This document discusses various pseudosarcomas, which are non-neoplastic lesions that can be mistaken for sarcomas due to their rapid growth and cellular appearance. It describes several categories of pseudosarcomas, including reactive fibroblastic/myofibroblastic proliferations (e.g. nodular fasciitis), reactive endothelial proliferations (e.g. papillary endothelial hyperplasia), mass forming inflammatory/infective lesions (e.g. Rosai-Dorfman disease), and benign connective tissue tumors (e.g. cellular fibrous histiocytoma). The document emphasizes that accurate recognition of these pseudosarcomas helps prevent excessive or

1. Pseudosarcoma
Subas maharjan

2. • Soft tissue is defined ascomplex of
nonepithelial extra skeletal structure ofbody
exclusive of supportive tissue of various
organs and the hematopoietic/ lymphoid
tissue.

3. • It is composed of fibrous tissue, adipose
tissue, skeletal muscle, blood and lymph
vesselsand peripheral nerve.
• Most of the soft tissue derived from
mesoderm with neuroectodermal
contribution corresponding to peripheral
nerve.

5. Pseudosarcoma
• One of the most common and important pitfalls
in soft tissue pathology are the so-called
pseudosarcomas. These lesions are
nonneoplastic; however, their rapid growth,
hypercellularity, cytologic atypia, and mitotic
activity makes them prone to be misinterpreted
as sarcoma.
• Most of these lesions rarely recur following
simple excision; therefore, their accurate
recognition helps prevent excessive therapy.

6. Pseudosarcoma
• Reactive pseudoarcomatous proliferations are
non neoplastic lesions that either develop in
response to trauma or idiopathic.
• Clinically they are alarming because they develop
suddenly and grow rapidly.

7. Example include
• Reactive fibroblastic and myofibroblastic
proliferation resembling soft tissue sarcoma
• Reactive endothelial proliferation resembling soft
tissue sarcoma
• Mass forming inflammatory histocytic and
infective lesion resembling soft tissue sarcoma
• Benign connective tissue tumors resembling soft
tissue sarcoma

8. Reactive fibroblastic and myofibroblastic
proliferation resembling soft tissue sarcoma
• Nodular fascitis
• Proliferative fasciitis and
proliferative myositis
• Myositisossificans

9. Nodular fascitis
• Most commonpseudosarcoma
• Most often occur in adults and volar aspect of
forearm.
• Gross– several centimeters in diameter , nodular
configuration, poorly definedmargins.

10. Sites of involvement
Nodular fasciitis is usually subcutaneous, occasional
are intramuscular.
Dermal localization is very Rare
the upper extremity, trunk, and head and
neck are most frequently affected.
Intravascular fasciitis is also chiefly subcutaneous.

11. • Microscopy –Nodular fasciitis is composed of plump
but regular spindle-shaped fibroblasts (or
myofibroblasts) lacking nuclear hyperchromasia and
pleomorphism.
• Mitotic figures may be plentiful, but atypical mitoses
would not be expected.
• there is often growth in S- or Cshaped fascicles, and
sometimes a storiform pattern.
• multinucleated osteoclastlike giant cells

12. Nodular fascitis

13. Afeature of diagnostic significance is the
presence of undulating wide bands of
collagen lined on the sidesby spindlecells.

14. • SMA and MSA
• but desmin positivity is rare
• CD68 staining is present in the osteoclast-like
giant
• Keratin and S100 protein are typically
negative.

15. Proliferative fasciitis and
proliferative myositis
• Definition
• mass-forming subcutaneous proliferation
characterized by large ganglion-like cells
• plump fibroblastic / myofibroblastic
• Proliferative myositis has the same cellular
composition but occurs within skeletal muscle.

16. Proliferative fasciitis and
proliferative myositis
• Theskeletal muscles of the shoulder, thorax,and
thigh are those most commonlyaffected.
• Most patients are over the ageof45 years
• Gross- ill defined scar-like indurations of
the muscle .

