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Rotation - Cytopathology > Ch. 17 - Soft Tissue > Flashcards

Ch. 17 - Soft Tissue Flashcards

1
Q

Into what categories are soft tissue lesions categorized? (Hint: 7 categories)

A 
Adipocytic
Myxoid
Spindle cell
Fibrohistiocytic
Round cell
Epithelioid
Pleomorphic
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2
Q

What auxiliary studies are helpful in soft tissue cytology?

A

Cell blocks are essential for staining. FISH is very valuable for identifying translocations. Electron microscopy is rarely used…

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3
Q

What are the clinical features of lipoma? What is their most typical molecular aberration?

A

Slow-growing, subQ or intramuscular (rarely retroperitoneal. Abnormalities of HMGA2 on chr 12.

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4
Q

Describe the cytology of lipoma.

A

Small tissue fragments iwth large, univacuolate adipocytes. Maybe some lipophages. Very rarely myxoid stroma or metaplastic bone can be seen.

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5
Q

What are the clinical features of hibernoma? What is their most typical molecular aberration?

A

Fatty slow-growing lesion affecting adults, usually in the thigh but also the trunk or head & neck. Features 11q13 rearrangements.

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6
Q

Describe the cytology of hibernoma.

A

Large tissue fragments containing multivacuolated adipocytes. Many delicate capillaries should be seen.

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7
Q

What are the lesions closely related to spindle cell lipoma? What are the molecular features?

A

Possibly related to cellular angiofibroma and mammary type myofibroblastoma. Both show 13q deletions.

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8
Q

What are the clinical features of pleomorphic lipoma? What is their histologic hallmark?

A

Pleomorphic lipoma tends to grow in the upper body and is rarely >5cm. Features floret giant cells.

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9
Q

Describe the cytology of spindle cell lipoma

A

Bland spindled cell, ropey collagen, and mast cells.

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10
Q

What are the clinical features of intramuscular myxoma? What are its variants?

A

Well-circumscribed but unencapsulated lesion involving large muscles. Variants include cellular myxoma and juxta-articular myxoma (usually near knee).

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11
Q

Describe the cytology of intramuscular myxoma.

A

Hypocellular with some granular matrix material in background. Uniform bland spindled cells have long fibrillary cytoplasmic processes. Expect to see some muscle fibers, but not much vessel.

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12
Q

What is the origin of soft tissue perineurioma? What is its classic staining pattern?

A

A benign peripheral nerve sheath neoplasm usually found in the subcutis. It stains for EMA, Claudin1, and usually CD34 but is S100-.

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13
Q

Describe the cytology of soft tissue perineurioma.

A

Variable cellularity, with myxoid or collagenous stroma. Classic feature: bipolar cytoplasmic processes.

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14
Q

What are the clinical features of myxofibrosarcoma? What is the typical histologic description?

A

Affects extremities of older patients, often recurrent. Histologically distinguished by myxoid spindle cells condensing around curvilinear vessels.

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15
Q

Describe the cytology of myxofibrosarcoma.

A

Variable myxoid matrix, spindle to stellate cells with variable atypia. May see the cvurved, collagenized vessels. May see pseudolipoblasts (contain acidic mucin, not lipid)

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16
Q

What are the clinical features of LGFMS? What is their most typical molecular aberration?

A

Affects younger adults (than myxofibrosarcoma) in deep tissue compartments. Usually bland-looking. FUS rearrangements t(7;16), t(1;16).

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17
Q

Describe the cytology of LGFMS.

A

Abundant myxoid matrix with uniform fibroblast-like spindle cells and no significant vascularity. Low-grade!

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18
Q

What are the clinical features of myxoid liposarcoma? What is their most typical molecular aberration?

A

On a spectrum with round cell liposarcoma, featuring the same DDIT3 fusions t(12;16) with FUS or t(12;22) with EWSR1.

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19
Q

Describe the cytology of myxoid liposarcoma.

A

Distinctive: Monotonous cells with granular myxoid stroma, thin-walled vessels, and lipoblasts (usually near vessels).

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20
Q

What are the clinical features of lipoblastoma? What is their most typical molecular aberration?

A

A (benign!) tumor of childhood affecting the superficial extremities. Many harbor abnormalities of chr 8.

