non-skeletal mesodermal tissues: adipose tissue, fibrous tissue, muscle, blood vessels and peripheral nerves (despite neuroectodermal origin) benign, malignant and intermediate (low-grade malignant – locally aggressive, can recur, no metastatic potential) originate from primitive mesenchymal stem cells classification according to differentiation lines (e.g. liposarcoma is not a tumor arising from adipose tissue but exhibiting lipoblastic differentiation)

1. Soft Tissue Tumours

2. Soft tissue tumors
non-skeletal mesodermal tissues: adipose tissue, fibrous tissue, muscle,
blood vessels and peripheral nerves (despite neuroectodermal origin)
benign, malignant and intermediate (low-grade malignant – locally
aggressive, can recur, no metastatic potential)
originate from primitive mesenchymal stem cells
classification according to differentiation lines (e.g. liposarcoma is not a
tumor arising from adipose tissue but exhibiting lipoblastic differentiation)

3. Classification of soft tissue tumors
Lipomatous tumors
Lipoma
Liposarcoma
Smooth muscle tumors
Leiomyoma
Leiomyosarcoma
Skeletal muscle tumors
Rhabdomyoma
Rhabdomyosarcoma
Fibroblastic tumors
Nodular fasciitis
Fibromatoses
Fibrosarcoma
Fibrohistiocytic tumors
Benign fibrous histiocytoma
Malignant fibrous histiocytoma
Vascular tumors
Hemangioma
Angiosarcoma
Tumors of peripheral nerves
Schwannoma
Neurofibroma
Malignant peripheral nerve sheath
tumor
Tumors of uncertain origin
Synovial sarcoma

4. Lipoma
the most common soft tissue tumor in adults
middle-aged and elderly people
subcutaneous tissue of the trunk and limbs (superficial lipoma)
deep soft tissue (deep lipoma)
synovial membrane (lipoma arborescens)
soft, slowly growing mass
well circumscribed, lobular arrangement, yellow cut surface
well-defined lobules of mature adipose tissue
numerous histologic subtypes (angiolipoma, myolipoma, chondroid lipoma,
pleomorphic/spindle cel lipoma)

5. Liposarcoma
most common malignant soft tissue tumor
adults (peak incidence 40-60 years)
lower limb and retroperitoneal space
key diagnostic feature: multivacuolated lipoblast (two or more lipid droplets within
the cytoplasm)
well-differentiated lipoma-like liposarcoma (atypical lipomatous tumor): closely
resemble lipoma, but a few spindle or stellate cells with hyperchromatic atypical
nuclei, high recurrence rate, no meastases (intermediate behaviour)
myxoid liposarcoma: small undifferentiated mesenchymal cells and lipoblast set in
a myxoid stroma, plexiform „chicken-wire“ network of capillaries, good prognosis,
rare metastases
pleomorphic liposarcoma: mixed cell population (spindle cells, tumor giant cells
and small number of lipoblasts), poor prognosis, frequent metastases

6. Leiomyoma
skin, subcutaneous tissue, uterus, gastrointestinal tract
interlacing bundles of well-differentiated smooth muscle cells with bright
eosinophilic cytoplasm and blunt-ended nuclei

7. Leiomyosarcoma
mesentery, retroperitoneal space, wall of large veins, skin, subcutaneous tissue,
deep soft tissues of limbs
signs of malignancy: large size, high mitotic rate, areas of necrosis, marked
cellular pleomorphism

8. Rhabdomyoma
extremely rare lesions
adult type: head and neck of middle aged individuals, large round or polygonal cells
with eosinophilic cytoplasm and abundant cytoplasmatic glycogen
genital type: polypoid growth of the cervix, vagina or vulva in middle age, large
rhabdomyoblasts with cross-striations
fetal type: boys younger than 3 years, head and neck, mixture of immature skeletal
muscle and loose, rather myxoid stroma
cardiac rhabdomyoma: infancy, fatal by the age of 5 years, association with
tuberous sclerosis (50%)
usually multiple rounded nodules involving heart ventricles
large polygonal cells with central mass of eosinophilic cytoplasm, abundant
glycogen and narrow processes extending to the periphery (“spider cells“)

9. Rhabdomyosarcoma
most common malignant soft tissue tumour in infants and young children
rhabdomyoblasts (round, elongated or oval cells with excentric eosinophilic
cytoplasm – “tadpole cells, strap cells, racket cells“)
embryonal rhabdomyosarcoma: most common, early childhood, head and neck
region (orbit, nasopharynx, middle ear) and genitourinary system, small rounded or
spindle-shaped cells within a myxoid matrix
bothryoid rhabdomyosarcoma (grape-like): embryonal rhabdomyosarcoma with
polypoid configuration and myxoid consistency, occurs in mucosa-lined organs
alveolar rhabdomyosarcoma: 10 - 20 years, muscles of limbs and trunk,
honecomb-like spaces bounded by fibrous septa, spaces lined by small round or
oval undiffernentiated cells, loss of cohesion towards the centre of spaces
pleomorphic rhabdomyosarcoma: limbs of adults, large cells with eosinophilic
cytoplasm and either single or multiple highly atypical nuclei

