(Radiographics. 1999;19:S63-S72.)
© RSNA, 1999
Mammography of Autologous Myocutaneous Flaps1
Jacquelyn P. Hogge, MD,
Rebecca A. Zuurbier, MD and
Ellen S. de Paredes, MD
1 From Radiology Associates of Richmond, Richmond, Va (J.P.H.); the Department of Radiology, Georgetown University Medical Center, 3800 Reservoir Rd NW, Washington, DC 20007 (R.A.Z.); and the Department of Radiology, Medical College of Virginia/Virginia Commonwealth University, Richmond (E.S.d.P.). Recipient of a Certificate of Merit award for a scientific exhibit at the 1998 RSNA scientific assembly. Received March 2, 1999; revision requested April 7 and received July 22; accepted July 22. Address reprint requests to R.A.Z.
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Abstract
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Autologous myocutaneous flaps (AMFs) are used increasingly as a method of breast reconstruction after mastectomy for breast cancer. Autogenous breast reconstruction may be performed with a rectus abdominis, latissimus dorsi, or gluteus maximus myocutaneous flap. Mammographic imaging of AMFs is controversial but has been recommended by some authors because mammographic detection of nonpalpable local recurrences in AMFs continues to be reported. At mammography, AMFs have a predominantly fatty appearance with variable density due to the muscle component and postoperative scarring. Normal mammographic findings include the vascular pedicle, surgical clips, and surgical scars, which produce radiopaque lines in predictable locations. Abnormal mammographic findings include fat necrosis appearing as a spiculated mass, noncalcified or calcified lipid cysts, calcifications, lymph nodes, epidermal inclusion cysts, and locally recurrent carcinoma.
Index Terms: Breast, surgery, 00.4545 • Grafts, 00.4545
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INTRODUCTION
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Breast reconstruction is an integral component of the surgical management of breast cancer. Methods of breast reconstruction include placement of tissue expanders, implants, and autologous myocutaneous flaps (AMFs). AMFs are increasingly used after mastectomy for breast cancer (1–9). Breast reconstruction is frequently performed at the time of mastectomy, although delayed reconstruction can also be performed. Better and more aesthetic long-term results are achieved with immediate breast reconstruction because uninvolved skin can be preserved for the reconstruction and normal anatomic landmarks, such as the inframammary fold, are present at the time of reconstruction (10).
Reconstruction with tissue expanders or implants is the most common form of breast reconstruction performed in the United States (11). This type of breast reconstruction is a relatively simple surgical procedure that does not significantly extend operating room time or patient convalescence. It also does not produce additional scars or loss of muscle function. Potential complications include infection, poor healing with exposure of the implant, and late capsular contracture. Relative contraindications are obesity and a large, pendulous contralateral breast (11). Also, the silicone gel controversy has decreased requests for breast reconstruction with implants (11). Patients who have had a complete mastectomy with implant or tissue expander reconstruction do not undergo follow-up mammographic screening because the implant obscures any remaining subcutaneous tissues. Ul-trasonography has been suggested as a method of evaluating the mastectomy patient after implant reconstruction (12).
AMFs allow transposition of a substantial volume of skin, fat, and muscle from the abdomen, back, or buttocks to the chest for breast reconstruction without the use of synthetic materials. Hartrampf et al (1) noted that "It is an attractive concept to take fat from where it is present in excess and transpose it to a chest wall defect where it is absent and needed." With the silicone gel controversy, requests for breast reconstruction with AMFs have increased and the patient population has expanded to include patients previously not considered candidates for AMFs due to obesity, diabetes, smoking, abdominal scars from previous surgery, or adjunctive radiation therapy and chemotherapy. AMFs are indicated primarily in cases where additional skin is required for adequate reconstruction, the contralateral breast is large or pendulous, or there is a significant residual deformity from radical mastectomy or radiation therapy (7).
Radiologists performing mammography should be familiar with the normal and abnormal findings in AMFs. In this article, we describe the types of AMFs and mammographic findings in AMFs.
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TYPES OF AMFS
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Autogenous breast reconstruction may be performed with a rectus abdominis, latissimus dorsi (LD), or gluteus maximus myocutaneous flap. Each of these has advantages and disadvantages. The most common AMF is the transverse rectus abdominis myocutaneous (TRAM) flap (7,13). With a modified abdominoplasty, an ellipse of lower abdominal skin and fat is moved on a musculovascular pedicle to reconstruct the breast (1) (Fig 1). Multiple modifications of this procedure have been successfully performed, including the upper TRAM flap (1), vertical rectus abdominis flap (5), extended vertical rectus abdominis flap (8), extended TRAM flap (9), L-shaped vertical and transverse rectus abdominis flap (6), and lower TRAM flap (1) on single, bilateral, ipsilateral, or contralateral pedicles. Free TRAM flaps were developed to reduce the incidence of flap necrosis by improving blood supply to the flap via direct anastomoses to chest wall vessels (2). Microvascular surgery can also be used to augment pedicled TRAM flaps ("supercharged" flaps) (11). Breast reconstruction with an innervated rectus abdominis flap (14) and breast reconstruction in a male patient with a TRAM flap (15) have been described.
