Introduction

Breast cancer is the most frequent malignant tumor among women worldwide and represents a major public health problem. In Brazil, excluding non-melanoma skin tumors, an estimated 73,610 new cases per year are expected for the 2023–2025 triennium, corresponding to an adjusted incidence rate of 41.89 cases per 100,000 women.¹ Modern surgical approaches range from breast-conserving surgery (tumorectomy or lumpectomy) to mastectomy with complete axillary dissection.² Despite surgical advances, reconstruction after extensive resections remains challenging. A broad spectrum of techniques is available, allowing complex resections and reconstructions in tumors involving breast tissue or chest wall structures, while preserving function, providing adequate coverage, and achieving tumor-free margins, which are crucial for reducing recurrence.³ Options range from local fasciocutaneous flaps and alloplastic materials to autologous and microsurgical flaps, and, in patients eligible for adjuvant radiotherapy, reconstruction with autologous tissue is often preferred.⁴

The Keystone flap is widely used and recognized for the reconstruction of large defects of the trunk and extremities; however, its application in breast reconstruction remains poorly described in the literature. It consists of a trapezoidal or elliptical fasciocutaneous flap adjacent to the defect, with viability depends on the preservation of musculocutaneous or fasciocutaneous perforating vessels, ensuring excellent vascularization even in irradiated areas or regions with impaired healing. The design involves lateral marking adjacent to the defect, with equivalent width, followed by flap elevation through blunt dissection while preserving the subcutaneous vascular plexus and perforating vessels. This arrangement allows flap advancement through V-Y advancement, uniformly distributing tension forces, facilitating primary closure of the donor site, and minimizing complications such as necrosis or dehiscence.⁵, ⁶

Given the advantages of the Keystone flap, including its reproducible technique, rapid recovery, and safety in extensive defects,⁵ this study reports its application in post-hygienic mastectomy reconstruction in a patient with a locally advanced tumor, contributing to the expansion of the surgical options available for breast reconstruction.

Case report

A 44-year-old female patient presented with a locally advanced left breast tumor after neoadjuvant chemotherapy. She reported the presence of a nodule for two years, with progressive growth during treatment. The diagnosis was invasive ductal carcinoma, staged as T4bN1M1 (►Fig. 1), with a Ki-67 index of 30% and evidence of tumor progression.

Fig. 1 - Locally advanced breast tumor staged as T4bN1M1.

Fig. 1 - Locally advanced breast tumor staged as T4bN1M1.

Physical examination revealed an ulcerated lesion measuring approximately 6 × 6 cm in the left breast (►Fig. 2), with confluent lymph nodes at levels II and III. Chest computed tomography demonstrated a retroareolar mass measuring 4.1 × 2.6 × 3.1 cm, diffuse skin thickening, axillary lymphadenopathy (1 cm), and multiple non-calcified pulmonary nodules, without bone lesions.

Fig. 2 - Left breast tumor with central ulceration.

Fig. 2 - Left breast tumor with central ulceration.

The patient underwent a left hygienic mastectomy (►Fig. 3), followed by reconstruction using a fasciocutaneous island flap with flap design, incision, and advancement as shown in ►Fig. 4a–c. Closure was performed in layers, with satisfactory tissue approximation.

Fig. 3 - Left hygienic mastectomy.

Fig. 3 - Left hygienic mastectomy.

Fig. 4 - (a) Reconstruction of the large defect using a Keystone flap – Surgical marking. (b) Reconstruction of the large defect using a Keystone flap – Flap advancement. (c) Reconstruction of the large defect using a Keystone flap – Immediate postoperative period.

Fig. 4 - (a) Reconstruction of the large defect using a Keystone flap – Surgical marking. (b) Reconstruction of the large defect using a Keystone flap – Flap advancement. (c) Reconstruction of the large defect using a Keystone flap – Immediate postoperative period.