10. Nodular fasciitis
benign fibroblastic proliferation
adolescents and young adults
rapidly growing nodule within subcutaneous tissue, forearm is the most common
site
plump immature fibroblasts arranged in short bundles, numerous mitoses, cellular
pleomorphism not present

11. Superficial fibromatoses
palmar fibromatosis (Dupuytren’s contracture): middle-aged men, nodular
thickening of palmar aponeurosis leading later to flexion deformities of fingers
plantar fibromatosis (Ledderhose’s disease): nodular thickening of plantar
aponeurosis
penile fibromatosis (Peyronie’s disease): abnormal curvature of penis-
nodules of well-differentiated fibroblasts arranged in long sweeping bundles

12. Deep fibromatoses (desmoid* tumors)
abdominal: abdominal wall, young adults, particularly women, often in
peripartum or postpartum period, sometimes in surgical scars
intra-abdominal: young adults, mesentery, association with Gardner’s
syndrome (intestinal polyposis)
extra-abdominal: the most aggressive, adults in the third and fourth
decades, pectoral and pelvic girdles
deep intramuscular location, large size (up to 10-15cm), infiltrative growth
pattern, high risk of recurrence after excision
(* desmoid tumor is an abnormal growth that arises from connective tissue, which
is the tissue that provides strength and flexibility to structures such as bones,
ligaments, and muscles. Typically, a single tumor develops, although some people
have multiple tumors. The tumors can occur anywhere in the body)

13. Fibrosarcoma
uncommon malignant neoplasm
middle aged adults
deep soft tissues of lower limbs and trunk
bundles of spindle shaped cells arranged at angles to one another (“herring-bone
pattern“), frequent mitoses
infantile fibrosarcoma: within the first two years of life, much better prognosis

14. Benign fibrous histiocytoma (dermatofibroma)
common lesion, most frequently on the skin of lower leg
papule or nodule, often deeply pigmented
situated within the mid-dermis
spindle cells arranged in curious whorled pattern (storiform pattern)

15. Malignant fibrous histiocytoma (MFH)
deep soft tissues of limbs, retroperitoneum
irregularly arranged plump, eosinophilic, spindle-shaped cells with darkly staining
and often bizarre nuclei, numerous mitoses, interspersed macrophage-like cells,
storiform pattern in some areas
MFH represents merely a morphological pattern shared by wide variety of poorly
differentiated malignant neoplasms, it is a heterogeneous group of unrelated
lesions (pleomorphic sarcomas, dedifferentiated carcinomas, high-grade
lymhomas etc.)
MFH (synonymous designation: undifferentiated pleomorphic sarcoma) –
diagnosis of exclusion following thorough sampling and judicious use of ancillary
techniques (immunohistochemistry, electron microscopy)

16. Haemangioma
hamartomas rather than true neoplasms
capillary haemangioma: skin, mass of proliferated capillaries
pyogenic granuloma: rapidly developing polypoid nodule, many small capillaries
similar to those seen in granulation tissue, myxoid stroma, surface often eroded
cavernous haemangioma: skin, liver, aggregates of large dilated thin-walled
vessels lined by flattened endothelium

17. Angiosarcoma
irregular anastomosing vascular spaces lined by endothelial cells with large
hyperchromatic nuclei
highly aggressive tumor with poor prognosis
Kaposi’s sarcoma
variant of angiosarcoma
often patients with AIDS
multiple bluish plaques and nodules on the skin of lower extremities
spindle-shaped cells with the presence of red cells containing slits and
haemosiderin deposition

18. Schwannoma (neurilemmoma)
smooth lobulated lesion usually attached to a nerve
Antoni A – compact areas formed by regular interlacing bundles of uniform spindle-
shaped cells, often foci of nuclear palisading
Antoni B – looser open areas, small cells with rounded nuclei

19. Neurofibroma
not infrequently multiple
sometimes part of neurofibromatosis
fusiform expansion of affected nerve
spindle-shaped cells with elongated wavy nuclei set in myxoid stroma

20. Malignant peripheral nerve sheath tumor (MPNST)
adults
most common locations: neck, forearm, lower leg, buttock
large mass producing fusiform enlargement of a major nerve
relatively uniform spindle-shaped cells with hyperchromatic nuclei and high mitotic
activity

21. Synovial sarcoma
neither derived from nor differentiates to synovial lining cells (historical name has
been retained)
young adults (15-40 years)
extraarticular soft tissues, often near joint capsules and tendons
two cell types:
epithelial (forming nests and gland-like spaces – resembles carcinoma)
spindle (arranged in sheets – resembles fibrosarcoma)
biphasic (both cell types)
monophasic (spindle or epithelial cells only)
frequent reccurences, metastases in lymph nodes and lungs