SOFT TISSUE & SKELETAL
SYSTEM
LABORATORY
Soft Tissue Tumors
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Tumors of adipose Tissue
Tumors and Tumor Like conditions of Fibrous Tissue
Fibrohistiocytic Tumors
Skeletal Muscle Tumors
Smooth Muscle Tumors
Vascular Tumors
Peripheral Nerve Tumors
Tumors of Uncertain Histogenesis
Liposarcomas:
One of the most common sarcomas of adulthood
(40-60 years)
• Well-differentiated
• Myxoid
• Round cell
• Pleomorphic
Variants are found.
Malignant adipocytes are called lipoblasts
mimicing fetal fat cells. They contain cytoplasmic
fat vacuoles.
Liposarcoma
Liposarcoma
Myxoid Liposarcoma
Fibrosarcomas
• Rare tumors
• 50% recur, 25% metastasize; more
metastases if more cellular and higher
mitotic activity
• Gross: may appear well circumscribed but
nonencapsulated; fleshy, infiltrative,
hemorrhagic, necrotic
• Micro: fibroblastic proliferation in
herringbone pattern (fascicles intersect at
right angles); usually lacks giant cells
Tumors of Skeletal Muscle
Benign:
Rhabdomyoma
Malignant:
Rhabdomyosarcoma
• Embryonal
• Alveolar
• Pleomorphic variants
Rhabdomyosarcoma-general
• Most common soft tissue sarcoma of
childhood/adolescence (5-8% of solid pediatric tumors)
• Rhabdomyoblast: cell of origin; eccentric eosinophilic
granular cytoplasm rich in thick and thin filaments; if
round and elongate, are called strap cells or tadpole
cells
• Subtypes: alveolar, anaplastic, embryonal, pleomorphic,
sclerosing
• Note: subtypes overlap and mixtures are common
• Positive stains: actin, desmin, myoglobin, vimentin,
myogenin, myoD1, myosin
• EM: rhabdomyoblasts contain sarcomeres (thick and thin
filaments)
• In embryonal
lesions (A), note
the small nuclear
size and
pleomorphism,
compared with
the alveolar
subtype (B), in
which the nuclei
are larger and
more uniform in
appearance.
Tumors of Smooth Muscle
Leiomyoma (Benign)
• Usually in uterus (most common neoplasm
in women)
• Also skin, subcutis
• Patients with multiple leiomyomas may
have autosomal dominant disorder
• Micro: blunt ended, elongated nuclei,
minimal atypia, few mitotic figures, no
coagulative tumor necrosis
Leiomyosarcoma (Malignant)
• Third most common sarcoma of retroperitoneum, after
liposarcoma, MFH
• Constitute 10% of adult soft tissue sarcomas; F > M
• Usually in extremities, arising from vessels (luminal), most
commonly inferior vena cava, saphenous vein, femoral vein,
pulmonary artery, femoral artery; also in superficial or deep
soft tissues
• Somatic soft tissue tumors may be of vascular origin,
causing them to be well circumscribed and frequently mobile
• Definition: mitotic activity (1 MF/50 HPF may be associated
with metastasis) or tumor cell necrosis or > 10 cm
Leiomyosarcoma
Leiomyosarcoma
Leiomyosarcoma
BONE TUMORS
OSTEOSARCOMA
Osteosarcoma
Osteosarcoma
Osteosarcoma
Ewing sarcoma
Small round blue neoplastic
cells of Ewing Sarcoma
Plasmocytoma
Bone biopsy representing more than
90 percent replacement of normal
marrow with plasma cells. Definitive
diagnosis of multiple myeloma
requires a 10 to 15 percent plasma cell
involvement of the bone marrow.
• Atypical plasma cells of multiple myeloma