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21
Q

Describe the cytology of lipoblastoma.

A

Moderate cellularity with cohesive clusters of bland lipoblasts, some primitive spindle cells and mature adipocytes. Not much nuclear atypia.

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22
Q

What should come to mind when evaluating a cytologic case resembling myxofibrosarcoma but with thick-walled branching vessels and marked atypia?

A

Myxofibrosarcoma-like dedifferentiated liposarcoma.

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23
Q

What are the clinical features of myxoinflammatory fibroblastic sarcoma? What is their most typical molecular aberration?

A

Very locally aggressive neoplasm. Defined by the t(1;10) TGFBR3-MGEA5 translocation.

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24
Q

Describe the cytology of myxoinflammatory fibroblastic sarcoma.

A

Prominent myxoid background, spindle cells with bipolar processes, epithelioid cells which can look HRS-like. Inflammatory cells.

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25
Q

Describe the cytology of chordoma.

A

Granular and fibrillary myxoid background, large neoplastic physaliphorous cells and some signet ring cells. *Stains for brachyury.

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26
Q

What are the clinical features of extraskeletal myxoid chondrosarcoma? What is their most typical molecular aberration?

A

Slow growing malignant tumor usually involving the thigh/popliteum. Despite the name, it has no evidence of cartilaginous differentiation. Defined by a NR4A3 gene rearrangement.

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27
Q

Describe the cytology of extraskeletal myxoid chondrosarcoma.

A

Chondromyxoid background, epithelioid to spindled cells with nuclear grooves and small nucleoli. Distinctive lacelike pattern of anastomosing cords/nests.

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28
Q

What are some possible origins of spindle cell neoplasms, and what stains may identify them?

A

Muscle: SMA/desmin
Neural: S100
Vascular: CD34
GIST: C-KIT/DOG1

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29
Q

What are the four major subtypes of leiomyosarcoma? Who do they affect?

A

Intra-abdominal (affects older women)
Subcutaneous/deep (male predominance)
Cutaneous (men; painful)
Vascular

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30
Q

Describe the staining pattern and gene rearrangements in leiomyosarcoma.

A

Positive for SMA, desmin, and caldesmon. May be positive for cytokeratins and EMA.

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31
Q

Describe the cytology of leiomyosarcoma.

A

Fascicular tissue fragments with spindled cells and cigar-shaped nuclei. May be myxoid or pleomorphic (variants).

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32
Q

What is the origin of MPNST?

A

Arises from a peripheral nerve or existing neurofibroma (may be sporadic or NF-related).

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33
Q

Describe the cytology of MPNST.

A

Depends on the grade or subtype, but expect rosette-like or pseudoglandular configurations. Large tumor cells, high N:C ratios, rare nuclear palisading.

34
Q

What are the clinical features of schwannoma? What is their most typical molecular aberration?

A

Painful nerve sheath tumor with a wide distribution. Expect to see deletion of 22q.

35
Q

Describe the cytology of schwannoma.

A

Cohesive fragments with sharp edges. Antoni A/B areas are hard to distinguish, but Verocay bodies are easier to see. Cells may be fishhook-like.

36
Q

What are the clinical features of synovial sarcoma? What is their most typical molecular aberration?

A

A malignant tumor of young adults that actually has no anatomic relationship with synovium. Features a t(x;18) SS18-SSX fusion.

37
Q

Describe the cytology of synovial sarcoma.

A

Highly cellular with myxoid or fibrous matrix. Fascicles with shaggy edges and branching capillaries. Uniform cells with “tapering” cytoplasm. Mast cells.

38
Q

What are the clinical features of solitary fibrous tumor? What is its classic staining pattern?

A

Tends to involve serosal cites, and can affect many organs. Usually benign. CD34+, usually CD99 and BCL2+. Keratin-.

39
Q

Describe the cytology of solitary fibrous tumor.

A

Bloody background with ropey collagen. Irregular fascicles and isolated spindle cells with fusiform nuclei and elongated cytoplasmic processes.

40
Q

Recall the superficial and deep fibromatoses. Which stain beta-catenin?

A

Superficial: Palmar, plantar, penile

Deep/desmoid: Abdominal, extra-abdominal, intra-abdominal. *Stains beta-catenin.

41
Q

Describe the cytology of fibromatosis.

