Dermatofibrosarcoma: A sarcoma of the deep layers of the skin. The tumors are locally aggressive tends to recur but rarely metastatic. It can be classified into variants depending on the cell type tumors are derived from or by its characteristics: Pigmented variant from MELANIN-containing DERMAL DENDRITIC CELLS; Myxoid variant, myxoid STROMAL CELLS; Giant cell variant characterized by GIANT CELLS in the tumors; and Fibrosarcomatous variant chracterized by tumor areas histologically indistinguishable from FIBROSARCOMA.Genes, sis: Retrovirus-associated DNA sequences (v-sis) originally isolated from the simian sarcoma virus (SSV). The proto-oncogene c-sis codes for a growth factor which is the B chain of PLATELET-DERIVED GROWTH FACTOR. v-sis or overexpression of c-sis causes tumorigenesis. The human sis gene is located at 22q12.3-13.1 on the long arm of chromosome 22.Histiocytoma, Benign Fibrous: A benign tumor composed, wholly or in part, of cells with the morphologic characteristics of HISTIOCYTES and with various fibroblastic components. Fibrous histiocytomas can occur anywhere in the body. When they occur in the skin, they are called dermatofibromas or sclerosing hemangiomas. (From DeVita Jr et al., Cancer: Principles & Practice of Oncology, 5th ed, p1747)Mohs Surgery: A surgical technique used primarily in the treatment of skin neoplasms, especially basal cell or squamous cell carcinoma of the skin. This procedure is a microscopically controlled excision of cutaneous tumors either after fixation in vivo or after freezing the tissue. Serial examinations of fresh tissue specimens are most frequently done.Skin Neoplasms: Tumors or cancer of the SKIN.Scalp: The outer covering of the calvaria. It is composed of several layers: SKIN; subcutaneous connective tissue; the occipitofrontal muscle which includes the tendinous galea aponeurotica; loose connective tissue; and the pericranium (the PERIOSTEUM of the SKULL).Factor XIIIa: Activated form of FACTOR XIII, a transglutaminase, which stabilizes the formation of the fibrin polymer (clot) culminating the blood coagulation cascade.Oncogene Fusion: The GENETIC RECOMBINATION of the parts of two or more GENES, including an ONCOGENE as at least one of the fusion partners. Such gene fusions are often detected in neoplastic cells and are transcribed into ONCOGENE FUSION PROTEINS.Giant Cell Tumors: Tumors of bone tissue or synovial or other soft tissue characterized by the presence of giant cells. The most common are giant cell tumor of tendon sheath and GIANT CELL TUMOR OF BONE.Oncogene Proteins, Fusion: The GENETIC TRANSLATION products of the fusion between an ONCOGENE and another gene. The latter may be of viral or cellular origin.Chromosomes, Human, Pair 22: A specific pair of GROUP G CHROMOSOMES of the human chromosome classification.Soft Tissue Neoplasms: Neoplasms of whatever cell type or origin, occurring in the extraskeletal connective tissue framework of the body including the organs of locomotion and their various component structures, such as nerves, blood vessels, lymphatics, etc.Benzamides: BENZOIC ACID amides.