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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
Lipoma Overview
* **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
Spindle Cell Lipoma
* **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
Angiolipoma
Painful subcutaneous mass in forearm of young adult Vascular channels with microthrombi
28
Intramuscular Lipoma
**Lipomatous growth within skeletal muscle fibers** Diagnostic problem to differentiate from liposarcomas involving skeletal muscle
29
Lipomatosis
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
Lipoblastoma / Lipoblastomatosis
* **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
Liposarcoma Overview
**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
Well-differentiated Liposarcoma
* **Lipoma-like** (lipoma with atypical cells) * **Sclerosing-spindle cell** * **Dedifferentiated** (WD with areas of Fibrosarcoma and/or MFH)
33
Dedifferentiated Liposarcoma
* **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
Myxoid Liposarcoma
**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
Pleomorphic Liposarcoma
* **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
Liposarcoma Subtypes Table
37
Striated Muscle Tumors
* _Benign_ * **Rhabdomyoma** * Heart (children) * _Malignant_ * **Rhabdomyosarcoma**
38
Rhabdomyosarcoma Overview
* **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
Embryonal Rhabdomyosarcoma
* **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
Alveolar Rhabdomyosarcoma
* **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
Smooth Muscle Tumors
Benign ⇒ Leiomyoma Malignant ⇒ Leiomyosarcoma
42
Leiomyoma
**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
Intravenous Leiomyomatosis | (IVL)
Benign smooth muscle tumor of the _uterus_ that **grows within the veins but does not invade the surrounding tissue**
44
Leiomyosarcoma Overview
* **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
Leiomyosarcoma Characteristics
* **Short 90° interweaving fascicles** * **Atypical cigar-shaped nuclei** * **Atypical mitoses** * Fibrillar cytoplasm (trichrome) * _Variants_: **myxoid, epithelioid** * _Immunohistochemistry:_ **Desmin, Actin, Vimentin ⊕**
46
Synovial Sarcoma
* **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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