Tumors of bone and soft tissue

Question 1

X-ray

Answer 1

purpose is to localize and assist in the biopsy of a lesion

- Osseous lesions must be 40-50% destructive before they can be seen on plain films

Question 2

CT scan

Answer 2

good evaluation of bone, but not of soft tissue

Question 3

MRI

Answer 3

good evaluation of soft tissue but not bone

Question 4

Bone tumors

Answer 4

osteoma, osteoid osteoma, osteoblastoma, osteosarcoma

Question 5

Osteoma

Answer 5

1. usually benign tumors that grow on another piece of bone (typically the skull)
   a. Usually incidentally identified on X-ray as a dense radioopaquue circumscribed mass
   b. Multiple osteomas are seen in the setting of Gardner syndrome (familial colorectal polyposis)
   c. Histologically bone is a little thick but it is relatively normal

Question 6

Osteoid osteoma

Answer 6

a. 75% occur between 5-25 years, 2:1 to 3:1 M:F ratio
b. Any bone; common is long tubular bones – diaphyseal – cortical
c. painful lesion – relieved by aspirin; pain most common at night
i. pain is because increased nocturnal prostaglandin-mediated inflammation
d. X-ray central lucent nidus (

Question 7

Osteoblastoma

Answer 7

a. Occurs between 10-35 years
b. Axial skeleton – spine common
c. Pain NOT relieved by aspirin
d. X-ray is not specific – mimics other lesion
e. Size is > 2 cm – histology identical to osteoid
f. Complete excision is curative – rare local aggressiveness

Question 8

Osteosarcoma

Answer 8

a. Most common primary malignant tumor of bone
i. Seen in metaphysis of long bones, often around the knee (distal femur, proximal tibia)
b. Bimodal age distribution, 2nd decade and 6th decade
c. Aggressive, metastasizes to lungs (most common), liver, and skeletal system
d. Treat with chemotherapy followed by a limb sparing resection and post operative chemotherapy -> greater than 90% chemotherapy response/necrosis is prognostically significant
i. 5 year survival is 60-70%
e. Histologically: hyperchromatic tumor cells, mitotic activity is high, osteoid formation, necrosis
f. On X-rays can see sunburst pattern or Codman triangle - bone lesion grows faster than new periosteum can beossified. Only the periosteum at the very margin of the lesion has time to ossify creating a triangular lip of new bone.

Question 9

Cartilage forming tumors

Answer 9

Osteochondroma, enchondroma, chondrosarcoma

Question 10

Osteochondroma

Answer 10

1. Most common benign tumor (an exostosis of the bone)
   a. 85% solitary, the remainder are part of the multiple hereditary exostosis syndrome
   b. Develops only in bone with endochondral ossification, usually near the ends
   c. Tumors are mature bony projections on the surface of bone (seen on X-ray); have a cartilaginous cap
   d. Histologically: tumor can be 1-20 cm, cartilage undergoes endochondral ossification, resulting in the bone in the center of the lesion

Question 11

Enchondroma

Answer 11

a. Neoplasm consisting of mature hyaline cartilage at the metaphyseal ends of tubular bones (common in hands and feet) in the medullary cavity
b. X-rays shows radiolucent lesions with ring like calcification
c. Histologically: look similar to normal cartilage, except in the digits
d. Ollier’s disease – multiple enchondromas
e. Mafucci’s syndrome – endochondromas and soft tissue hemangiomas

Question 12

Chondrosarcoma

Answer 12

2nd most common primary malignant tumor of bone

a. Affects 40 and older, males are more common
b. Dull aching pain waking the patient at night
c. Malignant tumor of cartilage, in the pelvis, ribs, shoulder, or long bones
d. Survival and tumor progression are based on grade
e. Histologically: hypercellular lesion containing numerous malignant chondrocytes in a pale grey cartilaginous background
f. Treatment: surgery

Question 13

Fibrous dysplasia

Answer 13

a. Benign lesion of bone made up of fibro-osseous tissue proliferating in an irregular manner; some think of as localized developmental arrest
i. Rare transformation to sarcoma
b. X-ray shows lucent lesion with “ground glass” appearance
c. Histologically: fibrous stroma containing osteoid and woven bone – “Chinese letters”or the letter “C”
d. McCune-Albright syndrome (3% of all cases)
i. Polystotic FD (multiple bones involved)
ii. Precocious puberty (early puberty, before early 10 years old)
iii. Flat maculopapular spots (café-au-lait spots)

Question 14

Tumor of uncertain histogenesis

Answer 14

Ewing sarcoma, Giant cell tumor

Question 15

Ewing sarcoma

Answer 15

a. Affects young children, peak incidence second decade
b. Permeative with “onion-skin” periosteal reaction
c. Histologically: sheets of small round blue cells, not much larger than lymphocytes make up the lesion, scant cytoplasm with white halos due to glycogen production, necrosis may be prominent
d. Characterized by unique chromosomal translocations
i. T(11;22)(q24;q12)(EWS-FLI-3)
e. CD99
F. Derived from neuroectoderm

Question 16

Giant cell tumor

Answer 16

a. ONLY develops in skeletally mature individuals (20-40 years)
b. Benign but locally aggressive tumor, most commonly in long bones at the epiphysis (only tumor at this site)
c. X-rays shows non-sclerotic border
d. Histology: uniform distribution of giant cells with interspersed mononuclear cells with similar nuclei
e. Treatment: resection, no radiation of the tumors because of risk for sarcoma
i. Notorious for reoccurrence, 35% locally

Question 17

Where are most soft tissue tumors location?

