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4. HDS Multisystem > Soft Tissue Pathology > Flashcards

Soft Tissue Pathology Flashcards

1
Q

Soft Tissues

A

Non-epithelial extraskeletal tissues except CNS and reticuloendothelial system.

Mesodermal in origin:

Fat, fibrous tissue, smooth and skeletal muscle, blood vessels

and lymphatics

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2
Q

Soft Tissue

Tumors

A
  • Uncommon
  • Most are benign (5:1)
  • Often present diagnostic difficulties
  • Frequently located deep in the extremities and present as a painless mass
  • ~ 1,600 deaths/year from soft tissue tumors in USA
  • Most are in children and young adults
  • 5th leading cause of death from cancer in children
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3
Q

WHO Classification

A

50 subtypes of sarcoma:

  • Adipocytic
  • Fibroblastic/myofibroblastic
  • Fibrohistiocytic
  • Smooth muscle
  • Pericytic (perivascular)
  • Skeletal muscle
  • Vascular
  • Chondro-osseous
  • Tumours of uncertain differentiation
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4
Q

Biological Potential

A
  • Benign
    • Rarely recur and if so, in a non-destructive fashion
    • < 1/50,000 metastasize
      • Unpredictable based on histology
    • Ex. cutaneous fibrous histiocytoma
  • Intermediate (locally aggressive)
    • Often recur
    • Infiltrative and locally destructive
      • Ex. desmoid fibromatosis
    • Very low metastatic potential
  • Intermediate (rarely metastasizing)
    • Locally aggressive with < 2% metastases
    • Ex. plexiform fibrohistiocytic tumor
  • Malignant
    • Locally destructive growth
    • Potential for recurrence
      • Recurrences may be of higher grade and greater potential for spread
    • Significant risk of distant metastasis (20–100%)
      • Low grade sarcomas may have only 2–10% rate of metastasis
      • Typically spread via blood to lungs
      • Does not usually invade lymph nodes
    • Ex. myxofibrosarcoma, leiomyosarcoma
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5
Q

Sarcomagenesis

A

Not clearly understood:

  • Progressive pattern not well established
    • Unlike epithelial neoplasms: in situ precursor lesions ⇒ dysplasia ⇒ malignancy
  • Often do not arise from their corresponding mature adult tissue
    • Progenitor cell remains unclear
  • Histogenesis or cell of origin replaced by differentiation
    • Rhabdomyosarcoma dx by presence of primitive skeletal muscle cells and IHC of muscle markers
      • Many tumors arise in sites where skeletal muscle is sparse or absent
    • No evidence that liposarcomas either originate from mature fat or represent malignant transformation of lipomas
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6
Q

Histologic Grading

A

3 grade system

  • Mitotic index & tumor necrosis ⇒ most important features
  • Indicates probability of metastasis and overall survival
    • High grade tumors usu. more responsive to chemotherapy
  • Does NOT predict recurrence (mainly related to surgical margins)
  • Only for untreated primary soft tissue sarcomas
  • Not applicable for all sarcomas
    • E.g. MPNST, angiosarcoma, extraskeletal myxoid chondrosarcoma, alveolar soft part sarcoma, clear cell sarcoma and epithelioid sarcoma
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7
Q

Sarcomas

Clinical Pearls

A
  • Some benign lesions may not be well-delineated
  • Often appear well-circumscribed grossly but almost always infiltrate adjacent tissue at the microscopic level
  • No true capsule exists
  • Any deeply seated soft tissue tumor should be considered malignant until proven otherwise
  • Metastasize via bloodstream (hematogenous spread)
  • Most have a predilection for a certain anatomic region and age group
  • Histomorphologic pattern and cellularity may vary in different areas
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8
Q

Fibrous Tumor-like Conditions

A
  • Reactive pseudosarcomatous lesions
    • Nodular fasciitis
    • Myositis ossificans
  • Fibromatoses
    • Superficial fibromatoses
      • Palmar (Dupuytren contracture), knuckle pads, plantar, penile (Peyronie disease)
    • Deep fibromatoses (Desmoid tumor)
      • Extra-abdominal
      • Abdominal (mesenteric)
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9
Q

