The Evolving Role of Mammary Ductoscopy

Kefah Mokbel, Abd Elrafea Elkak

Disclosures

Curr Med Res Opin. 2002;18(1) 

Summary and Introduction

Mammary ductoscopy (MD) is an emerging technique that allows direct visualisation of the mammary duct system, and that produces sharp and clear video images and ductal washings for cytological analysis. There is a growing body of evidence that MD may have a role in the management of women with pathological nipple discharge, the guiding of breast conserving surgery for cancer, and the screening of high risk women. Further research is required to confirm these potential applications and the feasibility of its use in the rapid intervention and outpatient setting under local anaesthesia. Furthermore, the addition of molecular and genetic analysis of cells obtained by MD and the emergence of newer generations of microendoscopes are likely to enhance the use of this technique.

The evidence that most breast cancers originate in the mammary duct and the fact that current imaging techniques (such as mammography) are associated with significant false-negative results[1] have made it logical to explore the role of endoscopic visualisation of the mammary duct system. Mammary ductoscopy has been evolving over the last 13 years[2,3,4,5,6,7,8,9]. The earlier attempts[2,3,4,5,6] were constrained by limited optics, large calibre scopes and lack of working channels for insufflation and biopsy under direct visualisation. Furthermore, the images generated by the earlier scopes were too small and imprecise to allow accurate clinical judgement. Recent technological advances in endoscopic techniques, however, have overcome many of these obstacles[7,8,9]. The current generation of microendoscopes (Acueity Inc., Larkspar, California, USA) use excellent fibre optics and measure 0.9 mm and 1.2 mm in external diameter. Such microendoscopes yield large, clear and sharp video images of the mammary duct system (Figure 1(c)) and provide working channels for insufflation, extraction of cells for diagnosis and possible therapeutic intervention.

Findings of intraoperative MD in women undergoing breast-conserving surgery for breast cancer. Abbreviations: DCIS = ductal carcinoma in situ; ADH = atypical ductal hyperplasia (reproduced with the kind permission of Acueity Inc.).

In a feasibility study using human mastectomy specimens, Dietz et al.[10] were able to cannulate the mammary duct system in 42 (100%) of 42 cases. The authors used a rigid (1.2 mm) fibre optic ductoscope containing an 0.35 mm working channel. The normal ductal epithelium often appeared smooth and shiny with visible blood vessels (Figure 1C). Endoscopic visualisation of the proximal ductal system was possible in 34 (81%) of 42 cases compared with 22 (52%) of 42 cases for the distal ductal system.

The limited success rate associated with distal ductal (beyond 2 cm) ductoscopy can be attributed to the use of rigid microendoscopes, acute angulation owing to ductal bifurcation, or to ductal occlusion owing to atrophy, scarring or pathology. The authors, however, observed that successful distal ductoscopy was significantly associated with the visualisation of ductal discharge at the time of endoscopy (45% vs. 0%).

Dooley[11] used a flexible fibre optic microendoscope (Acueity Inc, California, USA) in 55 women undergoing lumpectomy for breast cancer. The index quadrant was massaged to express nipple discharge prior to endoscopy. The procedure was successful in 47 (85.5%) of 55 patients. The target lesion was identified by fibre optic ductoscopy in 41 (75%) of 47 cases. Furthermore, the authors found more extensive disease than predicted by preoperative assessment in 21 (45%) of 47 cases. These initial observations suggest that MD can guide breast-conserving surgery and has the potential of reducing the need for re-excision procedures, especially in patients with ductal carcinoma in situ (DCIS).

Another important potential clinical application of MD is pathological nipple discharge where current imaging techniques and cytological examination of the discharge fluid usually fail to demonstrate the underlying pathology. Shen et al.[8] have recently reported their findings regarding the use of MD in women (n = 415) with pathological nipple discharge. The technique revealed a papillary lesion in 40% of cases. Most of these lesions were found in the main segmental ducts (37.6%) or in the first ductal branch (35.3%). The positive predictive value (PPV) for the procedure was 83%, but improved to 90% when combined with cytological examination of endoscopic washings of the examined ducts. Surgical pathology review of the specimens showed that 11 patients had DCIS, all of whom had an atypical ductal abnormality on MD. Six of these patients had negative mammograms. The authors concluded that MD, when combined with ductal lavage cytology, was a useful technique for diagnosing DCIS prior to definitive surgical treatment, and a safe alternative to ductography in women with pathological nipple discharge. The authors did not, however, compare MD directly with ductography in the management of such patients. Furthermore, no pathology was demonstrated in 54.5% of patients.

Dietz et al.[7] compared preoperative fibre optic ductoscopy (Acueity®) with ductography in women (n = 51) undergoing ductal excision for pathological nipple discharge. Patients underwent four-quadrant nipple block with local anaesthetic prior to cannulation of the discharging duct. The procedure identified abnormal pathology in 48 (88%) of 51 cases compared with 38 (75%) of 51 cases for preoperative ductography. Ductal obliteration and false tract formation were blamed for the three failures. The pathological abnormalities included papilloma in 36, DCIS in five, hyperplasia in seven and periductal inflammation in one. MD was well tolerated by the conscious sedated patient and assisted in guiding surgical excision of the discharging duct. The authors reported one wound infection. Future applications include the use of MD in the outpatient setting and the addition of LASER or radio frequency to allow therapeutic ablation of pathology.

The growing evidence that ductal lavage using microcatheters is effective in identifying atypical hyperplasia and malignant cells in high-risk women[11] has stimulated interest in exploring the potential role of MD in breast cancer screening. MD has the ability of directly visualising the occult ductal pathology and ductal lavage of abnormal areas under direct vision in high-risk women. This technique can be combined with the use of molecular and genetic markers of malignancy[12]. We are currently evaluating the potential role of human reverse transcriptase (hTERT) expression[13] in cells obtained by MD for the detection of early malignancy and premalignant change. The Acueity MD system has recently been approved by the FDA in the USA for use in humans. The manufacturers were due to market their second-generation microendoscopes in the second half of 2001. The new scope will be significantly cheaper than the current device and suitable for multiple use. Furthermore, it provides better working channels for biopsy and possible therapeutic intervention.

Further research is required in order to assess the potential role of MD in guiding breast-conserving surgery for DCIS, in screening high-risk women, in the ablation of atypical ductal hyperplasia and early DCIS using LASER or radiofrequency, and the feasibility of its use under local anaesthesia in the outpatient setting.

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