A

Low cellularity, with bland spindle cells and fragments of dense collagenous stroma. Maybe some muscle cells.

42
Q

What are the clinical features of nodular fasciitis? What is their most typical molecular aberration?

A

Self-limited proliferation of the subcutis, often presenting with rapid growth. Defined by clonal USP6 rearrangements.

43
Q

Describe the cytology of nodular fasciitis.

A

Myxoid background, polymorphous myofibroblastic cells, occasional ganglion-like cells.

44
Q

What are the clinical features of DFSP? What is their most typical molecular aberration?

A

Slow growing tumor of dermis/subcutis. Defined by COL1A1-PDGFB fusion.

45
Q

Describe the cytology of DFSP

A

Dense, storiform cell clusters in a collagenous stroma with some entrapped fat. Minimal atypia/pleomorphism.

46
Q

What are the clinical features of inflammatory myofibroblastic tumor? What is their most typical molecular aberration?

A

Rare low-grade lesion of mostly children. Affects visceral organs and the abdominal cavity. Features 2p23 ALK rearrangements.

47
Q

Describe the cytology of inflammatory myofibroblastic tumor.

A

Highly cellular with many lymphocytes and plasma cells as well as myofibroblastic spindle-shaped tumor cells (plump nuclei, finely granular chromatin, cytoplasmic vacuolization).

48
Q

Distinguish between localized and diffuse tenosynovial giant cell tumor. What molecular aberrations do they exhibit?

A

Localized: Slow growing, usually affecting adult women.
Diffuse: AKA Pigmented villonodular synovitis. Destructive and infiltrative, affects younger patients.

Both harbor COL6A3-CSF1 fusions.

49
Q

Describe the cytology of tenosynovial giant cell tumor.

A

Foamy histiocytes and osteoclast-type giant cells. Hemosiderotic with minimal anisokaryosis.

50
Q

What exactly is angiomatoid fibrous histiocytoma? What molecular aberration does it exhibit?

A

A mesenchymal neoplasm of uncertainlineage that mostly affects the deep dermis of young patients. Characterized by EWSR-FUS1 rearrangements?

51
Q

Describe the cytology of neuroblastoma.

A

Fibrillary (neuropil) matrix, necrotic debris and dystrophic calcifications. Tumor cells (small and undiff’d) are noncohesive, may be arranged in rosettes.

52
Q

What are the clinical features of Ewing sarcoma? What is their most typical molecular aberration?

A

Presents as rapidly enlarging, painful mass usually in the thigh. EWSR-FLI1 > EWSR-ERG fusions.

53
Q

Describe the cytology of Ewing sarcoma.

A

Numerous naked nuclei, “tigroid” background, biphasic population of “light” (viable)” and dark (apoptotic/necrotic) cells.

54
Q

What are the clinical features of DSRCT? What is their most typical molecular aberration?

A

An aggressive malignant tumor usually of young men which affects serosal surfaces. Defined by a t(11;22) EWSR-WT1 fusion.

55
Q

Describe the cytology of DSRCT.

A

Small to intermediate cells with oval or slight angulation (some nuclear molding), desmoplastic stroma, and small acinar structures.

56
Q

What are the four subtypes of rhabdomyosarcoma?

A

Embryonal
Alveolar
Pleomorphic
Spindle cell / sclerosing

57
Q

What are the clinical features of embryonal rhabdomyosarcoma? How does it stain?

A

Affects mainly children (most common sarcoma of childhood). Stains for skeletal muscle markers (desmin, muscle-specific actin, myogenin, myoD1).

58
Q

What are the clinical features of alveolar rhabdomyosarcoma? What is their most typical molecular aberration?

A

Worse prognosis than embryonal rhabdomyosarcoma, affecting older children. Tends to have t(1;13) or t(2;13) FOXO1 rearrangements.

59
Q

Describe the cytology of embryonal and alveolar rhabdomyosarcoma.

A

Isolated cells with frothy “tigroid” or myxoid backround. Cells are round to spindled, sometimes with tadpole/strap shape. Pronounced anisonucleosis/pleomorphism.

Note: Alveolar has larger cells and some giant cells.

60
Q

What exactly is extraskeletal mesenchymal chondrosarcoma? What is their most typical molecular aberration?

