Microanatomy of Milk Ducts in the Nipple

Usefulness of X-ray dark-field imaging in the evaluation of local recurrence after nipple-sparing mastectomy

PURPOSE

Our previous study suggests that the cross-sectional morphology of ducts and branching of ducts in the nipple are associated with the presence of breast cancer. In this study, we evaluated whether cross-sectional morphology and duct branching of human nipple obtained by X-ray dark-field imaging tomographic technique (XDFI-CT) could predict the likelihood of the presence of intraductal cancer into the nipple.

METHODS

A total of 51 nipple specimens were obtained from consecutive total mastectomies performed for breast cancer in Nagoya Medical Center. After reconstructing 3D images of the nipple using XDFI-CT, the cross-sectional images and the 3D arrangement of ducts were extracted. These cross-sectional images of ducts were classified into four patterns based on the status of the lumen without being informed of pathology results.

RESULTS

Of the four patterns, the distended ducts with heterogenous content were highly correlated with the presence of ductal carcinoma in situ confirmed by histopathology. The total number of orifices identified in the 51 specimens was 1298, and 182 (14%) at the tip and 19 (1.5%) at least 5 mm depth from the tip were composed of two or more ducts.

CONCLUSIONS

Anatomy of nipple ducts is essential to evaluate risk of local recurrence after nipple-sparing mastectomy because cancerous spread occurs within the duct of the same segment of the mammary duct-lobular system in the in situ stage. The 3D microscale anatomy of nipple ducts revealed by XDFI-CT provides useful information to assess the risk of breast cancer involvement at the preserved portion in nipple-sparing mastectomy.

Biological gel-based microchamber array for tumor cell proliferation and migration studies in well-controlled biochemical gradients

Breast cancer metastasis is a complex process controlled by multiple factors, including various cell-cell interactions, cell-environment coupling, and oxygen, nutrient and drug gradients that are intimately related to the heterogeneous breast tissue structure. In this study, we constructed a high-throughput in vitro biochip system containing an array of 642 microchambers arranged in a checkerboard configuration, with each chamber embedded in a composite extracellular matrix (ECM) composed of engineered collagen and Matrigel to mimic local heterogeneous environment in vivo. In addition, a controllable complex tetragonal chemical concentration profile can be achieved by imposing chemical compounds at the four boundaries of the chip, leading to distinct local nutrient and/or drug gradients in the individual microchambers. Here, the microchamber array with composite ECM (MACECM) device aims to simulate multiple tumor cell niches composed of both breast epithelial cells (MCF-10A-GFP) and metastatic breast cancer cells (MDA-MB-231-RFP), which enables systematic studies of cell responses to a variety of biochemical conditions. The results obtained from the MACECM studies indicate that discoidin domain receptor 1 (DDR1) inhibitor 7rh and matrix metalloproteinase inhibitor batimastat, in association with epidermal growth factor (EGF) had no significant effects on the growth of MCF-10A-GFP cells, but had significant effects on DDR1 expression and the related migratory behavior of MDA-MB-231-RFP cells. The MACECM design not only enables the construction of a more realistic in vitro model for investigating cancer cell migration mechanisms but also has considerable potential for further development as a platform for next-generation high-throughput and therapeutic screening (e.g., anti-cancer drug evaluation) and personalized medicine.

Three-dimensional microanatomy of human nipple visualized by X-ray dark-field computed tomography

PURPOSE

The three-dimensional (3D) structure of the human nipple has not been fully clarified. However, its importance has increased in recent years because it has become common practice to preoperatively explore the spread of breast cancer to the nipple with needle biopsy, ductoscopy, and/or ductal lavage for nipple-sparing mastectomy. Here, we demonstrated that X-ray dark-field computed tomography (XDFI-CT) is a powerful tool for reconstructing the 3D distribution pattern of human lactiferous ducts non-destructively, without contrast agent, and with high tissue contrast.

METHODS

Nipples amputated from mastectomy specimens of 51 patients with breast cancer were visualized three-dimensionally by XDFI-CT. First, CT images and conventionally stained tissue sections were compared to demonstrate that XDFI-CT provides 3D anatomical information. Next, the number of ducts in the nipple and the number of ducts sharing an ostium near the tip of the nipple were measured from the volume set of XDFI-CT. Finally, the 3D distribution pattern of the ducts was determined.

