rhabdomyosarcoma ( rms ) is a common soft tissue malignancies in pediatric age that accounts for 12% of all solid malignancies . whereas , rms of breast is very rare , accounting for much less than 1% of all breast malignancies and being mainly confined to adolescent women . the extrammamary primary origin is usually trunk , neck , orbit , and the extremities . unfortunately , the prognosis of metastatic breast rms is very poor and there is no consensus about the treatment of breast metastasis due to its rarity . therefore , to add further evaluation on this disease , we report our experience about metastatic rms from the anus . an 18-year - old female patient was referred to our department for evaluation of a lump in the left breast noticed 1 week earlier . the patient had a past medical history of acute lymphoblastic leukemia ( all ) and anal rms . eleven years earlier , at age seven , she was referred to our hospital because of fever and both knee pain . on femur and leg simple x - ray , there was irregular marginated osteolytic lesion with cortical destruction in distal femur and proximal tibia . the complete blood count was as follow : hemoglobin 12 g / dl , white blood cell count 5,000/l with 37% of blast cell and platelet count 106,000/l . we performed bone marrow biopsy and aspiration on iliac crest and the bone marrow specimen was packed with leukemic blasts ( more than 95% ) . the immunohistochemical stain revealed the blast cells were positive for myeloid lineage ( cd33 and cd13 ) and b - cell lineage ( cd79a , cd20 , and cd19 ) . finally , she had been diagnosed as biphenotype all and treated with the children 's cancer group ( ccg)-106b protocol and prophylactic 18 gy cranial irradiation . during follow - up , she had remained in complete remission state . one year earlier , she visited our hospital due to an anal mass and accompanying pain . pelvic computed tomography ( ct ) scan revealed an 8.5 cm sized heterogenous enhancing mass around the anus . multiple enlarged lymph nodes were found on both inguinal area and bilateral iliac chain ( figure 1 ) . there was no evidence of distant metastasis on fluorodeoxyglucose - positron emission tomography and computed tomography ( fdg - pet / ct ) . the cells were small and round shaped on hematoxylin and eosin ( h&e ) stain and the mass was negative for cd3 , cd20 , cd79a and ets-1 , and positive for cd56 , cd99 and desmin based on immunohistochemical stain . the patient underwent vincristine , adriamycin , and cyclophosphamide based chemotherapy . and a total of 4,500 cgy in 25 fractions of radiotherapy dose was given to the pelvis . following treatment , fdg - pet / ct showed no uptake at the primary tumor site with complete remission state . upon clinical examination , a firm , round and nontender mass was found in her left breast , measuring 33 cm . breast ultrasonography showed a 2.3 cm sized circumscribed oval hyperechoic mass with central hypoechoic portion ( figure 2a ) . chest , abdominal , and pelvic ct scans and fdg - pet / ct were evaluated for metastatic disease . intense fdg uptake was present in the left breast and retrocrural space at the level of l1 verterbra ( figure 2b and 2c ) . for the decreasing tumor burden , the mass was well - circumscribed and , on section , shows a pale - tan solid fleshy cut surface with focal hemorrhage . the mass was composed predominantly of primitive small round blue cells which were surrounded by collagenous fibrous septa . some cells with rhabdoid feature immunohistochemical stain demonstrated strong positivity for cd56 , cd59 and desmin as identical to anal mass ( figure 3c ) . the breast mass was finally diagnosed as metastatic alveolar rms based on h&e and immunohistochemical stain . the largest series about breast rms was included 7 cases of primary breast rms and 19 more cases with breast metastasis registered from 1972 to 1992 . and the second largest series were 7 patients with metastatic breast rms reported by howarth et al .   and d'angelo et al . reviewed published articles about breast rms and most of published reports were single case reports . therefore , the characteristics and the treatment strategies of breast metastasis have been under - ascertained . we report this rare disease with hopes that our experience will aid reader in clinical decision - making . to the best of our knowledge , hays et al .   reported that most of primary rmss were initially regarded as fibroadenomas and some patients with metastatic rms were not recognized . the gross features are round or oval and circumscribed . because of predominant fibroglandular composition of adolescent breast , ultrasonography is reliable imaging method . however , a report described a metastatic rms mimicking normal breast parenchyme on ultrasonography . therefore , careful physical examination , tissue biopsy and further imaging study such as magnetic resonance imaging or fdg - pet / ct are needed for accurate diagnosis . for the differential diagnosis including other malignancies , immunohistochemical study is essential . at first , our patient was tentatively diagnosed as lymphoblastic lymphoma based on h&e stain morphology from core needle biopsy of anal mass . immunohistochemistry was negative for cd3 , cd20 , cd79a , and ets-1 , and positive for cd56 , cd99 , and desmin . besides rms , although rarely reported , metaplastic carcinoma or malignant phyllodes tumor might have sarcomatous component . unlike rhabdomyosarcoma which is aroused from stromal cell , metaplastic carcinoma is characterized by differentiation of the neoplastic epithelium into squamous cells and/or mesenchymal - looking elements . however , in this case , the specimen from anus and breast were entirely composed of sarcomatous element . systemic chemotherapy and/or local therapy have been applied in previous reports , however it is not known if aggressive local treatment could improve prognosis . in this case , we decided to do a lumpectomy and radiation therapy despite of multiple organ involvement because we hoped that local therapy could decrease tumor burden in adjuvant chemotherapy . previous studies have reported that cumulative incidences of second malignant neoplasm ( smn ) after treatment of childhood all has varied from less than 1% to 10% or more according to treatment method , duration and completeness of follow - up . although , this single rare case could not suggest that treatment of all would be associated with breast rhabdomyosarcoma , clinicians should carefully checkup the patient 's condition with the suspicion of smn . in conclusion , it is necessary to be aware of the risk of breast metastasis of primary rms . tissue biopsy is recommended when clinically suspected lesion is detected in patients with primary rms .
rhabdomyosarcoma ( rms ) of the breast is rare and there is scant information about the clinical behavior and treatment strategies . 
 we report an adolescent female patient with metastatic rms of the breast from the anus . 
 an 18-year - old female patient was referred to our clinic due to palpable mass in the left breast . at age seven , she was diagnosed with acute lymphoblastic leukemia and treated with chemoradiation therapy . 
 after 10 years of complete remission state , she presented with anal mass which was diagnosed as rms and she received chemoradiation therapy . 
 after 1 year of complete remission state , she noticed a palpable mass in her left breast . 
 the breast mass was diagnosed as metastatic rms based on core needle biopsy specimen . 
 the rms in breast was excised for the decreasing tumor burden despite of another metastatic lesion . 
 although rarely reported , metastasis of rms should be considered as a cause of breast mass . 
 tissue biopsy is recommended when clinically suspected lesion is detected .