17. • Microscopic- Both proliferative fasciitis and
myositis contain plump
fibroblastic/myofibroblastica
• Thehallmark ganglion-like cell
demonstrate large cells with rounded nuclei,
prominent nucleoli, and abundant
amphophilic to basophilic cytoplasm.
ganglion-like cell

18. Proliferative myositis

19. Myositis ossificans
• It is areactive condition that is sometimesmistaken
microscopically for osteosarcoma.
• Theterm is inaccurate becausethe muscle may notbe
involved, and inflammation is virtuallyabsent.
• Ahistory of trauma is obtained in only half of the
patients.
• Themost common locations are the flexor musclesof
the upper arm (especially the brachialis anticus), the
quadriceps femoris, the adductor muscles of the thigh,
the glutealmuscles,

20. • Microscopic- there is ahighly cellular stroma
associated with new bone and, lesscommonly,
cartilage formation.
• Themost important diagnostic feature is
provided by the maturation pattern(‘zonal
phenomenon’), characterized by acentral cellular
area, an intermediate zoneof osteoid formation,
and aperipheral shell of highly organized bone

21. Low power view showing typical zonation with fasciitis-like
features (centre right), immature osteoid (centre) and bone
formation at the periphery (left).

22. Reactive endothelial proliferation resembling
soft tissue sarcoma
• Papillary endothelial hyperplasia
• Spindle cell hemangioendothelioma

23. Papillary Endothelial Hyperplasia
Masson’s tumor
• Papillary endothelial hyperplasia is an exuberant,
usually intravascular, endothelial proliferation
that, in many respects,mimics an angiosarcoma.
• almost always solitary
• the skin, subcutaneous tissue, or even muscle
with the head and neck region and the upper
extremities.
• The fingers especially are the most common sites

24. Primary lesions are usually tender nodules 2 cm
in size, whereas
secondary lesions occur because some
preceding vascular abnormality increases in
size.

25. • purple-red, multicystic mass containing
clotted blood and
• surrounded by a fibrous pseudocapsule

26. Microscopy
• In the early lesion, the ingrowth of endothelium
along the contours of the thrombus partitions it
into coarse papillae with fibrin cores
• In the well-established or typical lesion, myriad
small delicate papillae project into the lumen
• These papillae are composed of a single layer of
endothelium surrounding a collagenized core.
• The endothelial cells appear plump or swollen
but lack significant pleomorphism and mitotic
figures.

27. A: Early stage is characterized by
thrombus with ingrowth of
endothelial cells.
B: Endothelium gradually
subdivides the partially
collagenized thrombus into
coarse clumps
C:followed by papillae

28. • A helpful point in the differential diagnosis is
its intravascular location because
angiosarcomas are almost never confined to a
vascular lumen.
• papillary endothelial hyperplasia lacks the
frank tissue necrosis, marked pleomorphism,
and high mitotic rate that characterize many
angiosarcomas.

29. Spindle cell hemangioendothelioma
• Any age, usually males, usually distal extremities
• Low grade lesion which recurs commonly and
may be multicentric, but only one reported
metastases after repeated recurrence and
radiation therapy
• May be a hamartoma due to aberrations in local
blood blow; perhaps should be called spindle cell
hemangioma
• Associated with Mafucci's syndrome

30. Microscopy
• Cavernous hemangioma and Kaposi sarcoma
like features
• Cavernous spaces with solid areas composed
predominantly of bland spindle cells
• minor component of epithelioid ,often
vacuolated,
• endothelial cells, usually associated with
irregular fascicles of smooth muscle fibers and
adjacent malformed vessels

31. The image shows cavernous angiomatous
areas and solid foci composed of bland spindle and
epithelioid cells

32. • (a) cavernous blood vessels
filled partly or completely
with erythrocytes or
thrombus admixed with
cellular zones
• (b) High-power view of
juxtaposition of the
cavernous and cellular areas
illustrating blood-filled
dilated vessels lined by
flattened endothelial cells
and spindle-shaped cellular
components. There is no
evidence of abnormal
mitotic activity or nuclear
atypia in spindled cells