RESULTS

XDFI-CT can provide images almost equivalent to those of low-magnification light microscopy of conventional hematoxylin-eosin-stained histological sections. The mean number of ducts in all cases was 28.0. The total number of ducts sharing an ostium near the tip of the nipple was 525 of 1428. The 3D distribution patterns of the ducts were classified into three types that we defined as convergent (22%), straight (39%), or divergent (39%).

CONCLUSIONS

XDFI-CT is useful for exploring the microanatomy of the human nipple and might be used for non-invasive nipple diagnosis in the future.

Nipple Deformation and Peripheral Pressure on the Areola During Breastfeeding

Breastfeeding is a complex process where the infant utilizes two forms of pressure during suckling, vacuum and compression. Infant applied compression, or positive oral pressure, to the breast has not been previously studied in vivo. The goal of this study is to use a methodology to capture the positive oral pressure values exerted by infants' maxilla (upper jaw) and mandible (lower jaw) on the breast areola during breastfeeding. In this study, the positive and negative (vacuum) pressure values are obtained simultaneously on six lactating mothers. Parallel to the pressure data measurements, ultrasound images are captured and processed to reveal the nipple deformations and the displacements of infants' tongues and jaw movements during breastfeeding. Motivated by the significant differences in composition between the tissue of the breast and the nipple–areola complex, the strain ratio values of the lactating nipples are obtained using these deformation measurements along with pre- and postfeed three-dimensional (3D) scans of the breast. The findings show an oscillatory positive pressure profile on the breast under both maxilla and mandible, which differs from clinical indications that only the mandible of an infant moves during breastfeeding. The strain ratio varies between mothers, which indicates volume changes in the nipple during feeding and suggests that previous assumptions regarding strain ratio for nonlactating breasts will not accurately apply to breast tissue during lactation.

Stimulated echo diffusion tensor imaging (STEAM-DTI) with varying diffusion times as a probe of breast tissue

PURPOSE

To explore the application of diffusion tensor imaging (DTI) for breast tissue and breast pathologies using a stimulated-echo acquisition mode (STEAM) with variable diffusion times.

MATERIALS AND METHODS

In this Health Insurance Portability and Accountability Act-compliant study, approved by the local institutional review board, eight patients and six healthy volunteers underwent an MRI examination at 3 Tesla including STEAM-DTI with several diffusion times ranging from 68.5 to 902.5 ms. A DTI model was fitted to the data for each diffusion time, and parametric maps of mean diffusivity, fractional anisotropy, axial diffusivity, and radial diffusivity were computed for healthy fibroglandular tissue (FGT) and lesions. The median value of radial diffusivity for FGT was fitted to a linear decay to obtain an estimation of the surface-to-volume ratio, from which the radial diameter was calculated.

RESULTS

For healthy FGT, radial diffusivity presented a linear decay with the square root of the diffusion time resulting in a range of estimated radial diameters from 202 to 496 µm, while axial diffusivity presented a nearly time-independent diffusion. Residual fat signal was reduced at longer diffusion times due to the shorter T1 of fat. Residual fat signal to the overall signal in the healthy volunteers' FGT was found to range from 2.39% to 2.55% (shortest mixing time), and from 0.40% to 0.51% (longest mixing time) for the b500 images.

CONCLUSION

The use of variable diffusion times may provide an in vivo noninvasive tool to probe diffusion lengths in breast tissue and breast pathology, and might aid by improving fat suppression at longer diffusion times.

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:84-93.

Anatomy relevant to conservative mastectomy

Knowledge of the anatomy of the nipple and breast skin is fundamental to any surgeon practicing conservative mastectomies. In this paper, the relevant clinical anatomy will be described, mainly focusing on the anatomy of the "oncoplastic plane", the ducts and the vasculature. We will also cover more briefly the nerve supply and the arrangement of smooth muscle of the nipple. Finally the lymphatic drainage of the nipple and areola will be described. An appreciation of the relevant anatomy, together with meticulous surgical technique may minimise local recurrence and ischaemic complications.

Evaluation of factors associated with pain experienced during mammary ductoscopy

BACKGROUND

The aim of this study was to evaluate patient characteristics and findings after mammary ductoscopy in an effort to reduce the pain experienced during the procedure.

