Objective: To introduce a method of breast reconstruction using only an enlarged latissimus dorsi muscle flap. METHODS: The adipose tissue around the latissimus dorsi muscle was divided into 5 zones, and a semilunar skin incision was designed in the back to excise the latissimus dorsi muscle and surrounding adipose tissue without applying breast implants for immediate or late breast reconstruction. RESULTS: There were 35 cases of breast reconstruction using this method, and the reconstructed breasts were in good shape. CONCLUSION: Expanded latissimus dorsi muscle flap breast reconstruction is safe and effective, with good reconstructed breast shape, and is an important advancement in breast reconstruction. Expanded latissimus dorsi muscle flap breast reconstruction The female breast has the dual functions of lactation and nursing and aesthetics, and the removal of breast from breast cancer patients causes serious physical and psychological impact on the patients. There are two major types of breast reconstruction methods: autologous tissue transplantation and application of artificial breast prosthesis, and autologous tissue transplantation breast reconstruction has received wide attention in recent years [1]. The transverse rectus abdominis muscle flap (TRAM) of the lower abdomen can meet the requirements for reconstruction after various types of breast loss and is a good treatment method, but TRAM surgery is traumatic, has a long recovery time, and is prone to serious complications when not handled properly. The traditional latissimus dorsi muscle flap does not carry the surrounding fat tissue and has a small amount of tissue, which requires the combined application of breast implants for breast reconstruction to achieve symmetry with the healthy side of the breast. As a foreign body, breast implants have complications such as implant leakage and rupture, and contracture of the envelope, which have become one of the major concerns of the debate. To avoid the use of breast prosthesis, Bohme, Song Juyao [2], Hokin [3] and others proposed the application of the latissimus dorsi muscle flap alone for breast reconstruction without the use of breast prosthesis. Recently, we started to apply expanded latissimus dorsi muscle flap for breast reconstruction with good results, which are reported as follows. 1. Surgical method (1) Preoperative examination and flap design In addition to the routine examination and the examination of systemic tumor recurrence, focus on the condition of the healthy side of the breast and the donor area. (1) Tissues available on the back. Place the index finger and thumb on the anterior border of the latissimus dorsi muscle, pinch up the skin, and estimate the thickness of the fat that can be utilized on the side. Note the thickness and extent of fat above the iliac crest. A thin back can be used to reconstruct only smaller sized breasts, a medium physique can be used to reconstruct medium sized breasts, and a thick fat can be used to reconstruct larger breasts. (2) Test the function of the latissimus dorsi muscle. A good function of the latissimus dorsi muscle means that the vascular nerves of the thoracic dorsum remain intact and are not damaged. The patient is drawn in the standing or sitting position with the thoracic separation range cavity and the excision range of the dorsal muscle fat flap (Figure 1). The flap was partially crescent-shaped and curved cephalad, with the medial side of the crescent-shaped flap 3 cm from the midline of the back and the lateral side to the anterior border of the latissimus dorsi muscle, with a flap width of more than 7 cm, so that it could be directly pulled together and sutured. A flap that is too wide increases the amount of adipose tissue to a limited extent, but can cause serious complications in the donor area. (2) Surgical operation The patient is placed in a lateral position with the affected side facing upward, and the immediate reconstructor is placed in a lateral position for mastectomy and axillary lymph node dissection. The donor area is injected with subcutaneous infiltration of local anesthetic diluted with epinephrine to facilitate hemostasis and subcutaneous separation. After excision of the skin, the subcutaneous 0.5 cm thick fat is preserved and the extent of excision of the muscle and fat flap is peeled subconsciously, with the rest of the fat retained on the muscle surface. When subcutting, a certain thickness of subcutaneous fat should be maintained to protect the subdermal vascular network and prevent partial necrosis of the skin in the donor area. After excision of the fat flap around the latissimus dorsi muscle, the flap is removed submuscularly toward the axilla. When the anterior serratus muscle branch of the thoracic dorsal artery is reached, the blood vessels around it are freed to form a vascular tip of the anterior serratus muscle beyond the thoracic dorsal vessels, which not only facilitates the transfer of the flap but also increases the safety of the operation. The stop of the latissimus dorsi muscle was completely cut to protect the subscapular thoracodorsal vascular tip. After the myocutaneous flap is free, it is transferred to the anterior thoracic region through a subcutaneous tunnel and temporarily fixed. The donor area was carefully hemostatic, and a negative pressure drainage tube was placed and pulled together and sutured. The patient’s body was adjusted in a semisitting position and flap shaping was performed. The flap is folded, the fat flap is placed under the flap, adjusted for symmetry with the healthy side, excess epidermis is removed, a drainage tube is placed, and the skin incision is sutured. For subcutaneous mastectomy, all epidermis of the flap should be removed; after modified radical breast cancer surgery with skin preservation, only the skin of the flap equivalent to the nipple areola area should be preserved; after modified radical surgery, excess epidermis should be removed as needed. The volume of the reconstructed breast should be slightly larger than that of the healthy side, and the thoracic dorsal