incomplete regression of the mammary ridges may result in aberrant breast tissue , which can be classified based on its components . among the various types of breast choristoma , ectopic breast tissue , comprised of only glandular tissue without a nipple or areola ,
although ectopic breast tissue does not have a secretory ductal system , it is histologically no different from anatomically normal breast tissue .
ectopic breast tissue therefore shows physiologic and pathogenic processes similar to those of eutopic breast tissue .
clustered microcalcifications on mammography are a relatively common feature of invasive carcinoma or ductal carcinoma in situ . however
, the microcalcification of ectopic breast tissue is difficult to delineate on mammography , and is often not detected .
we report herein a case of ductal carcinoma in situ originating from axillary ectopic breast tissue that had revealed clustered microcalcifications on screening mammography .
a 52-year - old woman with bilateral accessory breast tissue attended a local breast clinic for annual mammography and ultrasonography screening , during which clustered microcalcifications were detected in ectopic breast tissue of the right axillary area .
it was decided to maintain observation only with close surveillance , because the mammography findings were assessed as breast imaging reporting and data system category 3 ( figure 1a , 1b ) .
after 3 months the patient was readmitted to the clinic with a palpable axillary mass .
the mass was hard and fixed in the right side of axilla and an irregularly shaped axillary mass including microcalcifications , was identified on ultrasonography .
a breast surgeon performed an excision biopsy of the axillary mass , and clustered microcalcifications were identified on specimen mammography ( figure 1c ) .
histologic observations revealed that the mammary ducts , within the fibrofatty stroma , were filled with and distended by a solid epithelial proliferation .
necrosis and multifocal microcalcification were noted ( figure 2a ) , and the epithelial cells showed a moderate to high degree of nuclear atypia ( figure 2b ) .
the patient was diagnosed as having high - grade ductal carcinoma in situ and was referred to our department for additional procedures .
preoperative evaluation via positron emission tomography and computed tomography did not reveal any metastatic lesions .
the patient underwent a wide local excision of the axillary ectopic breast tissue with a safety margin around the cavity of 1 cm ; sampling of sentinel lymph nodes was also performed . for the evaluation of sentinel lymph nodes , 2 ml of a blue dye ( indigo carmine )
the weight of the excised ectopic breast tissue was 60 g ; the contained microcalcifications were identified on specimen mammography . in a section of the excised specimen ,
a cavitary lesion was noted along with focal fat necrosis due to the excision procedure .
remnant tumor was not clearly detected on macroscopic examination , but on microscopic examination , remnant tumor measuring 0.5 cm in maximum diameter was observed around the cavity ; histologic findings were similar to those for the excision biopsy .
and there was no indication of metastasis to the lymph nodes among seven sentinel lymph nodes biopsied .
immunohistochemical assay showed positive and negative staining for the estrogen and progesterone receptors , respectively , and strong positive staining confirmed overexpression of the c - erbb-2 protein .
the patient continues to undergo surveillance up to 3 months after surgery , with no specific problems .
ectopic breast tissue , a choristoma of the breast , can occur anywhere along the mammary ridge , and almost every form of breast disease can occur in ectopic breast tissue .
primary breast carcinoma arising from accessory breast tissue has been reported in 60% to 70% of all forms of ectopic breast tumor .
and the invasive ductal carcinoma is the most frequent histologic variant of primary ectopic cancer .
however , ectopic breast cancer is not easily detected because of the late expression of pathologic symptoms , and is commonly misdiagnosed as axillary lymph node disease , lipoma , or a sebaceous cyst .
furthermore , we report a microcalcification in the axillary region , revealed on mammography ; such findings could lead to ectopic breast cancer being overlooked or misdiagnosed as a calcification of the axillary lymph nodes . as late detection of ectopic breast cancer
may lead to a worse prognosis , a precancerous sign or symptom should not be ignored .
we wish to report the present case because of its rarity , as well as to highlight the implications of microcalcifications being discovered during the regular surveillance of ectopic breast tissue when an abnormality is detected on imaging .
when an abnormal image or symptom of ectopic breast tissue is noted , it should be evaluated in the same manner as for eutopic breast tissue .
if a palpable mass is detected in ectopic breast tissue , a needle biopsy can be helpful for a differential diagnosis .
if a malignant microcalcification is detected on mammographic imaging of aberrant breast tissue , it should be evaluated as to whether the calcification is located in a choristoma of the breast or a lymph node ; a biopsy should be performed for further evaluation .
a malignant microcalcification on mammography strongly correlates with ductal carcinoma in situ or invasive cancer . when a malignant microcalcification is detected on mammography , a needle biopsy or excision biopsy
this principle would also apply to ectopic breast tissue , because the components of such tissue are the same as those of an anatomically normal breast .
when ectopic breast cancer has been diagnosed , it is classified according to the tnm staging system used for primary breast carcinoma .
there is a clear distinction between ectopic breast cancer and occult breast cancer that presents in axillary lymph nodes ; this is the reason for a thorough examination to accurately establish the location of a microcalcification .
ectopic breast cancer should be managed based on the treatment protocols for primary breast cancer , in contrast to the management of occult breast cancer . although francone et al .   strongly recommended the preventive excision of ectopic mammary tissue , the incidence of ectopic breast cancer is only 0.2% to 0.6% of all breast cancers , whereas the incidence of postoperative complications ( e.g. , severe scarring , infection in the remaining sweat glands , pain , or discomfort ) is reported to be as high as 4% to 10% .
however , preventive removal of ectopic breast tissue should be performed in cases that show abnormal signs or symptoms ; if it were not performed , routine screening would be sufficient .
a wide and complete resection of ectopic breast tissue is indicated after ectopic breast cancer has been diagnosed , and an evaluation of axillary lymph nodes is certainly indicated if the ectopic breast cancer occurs in the axillary region .
ectopic breast cancer can spread to the axillary lymph nodes more rapidly than a typical breast cancer . based on the tnm staging and characteristics of an ectopic breast cancer , adjuvant
chemotherapy or radiotherapy can be administered , and hormonal therapy or targeted therapy can also be used , in accordance with the status of the relevant biological markers . although ectopic breast cancer is very rare , diagnostic modalities are usually the same as for typical breast cancer .
however , it is not easily detected if a significant clinical symptom is not obvious , which may result in a delayed diagnosis and poor prognosis . a patient with aberrant breast tissue
when an abnormal finding is detected , such as clustered microcalcifications on mammography or a clinically palpable mass in ectopic breast tissue , a thorough evaluation should be undertaken . despite its rarity ,
symptomatic ectopic breast cancer is relatively easy to diagnose because of its similarity to typical breast cancer .
however , it is less easily delineated on diagnostic imaging , leading to a late diagnosis and poor prognosis .
examination of accessory or ectopic breast tissue in affected patients should take place at the same time as the evaluation of eutopic breast tissue .
 ectopic breast tissue can occur anywhere along the incompletely regressed mammary ridge . among the various types of breast choristoma , ectopic breast tissue , which has only glandular tissue without a nipple or areola , 
 is most commonly detected in axillary areas . 
 however , ectopic breast cancer is often not detected until significant clinical symptoms have been revealed , or diagnosis is delayed . 
 furthermore , an examination of ectopic breast tissue tends to be omitted from a screening mammography . 
 especially , the microcalcifications of ectopic breast tissue are difficult to delineate on mammography . 
 herein , the authors report a case of ectopic breast carcinoma that showed clustered microcalcifications on screening mammography , and discuss the interpretation and implications of microcalcification in ectopic breast tissue . 
INTRODUCTION
CASE REPORT
DISCUSSION