PATIENTS AND METHODS

We evaluated outpatients in whom mammary ductoscopy was performed under local or intraductal anesthesia without preference, and their clinical characteristics and findings were recorded. Average and maximum pain scores were determined after the examination for statistical analysis.

RESULTS

The overall average pain score was 3.74 ± 1.353, and the maximum pain score was 6.40 ± 1.681. The type of anesthesia, total operation time, nipple retraction, and discharge status significantly correlated with the pain score. Intraductal anesthesia lowered the average pain score by 0.60, whereas a total procedure time greater than 12 min increased the average pain score by 0.956. The pain score decreased if patients had nipple retraction, and intraductal anesthesia proved suitable for patients with normal nipples.

CONCLUSION

Intraductal anesthesia is suitable for most patients, and ductoscopy should not exceed 12 min to minimize the pain. Nipple retraction does not significantly increase pain, but local anesthesia should be used in patients with retracted nipples. Patient age, breastfeeding history, menstrual stage, and presence of intraductal tumors were not associated with the level of pain experienced.

In vivo assessment of number of milk duct orifices in lactating women and association with parameters in the mother and the infant

Background

In vitro and in vivo analyses differ between the number of milk ducts found in the lactating breast, and there is a lack of knowledge as to whether or not external factors in the mother or the child affect the number of ductal orifices. The aim of this study was to determine the number of milk duct orifices in vivo and to investigate the possible influence of variable parameters in mother and infant.

Methods

Study design: Prospective clinical trial. In 98 breastfeeding women we investigated the nipple surface in order to identify the number of milk duct orifices using Marmet’s manual milk expression technique. In addition mothers were interviewed on different parameters of birth and breastfeeding.

Results

Every nipple had 3.90 ± 1.48 milk duct orifices on average. There was no significant difference between left and right breasts. The use of a breast pump in addition to breastfeeding did not have any effect on the number of ductal orifices. Multiparous women exhibited more ductal orifices (8.5 ± 3.0) as compared to primipara (7.1 ± 2.7). Boys were associated with significantly more ductal orifices in their mother’s right breast (4.2 ± 1.7) than girls (3.5 ± 1.4). Furthermore boys were breastfed for longer per session. A shorter birth height of males correlated with more ductal orifices in left nipples. Fluid intake of mothers was associated with a higher number of ductal orifices. Restless infant behavior could not be explained by less milk duct orifices. Pain in the breast during breastfeeding did not have an influence on ductal orifices either. Psychological criteria, such as duration of maternity leave and total intended breastfeeding period, did not affect the number of orifices in the papilla mammaria of breasts during lactation.

Conclusion

For the first time an in vivo investigation of the number of ductal orifices in lactating women was conducted non-invasively and associations with variables in the mother and the child, birth parameters in infants, and breastfeeding parameters in mothers and children were assessed. We conclude that the number of activated ductal orifices on the surface of the nipple is primarily associated with functional aspects.

Biomechanics of milk extraction during breast-feeding

How do infants extract milk during breast-feeding? We have resolved a century-long scientific controversy, whether it is sucking of the milk by subatmospheric pressure or mouthing of the nipple-areola complex to induce a peristaltic-like extraction mechanism. Breast-feeding is a dynamic process, which requires coupling between periodic motions of the infant's jaws, undulation of the tongue, and the breast milk ejection reflex. The physical mechanisms executed by the infant have been intriguing topics. We used an objective and dynamic analysis of ultrasound (US) movie clips acquired during breast-feeding to explore the tongue dynamic characteristics. Then, we developed a new 3D biophysical model of the breast and lactiferous tubes that enables the mimicking of dynamic characteristics observed in US imaging during breast-feeding, and thereby, exploration of the biomechanical aspects of breast-feeding. We have shown, for the first time to our knowledge, that latch-on to draw the nipple-areola complex into the infant mouth, as well as milk extraction during breast-feeding, require development of time-varying subatmospheric pressures within the infant's oral cavity. Analysis of the US movies clearly demonstrated that tongue motility during breast-feeding was fairly periodic. The anterior tongue, which is wedged between the nipple-areola complex and the lower lips, moves as a rigid body with the cycling motion of the mandible, while the posterior section of the tongue undulates in a pattern similar to a propagating peristaltic wave, which is essential for swallowing.

