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it accounts for approximately 3% of all adult neoplasms and in about 30% of patients it has a tendency to metastasize , usually to the lung ( 70% ) , lymph - nodes ( 55% ) , bone ( 42% ) , liver ( 41% ) , adrenal gland ( 15% ) and brain ( 11% ) .
breast metastases from extra - mammary tumors are much less common with respecto to primary breast tumors ( 0.52% of breast cancer ) , and are usually due to melanoma , lymphoma and leukemia ; metastases to the breast from rcc are a rare occurrence and take place in 3% of all metastatic rcc .
overall , 25 such cases have been reported in the literature : eleven cases presented with metastasis as the initial sign of the disease and fourteen , among which 2 were bilateral , occurred as metachronous lesions after a former nephrectomy .
we report a case of rcc metastasis to the breast occurring 9 years after primary surgery for rcc .
the difficulties in obtaining a correct diagnosis , which is crucial to avoid unnecessary mastectomy , and the management of axillary ipsilateral axillary lymph nodes are discussed .
a 70-year - old woman was referred to our institution on april 2013 due to a quickly enlarging lump located in the upper inner quadrant of her right breast . in her medical history , she reported having undergone a right radical nephrectomy in 2004 for rcc . at the time of the operation
the tumor was limited to the kidney compressing the renal capsule but with no sign of infiltration and there was no vascular invasion as well ; surgical margins were free and the disease was therefore staged as t3n0m0 ( g2 ) .
the patient received no further treatment and was followed up with annual whole - body computed tomography ( ct ) scan and mri . in april 2011
she underwent a pylorus - preserving pancreatic head resection because of a solitary , hypervascular and homogeneous mass located in close proximity to the head of the pancreas , measuring 16  mm .
the patient was thereafter asymptomatic until december 2011 , when she noted a quickly enlarging lump in the right breast . on admission ,
clinical examination revealed a palpable and mobile mass in the upper inner quadrant of the right breast with an enlarged ipsilateral axillary lymph node ; no skin or nipple retraction were noticed .
a mammogram showed a dense well circumscribed solid mass , not spiculate , measuring 3  cm in diameter , with no adjacent parenchymal distortion and no sign of microcalcification ; there were no signs of infiltration of the skin .
sonography showed a hypoechoic homogeneous solid nodule with no posterior attenuation of the acoustic wave but with prominent peripheral vascularity and penetrating vessels detected at color and power doppler .
the adjacent parenchyma was just displaced without obvious distortion , again with no skin thickening or duct ectasia .
multiple subcentimetric axillary lymphnodes were present , with a single one measuring 2  cm in diameter , with a preserved architecture .
a contrast - enhanced whole body ct showed an enhancing , homogeneous right breast mass ( fig .
1 ) , and fine needle aspiration citology ( fnac ) was unable to show malignancy .
a tru - cut biopsy was then performed and revealed a tumor composed of nests and cords of cells with clear cytoplasm separated by a prominent sinusoidal vascular network ( fig .
2 ) , which showed , at immunohistochemistry , positive vimentin and cd10 staining while ck7 and ck20 were negative . such pattern was consistent with renal cell carcinoma of clear cell type ( fig .
3 ) . after a multidisciplinary discussion , the patient underwent metastasectomy and exeresis of the largest palpable axillary lymph node , that resulted unaffected at frozen section .
the breast is a rare site of metastatic deposits , as emerges from the small number of cases reported in the literature .
however , it is possible that the incidence of such finding will become more and more frequent because of the increasing number of patients who live longer bearing malignant disease . in facts ,
the 5-year and 10-year survival rates for the patients with rcc treated with nephrectomy are 95% and 91% for pt1 ; 80% and 70% for pt2 ; 66% and 53% for pt3a ; 52% and 43% for pt3b ; and 43 and 42% for pt3c , respectively .
metastases can take place either in a synchronous or metachronous fashion with respect to the primary tumor : out of 25 cases reported in the literature , 14 actually occurred after nephrectomy for rcc . a former history of rcc should therefore arouse suspicion of metastatic escape to the breast despite the fact that primary carcinoma of the breast is much more common .
