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Rhabdomyosarcoma : Locations & Gross

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LOCATIONS: Rhabdomyosarcomas (RMS) can occur anywhere in the body, but affect three regions more commonly - the head and neck, genitourinary tract and retroperitoneum, and upper and lower extremities.

Head & Neck: This region is the most common location for RMS accounting for about 26% of all cases. The head & neck sites include parameningeal (the most common), orbit (2nd most common), nasal cavity, nasopharynx, ear and ear canal, paranasal sinuses, soft tissues of face and neck, and oral cavity.

Genitourinary (GU) Tract: It is the second most common site for RMS (17% of cases). Embryonal and spindle cell/sclerosing are the usual subtypes seen in this location. The sites include paratesticular region, spermatic cord, and epididymis. Testis proper is generally spared. Retroperitoneum and pelvis are also commonly involved.

RMS of urinary bladder and prostate account for about 5% of all cases. RMS is the most common urinary bladder tumor in children under 10 years of age. The main subtypes in this location are embryonal and botryoid. Adult RMS of the urinary bladder are more often alveolar subtype. Rare GU sites include fallopian tubes, uterus, cervix, vagina, vulva, perineum and perianal region. RMS in these locations are often of botryoid type.

Extremities: About 15% of all RMS arise in the extremities. Upper and lower extremities are equally involved. Alveolar RMS are slightly more common than embryonal RMS in this location. Pleomorphic RMS usually arise in the deep soft tissues of extremities in adults.

Rare Sites: Common bile duct is a rare site of RMS, usually botryoid type.

GROSS PATHOLOGY: Gross Pathology: The gross features of RMS depend upon the degree of cellularity, the relative proportions of collagenous or myxoid stroma, and the presence or absence of secondary changes. Tumors growing into body cavities such as urinary bladder or nasopharynx are well-circumscribed, multinodular or polypoid in configuration. The cut surface is glistening, gelatinous or mucoid, and pink-tan with areas of cyst formation, hemorrhage or necrosis.

Deep-seated tumors in the extremities or retroperitoneum have infiltrative borders and are less well-defined. They appear gray-white or pink-tan with a fleshy, bulging cut surface. They are usually 3-4 cm in size. Foci of necrosis and cystic change are frequently present.

The image shown is a specimen of embryonal rhabdomyosarcoma of the orbit in a 7 year-old boy. The cut surface shows firm, yellowish-white areas, foci with gelatinous consistency and areas of necrosis and hemorrhage. Note the eye globe at the top right. With rapid advances in adjuvant radiation therapy and combination chemotherapy, radical surgical procedures such as orbital exenteration have become rare. About 9% of all rhabdomyosarcomas involve the orbit. Majority of them are embryonal rhabdomyosarcomas.

Case courtesy of Prof. K.V. Santosh, Dept. of Pathology, Vydehi Institute of Medical Sciences, Bengaluru, India; used with permission.

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