A

An uncommon bimorphic tumor with SBRCs and well-diff’d cartilage. Involves orbit, cranium, spinal meninges…

HEY1-NCOA2 fusion.

61
Q

What are the clinical features of epithelioid sarcoma? What is their most typical molecular aberration?

A

Slow-growing and usually superficial lesion of distal extremities (exception: “proximal type”). Has aberrations of INI-1 (results in loss by IHC).

62
Q

Describe the cytology of epithelioid sarcoma.

A

Dispersed round to spindled cells in loosely cohesive clusters. Dense cytoplasm with small vacuoles. Necrotic, often multinucleated.

63
Q

How can epithelioid sarcoma be distinguished from extrarenal malignant rhabdoid tumor?

A

The former is CD34+, the latter is CD34-.

64
Q

What exactly is a clear cell sarcoma? What are its molecular features?

A

A sarcoma of young adults with melanocytic differentiation. t(2;22) or t(12;22) EWSR1-ATF fusions.

65
Q

Describe the cytology of clear cell sarcoma.

A

Dispersed round to spindle shaped cells with prominent nucleoli and pseudoinclusions. Background may be tigroid and with giant cells.

66
Q

What are the clinical features of alveolar soft part sarcoma? What is their most typical molecular aberration?

A

A tumor of older adolescents and young adult women, affecting the lower extremities or head & neck. Associated with t(x;17) ASPSCR1-TFE3 fusion resulting in overexpression of TFE3 by IHC.

67
Q

Describe the cytology of alveolar soft part sarcoma.

A

Naked nuclei and large polygonal cells with prominent nucleoli. Granular and “fragile” cytoplasm, with PAS+ rhomboid crystals.

68
Q

What are the clinical features of epithelioid hemangioendothelioma? What is their most typical molecular aberration?

A

A malignant vascular neoplasm of young adults with tendency towards visceral sites. Can be multicentric. Many cases have WWTR1-CAMTA1 fusions.

69
Q

Describe the cytology of epithelioid hemangioendothelioma.

A

Round to polygonal plasmacytoid cells, fragments of variable stroma. Cells may form rosettes or pseudoacini and have grooves/pseudoinclusions and dense cytoplasm with intracytoplasmic lumina.

70
Q

Describe the cytology of epithelioid angiosarcoma.

A

Extensively bloody background, with noncohesive pleomorphic cells that are occasionally angioformative.

71
Q

Describe the cytology of granular cell tumor.

A

Bare nuclei in a granular background, maybe some granular cytoplasm. Uniform small nuclei.

72
Q

Describe the cytology of undifferentiated pleomorphic sarcoma.

A

Hypercellular smers with variable cell clusters and dispersed cells with frank anaplasia, giant cells, mitoses and necrosis. Looks like shit.

73
Q

Describe the cytology of pleomorphic rhabdomyosarcoma.

A

Hypercellular smear with large rhabdoid cells, frequent multinucleation and necrosis.

74
Q

What tumors can dedifferentiate?

A

Chondrosarcomas (10%)
Liposarcomas (10%, overall most common)
Chordomas (very rare).

75
Q

Describe the pathophysiology of retroperitoneal fibrosis.

A

Thought to be IgG4-mediated, mostly affecting adult men. Fibrosis starts at L4 and can encase the entire aorta.

76
Q

Describe the cytology of retroperitoneal fibrosis.

A

Mixed inflammatory infiltrate with crush artifacting, fragments of fibrous tissue, and spindled fibroblasts. No atypia.

77
Q

What is an elastofibroma?

A

A lesion probably resulting from repeated trauma that manifests with a subscapular mass.

78
Q

Describe the cytology of elastofibroma.

A

Hypocellular wavy matrix, linear rod-like structures, serrated globular bodies, and bland fibroblasts.

79
Q

Describe the cytology of amyloidoma.

A

Fragments of waxy amorphous material with embedded fibroblasts, giant cells, and other inflammatory cells (plasma cells).

80
Q

What tumors harbor EWSR rearrangements?

A

Ewing sarcoma, DSRCT, extraskeletal myxoid chondrosarcoma, clear cell sarcomas, AFH, myxoid liposarcoma, myoepithelial tumor of soft tissue

Rotation - Cytopathology (33 decks)

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