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Figure 1. Classic TRAM flap. An elliptical island of skin and fat is elevated from the lower abdomen on a pedicle of the contralateral rectus abdominis muscle and rotated into the mastectomy defect. The origin of the C line is the umbilicus defect.
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Advantages of the TRAM flap include a large volume of skin and underlying fat for reconstruction to create a natural-appearing breast without the use of synthetic materials, long-term durability, and radiolucency, which allows mammographic imaging (7,16). Potential complications of both free and pedicled TRAM flaps include postoperative abdominal wall weakness or hernias, hematoma, delayed healing, fat necrosis, and partial or complete flap loss (17). Also, the TRAM flap requires a complex and expensive surgical procedure with extended operating room time, postoperative hospitalization, convalescence, and physical therapy. Relative contraindications include smoking, obesity, previous chest wall irradiation, extreme thinness, and previous abdominal surgery. A recent review found that the most significant risk factor for any complication was smoking (18). Other risk factors in decreasing order of significance were previous radiation therapy to the chest, significant abdominal scarring, and obesity. Diabetes, age, and hypertension had no significant association with postoperative complications of TRAM flaps (18).
The LD flap is the second most common AMF and is frequently selected when additional tissue is needed to rebuild mastectomy defects and the TRAM flap cannot be used. For the LD flap, skin, subcutaneous fat, and the LD muscle are elevated and rotated anteriorly to reconstruct the ipsilateral breast (Fig 2). The LD flap usually requires an implant or tissue expander to provide additional volume for the reconstruction because most women do not have sufficient tissue on their upper back for an adequate reconstructive result (7,11). An extended LD flap has been described that harvests additional skin and fat from the lower back so that an implant may not be required (19). The LD flap is also indicated when additional muscle coverage or tissue volume is needed for implant or expander reconstruction (7), when a TRAM flap cannot be used, in obese patients, and in some patients who are heavy smokers or have chronic obstructive pulmonary disease (11). LD flaps are contraindicated in patients who have undergone ipsilateral posterolateral thoracotomy (19). Advantages of this flap include low postoperative morbidity, good blood supply to the flap, and avoidance of additional abdominal scarring. Potential complications include periprosthetic infection, postoperative dorsal hematoma, partial or complete flap loss (2%) (7), persistent dorsal pain, and late capsular contracture (11,19).
The gluteus maximus free flap is the least performed and most technically demanding of the AMFs (7). Usually, this flap is selected when neither the TRAM nor the LD flap is technically feasible (7). Skin, subcutaneous fat, and a portion of the gluteus maximus muscle are transposed to the mastectomy site and the vasculature is reattached with microvascular surgery (Fig 3). This flap has the advantage of hiding the residual scar in the buttocks crease. Liposuction is usually performed on the opposite buttock to restore symmetry. Complications include seroma, hematoma, infection, fat necrosis, and partial or complete flap loss.
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MAMMOGRAPHIC FINDINGS
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Normal mammographic findings in TRAM (13) and LD (20) flaps have been described. Unlike implants, which are radiopaque, AMFs are radiolucent and are readily imaged at mammography (13,20). AMFs have a predominantly fatty appearance with variable density due to the muscle component and postoperative scarring. The muscle component is seen more frequently on the mediolateral oblique view and is visualized anterior to the pectoralis muscle (13) (Fig 4). Surgical clips are frequently seen posteriorly (Fig 4). Loyer et al (13) described six predictable radiopaque lines that correspond to surgical scars from the reconstruction (Fig 5). The A line represents the superior edge of the flap (Figs 6, 7); the B line represents the lateral edge of the flap or the original mastectomy scar (Fig 8); the C line represents the sutured umbilicus defect (Fig 6); the D line represents the inferior edge of the flap (Fig 8); the G line also represents the lateral edge of the flap (Fig 7); and the H line represents the medial edge of the flap (Fig 7). Lines A and C may be seen on both mediolateral oblique and craniocaudal views but are more commonly seen on the mediolateral oblique view. Lines B and D are seen only on the mediolateral oblique view. Lines G and H are seen only on the craniocaudal view.
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Figure 4a. Normal mammographic appearance of a large TRAM flap. Craniocaudal (a) and mediolateral oblique (b) views of the reconstructed breast show primarily fatty tissue with a convex area of soft-tissue opacity in the central and posterior regions that corresponds to the pedicle of rectus abdominis muscle (arrows). Surgical clips are also seen.