Nodular Fasciitis

Overview

A

Reactive pseudosarcomatous lesion:

  • Most common pseudosarcoma
  • Adults
  • Locations:
    • Volar aspect of forearm
    • Chest
    • Back
  • Solitary, rapidly growing (within weeks), sometimes painful mass
  • Preceding trauma reported in 10-15% of cases
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10
Q

Nodular Fasciitis

Characteristics

A
  • Plump fibroblasts (myofibroblasts)
  • Myxoid to fibrous background
    • Collagenization progresses with time
    • Extravasated RBCs and microcysts are common
    • Lymphocytes and giant cells often present
  • Mitotic rate is high (no atypical mitotic figures)
  • Typical myofibroblastic IHC:
    • SMA and calponin ⊕
    • Desmin and caldesmon ⊖
  • Recent data indicates fusion of non-muscle myosin (MYH9) gene with USP6 oncogene in NF ⇒ suggests that it is a benign self-limiting neoplasm
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11
Q

Myositis Ossificans

A

Reactive pseudosarcomatous lesion:

  • Athletic adolescents and young adults
  • 50% of cases report previous trauma
  • Early phase:
    • Swollen and painful
    • Appearance similar to nodular fasciitis
  • Middle phase (within three weeks):
    • Less painful, firmer
    • Zonation ⇒ bone trabeculae at periphery and immature fibroblasts in center
  • Late phase:
    • Painless, hard, well-circumscribed mass
    • Complete bone metaplasia
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12
Q

Fibromatosis

Overview

A

Fibrous overgrowths of dermal and subcutaneous connective tissue develop tumours called fibromas.

Are usually benign.

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13
Q

Superficial Fibromatoses

A
  • Palmar ⇒ Dupuytren contracture
  • Knuckle pads
  • Plantar ⇒ Ledderhose disease
  • Penile ⇒ Peyronie disease
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14
Q

Deep Fibromatoses (Desmoid Tumors)

Overview

A
  • No metastases
  • Infiltrative pattern
  • Local destruction
  • Therapy:
    • Complete and wide excision
      • Recurrence rate 25-80%
    • Radiation therapy
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15
Q

Deep Fibromatoses

Types

A

Abdominal vs Extra-abdominal

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16
Q

Gardner Syndrome

A

Associated pathologies include:

  • Familial adenomatous polyposis (FAP)
  • Osteomas
  • Dental anomalies
  • Epidermal inclusion cysts
  • Colorectal carcinoma
  • Desmoid tumor
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17
Q

Turcot Syndrome

A

Associated pathologies include:

  • Familial adenomatous polyposis (FAP)
  • Desmoid tumor
  • Medulloblastoma
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18
Q

Fibrohistiocytic Tumors

A
  • Benign
    • Benign Fibrohistiocytoma
      • Dermatofibroma (DF)
      • Sclerosing hemangioma
      • Histiocytoma
  • Malignant
    • Dermatofibrosarcoma protruberans (DFSP)
    • Malignant fibrohistiocytoma (MFH)
      • Storiform
      • Pleomorphic
      • Myxoid
      • Giant cell
      • Inflammatory
      • Angiomatoid
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19
Q

Dermatofibroma

A

“Benign Fibrohistiocytoma”

  • Dermis and subcutanous tissue
  • Slow growing, painless, mobile nodule
  • Small (up to 1 cm) and well-circumscribed
  • Bland spindle cells with delicate cytoplasm
  • Storiform pattern
  • Collagen production
  • No mitosis, necrosis, atypia
20
Q

Dermatofibrosarcoma Protuberans

(DFSP)

A
  • Low grade sarcoma
  • Young adults
  • Dermis and subcutis of trunk and extremities
  • Recurrence in 30% of cases
  • Metastases are rare (<5%):
    • Lung, lymph nodes
    • More frequent after multiple recurrences
  • Storiform pattern
  • Honeycomb pattern of infiltration into surrounding adipose tissue
21
Q

Fibrosarcoma

A
  • Adults 40-60 y/o
  • Locations:
    • Deep soft tissue of lower extremities, upper extremities, trunk, head and neck
    • Subcutis if associated with DFSP, cicatrix, burn, or radiation therapy history
  • Usu. a dx of exclusion
  • Many sarcomas can have FS-like growth patterns
  • Histology:
    • Solid growth of hyperchromatic, malignant spindle cells
    • Very cellular
    • Herringbone pattern
22
Q