33. Mass forming inflammatory histocytic and
infective lesion resembling soft tissue sarcoma
• Extranodal (Soft Tissue) Rosai-Dorfman
Disease
• Malakoplakia
• Xanthogranulomatous pyelonephritis
• Polyvinylpyrrolidone (PVP) reaction
• Mycobacterial spindle cell nodule
• Bacillary angiomatosis

34. Extranodal (Soft Tissue) Rosai-Dorfman
Disease
• Rosai-Dorfman disease is a polyclonal histiocytic
disorder of uncertain etiology, which, although
originally described as a lymph node disease
• occurs in sundry locations, including soft tissue 10%
of all cases
• its appearance and immunophenotype most closely
approximate an activated macrophage

35. • Microscopically, the lesions consist of sheets or
syncytia of large, pale histiocytes with large, round,
vesicular nuclei with some degree of
• Mitotic figures are absent
• The cytoplasm of the histiocytes may contain
lymphocytes (emperipolesis), although this is seldom
as striking as in the
• Microabscesses, when present, suggest the
possibility of an infectious process.

36. Extranodal Rosai-Dorfman disease
characterized by sheets of pale histiocytes with
voluminous cytoplasm.

37. • strongly express S-100 protein and, occasionally,
• other histiocytic antigens, including CD1a. However,
they do not contain Birbeck granules.
• A feature of diagnostic significance
• S-100 protein is useful for discriminating
undifferentiated pleomorphic sarcomas
• Rosai-Dorfman disease from Langerhans cell
histiocytosis,
cytologic differences between the proliferating

38. Malakoplakia
• Malacoplakia is a rare inflammatory disease believed
to represent an unusual host response to infection
with a variety of organisms, including Escherichia
coli, Klebsiella, and acid-fast bacilli.
• The reaction results in the formation of yellow
plaquelike lesions on the mucosal surface of the
affected organs.
• typically genitourinary tract, particularly the bladder,
although it may affect the soft tissues of the
retroperitoneum as well.

39. • Microscopy
• It is characterized by sheets of pale, slightly granular,
or vacuolated histiocytes (von Hansemann cells)
containing PAS-positive, diastase-resistant inclusions
in the cytoplasm
• Lymphocytes, plasma cells, and neutrophils are
typically abundant.
• The distinctive Michaelis-Gutmann bodies, small
calcospherites
• numerous phagolysosomes, occasional bacterial
forms, and lamellated crystalline

40. High-power view of malacoplakia
showing Michaelis-Gutmann bodies (arrows) in
occasional cells.

41. Xanthogranulomatous pyelonephritis
• Definition / general
• Rare, severe, atypical form of chronic
pyelonephritis due to infection (E. coli,
Proteus) or stones, but resembling renal cell
carcinoma; correct preoperative diagnosis is
unusual
• Characterized by foamy histiocytes replacing
renal parenchyma, due to

42. • Gross description
• Multiple yellow nodules around calyces, may form a
mass and be infiltrative
• Numerous dilated calyces with yellow-brown calculi
are seen. The central necrotic areas are surrounded
by dense fibrosis

43. • Replacement of renal parenchyma with CD68+
foamy histiocytes, occasional multinucleated
giant cells and inflammatory cells

44. • A feature of diagnostic significance
• intraoperative urine culture may be helpful
• Malakoplakia: Michaelis-Gutmann bodies
• Renal cell carcinoma: Cells with clear cytoplasm may
resemble histiocytes, but are keratin+, CD68-;
arranged in compact, tubulocystic, alveolar or rarely
papillary patterns; often glassy hyaline globules;)
• Renal replacement lipomatosis: atrophic renal
parenchyma is replaced by fatty tissue, not
xanthoma cells

45. Polyvinylpyrrolidone (PVP) reaction
• Polyvinylpyrrolidone (PVP) is a polymer of
vinylpyrrolidone, which was used notably as a
plasma expander during
• Because of its hydroscopic properties, it has also
been used as a retardant in various injectable
medicines (hormones, antihypertensives, local
anesthetics), as a clarifier in fruit juices, and as a
resin in hair sprays.

