Scalp angiosarcoma is a rare vascular malignancy comprising less than 1% of soft tissue sarcomas and typically arises in elderly patients [1,2]. Despite multimodal therapy, prognosis remains poor, and local control is particularly challenging in cases with diffuse or multifocal scalp involvement [2,3]. Multifocal presentation with satellite lesions has been associated with higher local recurrence and poorer survival, often necessitating wide excision with generous margins and adjuvant radiotherapy as part of a multidisciplinary approach [4,5]. However, highdose radiotherapy to the scalp can lead to chronic nonhealing wounds, soft tissue breakdown, and osteoradionecrosis, especially in previously skin-grafted or thinly covered areas [6,7]. These late wound complications primarily reflect radiation-induced microvascular injury and fibrosis and may be exacerbated by limited soft-tissue thickness in previously grafted areas.

In this context, reconstruction of irradiated scalp defects is particularly demanding. Local flaps are frequently unreliable because of compromised vascularity, whereas microvascular free tissue transfer provides well-vascularized coverage and more durable long-term results for extensive scalp defects in oncologic patients [8,9]. When a single flap is insufficient to address separate defects or different tissue requirements, double or dual free flap reconstruction may be considered [10]. In vessel- limited irradiated fields, a piggyback anastomosis can allow two free flaps to share a limited recipient vessel pool while preserving alternative recipient vessels for possible future reconstruction [11]. At the same time, systemic therapies such as weekly paclitaxel and newer targeted or immune-based approaches are increasingly incorporated into the management of angiosarcoma, reflecting an evolving understanding of its disease biology [12,13].

Here, we present a case of radiation-induced scalp necrosis after treatment for multifocal scalp angiosarcoma, successfully reconstructed with a radial forearm free flap (RFFF) and an adipofascial anterolateral thigh (ALT) free flap using a piggyback technique on a single recipient vessel pair.

A 62-year-old woman with no significant comorbidities presented with progressive scalp lesions. Dermatologic biopsy confirmed cutaneous angiosarcoma. Multifocal disease was identified, including a 3.5×3.5 cm ulcerated vertex lesion within an approximately 10×10 cm clinically abnormal vertex field and three 1×1 cm temporal satellite lesions (two in the right temporal region and one in the left temporal region) (Fig. 1).

Intraoperative frozen biopsy-guided wide excision was performed, resulting in a 17×7 cm vertex defect that was covered with a large occipital rotation flap, and multiple secondary defects that were closed with split-thickness skin grafts (STSG) (Fig. 2). Adjuvant radiotherapy with a total dose of 60 Gy was delivered. This initial local flap/STSG approach was selected to provide immediate coverage with a shorter operative time and to facilitate timely adjuvant radiotherapy, while minimizing additional recipient-vessel dissection or sacrifice during the index oncologic surgery.

At 7 months after completion of radiotherapy, full-thickness soft tissue necrosis with calvarial bone exposure developed in the frontal and occipital regions (Fig. 3). Multiple biopsies confirmed the absence of tumor recurrence. Conservative management, including local wound care, failed, and the exposed area gradually progressed, consistent with radiation-induced scalp necrosis. Although areas reconstructed with STSG or thin softtissue coverage may be more vulnerable, the clinical course was most consistent with radiation-induced soft-tissue necrosis/osteoradionecrosis rather than graft-related failure, supported by repeated biopsies negative for recurrence.

At 11 months after radiotherapy, neurosurgery performed debridement and burr drilling of the outer table of the calvarium. Double free flap reconstruction was then performed using only the left superficial temporal artery and vein as recipient vessels. A thin RFFF was harvested and anastomosed end-to-side to the left superficial temporal artery and vein to reconstruct the frontal defect. An adipofascial ALT flap was harvested and inset into the occipital defect to restore posterior scalp bulk and contour (Fig. 4). This vessel-sparing strategy intentionally preserved the contralateral superficial temporal system as a potential lifeboat for future resection and reconstruction in the event of local recurrence.

An 11.5 cm cephalic vein graft was harvested from the ipsilateral forearm for venous interposition. The ALT artery was anastomosed to the distal radial artery of the RFFF, and the ALT vein was anastomosed to the superficial temporal vein via the interposed cephalic vein graft, completing the piggyback configuration between the two free flaps. The overall configuration is illustrated schematically (Fig. 5) and documented intraoperatively (Fig. 6).