Malignant Fibrohistiocytoma (MFH)

Overview

A
  • Most common sarcoma of adults
  • Location:
    • Musculature of proximal extremities
    • Retroperitoneum
    • Cutaneous variant ⇒ Atypical fibroxanthoma
  • Cell of origin is not identified (IT IS NOT HISTIOCYTIC)
  • Can represent the pleomorphic variant of many sarcomas
  • Aggressive tumors
    • Recurs unless widely excised
    • Metastatic rate: 30-50% (except cutaneous)
      • Cutaneous form (atypical fibroxanthoma) very rarely disseminates
23
Q

Malignant Fibrohistiocytoma

Subtypes

A

Subtype is not significant except for angiomatoid type (indolent)

  • Storiform
  • Pleomorphic
  • Undifferentiated Pleomorphic Sarcoma
  • Myxoid
  • Giant cell
    • Giant Cell Rich Osteosarcoma
    • Giant Cell Tumor (Osteoclastoma) of Soft Tissue
    • Leiomyosarcoma with Osteoclastic Giant Cell Reaction
    • Giant Cell Rich Anaplastic Carcinoma
  • Inflammatory
  • Dedifferentiated Liposarcoma with prominent neutrophilic infiltrate
  • Angiomatoid (adolescent, young adult; indolent)
24
Q

Lipomatous Tumors

A
  • Benign
    • Lipoma
      • Spindle cell
      • Angiolipoma
      • Intramuscular
    • Lipomatosis
    • Lipoblastoma
  • Malignant
    • Liposarcoma
25
Q

Lipoma

Overview

A
  • Most common primary soft tissue tumor of adult
  • Well-encapsulated mass of lobulated adipose tissue
  • Microscopically shows lobules of mature adipose tissue (adipocytes and thin strings of connective tissue and capillaries)
  • Clinically significant subtypes:
    • Spindle-cell
    • Angiolipoma
    • Intramuscular
26
Q

Spindle Cell Lipoma

A
  • Middle aged (45-60 y/o) male
  • Lipomatous tumor of the back or the posterior neck
  • Gross: lobulated adipose tissue
  • Microscopic: abundant spindle cells, may be very cellular and show some atypia
27
Q

Angiolipoma

A

Painful subcutaneous mass in forearm of young adult

Vascular channels with microthrombi

28
Q

Intramuscular Lipoma

A

Lipomatous growth within skeletal muscle fibers

Diagnostic problem to differentiate from liposarcomas involving skeletal muscle

29
Q

Lipomatosis

A

Systemic disorder

Painless symmetrical diffuse deposits of fat beneath the skin of the neck, upper trunk, arms and legs

Thought to be genetic but mode of inheritance is uncertain

30
Q

Lipoblastoma / Lipoblastomatosis

A
  • Children < 3 y/o
  • Upper or lower limb
  • Males 2x > female
  • Localized form:
    • Lipoblastoma
      • Subcutis
  • Diffuse form:
    • Lipoblastomatosis
      • Subcutis and skeletal muscle
      • Recurrences
      • Maturation to adult fat
31
Q

Liposarcoma

Overview

A

Malignant fatty tumor

Can occur in fat cells in any part of the body

Most cases occur in the muscles of the limbs or abdomen

32
Q

Well-differentiated Liposarcoma

A
  • Lipoma-like (lipoma with atypical cells)
  • Sclerosing-spindle cell
  • Dedifferentiated (WD with areas of Fibrosarcoma and/or MFH)
33
Q

Dedifferentiated Liposarcoma

A
  • Areas of transformation into Fibrosarcoma or Malignant Fibrohistiocytoma (MFH)
  • Occurs more frequently in the retroperitoneum (local aggressiveness)
  • Can also happen in the extremities
  • Usu. after multiple recurrences
  • May then be associated with metastatic disease (lung)
34
Q

Myxoid Liposarcoma

A

Gelatinous, lipomatous tumor

  • Low grade
    • Lipoblasts
    • Chicken-wire vessels
    • Myxoid background
  • High grade
    • Round cell ⇒ Low grade plus solid areas of round cells with scant cytoplasm)
35
Q