The patient had a favorable postoperative course, with mild pain (visual analog scale [VAS], 3), and was discharged on the first postoperative day. The drain was removed on the seventh day after serous drainage decreased to < 50 mL/day, and satisfactory healing was observed (►Fig. 5).

Fig. 5 - Fifteenth postoperative day.

Fig. 5 - Fifteenth postoperative day.

The case was approved by the Research Ethics Committee of Fundação Benjamin Guimarães – Hospital da Baleia (CAAE 83112524.6.0000.5123), and written informed consent was obtained from the patient.

Surgical Technique

Surgical marking was initially performed (►Fig. 6a) after the mastology team had defined the excisional limits, with the flap designed in a 1:1 proportion relative to the defect size (►Fig. 6b).

Fig. 6 - (a) Surgical flap marking in a 1:1 proportion relative to the excisional limits – Surgical marking. (b) Surgical flap marking in a 1:1 proportion relative to the excisional limits – Marking with dimensions equivalent to the excisional limits.

Fig. 6 - (a) Surgical flap marking in a 1:1 proportion relative to the excisional limits – Surgical marking. (b) Surgical flap marking in a 1:1 proportion relative to the excisional limits – Marking with dimensions equivalent to the excisional limits.

Subsequently, incision and advancement of the fasciocutaneous island (Keystone) flap were performed, with vascularization in the present case originating from the intercostal and superior epigastric arteries (►Fig. 7).

Fig. 7 - Incision and advancement of the Keystone flap.

Fig. 7 - Incision and advancement of the Keystone flap.

Closure was performed in layers, with compensatory adjustments in the angulated regions (►Fig. 8).

Fig. 8 - Layered closure.

Fig. 8 - Layered closure.

Discussion

Locally advanced breast carcinoma comprises stage III disease (IIIA, IIIB, and IIIC), including tumors > 5 cm (T3), tumors involving the chest wall (T4a), skin (T4b), or both (T4c), as well as extensive lymph node involvement (N2/N3) affecting one or more lymphatic chains and inflammatory carcinoma.⁷

Radical surgical excision in these patients results in extensive skin loss in the thoracic region that cannot be repaired with primary closure. The use of myocutaneous flaps provides effective coverage for large defects; however, these procedures require longer operative time, increasing morbidity and potentially delaying adjuvant oncologic treatment.⁷

Although myocutaneous flaps remain However, despite the well-established indication for myocutaneous flaps in chest wall reconstruction after mastectomy, the role of locoregional reconstruction has already been widely discussed in the literature. Its advantages include shorter operative time, lower morbidity, and stable vascularization, with rates of partial necrosis similar to those of myocutaneous fl aps.⁷, ⁸ For these reasons, the Keystone technique was selected in the present case.

In 2003, Behan et al.⁵ described the Keystone flap as a fasciocutaneous island flap whose trapezoidal geometry, with its longest axis parallel to the defect, ensures recruitment of perforating vessels adjacent to the wound, providing reliable vascularization.⁷, ⁸, ⁹ This design also allows tissue advancement with low donor-site morbidity, with closure at one extremity resembling a V-Y flap.¹⁰

Vascularization of the flap is proportional to the extent of the designed skin island, provided that the area of contact with the underlying fascia, through which the perforating vessels emerge, is preserved.⁵,¹⁰ In this way, the possibility of ischemia, necrosis, and chest wall destabilization is reduced.⁸, ⁹ In the present case, vascular supply originated from the intercostal and superior epigastric arteries.

These characteristics allow considerable versatility in the creation of Keystone flaps of varying sizes for a broad spectrum of reconstructions.⁸ The complication rate reported in the literature for the use of the Keystone flap is low, and in the present case no complications related to flap vascularization occurred.

Conclusion

The Keystone flap proved to be a satisfactory reconstructive option in this case. Description of this method is relevant, as it demonstrates that this alternative can provide adequate dermocutaneous coverage for the defect described, with reduced operative time and faster recovery. It is a safe, effective, and easily reproducible technique, representing a versatile resource in the armamentarium of the plastic surgeon involved in breast reconstruction.