46. Microscopy
• these lesions are composed of numerous histiocytes
massively engorged with PVP
• The material appears glassy blue or blue-gray in
sections stained with hematoxylin-eosin.
• Typically, there are few inflammatory cells and no
necrosis.
• Giant cells are occasionally present and may be
helpful in suggesting the diagnosis of a foreign body
reaction.

47. PVP characteristically does not stain with Alcian blue
and, therefore stains differently from all myxoid
tumors of soft tissue, such as liposarcoma,
chondrosarcoma, and chordoma.
A feature of diagnostic significance
• The best stains for demonstrating the cytoplasmic
material are Congo red or Sirius red.

48. Mycobacterial pseudotumors
• Mycobacterial pseudotumors, first recognized by
Wood
• most recently in AIDS patients in a variety of sites,
most commonly lymph nodes but also skin/subcutis

49. • The lesions are analogous to those of histoid leprosy in
that they consist of a tumorous proliferation of
spindled and epithelioid histiocytes
• arranged in vague fascicles and associated with
occasional
• chronic inflammatory cells
• The cells are laden with numerous acid-fast bacilli
easily demonstrable with appropriate stains (
• CD68 positive, confirming their histiocytic lineage

50. Bacillary angiomatosis
• Usually not distinctly lobular
• multiple pink, elevated skin lesions that may
resemble a pyogenic granuloma.
• Clusters of neutrophils within lesion
• Amphophilic collections
of organisms

51. • In the classic case, bacillary angiomatosis
• consists of lobules of capillary-sized vessels lined by plump
(epithelioid) endothelium with clear cytoplasm
• Mild atypia and occasional mitotic figures may be present in
the endothelial cells.

52. Benign connective tissue tumors resembling soft
tissue sarcoma
• Atypical and cellular benign fibrous
histocytoma
• Ancient schwannoma
• Pleomorphic /spindle cell lipoma

53. Benign
Dermatofibroma (Fibrous Histiocytoma/Sclerosing
Hemangioma)
• common skin
• occurring on the extremities or trunk of young
adults.
• Gross: They present as small, firm, solitary nodules
that are red to brown in color, often due to increased
intraepidermal melanin or tumoral hemosiderin.
• The cut surface is white to yellow or brown,
depending on the proportions of fibrous tissue,lipid,
and hemosiderin present

54. Gross appearance of a pedunculated
cutaneous fibrous histiocytoma. The light
color of the lesion is a result of the presence of
large amounts of lipid.
B: This dermatofibroma
shows prominent hyalinization and
pigmentation.
C: Hemosiderin and multinucleated giant cells
dominate in this zone of another
dermatofibroma.

55. Histopathology.
• The epidermis hyperplastic, with hyperpigmentation of the
basal layer and elongation of the rete ridges, separated by a
clear (Grenz zone)
• exhibit a storiform pattern of interwoven, fascicled spindle
cell
• This is composed of fibroblast-like spindle cells, histiocytes,
and blood vessels in varying proportions
• Foamy histiocytes and multinucleate giant
• cells containing lipid or hemosiderin
• sometimes in large numbers, forming xanthomatous
aggregates.
• Capillaries may be plentiful in the stroma
• “rounding up” of collagen fibers.

56. • nodular fasciitis, neurofibroma, and sclerotic
leiomyoma.

57. Cellular Fibrous Histiocytoma
• This is a rare, densely cellular variant with a
fascicular to storiform growth
• may mimic dermatofibrosarcoma protuberans
(DFSP)
• assists in making this differentiation factor
XIIIa staining is often negative

58. B: Densely packed spindle
cells are present, arranged in a
storiform
C: This DFSP exhibits an area with a
prominent fibrosarcoma-like
pattern.
A: The tumor consists of spindle cells
arranged in densely cellular fascicles with
storiform areas.