Ratio of benign to malignant?

Answer 17

100:1 benign to malignant
o 40% lower extremity
o 20% upper extremity

Question 18

Lipoma

Answer 18

1. Most common soft tissue tumor of adult
2. Conventional lipomas show genetic rearrangements in chromosome 12q13-15
3. Simple excision is curative

Question 19

Liposarcoma

Answer 19

1. One of the most common sarcomas of adulthood (40-60s)
2. Well differentiated liposarcoma contain mutations in MDM2 gene on 12q14-q15
3. Well differentiated liposarcoma has low recurrence rate (especially in the extremities) differently depending on where the tumor is
   a. Most other liposarcomas act malignantly
4. Histologically: see lipoblasts – mimic fetal fat cells

Question 20

Fibrous tumors and tumor like lesions

Answer 20

Nodular fasciitis, Superficial fibromatoses, Deep fibromatoses, Fibrosarcoma

Question 21

Nodular fasciitis

Answer 21

Most common of the reactive pseudosarcomas (will shrink away if left alone)

a. Most often occurs in adults on the forearm, chest, and back
b. Histologically: cellular lesion with plump myofibroblasts in an often myxoid stroma (lymphocytes and extravasated blood cells)

Question 22

Superficial fibromatoses

Answer 22

a. Include palmar (Dupuytren contracture), plantar, and penile (Peyronie disease) fibromatoses
b. All characterized by nodular thickenings of the affected area
c. Some recur after excision, pariculary the plmar variant
d. Histologically: pointy on the end and elongated in the middle -> “spindle shaped”, not mitotically active

Question 23

Deep fibromatoses

Answer 23

a. Present as large infiltrative masses, mostly commonly abdominal, and recur after excision, but the cells appear benign
i. Abdominal variant most commonly seen in women after C-section
1. Associated with Gardner syndrome
b. Grossly: tumors appear as grey/white, firm, poorly demarcated masses -> high reoccurrence rate
c. Histologically: composed of plump benign fibroblasts arranged in broad fascicles that invade the surrounding tissue
i. Wrap around skeletal muscle

Question 24

Fibrosarcoma

Answer 24

a. Occur anywhere in the body -> diagnosis of exclusion
b. Histologically: spindle cells grow in a herringbone fashion most commonly, although more pleomorphic examples have been cited

Question 25

Fibrohistiocytic tumors (skin)

Answer 25

Benign fibrous histiocytoma, Pleomorphic undifferentiated sarcoma (malignant fibrous histiocytoma)

Question 26

Benign fibrous histiocytoma

Answer 26

a. Presents in mid-adults as firm small nodule on the skin
i. Lesion is often pigmented
b. Histologically: crossing spindle cells in fascicles -> “spokes on a bicycle”

Question 27

Pleomorphic undifferentiated sarcoma (malignant fibrous histiocytoma)

Answer 27

a. Grossly, grey/white fleshy tumor with infiltrative margins -> “fish flesh”
b. Diagnosis of exclusion

Question 28

Rhabdomyosarcoma (skeletal muscle)

Answer 28

a. Most common soft tissue sarcoma of childhood and adolescence; usually presents before 20 years of age
b. Most occur in the head and neck or genitourinary tract
c. Only appear in relation to skeletal muscle in the extremities

Question 29

Embryonal rhabdomyosarcoma – most common (60%)

Answer 29

Strap cells – rhabomyoblasts that exhibit striation, reflecting sarcomere formation and differentiation -> more strap cells = better prognosis

Question 30

Aveolar rhadomyosarcoma – 20%

Answer 30

i. arly to middle adolescence
ii. Histologically: tumor is traversed by fibrous septa meshwork which allows a resemblance to alveoli of lung; center cells are discohesive, peripheral cells cling to septae

Question 31

Pleomorphic rhabdomyosarcoma

Answer 31

i. Seen more often see in adults
ii. Histologically: characterized by numerous large, sometimes multinucleated bizarre eosinophilic tumor cells
iii. Can resemble pleomorphic undifferentiated sarcoma but pleomorphic rhabdoymsarcoma has muscle differentiation

Question 32

Leiomyoma

Answer 32

a. Benign smooth muscle tumors, most commonly seen in the uterus
b. Hereditary leiomyomatosis and renal cell carcinoma syndrome
c. Histologically: composed of fascicles of spindle cells that tend to intersect each other at right angles

Question 33

Leiomyosarcoma

Answer 33

a. Usually in soft tissues of the extremities and retroperitoneum
b. Special subgroup exists in HIV patients and occurs in unusual sites such as the liver
c. Histologically: cigar shaped nuclei arranged in interweaving fascicles

Question 34

Synovial sarcoma

Answer 34

a. Majority arise in the deep soft tissues and 60-70% occur in the thigh
b. Histologically
i. Monophasic – compromised only of spindle cells or only of epithelioid
ii. Biphasic – mixture of both
1. Make glands (like adenocarcinoma), in background has spindle cells
c. Characteristic translocation: t(X;18)