11. Musculoskeletal System

Question 1

Marked by transient attacks of acute arthritis due to cystallization of monosodium urate within and around joints

Answer 1

Gout

Question 2

Pathognomonic hallmark of gout

Large aggreation of urate crystals surrounded by an intense inflammation of foreign body giant cells

Answer 2

Tophi

Question 3

What are the predisposing factors that contribute to the conversion of asymptomatic hyperuricemia into primary grout

Answer 3

Very high uric acid diet
Chronic alcoholism
Thiazide
Male and postmenopausal female
End-stage renal disease
Lead toxicities
Genetics: X-linked abnormalities of HGPRT

Question 4

What are the common sites of predilection

Answer 4

Ankles and toes

Question 5

Difference between gout and pseudogout based on the type and appearance of crystals

Answer 5

Crystals
G - MSU; P - CDDP
Histologic appearnce
G - neutrophils, negative birefringent crystals; P - positively birefringent

Question 6

Resemble cavernous hemangiomas

Large, dilated vascular spaces that may extend into the underlying adipose tissue

Answer 6

Intramuscular hemangioma

Question 7

May resemble angiosarcoma due to high cellularity with mitotic figures, intraluminal papillary projections, plump endothelial cells, perineural infiltration but no atypia

Answer 7

Intramuscular hemangioma

Question 8

Differentiate intramuscular hemangioma from angiosarcoma in terms of age, location and prognosis

Answer 8

Malignancy: I - benign; A - highly malignant
Age: I - largely congenital, A - older adults
Location: I - intramuscular, A - any sites (skin and soft tissue)
Prognosis: I - self-limited; A - 5 years

Question 9

Highly malignant bone tumor characterized by formation of bone tissue by tumor cells
Fine, lacelike pattern
Very pleomorphic cells, islands of reactive new woven bone

Answer 9

Osteosarcoma

Osteogenic sarcoma

Question 10

Osteosarcoma often arise in the ___

Answer 10

Distal femur, proximal tibia, fibula

Question 11

Proximal triangle shell of reactive bone

Answer 11

Codman triangle

Question 12

Differentiate osteosarcoma from chondrosarcoma on the basis of age, gender, incidence, site of predilection, typical x-ray appearance, histologic features, prognosis

Answer 12

Age:
O - early adolescents, C - middle aged and elderly
Gender:
O, C - M > F
Incidence:
O - bimodal age distribution, C - 4th to 6th decades
Sites of predilection:
O - distal femur, metaphyses; C - axial skeleton
X-ray appearance
O - Codman triangle, C - Ring-shaped and popcorn like calcification
Histologic feature:
O - polygonal, splindle; C - pronounced atypia
Prognosis:
O > C

Question 13

Benign tumor of fat

Most common soft tissue tumor of adulthood

Answer 13

Lipoma

Question 14

Classification of lipoma

Answer 14

Conventional lipoma
Fibrolipoma
Angiolipoma
Spindle cell lipoma
Myelolipoma

Question 15

Most common subtype of lipoma

Well encapsulated mass of mature adipocytes

Answer 15

Conventional lipoma

Question 16

Differentiate lipoma from liposarcoma grossly and histologically

Answer 16

Gross:
L - bright yellow homogenous fat with fine fibrous capsule; shoulder, neck, trunk, arms
S - fatty cancer on thigh, groin, back of abdomen
Histology
L - well-differentiated encapsulated mass of mature adipocytes
S - well-differentiated (normal adiposcytes), myxoid (abundant mucin deposition), pleomorphic liposarcoma (frankly atypical mesenchymal cells)

Question 17

Aggressive, largest category of adult sarcomas
Sheets of large, anaplastic spindle to polygonal cells with hyperchromatic irregular nuclei
Necrosis and hemorrhage are common

Answer 17

Malignant fibrous histiocytoma/ Undifferentiated pleomorphic sarcoma