Pleomorphic Liposarcoma

A
  • High grade sarcoma with high metastatic potential
  • Similar to pleomorphic MFH
  • Deep soft tissue of limbs and limb girdle
  • Very aggressive
  • Very poor prognosis
36
Q

Liposarcoma Subtypes

Table

A
37
Q

Striated Muscle Tumors

A
  • Benign
    • Rhabdomyoma
      • Heart (children)
  • Malignant
    • Rhabdomyosarcoma
38
Q

Rhabdomyosarcoma

Overview

A
  • Malignant tumor of skeletal muscle origin
  • Most common soft tissue sarcoma of childhood and adolescence (< 20 y/o)
  • Location:
    • Head and neck
    • Genitourinary tract
    • Extremities
  • Aggressive tumors
    • 65% of children are cured
    • Adults have worse prognosis
  • Treatment:
    • Surgery
    • Chemotherapy
    • Radiation therapy
  • Subtypes:
    • Embryonal
      • Botrioid (better prognosis)
      • Spindle cell
    • Pleomorphic
    • Alveolar (worse prognosis)
  • Immunohistochemistry:
    • Desmin, Myoglobin, Myogenin ⊕
39
Q

Embryonal Rhabdomyosarcoma

A
  • 66% of all RMS
  • < 10 y/o
  • Location:
    • Nasal cavities, orbit, middle ear, prostate, paratesticular region
    • Botrioid: hollow organs
      • Vagina, bladder, nasopharynx, biliary tract
40
Q

Alveolar Rhabdomyosarcoma

A
  • Adolescence (10-25 y/o) peak
  • Deep musculature of extremities
  • Small cells with high N/C ratio
  • Pseudoalveolar pattern
  • Worse prognosis
  • Associated with a translocation mutation ⇒ t (2;13) or t (1;13)
41
Q

Smooth Muscle Tumors

A

Benign ⇒ Leiomyoma

Malignant ⇒ Leiomyosarcoma

42
Q

Leiomyoma

A

Benign smooth muscle tumors

  • Histology:
    • Fascicles of spindle cells intersecting at 90°
    • Cigar shaped nuclei
    • Fibrillary cytoplasm
    • No mitoses, atypia, necrosis
  • Immunohistochemistry:
    • Desmin, Actin, Vimentin ⊕
  • Location:
    • Skin and subcutaneous tissue (somatic soft tissue)
      • Erectores pilorum
      • Erector muscle of nipple
      • Media of blood vessel
    • Deep soft tissue
      • Retroperitoneum
      • Omentum
      • Mesentery
      • Broad ligament
43
Q

Intravenous Leiomyomatosis

(IVL)

A

Benign smooth muscle tumor of the uterus that grows within the veins but does not invade the surrounding tissue

44
Q

Leiomyosarcoma

Overview

A
  • Malignant tumor of smooth muscle origin
  • Locations:
    • Cutaneous
    • Female genital tract
    • Deep soft tissue of extremities
    • Retroperitoneum
  • 10-20% of all sarcomas
  • Women > men
  • Death by local extension or metastasis (lung)
45
Q

Leiomyosarcoma

Characteristics

A
  • Short 90° interweaving fascicles
  • Atypical cigar-shaped nuclei
  • Atypical mitoses
  • Fibrillar cytoplasm (trichrome)
  • Variants: myxoid, epithelioid
  • Immunohistochemistry: Desmin, Actin, Vimentin ⊕
46
Q

Synovial Sarcoma

A
  • Unclear cell of origin
  • Seems to resemble synovium
  • 10% of all sarcomas
    • 4th most common sarcoma
  • Only 10% intra-articular
  • 20-40 y/o
  • Locations:
    • Lower extremities, deep seated
    • Parapharyngeal, abdominal wall
  • Metastasis to lung
  • Genetic signature: t (x;18) SYT-SSX gene fusion
  • Biphasic
    • Spindle and epithelial (glands)
  • Monophasic
    • Spindle (Fibrosarcoma-like)
    • Epithelial (glands)

4. HDS Multisystem (43 decks)

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