fibroadenoma is a benign lesion of the breast that is frequently reported in young women ( in their twenties or early thirties ) , but much less commonly reported in women older than 40 years ( 1 ) . this lesion is frequently associated with other benign pathologies ( 1 , 2 ) , but also has been reported as associated , or concomitant , with malignancies in up to 5% of cases , mainly in older patients ( 2 ) . in extremely rare cases , these malignancies may be co - located with , or even within a fibroadenoma ( 0.02% ) ( 3 ) . it has been reported that a high percentage of these concurrent malignancies may be missed ( 1 , 2 ) , and for this reason , radiologists should be very cautious when evaluating fibroadenomas of a given patient within this specific age group . in recent years , new imaging methods have been developed , which increase the sensitivity for the diagnosis of breast cancers using contrast media . of these , contrast - enhanced breast magnetic resonance imaging ( mri ) currently appears as the most sensitive technique to detect and stage breast cancer ( 4 , 5 ) . however , several recent studies have shown that the emerging dual - energy , contrast - enhanced digital mammography ( cesm ) method enables accurate detection of malignant breast lesions with a similar performance to that of mri ( 4 , 6 - 8 ) , making it a good alternative to this expensive technique . in this paper , we present a case of a complex breast lesion consisting of the co - localization of triple negative invasive carcinoma of no special type ( tnbc - nst ) and a fibroadenoma . the malignant lesion was mammographically indistinguishable from the fibroadenoma , and was negative on the image - guided biopsy of an only - subtly suspicious area on breast ultrasound ( bus ) . however , the malignancy could be clearly visualized in the second stage of the imaging diagnosis , using cesm . this case is presented to reveal the potential of cesm , as an easy , rapid and inexpensive alternative to mri for the diagnosis of malignancies , which are occult to mammography plus bus . a 60-year - old woman underwent a screening mammogram ( mx ) in the breast imaging section of our hospital . skin retraction , nipple discharge or palpable lymph nodes were not observed on clinical examination previous to the mx . the right breast mx showed a 1.5 cm oval - shaped nodular mass with well - defined borders located in the upper - outer quadrant with imaging features of probable fibroadenoma . the left breast mx showed a well - circumscribed mass of irregular shape of about 1.7 cm , also in the upper - outer quadrant , with imaging features that were compatible with either a single irregularly shaped fibroadenoma , or with two smaller adjacent round - shaped fibroadenomas . a whole breast ultrasound ( us ) the right breast us gave an image of 1.5 cm , compatible with simple fibroadenoma . the left breast us showed an image compatible either with fibroadenoma or intramammary ganglion , but also showed an adjacent suspicious 0.7  1 cm hypoechoic area with an abrupt boundary and posterior acoustic enhancement ( figure 1 ) . we proceeded to perform an ultrasound - guided biopsy of the lesions of the right and left breasts , and the histopathological result was fibroadenoma with areas of microcalcification in all three cases . because us suspicion of malignancy in the left breast was not confirmed ( and taking into account the age of the patient ) , we decided to perform a dual - energy , contrast - enhanced spectral mammography ( cesm ) . with the patient in the seated position the iodinated contrast was administered ( 1.5 mg / kg iv , at 3 ml / s ) , and after two minutes the acquisition of low - energy ( 28 kvp ) and high - energy ( 47 kvp ) images began in the following order : a ) medial - lateral oblique view , non - suspicious breast ; b ) cranial - caudal view , non - suspicious breast ; c ) cranial - caudal view , suspicious breast ; and d ) medial - lateral oblique view , suspicious breast , with a total time for the acquisition of all images of five minutes . the low - energy image of cesm of the left breast ( equivalent to conventional digital mammography ) showed the same lesion with the aspect of fibroadenoma as seen in mx ( figure 2a and b ) , but the combined image revealed a 9.8 mm nodular enhancement with irregular and ill - defined contours ( figure 3 ) , which corresponded with one of the two sections of the irregular lesion seen both in mx and in the low - energy image of cesm ( figure 2c and d ) . a us - guided implantation of a metallic marker was performed for the localization of this lesion , which was surgically excised . the histopathology revealed triple - negative invasive carcinoma of no special type ( tnbc - nst ) , plus an independent fibroadenoma ( figure 4 ) . fibroadenoma of the breast is a very common benign lesion , especially in younger women , and is considered more closely related to an aberrant development of the breast tissue than to a true neoplasm ( 2 ) . although in general fibroadenoma is not considered to increase the risk of cancer , it is often associated to other pathologies such as sclerosing adenosis , duct ectasia , epithelial apocrine metaplasia , fibrocystic disease , and papillomatosis ( 1 ) . however , in women over 40 years of age with fibroadenoma , the concomitant occurrence of invasive cancers has been reported in up to 5% of cases ( 2 ) . so , the case presented here is not particularly rare , but two facts made the imaging diagnosis of this case particularly