nerve should be protected to avoid muscle atrophy later. The wound dressing should be applied to prevent pressure on the tip. Postoperative treatment After surgery, the affected side should be padded with soft pillows under the shoulder and hip, and the healthy side should be encouraged to lie down after recovery from anesthesia to prevent necrosis of the dorsal donor flap under pressure. On the second postoperative day, the position was changed to semi-seated, and the movement to the floor was started. Postoperatively, the chest and back were bandaged with a chest strap and the drains in the chest and axilla were removed 5-6 days postoperatively. The drainage from the back was high within 3 days after surgery, about 100-200 ml, and then gradually decreased and was removed around 7-10 days, and individual patients needed to put it into about 2 weeks. When moving the upper limbs after surgery, patients will feel the contraction of the reconstructed breast, which will gradually reduce and disappear with time. Functional exercise of the shoulder starts 1 month after surgery, encouraging participation in daily labor and upper limb suspension, swimming and other moderate physical activities. Application of local flaps and tattooing for nipple areola reconstruction 3 months after surgery, special cases request can be advanced to 2 weeks after surgery. 2. Clinical data There were 35 cases of breast reconstruction with enlarged latissimus dorsi flap, with a mean age of 40.6 (23-56) years, one case of unilateral breast giant fibroma, and the remaining 34 cases of breast cancer patients. 4 of the 35 cases were late reconstructions, all of which were after modified radical surgery; 31 cases were immediate breast reconstructions, including 3 cases after modified radical surgery, 7 cases after skin preservation modified radical surgery, and 21 cases after nipple areola preservation modified radical surgery. There were 21 cases after radical surgery. One case of partial dry necrosis in the dorsal donor area after surgery (Figure 2) was healed after drug replacement; one case of partial necrosis of the cut edge of the breast skin after immediate reconstructive surgery with skin-preserving modified radical treatment of breast cancer. 14 of the 21 patients with immediate reconstructive surgery with nipple areola preservation had partial necrosis of the epidermis of the nipple areola, scab formation, healing after peeling, and some nipples were shortened or partially depigmented (Figure 8). In this group of patients, the dorsal drainage was adequate and no hematoma or seroma was formed. The reconstructed breast was slightly reduced in size within 3 months after surgery, with a maximum follow-up of 26 months. One case of a 23-year-old patient had a soft texture of the reconstructed breast. Early 3 cases had a slight deformity of the axillary tip. 3. Case report Case 1: 23-year-old patient with a large left breast tumor, preoperatively diagnosed as “left breast lobulated cystic sarcoma”, underwent subcutaneous simple mastectomy and immediate reconstruction with expanded latissimus dorsi muscle flap, postoperative pathology reported as giant fibroma. Six months later, the reconstructed breast was in good shape, with a softer texture than the healthy side, no depression deformity in the dorsal donor area, insignificant scar growth, and a mild bulge deformity in the axillary tip, and the patient was satisfied (Figure 3). Case 2: 56-year-old, 2 years after modified radical surgery for right-sided breast cancer with a small left breast, the patient refused to operate on the healthy breast. An extended late-stage breast reconstruction with an expanded latissimus dorsi muscle flap was performed electively, and a local flap nipple-areola reconstruction was applied 2 weeks after surgery. The reconstructed breast was in good shape, slightly larger than the healthy side, and the patient was satisfied (Figure 4). Case 3: 46-year-old patient with right-sided breast cancer (stage I), immediate breast reconstruction with an expanded latissimus dorsi muscle flap after skin-preserving modified radical mastectomy and postoperative chemotherapy. The reconstructed breast was in good shape and the patient was satisfied (Figure 5). Case 4: 23-year-old patient with ductal carcinoma in situ of the right breast, immediate breast reconstruction with an enlarged latissimus dorsi flap after modified radical treatment with preservation of the nipple areola and skin through an axillary incision. The reconstructed breast was in good shape and the patient was satisfied (Figure 6). Discussion There are two major types of breast reconstruction methods, breast implants and autologous tissue grafts, the advantages and disadvantages of which have been one of the focal points of discussion and should be applied according to different situations. Recent studies have shown that the systemic safety of breast implants has been demonstrated without causing autoimmune diseases or increasing the incidence of breast cancer, but there is still the possibility of local complications such as infection, contracture of the envelope, rupture of the implant and the longevity of the implant [2]. The TRAM flap and the latissimus dorsi muscle flap are the most commonly used for autologous tissue graft breast reconstruction, which is highly invasive and leaves scarring in the donor area. Conventional reconstructive surgery with the latissimus dorsi muscle flap has insufficient tissue volume and requires the combined use of a breast prosthesis, combining the disadvantages of both. Therefore, the sole application of the latissimus dorsi muscle flap tissue without prosthetic reconstruction has become one of the directions to be explored. The application of expanded latissimus dorsi muscle flap for breast reconstruction has been used for a long time, and Song Ruyao consciously took more tissue for breast reconstruction in 1981 due to the limitation of lack of breast prosthesis at that time [3], and became the earliest experimenter of expanded latissimus dorsi muscle flap in China. After that, many