SOFT TISSUE SKELETAL SYSTEM LABORATORY Soft Tissue Tumors

SOFT TISSUE & SKELETAL SYSTEM LABORATORY

Soft Tissue Tumors • • 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 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

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, myo. D 1, 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

BONE TUMORS

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