challenging : the type of tumor and its location . first , the tumor type , triple negative invasive ductal carcinoma of no special type , has been described as a tumor that often does not exhibit major suspicious findings of malignancy by mammography or us such as an irregular shape , ill - defined margins , or microcalcifications ( 9 ) . in this case , secondly , its location was adjacent to a true fibroadenoma , and the two masses appeared partially superimposed on the mammographic image , giving the appearance of either an irregularly shaped single fibroadenoma or of two adjacent rounded and smaller fibroadenomas . it has been reported that a small percentage of fibroadenomas in older women may harbor malignant tumors inside ( 0.02% to 0.125% ) ( 3 ) . however , the pathology of the surgical specimen revealed that in this case , these two lesions were completely independent , although located very close to each other . for these two reasons , this case could easily have fallen within the 4- 19% of malignant breast lesions that are missed by mammography ( 10 ) . moreover , in this case , although bus gave a suspicion of malignancy in a part of the lesion , the guided biopsy resulted in a histopathological diagnosis of fibroadenoma . probably due to the proximity of both lesions , the biopsy procedure was imprecise and incorrectly took a sample of the benign lesion instead of the carcinoma . mainly due to the age of the patient , additional imaging studies were recommended , since it has been reported that fibroadenomas may be associated with malignant lesions with some frequency in older women ( 2 ) . in the last decade , new methods have been developed to improve the sensitivity in the diagnosis of breast lesions , focusing on characteristics such as the neoangiogenesis of malignancies . thus , techniques , such as contrast - enhanced breast mri or cesm , have been developed ( 4 ) . currently it is accepted that mri is the most sensitive imaging technique for the diagnosis and staging of breast cancer ( 5 ) . however , mri is an expensive technique that is not yet readily available in many developing countries . in addition , mri also presents limitations for some patients such as overweight or claustrophobic women , or patients wearing pacemakers or metallic prostheses . cesm is a recently introduced imaging modality ( 2011 ) , which is based on the attenuation of radiation as it passes through different materials , in this case iodine and soft tissue . hence , after injecting iodinated contrast the usual mammographic views are presented , with the difference being that two consecutives images are acquired for each view : one of low energy and the other one of high energy ( 8) . post - processing allows for the creation of one combined image , where contrast uptake - areas are enhanced , and the normal tissue areas are suppressed ( 8) . thus , cesm is both a routine mammographic study and a contrasted image capable of finding angiogenesis . this technique is very new , and the characterization of benign and malignant breast lesions on cesm is still a subject of research . to date , some pitfalls and disadvantages of cesm have been described such as its limited performance with malignant microcalcifications with no underlying mass ( 8 , 11 ) , with the interpretation of ganglions and adenopathies ( 8) , or in patients with silicone breast implants ( 8) . in addition , the fact that cesm requires approximately a 1.5 times greater radiation dose than conventional mammography ( 8 , 11 ) has been seen as a disadvantage . however , to date , the false negative and false positive rates of cesm have been reported to be very low ( 11 ) , and recent studies have demonstrated that it could have a sensitivity and sensibility similar to that of mri , while having the advantage of being faster , much more economical , and not presenting the aforementioned contraindications of mri ( 4 , 6 , 7 ) . as such , cesm is a very promising imaging diagnostic tool , which may be useful in the diagnosis of complex breast lesions , as illustrated by this presented case report .
up to 19% of breast malignancies may be missed by conventional imaging techniques , especially when they are concurrent or co - located with other benign lesions . however , more sensitive techniques , such as magnetic resonance imaging ( mri ) , are often too expensive for routine use in developing countries . 
 contrast - enhanced , dual - energy digital mammography ( cesm ) is a recently introduced imaging modality whose performance has been reported to be similar to that of mri . 
 being much cheaper , cesm may constitute a good alternative for improving diagnostic sensitivity in these countries . in this paper 
 , we present a challenging case of the concurrent and co - located presentation of a fibroadenoma and a triple negative invasive carcinoma of no special type ( tnbc - nst ) . 
 the malignancy was indistinguishable from the fibroadenoma by mammography . by ultrasound , 
 a suspicious area was observed and biopsied , but the histopathology did not confirm a cancer diagnosis . as the suspicion was not confirmed , 
 a second stage of the imaging diagnosis using cesm was recommended . 
 this technique allowed clear visualization of the malignancy , which was finally excised by breast - conserving surgery . 
 this case reveals the potential of cesm as an easy , rapid and inexpensive new technique for the diagnosis of malignancies that might easily remain occult to mammography plus breast ultrasound ( bus ) .