Case 8

A 14-year-old female presented with a slowly-growing, painful mass over the midportion of the dorsum of the left hand. The mass was fixed to the deep structures, but the tendons and skin moved freely over it.
    A: The hand at presentation. The mass over the second metatarsal is poorly defined. The transverse biopsy scar is seen over the base of the metatarsal.
    B: An underexposed AP radiograph of the hand at presentation. The metallic dot was placed over the most prominent area of the mass. There is no radiographic evidence of the mass.
    C: An axial T-2 weighted MRI cut through the base of the metacarpals. This image showed an elliptical soft tissue mass with a high-intensity signal on the dorsal aspect of the second metacarpal.
    D: A low-power field from the central portion of the lesion. This field shows a highly cellular anaplastic lesion with no specific pattern to the arrangement of the cells. In a few areas there is a suggestion of an alveolar pattern.
    E: A medium power field from the periphery of the lesion. This field shows hyperchromatic spindle shaped cells in a monotonous pattern. In several areas the cells appear to be forming an eosinophilic ground substance that separates the cells.
    F: The same field at higher-power. This higher power again shows a majority of the cells are spindle shaped hyperchromatic cells randomly distributed in a faint eosinophilic background.
    G: Cells from the previous field under oil immersion. The eosinophilic cytoplasm of the central cell shows well defined cross striation.

Diagnosis: Rhabdomyosarcoma

The histogenesis of such malignant sarcomatous tissue can often best be established by immunohistochemical staining, which in this lesion established a diagnosis of alveolar rhabdomyosacrcoma. This lesion is the most common soft tissue tumor in children under age of 15 and is the most common sarcoma in the hand. It is a high-grade malignacy with a rapid growth pattern and has a prediliction for the head and neck. Local recurrence after inadequate excision occurs in almost all instances. Distant metastases, mainly to the lung are frequent. Metastasis to lymphatic nodes are frequent. Treatment consists of preoperative chemotherapy and/or radiationtherapy followed by wide surgical excision (or amputation) for reliable local control. In the present case a wide excision of the second and third metacarpals, overlying soft tissues and tendons was done.