59. Atypical Fibrous Histiocytoma
• The atypical cells show enlarged, pleomorphic nuclei,
sometimes referred to as monster cells
• Mitoses of normal morphology may be evident.
• Multinucleated giant cells with bizarre, large,
hyperchromatic
• nuclei with little cytoplasm or irregular, vesicular nuclei
with abundant foamy cytoplasm may also occur
• Focal necrosis may be seen.
• Variable staining for
• smooth muscle actin and CD34, with no staining
• for factor XIIIa.

60. A: This tumor shows histiocyte-like cells with
enlarged and pleomorphic nuclei with prominent nucleoli.
B: At the border of this tumor the cells are arranged
around individual collagen bundles in the pattern typical of
the more usual form of dermatofibroma

62. Schwannoma(Ancient schwannoma)
• Truly encapsulated neoplasms
• Almost always solitary
• Its most common locations are the flexor surfaces
of the extremities, neck, mediastinum,
retroperitoneum, posterior spinal roots, and
cerebellopontine angle.
• The great majority of casesoccur sporadically.
• Asmall percentage of casesare associated with
neurofibromatosis type

63. Schwannoma

64. • Ancient schwannomas are those displaying marked
nuclear atypia of a degenerative type.
• They are usually large tumors of long duration, are
located in deep structures such as the
retroperitoneum.
• Degenerative changes
include cyst formation, calcification, hemorrhage, and
hyalinization
• large numbers of siderophages and histiocytes.
• One of the most treacherous aspects of this tumor is
the degree of nuclear atypia encountered.
• The Schwann cell nuclei are large,hyperchromatic,
and often multilobed but lack mitotic figures

65. Gross specimen of a schwannoma of the retroperitoneum
with extensive degenerative changes (ancient
schwannoma). Tumors are characterized by areas of old and new
hemorrhage, cyst formation, and calcification.
Ancient schwannoma with cyst
formation and interstitial hyalinization.

66. Ancient schwannoma with degenerative atypia and perivascular hyalinization.
Note the lipofuscin-like pigment in the Schwann cells.
Degenerative atypia in an ancient schwannoma.

67. • immunoreactivity for
• S-100protein,
• calretinin (incontrast to neurofibromas),
• calcineurin,
• basallaminacomponents
vimentin,
nerve growth factor receptor,
lipocortin-1,and
sometimes glial fibrillary acidic protein andKP-l

68. Spindle cell lipoma /
Pleomorphic lipoma
• Spindle cell and pleomorphic are circumscribed
composed of a variable admixture of bland spindled
cells, hyperchromatic rounded cells, and
multinucleate giant cells associated with ropey
collagen.
• Sites of involvement
• predominantly in the posterior neck and shoulder
area.
• Face, forehead, scalp,buccal-perioral area and upper
arm are less common sites

69. Macroscopy
• oval or discoid yellowish to greyish-
white mass depending on the relative
extent of the fatty and spindle cell
components.
• firmer texture than ordinary lipoma,
• gelatinous texture.

70. Histopathology
• spindle cell lipoma is composed of bland mitotically inactive
spindled cells
• thick rope-like collagen bundles are seen between the fat .
• Large numbers of mast cells are often seen
• show myxoid stromal changae or display slit-like cleavage
spaces resembling vascular slits

71. • At the opposite end of the spectrum, pleomorphic
lipoma is characterized by small spindled and
rounded hyperchromatic cells
• multinucleated giant cells with radially arranged
nuclei in a"floretlike“ pattern, like petals of flowers.

72. • Immunophenotype
• for CD34 and
• may rarely be positive for S100 protein

73. THANK YOU
• Ref
• Recent advance vol 19
• LEVER’ S Histopathology of the Skin
• WHO classification or bone and soft tissue
tumors
• sternbergs-diagnostic-surgical-pathology