Soft Tissue tumors

General aspects

Pseudosarcomas• Nodular fasciitis

• Proliferative fasciitis

• Proliferative myositis

• Proliferative peribursitis

• Postoperative spindle cell nodule

• Spindle cell and/or pleomorphic lipoma

• Lipoblastoma

• Cellular angiolipoma

• Bizarre leiomyoma

• Fetal rhabdomyoma

• Pyogenic granuloma

• Papillary endothelial hyperplasia

• Atypical fibrous polyps

• Myxoma

• Myositis ossificans

• Others

• Nonmesenchymal lesions

• Sarcomatoid renal cell carcinoma

• Pseudosarcomatous carcinoma

• Giant cell carcinoma

• Carcinoma with osteoclast-like giant cells

• Melanoma

• Lymphoma (anaplastic, interdigitating types)

• Follicular dendritic cell tumor

Patterns

Storiform Pattern

• Dermatofibrosarcoma• Undifferentiated pleomorphic

sarcoma (MFH and dedifferentiated tumors)

• Leiomyosarcoma (focal)• Nerve sheath tumors• Liposarcoma (focal)• Fibromatosis (focal)• Nodular fasciitis• Thymoma (focal)

Hemangiopericytoma-Like Pattern

• Cellular hemangioma (infantile hemangioendothelioma)

• Glomus tumor• Mesenchymal chondrosarcoma• Leiomyosarcoma (focal)• Undifferentiated pleomorphic

sarcoma/MFH (focal)• Synovial sarcoma• Nerve sheath tumors• Solitary fibrous tumor• Thymoma (rare)

Cytoplasmic Vacuolation in Soft Tissue TumorsTumor Substance Differential Features

• Liposarcoma Lipid Vacuole indents nucleus with scalloped appearance; positive fat stain; S-100 positive

• Vascular tumors (endothelial)

None (a lumen)

Vacuole may be septate; no effect on nucleus; reticulin outlines groups of cells; rare red blood cells in vacuoles; factor VIII antigen positive

• Smooth muscle tumors

None (artifact)

Vacuole not present in nonformalin fixatives; perinuclear with occasional indentation of nucleus; nonvacuolated spindle areas usually present

• Rhabdomyosarcoma Glycogen Juxtanuclear and PAS positive in larger tumor cells;

desmin and muscle actin positive

• Myxofibrosarcoma ProteoglycansNucleus not usually indented; seen mainly in pleomorphic cells; alcian blue-positive; fat stain, +/-; S-100-negative

• Chordoma Proteoglycans No effect on nucleus; PAS positive; cytokeratin positive• (Paraganglioma) ? Indents nucleus; positive argyrophilic stains

• (Melanoma) ? Rare cases are highly vacuolated; may be septate; S-100 +

• (Lymphoma) Immunoglobin Clear or eosinophilic PAS-positive inclusion; light chain positive in small-cell (“signet ring”) lymphoma; LCA +