Rhabdomyosarcoma C49.9

Rare malignant tumour occurring mainly in the urogenital tract and in the deep soft tissue of the head and neck region (orbit). The rhabdomyosarcoma is one of the most frequent childhood sarcomas (20%). However, it does not play a significant role in dermatological practice.

• Embryonic rhabdomyosarcoma (most common subtype)
• Alveolar rhabdomyosarcoma (Predominantly located on the extremities)
• Pleomorphic rhabdomyosarcoma (mainly located in the retroperitoneal space and on the head and neck); predominantly in men in the 6th-7th decade of life.
• Spindle cell rhabdomyosarcoma (in children: here mainly paratesticular and in adults: here soft tissue of the head and neck).

Soft or rough, moderately sharply definable tumor masses in the deep soft tissue. The skin remains smooth on the surface.

Small cell round cell sarcomas with rhabdomyoblasts characterized by an eosinophilic, fibrillar cytoplasm. Immunohistologically, the cells are reactive for myogenin, the markers MYF4, MYODI, desmin, caldesmon, actin). Pleomorphic forms are characterized by bizarre polygonal, round to spindle cells.

Molecularly, embryonic rhabdomyosarcomas show genetic alterations at 11p15.5. Alveolar rhabdomyosarcomas show fusions of PAX3/7-FOXO1, among others. Spindle cell rhabdomyosarcomas show 8q13 rearrangements.

Awkward. The prognosis is significantly improved by combined operative and radiochemotherapy. However, PX3/7-FOXO1 fusion positive alveolar and pleomorphic variants remain poor (Wilk M et al. 2018).

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