On postoperative day 1, venous congestion of the RFFF was noted. Urgent re-exploration revealed venous thrombosis at the venous outflow anastomosis; although a single discrete cause could not be definitively identified, mechanical kinking or compression within the tight irradiated scalp field was suspected. The venous outflow was revised with additional vein graft interposition to create a tension-free, non-kinked drainage pathway, restoring adequate venous outflow. Both flaps survived completely.

At long-term follow-up, more than 2.5 years after completion of radiotherapy, the patient was disease-free with stable contour and complete healing of both frontal and occipital regions (Fig. 7). No late complications such as wound breakdown, flap atrophy, or chronic pain have been observed.

Cutaneous angiosarcoma of the face and scalp is characterized by aggressive local behavior, a high rate of regional and distant metastasis, and poor overall survival despite aggressive multimodal treatment [1,2]. Even with wide excision and radiotherapy, local recurrence is common, and long-term control remains difficult, especially in lesions with diffuse or multifocal scalp involvement [2,3]. Multifocal lesions with satellite nodules, as in the present case, have been associated with adverse oncologic outcomes and frequently require extensive resections with complex reconstructive needs [4,5]. High-dose radiotherapy, while essential for local control, further compromises the vascularity of the remaining scalp and underlying bone, leading to chronic ulceration, soft tissue necrosis, and osteoradionecrosis [6,7]. In such heavily irradiated and reoperated fields, the reliability of local or regional flaps is limited, and microvascular free tissue transfer has emerged as the preferred reconstructive option for large scalp defects [8,9]. Free flaps provide well-vascularized tissue, improve resistance to infection and further breakdown, and allow restoration of contour and durable coverage over exposed calvarium in oncologic patients [8,9].

Double free flap reconstruction is particularly valuable when a single flap cannot adequately address the extent or three-di mensional requirements of the defect, or when separate regions require different tissue characteristics [10]. In this configuration, a piggyback anastomosis or shared recipient vessel strategy can be useful even in vessel-depleted or irradiated fields [11]. In the present case, the thin RFFF was well suited for the frontal region, providing a pliable surface that conformed to the curvature of the forehead, whereas the adipofascial ALT flap restored bulk and contour in the occipital region with acceptable donorsite morbidity [8,9]. The use of a single superficial temporal artery and vein as the recipient vessel pair, combined with a cephalic vein graft and piggyback configuration, allowed two large free flaps to be inset without additional neck dissection or sacrifice of alternative recipient sites [10,11]. Importantly, in multifocal scalp angiosarcoma with a high risk of local recurrence, this strategy is oncologically sound because it preserves the contralateral superficial temporal vessels as a lifeboat for potential future resection and reconstruction. Venous thrombosis remains one of the most feared complications in free flap surgery and may be more likely in settings with multiple anastomoses and vein graft interposition. In this case, prompt recognition of venous congestion and urgent re-exploration led to salvage of the flap, underscoring the importance of meticulous postoperative monitoring and early intervention in complex microsurgical reconstructions. At the index oncologic resection, we selected a rotation flap and STSG to achieve immediate coverage with reduced operative complexity and to avoid delaying adjuvant radiotherapy; free tissue transfer was reserved for definitive salvage if late radiation injury or complex defects developed.

From an oncologic standpoint, systemic therapy is increasingly integrated into the multidisciplinary management of angiosarcoma. Weekly paclitaxel has shown meaningful activity in unresectable or metastatic angiosarcoma and is frequently employed as part of a multimodal strategy [12]. Moreover, advances in the understanding of angiosarcoma biology have prompted the development of targeted agents and immunotherapeutic approaches, which may further improve outcomes when combined with optimized local and reconstructive management [13].

In conclusion, this case illustrates that double free flap reconstruction using a piggyback technique can be a safe, effective, and vessel-sparing option for extensive bilateral post-radiotherapy scalp defects in multifocal angiosarcoma. This strategy should be considered in selected patients with severe radiationinduced scalp necrosis and limited recipient vessels, as part of a multidisciplinary treatment plan that incorporates modern systemic therapies and long-term oncologic surveillance [8,10,13].