authors reported their experience of applying solely the latissimus dorsi muscle flap for breast reconstruction [3-7], but there was a lack of systematic study of the blood supply to the adipose tissue surrounding the latissimus dorsi muscle, and the concept of the expanded latissimus dorsi muscle flap was not explored in depth. McCraw and Papp [5-6] applied a four-week extended maple leaf-shaped latissimus dorsi muscle flap (fleurdelis flap) for breast reconstruction without the use of breast prosthesis. Based on the traditional latissimus dorsi muscle flap, the flap is extended in a winged shape around the flap, respectively, carrying some skin tissue, and the donor area is sutured directly. The winged skin is removed from the epidermis, folded and shaped to increase the volume of the reconstructed breast, with the disadvantage of significant dorsal scarring. This method increases the skin area of the flap and its subcutaneous fat without carrying the surrounding adipose tissue, and is suitable for patients with small and medium-sized healthy breast volumes. Delay [7] divided the available adipose tissue around the latissimus dorsi muscle into five zones, laying the groundwork for the expanded use of the latissimus dorsi muscle flap.Zone I is located in the tissue between the flap and the latissimus dorsi muscle (fatty zone under the skin paddle). Zone II is the fatty zone on the LD surface where the skin portion of the flap is removed. Like zone I, it is supplied by the myocutaneous and myofatty perforator vessels. The area of this zone is large, the available adipose tissue appears to be thin, and the amount of accumulated tissue is substantial. Assuming that the area of the latissimus dorsi muscle is 450 cm and there is 0.5 cm of fat on the surface of the muscle, the total amount of fat can reach 225 ml. zone III is the scapular fatty zone. It is located at the upper medial edge of the latissimus dorsi muscle and can be used as a continuation of the muscle flap, which can be folded to increase the volume of the myocutaneous flap. The IV zone is the anterior fatty zone of the latissimus dorsi muscle. It is located 3-4 cm anterior to the lateral border of the latissimus dorsi muscle and is supplied by small perforating vessels from the latissimus dorsi muscle. It is located above the iliac crest, also known as the love-handle, and is a continuation of the inferior border of the latissimus dorsi muscle, and is supplied by the myofatty vessels of the latissimus dorsi muscle. This part is located at the most distal part of the flap, where the latissimus dorsi muscle migrates into the tendinous portion, and the blood supply to this zone is most fragile (Figure 7). The design of the flap portion of the latissimus dorsi surface is divided into transverse and longitudinal. The transverse flap has a concealed postoperative scar that can be covered by the bra and the scar is relatively hidden; the longitudinal design facilitates excision of the fat tissue in the V area. Therefore, transverse flaps are preferable for small and medium-sized breasts, and oblique longitudinal design for larger breasts facilitates surgical operation. The main complications of the expanded latissimus dorsi flap are hematoma and seroma in the donor area. Careful intraoperative hemostasis and placement of negative pressure drainage is the key to prevention, and postoperative drainage is high, with drainage tubes generally placed for more than 7 days. After the onset of seroma, multiple puncture aspirations or repositioning of drains are often required. Compared with the traditional latissimus dorsi muscle flap combined with breast implants for breast reconstruction, the complications associated with artificial breast implants are reduced. However, the potential for donor area hematoma seroma and partial donor area necrosis is relatively increased due to the wider donor area separation. The volume of the reconstructed breast after expanded latissimus dorsi muscle flap breast reconstruction decreases with muscle atrophy and should be overcorrected intraoperatively, with the reconstructed breast being larger than the healthy side. The thoracic dorsal nerve should be brought into the flap to prevent postoperative denervation of the latissimus dorsi muscle. There are two ways to deal with the stops of the latissimus dorsi muscle flap during transfer, one is to cut off most of the stops and keep part of the tendon in order to protect the vascular tip and prevent the blood supply from being stretched during transfer; the other is to cut off all the stops of the latissimus dorsi muscle. In the early stage, we adopted the way of preserving part of the tendon, and found that some cases had thick axillary tissues, which was unsightly; in two cases, the reconstructed breast muscle contracted autonomously after surgery (Figure 8), which disappeared after cutting the muscle tissue through a small subcutaneous incision; later, we cut all the muscle stops, and practical experience proved that fully freeing the vascular tissues and cutting all the stops of the latissimus dorsi muscle would not lead to the obstruction of blood supply to the flap. In our group, we have a case of breast reconstruction with an enlarged latissimus dorsi muscle flap, a patient with a giant fibroma, and all the skin was removed from the latissimus dorsi muscle flap to fill the tissue defect. Considering that the patient was a young woman with a well-developed gland on the healthy side of the breast, the reconstructed breast carried a small amount of skin tissue. Therefore, the application of an expanded latissimus dorsi muscle flap for breast reconstruction should be based on direct suturing of the donor area, increasing the amount of skin as much as possible, removing the epidermis and filling in the anterior part of the breast to increase the texture of the breast. Expanded latissimus dorsi muscle flap carries fatty tissue around latissimus dorsi muscle, increases the amount of tissue, does not require joint use of breast prosthesis, and meets the requirements of breast reconstruction.