Nipple-sparing mastectomy in modern breast practice

Breast cancer management has evolved from the conventional radical Halsted to a fully integrated multidisciplinary approach. Nipple sparing mastectomy (NSM) is an innovative technique that preserves native breast envelope without mutilation of nipple-areola complex (NAC), thus providing a reasonable alternative for early cancers without NAC involvement and prophylactic high risk patients and avoids multiple surgical procedures required for reconstruction. This article aims to critically review indications, intra-operative protocols, radiotherapy planning and limitations of NSM. Patient selection should be based on study of breast duct anatomy by Magnetic Resonance Imaging, mammographic tumor-nipple distance and obligatory intra-operative frozen section from retro-areolar tissue. Tumor size, axillary lymph node status, lymphovascular invasion and/or degree of intraductal component are factors used to include NSM candidates based on institutional practice. Given the heterogeneity of patients and lack of standardization of preoperative investigations, surgical technique and pathologic sampling of retro-areola tissue so far, mandates a multi-institutional prospective study to define and validate a role for NSM in invasive breast cancer and DCIS. Nipple necrosis is an important NSM complication which can be greatly reduced using alternative skin incisions. Even if the nipple survives, an insensate nipple and lack of sexual function is common and requires preoperative counseling and discussion. Finally the relation and timing of intra-operative versus adjuvant breast radiation and tailoring of dosage and delivery methods has not been fully explored. Although NSM reduces psychological trauma associated with nipple loss, the oncologic safety as well as functional and aesthetic outcomes needs additional investigation.

A feasibility study of the intraductal administration of chemotherapy

Preclinical data have shown the potential of the intraductal administration of chemotherapy for breast cancer prevention. Direct translation of this work has been stymied by the anatomical differences between rodents (one duct per teat) and women (5-9 ductal systems per breast). The objective of this phase I study was to show the safety and feasibility of intraductal administration of chemotherapy drugs into multiple ducts within one breast in women awaiting mastectomy for treatment of invasive cancer. Thirty subjects were enrolled in this dose escalation study conducted at a single center in Beijing, China. Under local anesthetic, one of two chemotherapy drugs, carboplatin or pegylated liposomal doxorubicin (PLD), was administered into five to eight ducts at three dose levels. Pharmacokinetic analysis has shown that carboplatin was rapidly absorbed into the bloodstream, whereas PLD, though more erratic, was absorbed after a delay. Pathologic analysis showed marked effects on breast duct epithelium in ducts treated with either drug compared with untreated ducts. The study investigators had no difficulty in identifying or cannulating ducts except in one case with a central cancer with subareolar involvement. This study shows the safety and feasibility of intraductal administration of chemotherapy into multiple ducts for the purpose of breast cancer prevention. This is an important step toward implementation of this strategy as a "chemical mastectomy", where the potential for carcinogenesis in the ductal epithelium is eliminated pharmacologically, locally, and without the need for surgery.

Anatomy of the human mammary gland: Current status of knowledge

Mammary glands are unique to mammals, with the specific function of synthesizing, secreting, and delivering milk to the newborn. Given this function, it is only during a pregnancy/lactation cycle that the gland reaches a mature developmental state via hormonal influences at the cellular level that effect drastic modifications in the micro- and macro-anatomy of the gland, resulting in remodeling of the gland into a milk-secretory organ. Pubertal and post-pubertal development of the breast in females aids in preparing it to assume a functional state during pregnancy and lactation. Remarkably, this organ has the capacity to regress to a resting state upon cessation of lactation, and then undergo the same cycle of expansion and regression again in subsequent pregnancies during reproductive life. This plasticity suggests tight hormonal regulation, which is paramount for the normal function of the gland. This review presents the current status of knowledge of the normal macro- and micro-anatomy of the human mammary gland and the distinct changes it undergoes during the key developmental stages that characterize it, from embryonic life through to post-menopausal age. In addition, it discusses recent advances in our understanding of the normal function of the breast during lactation, with special reference to breastmilk, its composition, and how it can be utilized as a tool to advance knowledge on normal and aberrant breast development and function. Finally, anatomical and molecular traits associated with aberrant expansion of the breast are discussed to set the basis for future comparisons that may illuminate the origin of breast cancer.

