1. Pathology of the Soft Tissues & Nerves
Arlene L. Santos, M.D.
SY 10-11

2. Pathology of the Soft Tissues

3. I. Fatty Tumors
II. Fibrous Tumors & Tumor-like Lesions
III. Fibrohistiocytic Tumors
IV. Tumors of the Skeletal Muscle

4. V. Tumors of the Smooth Muscle
VI. Tumors of the Skeletal Muscle

6. I. Fatty Tumors

7. A. Lipoma

8. A benign tumor of fat
The most common soft tissue tumor of adulthood
Age group commonly affected: middle adulthood

9. Pathologic Findings- Conventional Lipoma
Single or multiple subcutaneous growths that are soft, rounded or lobulated & movable against overlying skin
A well-encapsulated mass composed of sheets of mature fat cells
Arises in subcutis of proximal extremities & trunk

10. Lipoma

11. Angiolipoma

13. B. Liposarcoma

14. A malignant tumor of fat
Age group commonly affected: y/o
Usually arises in the deep soft tissues of the proximal extremities & retroperitonemum

15. Liposarcoma

16. Histopathology Variants depending on morphologic features:
1) Well-differentiated
2) Myxoid/Round cell
3) Pleomorphic

17. Histopathology-Well differentiated Liposarcoma
Tumor cells are recognized as lipocytes
Tumor cells contain supernumerary rings & giant rod chromosomes

18. Histopathology-Myxoid & Pleomorphic Variants
Tumor contains lipoblasts (mimic fetal fat cells)

19. Liposarcoma

20. Myxoid Liposarcoma

22. II. Fibrous Tumors & Tumor-like Lesions

23. A. Fibromatoses

24. 1) Superficial Fibromatoses (Palmar,
Plantar & Penile Fibromatoses)
2) Deep-seated Fibromatoses (Desmoid
Tumors)

25. A1. Superficial Fibromatosis (Palmar, Plantar & Penile Fibromatoses)

26. Characterized by nodular or poorly defined broad fascicles of fibroblasts surrounded by abundant dense collagen
Male predominance

27. Fibromatosis

28. Variants of Superficial Fibromatoses
1. Palmar fibromatosis
2. Plantar fibromatosis
3. Penile fibromatosis

29. Palmar fibromatosis
Also known as Dupuytren contracture

30. Palmar Fibromatosis Irregular thickening of palmar fascia ↓
W/ attachment to overlying skin
Puckering & dimpling of skin
↓ After some time
Progressive flexion contracture of 4th & 5th fingers of hand

31. Plantar Fibromatosis Irregular or nodular thickening of plantar fascia
Flexion contractures are uncommon

32. Penile Fibromatoses Also known as Peyronie disease
Presents as a palpable induration or mass on dorsolateral aspect of the penis

33. Penile Fibromatosis May cause: 1) Abnormal curvature of the shaft
2) Constriction of the urethra
3) Both

35. A2. Deep-seated Fibromatosis (Desmoid Tumors)

36. Present as large, infiltrative masses that frequently recur after incomplete excision
Composed of well-differentiated fibroblasts
Age predilection: At any age but commonly in the teens-30 y/o

37. Types of Deep-setaed Fibromatosis
1) Extra-abdominal
2) Abdominal
3) Intra-abdominal
W/ similar gross & histologic features

38. Gross Pathology Gray-white, firm, poorly demarcated masses
Rubbery & tough
Infiltrative

39. Extra-abdominal Fibromatosis-Gross Pathology
Sites of Origin: Musculature of:
1) Shoulder
2) Chest wall
3) Back
4) Thigh

40. Abdominal Fibromatosis-Gross Pathology
Site of Origin: Musculoaponeurotic structures of anterior abdominal wall in ♀ during or after pregnancy

41. Intra-abdominal Fibromatosis
Site: Mesentery or pelvic walls in individuals w/ familial adenomatous polyposis (Gardner syndrome)
Mutations in APC or β-catenin genes

42. Histopathology
Plump fibroblasts arranged in broad sweeping fascicles w/c infiltrate the surrounding tissue

44. B. Fibrosarcoma

45. Gross Pathology Site: deep soft tissues of extremities
Unencapsulated, infiltrative, soft, fish-flesh masses
(+) hemorrhage & necrosis

46. Histopathology All degrees of differentiation
Resemble cellular fibromatosis
MTC arranged in a herringbone pattern
Tumors w/ architectural disarray, pleomorphism, mitotic figures & necrosis

47. Fibrosarcoma

48. Pleomorphic Fibrosarcoma

50. III. Fibrohistiocytic Tumors

51. A. Benign Fibrous Histiocytoma

52. Benign tumor of the soft tissue w/ a fibrohistiocytic origin

53. Gross Pathology
Firm, small, mobile nodule

54. Histopathology Variable mixture of : -Histiocyte-like cells
▪ Some foamy
▪ Others multinucleated
▪ Others containing hemosiderin
-Fibroblast-like cells

55. Histopathology Maybe: -Extremely cellular
Mitotic activity usually scanty or absent

57. B. Malignant Fibrous Histiocytoma

58. Phenotype of TC: fibroblastic
Now: dropped as a diagnostic entity

59. Histopathology Soft tissue tumors characterized by:
-Marked cytologic pleomorphism
-Bizarre multinucleate cells
-Storiform architecture

61. IV. Tumors of the Skeletal Muscle

62. A. Rhabdomyosarcoma

63. Types
1) Embryonal
2) Alveolar
3) Pleomorphic

64. Histopathology Rhabdomyoblast -Diagnostic cell in all types
-Eccentric eosinophilic granular
cytoplasm
-Round or elongate
-(+)Cross-striations