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Figure 4b. Normal mammographic appearance of a large TRAM flap. Craniocaudal (a) and mediolateral oblique (b) views of the reconstructed breast show primarily fatty tissue with a convex area of soft-tissue opacity in the central and posterior regions that corresponds to the pedicle of rectus abdominis muscle (arrows). Surgical clips are also seen.
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Figure 5. Locations of potential radiopaque scars on mediolateral oblique (MLO) and craniocaudal (CC) mammograms (13). Line A corresponds to the superior edge of the flap and may be seen on both views. Line B corresponds to the lateral edge of the flap and is occasionally seen on the mediolateral oblique view. Line C corresponds to the sutured umbilicus defect and can be seen on both views. Line D corresponds to the inferior edge of the flap and is seen only on the mediolateral oblique view. Lines G and H correspond to the lateral (line G) and medial (line H) edges of the flap and are rarely seen on the craniocaudal view.
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Figures 7, 8. (7) Normal right TRAM flap. Craniocaudal mammogram shows the A, G, and H lines. (8) Normal right TRAM flap. Mediolateral oblique mammogram shows the B and D lines. A large dystrophic calcification with adjacent suture calcifications is seen centrally (arrow).
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Figures 7, 8. (7) Normal right TRAM flap. Craniocaudal mammogram shows the A, G, and H lines. (8) Normal right TRAM flap. Mediolateral oblique mammogram shows the B and D lines. A large dystrophic calcification with adjacent suture calcifications is seen centrally (arrow).
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Although mammographic imaging of AMFs has not been recommended in the plastic surgery literature (21), several cases of mammographically detected, clinically silent local recurrences in TRAM flaps have been reported (10, 16), and we have also detected one such case (Fig 9). Helvie et al (16) reported eight cases of locally recurrent breast cancer in six patients with TRAM flaps who had an original diagnosis of multifocal DCIS. All eight cancers were visible at mammography; however, the recurrence was detected with screening mammography in only one case. Five of the six patients did not undergo follow-up mammography of their TRAM flaps, and all had palpable recurrences (Fig 10). All recurrences were invasive ductal carcinomas. Each patient with a suspicious finding underwent mammography. Mammographic findings included irregular masses (four cases), pleomorphic calcifications (two cases), and masses with associated calcifications (two cases). The recurrence was located in the upper central portion of the TRAM flap in four patients. Helvie et al (16) concluded with the recommendation that annual mammographic surveillance of TRAM flaps should be performed when the original diagnosis is multifocal DCIS.
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Figure 9a. Clinically silent recurrence of comedo-type ductal carcinoma in situ (DCIS) in a TRAM flap. (a) Original craniocaudal mammogram shows regional pleomorphic calcifications laterally in the right breast (arrowheads). Biopsy revealed DCIS of the comedo type. The patient underwent right mastectomy and reconstruction with a TRAM flap. (b) Follow-up mediolateral oblique mammogram obtained 2 years later shows clustered pleomorphic microcalcifications in the inferior aspect of the TRAM flap (arrow). An earlier mammogram of the TRAM flap was normal. Excisional biopsy revealed recurrent DCIS of the comedo type without evidence of invasion. The patient was treated with chest wall irradiation, and the TRAM flap was preserved.
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Figure 9b. Clinically silent recurrence of comedo-type ductal carcinoma in situ (DCIS) in a TRAM flap. (a) Original craniocaudal mammogram shows regional pleomorphic calcifications laterally in the right breast (arrowheads). Biopsy revealed DCIS of the comedo type. The patient underwent right mastectomy and reconstruction with a TRAM flap. (b) Follow-up mediolateral oblique mammogram obtained 2 years later shows clustered pleomorphic microcalcifications in the inferior aspect of the TRAM flap (arrow). An earlier mammogram of the TRAM flap was normal. Excisional biopsy revealed recurrent DCIS of the comedo type without evidence of invasion. The patient was treated with chest wall irradiation, and the TRAM flap was preserved.
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Figure 10a. Palpable early recurrence in a TRAM flap. (a) Original mediolateral oblique mammogram of the right breast shows a large, irregular soft-tissue mass with nipple retraction and tethering of the inferior pectoralis muscle (arrow). The patient underwent right mastectomy and immediate reconstruction with a TRAM flap. One year later, she presented with a palpable mass in the posterior central aspect of the reconstructed breast. (b) Craniocaudal mammogram of the TRAM flap shows an ill-defined, high-density mass posteriorly (arrows) with some tethering of the flap tissues. Biopsy revealed invasive ductal carcinoma.