Inside the lactating breast: the latest anatomy research

Although it is well recognized that a thorough understanding of the anatomy of an organ is essential to enable assessment of any abnormalities in that organ, there has been little investigation of the anatomy of the normal lactating breast since Sir Astley Cooper performed detailed dissections of the anatomy of the breast more than 160 years ago. Many mothers recognize that breast milk provides the ultimate nutrition and protection for the infant; however, a significant proportion of women experience difficulties breastfeeding, some of which lead to weaning the infant. Recently, a small number of studies have focused on the gross anatomy of the breast, and have found that the ductal system is comprised of fewer numbers of main ducts than previously thought. In addition, the ducts are compressible and do not contain large amounts of milk, the amount of fatty tissue in the breast is variable, and a proportion is situated within the glandular tissue. These findings add to our understanding of both the physiology and pathology of the lactating breast.

Terminal duct lobular units are scarce in the nipple: implications for prophylactic nipple-sparing mastectomy: terminal duct lobular units in the nipple

BACKGROUND

The use of nipple-sparing mastectomy (NSM) for both breast cancer treatment and risk reduction is increasing. There is no randomized data comparing nipple-sparing mastectomy with standard mastectomy techniques. There is evidence to suggest that ductal and lobular breast cancer arises in the terminal duct/lobular unit (TDLU). This study was undertaken to determine whether TDLUs exist in the nipple and if so, to what extent.

METHODS

At the time of mastectomy the nipple papilla was excised and submitted for separate pathological examination. The presence or absence of TDLUs was noted.

RESULTS

Thirty-two nipples were studied in 22 patients. There were no TDLUs in 29 specimens. Three of 32 nipple specimens were found to contain TDLUs. The three nipples contain one, two, and three TDLUs respectively. All TDLUs were found at the base of the nipple, with none located near the tip.

CONCLUSIONS

The infrequent occurrence of TDLUs in the nipple papilla supports the use of NSM for risk reduction surgery, including for those women with BRCA1/2 mutations.

Microscopic anatomy within the nipple: implications for nipple-sparing mastectomy

BACKGROUND

Precise anatomical relationships between ducts and vasculature within the nipple remain unknown. This study investigated nipple microvessels and their position relative to ducts.

METHODS

Nipple and duct bundle cross-sectional areas were measured in 48 specimens. Vessels located within the central duct bundle or within a peripheral rim were counted in 7 non-irradiated and 5 irradiated nipples.

RESULTS

Mean nipple diameter was 11.1 mm and duct bundle diameter 5.2 mm. A 2-mm and a 3-mm peripheral rim of nipple tissue would result in complete duct excision in 96% and 87% of sections, respectively. Twenty-nine percent of vessels are located in the duct bundle. A 2-mm rim contains 50%; a 3-mm rim contains 66%. Similar proportions were seen in irradiated nipples.

CONCLUSIONS

This study describes a strategy to balance duct removal with vascular preservation. Ducts can be excised leaving a rim of nipple tissue that contains a large proportion of microvessels.

Breast duct anatomy in the human nipple: three-dimensional patterns and clinical implications

BACKGROUND

The anatomy of the nipple has become clinically relevant. Diagnostic techniques access the breast through nipple ducts and surgeons offer nipple-sparing mastectomy. There is variation in the number of ducts reported and little is known about the spatial location of ducts, their size, and their relationship to orifices on the surface.

METHODS

Nipple specimens were taken from 129 consecutive mastectomies. Each was sectioned coronally into 3 mm blocks and one section was prepared from each block. The number of ducts and cross-sectional areas of nipple and duct 'bundle' were recorded. Three nipples were sectioned at 50 mum intervals and digitally reconstructed in three dimensions.

RESULTS

The median number of ducts was 23 (interquartile range 19-28). Reconstructions and summary data from 25 nipples show a central duct bundle narrowing to form a 'waist' as the ducts enter breast parenchyma. A three-dimensional reconstruction focusing on one nipple tip demonstrated 29 ducts arising from 15 orifices. Beneath the skin, most ducts are very narrow, gradually becoming larger deeper within the nipple.

CONCLUSIONS

This work demonstrates that many ducts share a few common openings onto the surface of the nipple, explaining the observed discrepancy between number of ducts and of orifices. Neither duct diameter nor position predicts whether a duct system will terminate close to the nipple or pass deeper into the breast. These new insights into nipple anatomy will be of use in considering the reliability of a ductal approach to diagnosis and in planning nipple-sparing mastectomy.