65. Rhabdomyosarcoma

66. Embryonal Rhabdomyosarcoma
Variants:
1) Sarcoma botryoides
2) Spindle cell type
3)Anaplastic type
Age predilection: < 10 y/o

67. Embryonal Rhabdomyosarcoma
Sites of Origin:
1) Nasal cavity
2) Orbit
3) Middle ear
4) Prostate
5) Paratesticular region

68. Sarcoma Botryoides Develops in wall of mucosal-lined structures s.a. :
-Nasopharynx
-Common bile duct
-Bladder
-Vagina
Histopathology:Cambium layer

69. Alveolar Rhabdomyosarcoma –Gross Pathology
Site of origin: deep musculature of extremities

70. Alveolar Rhabdomyosarcoma-Histopathology
Fibrous septae w/c divide cell into clusters or aggregates (pulmonary alveoli)
TC-moderate size & w/ little cytoplasm
Center- dyscohesive
-Periphery-TC line the septae

71. Alveolar Rhabdomyosarcoma

72. Pleomorphic Rhabdomyosarcoma-Gross Pathology
Site of origin: Deep soft tissue of adults

73. Pleomorphic Rhabdomyosarcoma-Histopathology
TC-large, maybe multinucleated, bizarre & eosinophilic

75. V. Tumors of the Smooth Muscle

76. A. Leiomyoma

77. A benign stromal tumor mainly composed of mature smooth muscle bundles

78. Types
1) Cutaneous
2) Genital
3) Vascular

79. Gross Pathology Yellow-yellowish pink Sharply circumscribed
Fairly firm

80. Leiomyoma

81. Histopathology Intersecting fascicles of smooth muscle cells:
-Encircle vascular lumina lined by
normal endothelial cells
No:
-Mitotic activity
-Necrosis
-Hemorrhage

82. Leiomyoma

84. B. Leiomyosarcoma

85. A malignant mesenchymal tumor w/ predominantly smooth muscle differentiation
Typically :
-Adults
-Elderly

86. Gross Pathology Location: anywhere but mostly in extremities
May arise from walls of arteries, veins, venules & arterioles

87. Gross Pathology Maybe as well-circumscribed as leiomyoma but: -Larger
-Softer
-Tendency for:
▪ Tumor necrosis
▪ Hemorrhage
▪ Cystic degeneration

88. Leiomyosarcoma

89. Histopathology Pattern of Growth: -Predominantly fascicular
-Tumor bundles intersect at wide angles

90. Histopathology Cellular features: -Elongated blunt-ended nuclei
-Acidophilic fibrillary cytoplasm

91. Leiomyosarcoma

93. VI. Synovial Sarcoma

94. Cell of origin is unclear
Age predilection: Mostly y/o

95. Gross Pathology Location: 1) Deep soft tissue (frequently the lower
extremity)
2) Head & Neck
3) Viscera

96. Histopathology
Maybe monophasic or biphasic
(+) Calcified concretions

97. Monophasic Synovial Sarcoma
Spindle cells only
Epithelial cells only

98. Biphasic Synovial Sarcoma
Both epithelial-like cells & mesenchymal-like cells
Epithelial cells:
-Cuboidal to columnar
-Pattern: form glands, cords or
aggregates

99. Biphasic Synovial Sarcoma
Spindle cells:
-Form fascicles that surround epithelial
cells

100. Biphasic Synovial Sarcoma

102. Pathology of the Nerves

103. Peripheral Nerve Sheath Tumors
A. Schwannoma
B. Neurofibroma
C. Malignant Peripheral Nerve Sheath
Tumor

104. A. Schwannoma

105. Usually adulthood
Location:
-Cerebellopontine angle
▪Nearly all produce hearing loss
▪Bilateral eighth nerve examples are
defining feature of neurofibromatosis
type 2

106. Location:
-Can present as interventricular masses
-May involve cranial nerves other than
acoustic

107. Gross Pathology Cerebellopontine angle:
-Nearly all originate in vestibular branch
of cranial nerve VII (Acoustic
schwannoma or neuroma)

108. Gross Pathology Lumbosacral spinal extramedullary space
-Predilection for sensory divisions,
typically the posterior roots
-Often “dumbbell” configuration

109. Gross Pathology NF-2-associated variant:
-Often multilobulated growth pattern

110. Schwannoma

111. Histopathology Antoni A and B structure Verocay bodies
Infiltration by foamy macrophages
Vascular hyalinization

112. Schwannoma

114. B. Neurofibroma

115. Most are manifestations of neurofibromatosis type 1

116. Types
1) Cutaneous Neurofibroma
2) Plexiform Neurofibroma

117. Cutaneous Neurofibroma-Gross Pathology
Location: demis & subcutaneous fat
Unencapsulated masses

118. Cutaneous Neurofibroma-Histopathology
Spindle cells
W/ a collagenous stroma w/ little myxoid material

119. Plexiform Neurofibroma-Gross Pathology
Site of origin: anywhere along a nerve
Affected nerves are irregularly expanded

120. Plexiform Neurofibroma-Histopathology
Cell types present:
-Schwann cells
-Fibroblastic sells
-Inflammatory cells
Loose myxoid stroma w/ areas containing collagen bundles

121. Plexiform Neurofibroma

123. C. Malignant Peripheral Nerve Sheath Tumor

124. Originate in:
-Cranial nerve roots
-Spinal Nerve roots
May arise in:
-Cerebral parenchyma
-Lateral ventricle

125. Often originate in neurofibroma

126. Histopathology Variable
Majority - fibrosarcomatous, herringbone pattern is detectable focally
Densely cellular tumor
Frequent mitotic figures

127. Histopathology
Geographic necrosis

128. Histopathology
Cytologic features:
-Elongated nuclei w/ tapered ends

129. MPNST

130. MPNST