femoral bone marrow, and
the rest comprises ¬broadipose tissue only.

Bones and Joints 499

8-36. A. Metastatic thyroid carcinoma in the skull
bone has been surgically resected. B. Histology
shows a well-differentiated follicular carcinoma
that closely mimics normal thyroid tissue in


500 Bones and Joints


8-37. A. Metastatic osteolytic secondary deposits of
breast carcinoma in two vertebral bodies. Prostatic
carcinoma may produce osteosclerotic secondary
deposits. B. Metastatic adenocarcinoma has pro-
duced a pathological fracture of the rib.

8-38. Metastatic chondrosarcoma affecting the toes
of the foot.

Bones and Joints 501

8-39. Osteosarcoma is the most common primary
malignant tumor of the mandible and has a better
prognosis than osteosarcoma of long bones. A.
Odontogenic ¬broblastic osteosarcoma of the
mandible. Note the absent teeth overlying the
tumor. B. Histology of odontogenic ¬broblastic
osteosarcoma showing new bone formation in an
atypical ¬broblastic stroma.


502 Bones and Joints
8-40. Squamous cancer of the buccal mucosa is
invading the surgically resected mandible.

8.41. Camptomelic skeletal dysplasia in a 34-week-
old fetus. A. Note the bowed upper and lower legs
plus the talipes equinovarus of the feet. B. Post-
mortem x-ray of the fetus shows a highly radiolu-
cent skull and bowed femurs and tibias. (continued
on next page)


Bones and Joints 503


8.41. (Continued) C. The skull bones are so thin
and attenuated that the brain is visible through
them. D. Histology con¬rms severe thinning of this
skull bone. E. Femur shows partial absence (arrows)
of greatly thinned cancellous cortical bone plus
compensatory thickening of bony lamellae in the
marrow. F. Healed intrauterine fracture of a rib.

504 Bones and Joints
8-42. Chronically in¬‚amed bursa of hip joint shows
central yellowish discoloration due to old pus cells,
and there is a surrounding paler zone of ¬brosis
with some calci¬cation.

8-43. A. Pigmented villonodular synovitis of the
knee joint. Note the characteristic nodular excres-
cences and infoldings of the synovium. B. Localized
nodular tenosynovitis (giant cell tumor of tendon


Bones and Joints 505


8-44. Gout. A. Lower femur in the knee joint is cov-
ered by chalky white deposits of uric acid. The kid-
ney shows focal coarse scarring probably secondary
to healed pyelonephritis. B. Gouty tophus in soft
tissues contains crystals of uric acid (X).

506 Bones and Joints
8-45. A. Rheumatoid nodules over an interpha-
langeal joint of a patient with rheumatoid arthritis.
B. Histology of a rheumatoid nodule shows central


. 7
( 10)