Background: The pectoralis minor muscle is increasingly preserved in women undergoing axillary clearance as part of 
either breast conservation or mastectomy. The aim of the study was to determine the number of nodes removed and the 
proportion of positive nodes for patients submitted to breast surgery, with and without preservation of the pectoralis minor. 
In addition, to determine the incidence of early and late complications including the surgical, and functional consequences. 
Patients and Methods: A prospective study was conducted in two groups of 30 patients each submitted to axillary dissection for breast cancer (46 mastectomies and 14 conservative procedures) with the pectoralis minor muscle spared in one group and removed in the other, The mean number of dissected lymph nodes in both procedures was counted. The immediate (1 month), early (1-3 months) and late (6 months up to 1 year) postoperative complications were recorded prospectively. 
Results: Clinical details were similar in the two groups. Twenty five percent of patients had negative nodes and 75% had 
positive nodes. When the node-positive patients were subdivided in terms of extent of involvement (1-3, 4-9 and 10 or more) there were similar proportions in both groups. The mean total number of nodes removed in the two groups was similar: 16.5 (range, 7-32) (muscle spared group) versus 17.5 (range 7-34) (muscle removed group). Furthermore, on analyzing the number of dissected lymph nodes in relation to the anatomical level, no difference was observed in numbers, at level I, II, and III in both groups. 
With respect to immediate postoperative complications there was no difference in the usual postoperative course between the two groups. Similarly, the early postoperative complications failed to demonstrate any difference between the two groups of patients apart from a slight increase in lymphoedema frequency and shoulder dysfunction in patients in whom the pectoralis minor was removed. The late postoperative complications revealed a higher difference in shoulder and arm movement restriction in favour of the spared muscle group (2/30 vs 6/30). Fewer patients with pectoralis minor muscle intact had lymphoedema (9/30) compared with those in which the muscle had been removed (14/30). We did not find differences in pain, winged scapula, or intercostobrachial syndrome at the 6-month to one-year follow-up. In contrast a highly significant statistical difference was found between the two groups with regard to the partial atrophy of the pectoralis major muscle (2/30) for the spared muscle group versus (18/30) for the removed muscle group. 
Conclusion: The comparison of the two groups showed that the mean number of dissected nodes in both procedures was similar. Retention of the pectoralis minor is not associated with understaging or undertreatment of the axilla and also appears to prevent the partial atrophy and fibrosis of the pectoralis major. Patients treated with conservation of the 
pectoralis minor muscle showed atrophy of the pectoralis major muscle in (6.6%) of cases versus (60%) observed in the muscle removed group.