reported a majority of metachronous presentation , that was claimed to carry a better prognosis than the synchronous metastases ; however , to the best of our knowledge , no strong evidence of a significant prognostic difference between metachronous and synchronous presentations can be argued from the data available in the literature . clinically ,
metastatic lesions in the breast present as painless and mobile discrete masses with rapid growth .
the findings of the traditional diagnostic workup most likely mimic a benign breast mass , due to the absence of desmoplastic reaction ; in particular the deposits of malignant cells do not show spiculation or microcalcification on the mammogram and the sonography does not reveal posterior attenuation of the ultrasounds .
the only finding that can be suggestive of malignancy is the prominent peripheral and penetrating vascular network , well evident to color and power doppler , that is common to all cases reported in the literature .
awareness of a former treatment for rcc should lead to stress the preoperative diagnosis because the treatment of breast secondary lesions differs from that of primary breast tumors , either as far as the lumpectomy margins width and the management of axillary lymph nodes are concerned . in facts ,
the malignant extension to the breast can be explained by the spread of neoplastic cells from the renal vein into the inferior vena cava and then through the pulmonary circulation , eventually reaching the arterial circulation , diffusing throughout the whole body and thereby reaching the breast : therefore , the high rate of multiple lesions that constitutes the rationale of the efforts aimed at obtaining wide tumor - free margins is pointless in secondary disease .
besides , the mechanism of metastatic diffusion renders the the biopsy of a sentinel lymph node void of sense in such cases ; since malignant cells reach the breast ( via ematogenous spread ) , sampling the efferent lymphatics that constitute a way of diffusion from the breast is pointless .
moreover , the staging role of slnb obviously only applies to primary tumors , while sampling breast loco - regional lympnodes for tumors originating elsewhere in the body makes no sense . in cases of metastatic rcc , citology may show atypical cells which differ from those of a primary breast tumor but which , on the other hand , are frequently reported as benign .
a diagnosis based on histopathological investigation is therefore crucial in order to avoid an unnecessary mastectomy with sentinel lymphnode biopsy ( or primary axillary dissection ) .
moreover , we suggest to avoid fnac for the additional reason that the vascular network that characterizes metastases from rcc may lead to a high false - negative rates .
in conclusion , we suggest to consider a micro - histological biopsy of any new breast lesion appearing in a patient with a history of treatment for rcc as mandatory .
a whole body ct scan may be included in the staging work - up . in the case of an isolated lesion ,
metastasectomy is the treatment of choice ; axillary lymph nodes should be removed only in cases of overt metastatic deposists .
so far , unfortunately , no effective adjuvant therapeutic option is available for disseminated rcc because of the great resistance to chemotherapy and radiotherapy of this kind of metastases .
a written and signed consent to publish the case report was obtained from the patient .
sanna paola angela was the radiologist ; dubini allessandra was the pathologist ; and folli secondo was the supervisor .
introductionmetastases to the breast from extra - mammary tumors are uncommon and few sporadic cases are reported in the international literature . 
 an accurate differential diagnosis of secondary cancer is mandatory because both prognosis and treatment differ with respect to primary breast tumors.presentation of casewe present the case of a 70-year - old woman with an isolated metastasis to the breast occuring 9 years after undergoing a nephrectomy for renal cell carcinoma ( rcc).clinical examination revealed a palpable and mobile mass in the right breast with an enlarged ipsilateral axillary lymph node . 
 mammographic findings showed a dense , well circumscribed solid mass and the breast ultrasonography findings were those of a hypoechoic homogeneous solid nodule with no posterior attenuation but with prominent peripheral vascularity . 
 a tru - cut biopsy was conclusive for a metastatic deposit by rcc . 
 a whole - body ct scan showed no evidence of further recurrences . 
 the patient underwent metastasectomy and exeresis of the papable lymphnode.discussionin patients with former surgery for rcc , a diagnosis based on a preoperative biopsy allows to indicate the proper surgical treatment : in facts , as compared to primary breast tumors treatment , the rationale to pursue wide surgical margins is pointless in cases of metastases and , similarly , the biopsy of the sentinel lymphnode is void of sense due to the lack of its physiopathological prerequisite.conclusionwe suggest to consider a micro - histological biopsy of any new breast lesion appearing in a patient with a history of treatment for rcc . 
 prompt diagnosis is necessary to choose the right treatment .