PRIMARY AND METASTATIC RHABDOMYOSARCOMA IN THE BREAST - NEOPLASMS OF ADOLESCENT FEMALES, A REPORT FROM THE INTERGROUP RHABDOMYOSARCOMA STUDY

The occurrence of rhabdomyosarcoma (RMS) primary in or metastatic to b reast has been regarded as an uncommon event, associated with an unfav orable outcome. Records of 26 patients with diagnoses of breast RMS, e ither primary or secondary, entered in the Intergroup Rhabdomyosarcoma Study (IRS) (1972-1992) were reviewed and compared with data regardin g 47 similar patients in published reports. Of the 26 IRS cases, the h istologic subtype was alveolar in 24, embryonal in 1, and not determin ed in 1. All were female with ages ranging from 11.5 to 20.2 years (me dian, 15.2 years; mode, 14-16 years). This compact age distribution of both primary (n = 7) and metastatic (n = 19)breast RMS was seen in pr eviously reported series. Among the 19 cases of RMS with initial disse mination to breast, primary tumor sites were: extremity (n = 8), nasop harynx/paranasal sinuses (n = 7), and trunk (n = 4). IRS treatment was risk-based according to site and extent of disease. Four of 7 patient s with primary RMS remain disease free 2.9 to 7 years post diagnosis. Among 19 patients with RMS initially metastatic to breast, including 7 in IRS clinical group IV at original diagnosis, three are disease fre e at 7.6, 15.7 and 17.0 years. Conclusions: primary or metastatic RIMS in breast is almost confined to adolescent females having tumors with alveolar histology. Approximately one-half of the patients with prima ry breast disease and 15% of those with metastatic breast disease as a n initial recurrence are long-term survivors. (C) 1997 Wiley-Liss, Inc .