1. SOFT TISSUE & SKELETAL SYSTEM LABORATORY

2. 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
Tumors of Uncertain Histogenesis

3. 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.

4. Liposarcoma

5. Liposarcoma

6. Myxoid Liposarcoma

7. 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

9. Tumors of Skeletal Muscle
Benign:
Rhabdomyoma
Malignant:
Rhabdomyosarcoma
Embryonal
Alveolar
Pleomorphic variants

10. 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)

13. 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.

14. 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

15. 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

16. Leiomyosarcoma

17. Leiomyosarcoma

18. Leiomyosarcoma

19. BONE TUMORS

20. OSTEOSARCOMA

21. Osteosarcoma

22. Osteosarcoma

23. Osteosarcoma

24. Ewing sarcoma
Small round blue neoplastic cells of Ewing Sarcoma

25. 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.

26. Atypical plasma cells of multiple myeloma