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Figure 10b. Palpable early recurrence in a TRAM flap. (a) Original mediolateral oblique mammogram of the right breast shows a large, irregular soft-tissue mass with nipple retraction and tethering of the inferior pectoralis muscle (arrow). The patient underwent right mastectomy and immediate reconstruction with a TRAM flap. One year later, she presented with a palpable mass in the posterior central aspect of the reconstructed breast. (b) Craniocaudal mammogram of the TRAM flap shows an ill-defined, high-density mass posteriorly (arrows) with some tethering of the flap tissues. Biopsy revealed invasive ductal carcinoma.
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Fat necrosis has been reported to occur in 10%–26% of free or pedicled TRAM flaps (17, 21) and in 2.0% of LD flaps (19). The diagnosis of fat necrosis in an AMF is usually a clinical one because many centers do not routinely perform mammography as follow-up for AMFs. At clinical examination, fat necrosis appears as a palpable nodule or area of focal thickening usually in the periphery of the flap, where the vascular supply is more tenuous (21). At mammography, fat necrosis has a spectrum of appearances: an irregular area of soft-tissue density (Figs 11, 12), a spiculated mass, noncalcified or calcified lipid cysts (Fig 13), and pleomorphic micro- or macrocalcifications (Fig 13) (22). Other pathologic entities that may be visualized at mammography of AMFs include lymph nodes (Fig 14) and epidermal inclusion cysts (Fig 15).
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Figures 11, 12. (11) Fat necrosis in a TRAM flap. Mediolateral oblique mammogram shows an ill-defined area of soft-tissue density (arrows). Excisional biopsy revealed fat necrosis. (12) Progressive changes of fat necrosis in a TRAM flap. (a) Mediolateral oblique mammogram shows fat necrosis as an ill-defined area of soft-tissue density (arrows). (b) Follow-up mediolateral oblique mammogram shows an interval decrease in density and numerous calcifications adjacent to surgical clips.
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Figures 11, 12. (11) Fat necrosis in a TRAM flap. Mediolateral oblique mammogram shows an ill-defined area of soft-tissue density (arrows). Excisional biopsy revealed fat necrosis. (12) Progressive changes of fat necrosis in a TRAM flap. (a) Mediolateral oblique mammogram shows fat necrosis as an ill-defined area of soft-tissue density (arrows). (b) Follow-up mediolateral oblique mammogram shows an interval decrease in density and numerous calcifications adjacent to surgical clips.
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Figures 11, 12. (11) Fat necrosis in a TRAM flap. Mediolateral oblique mammogram shows an ill-defined area of soft-tissue density (arrows). Excisional biopsy revealed fat necrosis. (12) Progressive changes of fat necrosis in a TRAM flap. (a) Mediolateral oblique mammogram shows fat necrosis as an ill-defined area of soft-tissue density (arrows). (b) Follow-up mediolateral oblique mammogram shows an interval decrease in density and numerous calcifications adjacent to surgical clips.
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Figure 13. Bilateral TRAM flap failure. Bilateral mediolateral oblique mammograms show extensive fat necrosis with large, calcified lipid cysts and pleomorphic and dystrophic calcifications.
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Figures 14, 15. (14) Enlarged lymph node in a TRAM flap. Craniocaudal mammogram shows an 8-mm-diameter, well-circumscribed nodule in the lateral aspect of a right TRAM flap (arrow). This nodule corresponded to a palpable nodule detected at routine physical examination. Excisional biopsy revealed a benign lymph node. (15) Epidermal inclusion cyst in a TRAM flap. Mediolateral oblique mammogram shows an 8-mm-diameter, oval nodule in the inferior aspect of a right TRAM flap (arrows). Interval enlargement of the nodule prompted a stereotaxic core biopsy. Final histopathologic results showed an epidermal inclusion cyst.
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Figures 14, 15. (14) Enlarged lymph node in a TRAM flap. Craniocaudal mammogram shows an 8-mm-diameter, well-circumscribed nodule in the lateral aspect of a right TRAM flap (arrow). This nodule corresponded to a palpable nodule detected at routine physical examination. Excisional biopsy revealed a benign lymph node. (15) Epidermal inclusion cyst in a TRAM flap. Mediolateral oblique mammogram shows an 8-mm-diameter, oval nodule in the inferior aspect of a right TRAM flap (arrows). Interval enlargement of the nodule prompted a stereotaxic core biopsy. Final histopathologic results showed an epidermal inclusion cyst.
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CONCLUSIONS
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AMFs will most likely continue to increase in prevalence, especially as silicone breast implants have decreased in popularity. Although mammographic imaging of AMFs remains controversial, recent reports of mammographically detected local recurrences suggest that follow-up mammography of AMFs may be helpful in the early detection of recurrent breast cancer. Radiologists performing mammography should be familiar with the normal and abnormal findings in AMFs.
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Footnotes
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Abbreviations: AMF = autologous myocutaneous flap
DCIS = ductal carcinoma in situ
LD = latissimus dorsi
TRAM = transverse rectus abdominis myocutaneous
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References
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Abstract
INTRODUCTION
