Rare Pseudotumor-like Hematoma at the Latissimus Dorsi Muscle Flap Donor Site: A Treatment Strategy Utilizing Negative Pressure Wound Therapy With Instillation and Dwell Time

The latissimus dorsi (LD) muscle is commonly used for several reconstructive purposes such as reconstructive procedures at the trunk (pedicled flap) or as a free flap at multiple anatomical sites. It presents a reliable and versatile option for reconstruction, especially for large or complex defects. However, seroma formation and early postoperative hematoma^1,2 at the donor site remain common donor-site complications after LD muscle transfer. As reported in previously published studies, chronic expanding hematomas can occur 1 month to 15 years after the initial surgery.^1-3 The development of a solidified hematoma at the donor site is a very rare late-onset complication, where aspiration is unable to be used as a treatment in these cases.² When dense, solid, tumor-like masses arise in the donor site up to 3 decades after the initial operation without any external trauma, secondary malignancies, and bacterial contamination must be ruled out.⁴ 

The main reasons for pseudotumor development are thought to be shear forces around the scapula causing damage to the adjacent tissue and consequently inducing bleeding as well as an impairment of coagulation due to medication or underlying disease.^2,3 Negative pressure wound therapy with instillation and dwell time (NPWTi-d) has led to several improvements in wound healing. Macrodeformation leads to a reduction of interstitial fluid (eg, hematoma, seroma) and opens capillaries close to the wound bed.⁵ These effects of macrodeformation facilitate contractile forces and wound shrinkage.⁵ In general, NPWT aims to improve perfusion of a wound and increase the release of growth factors, therefore supporting cellular growth.⁵ Furthermore, NPWTi-d has the potential to reduce the bacterial load in wounds.^5,6 

The authors report 2 cases of pseudotumor development at the LD donor site 12 and 29 years after the initial reconstructive procedures. The application of NPWTi-d (V.A.C. VERAFLO Therapy; 3M+KCI) followed by secondary suture were applied as the treatment strategy. Polihexanide 0.04% provided by the institutional pharmacy was used as antiseptic solution. The dwell time was set to 10 minutes. Continuous negative pressure was applied at -125 mm Hg. Dwelling phases were repeated every 3 hours. The same settings were applied in both cases. This study illustrates the application of NPWTi-d in cases with extremely late solid pseudotumors after LD transfer as a novel treatment strategy. 

Case 1 
A 69-year-old male was referred to the department of plastic and hand surgery for soft tissue coverage of a complex wound after an open tibia fracture as the result of a car accident. The wound at the right lower leg, with a pretibial located wound (10 cm x 5 cm and lateral located wound (15 cm x 4 cm) was covered by a free LD transfer. Besides 1 prolonged seroma formation (24 days after free LD transfer) at the donor site, which was located on the patient’s back, no further complications occurred during the initial postoperative course of 26 days (until hospital discharge). The drainage was removed 24 days after free flap transfer. At the 3-year follow-up examination, the flap presented well perfused, and the donor site showed no signs of a pseudotumor. The patient visited the authors’ emergency department with a palpable painless mass at the LD flap donor site (Figure 1) 12 years after initial reconstructive procedure. No history of trauma was evident in the patient’s history, and no anticoagulant medication was administered since free LD transfer. The patient received physical therapy at the LD donor site on a regularly basis. Magnetic resonance imaging confirmed an extensive, subcutaneous, partly lobulated hematoma at the posterior chest wall (1.5 cm x 1 cm x 2 cm) (Figure 2). Drainage of the hematoma formation was not possible due to its solidification. Therefore, surgical excision of the mass under general anesthesia was performed. The intraoperative finding revealed an encapsulated tumor (13 cm x 7 cm x 3.5 cm). The preexisting scar at the LD flap donor site was excised, and the subcutaneous mass, including its surrounding capsule, was completely removed (Figure 3). Specimens were sent for microbiological analysis and histological examination. No bacterial growth was found, and pathology report revealed an encapsulated old hematoma.

Negative pressure wound therapy with instillation and dwell time was applied for 13 days (Figure 4), and dressings were changed twice during the course of hospital stay. The size of the inserted black foam was gradually reduced to allow for wound size reduction every third day. After adequate wound shrinkage, wound closure was performed by secondary sutures on day 10 of NPWTi-d. At the patient’s back, 2 suction drainages were inserted, and compression garments were applied. Seroma formation at the donor site occurred 1 week after hospital discharge and was successfully aspirated during an outpatient visit 10 days after hospital discharge. No additional seroma or hematoma formation occurred.

Case 2
A 47-year-old female had undergone a mastectomy of the left breast due to breast cancer. A year later, autologous breast reconstruction with a pedicled LD flap was performed. Primary closure of the donor site was achieved. As an important finding for this case in the patient history, the patient took 100 mg of acetylsalicylic acid for the prevention of thrombosis due to a stenosis of the internal carotid artery. After hospital discharge, the patient endured a recurrent postoperative seroma formation. Initially, the recurrent seroma was drained by aspiration every 3 to 4 days for a total of 3 weeks in an outpatient setting. The seroma formation limited itself after 3 weeks. A total of 29 years after autologous breast reconstruction, the patient developed a large, palpable, painless mass at the LD donor site and was therefore admitted to the authors’ department for examination (Figure 5). The patient reported a slowly growing formation at the LD donor site without a trauma in the past. The patient first recognized it 3 weeks prior to the authors’ initial medical examination. Magnetic resonance imaging showed an extensive, subcutaneous, partly lobulated mass of the left dorsal thoracic wall (8.3 cm x 5 cm x 13.2 cm) (Figure 6). Similar to the first case, surgical intervention was required.

The encapsulated mass was completely removed (Figure 7). Acetylsalicylic acid was paused perioperatively. Microbiological analysis and histological examination were conducted. Bacterial cultures showed a wound colonization with saprophytic gram-positive bacteria. Antibiotics were administered according to the antibiogram results for 5 days postoperatively. The pathology report revealed an old hematoma (no specific age known).

For temporary wound coverage, NPWTi-d was applied, and 2 dressing changes with a 3-day interval were performed during the 14-day hospital stay. After 10 days, NPWTi-d was removed, and secondary wound closure was performed. After 11 days, drainage placed at the patient’s back was removed, and compression garments were applied for 10 weeks consistently day and night. During wound controls after hospital discharge, seroma formation at the donor site required aspiration on a weekly basis for 6 weeks. No further seroma formation or hematoma occurred in the last clinical examination. 

Early seroma formation is the most common perioperative complication after harvesting an LD muscle flap.^1,2,8 Various methods attempted to prevent seroma formation in this anatomical donor site, such as suction drainages and compression garments.^7,8 Some authors reported hematoma formations as long as 21 months after surgery.¹ 

An expanding pseudotumor is considered to be a very rare, late-onset complication after LD tissue transfer.² Although the exact etiology is not fully understood, various theories, like shearing forces or irregularity in blood coagulation, tried to explain its pathomechanism.² Shear stress between the fascia and the subcutaneous tissue can cause chronic bleeding.^9,10 During everyday life, the dorsum and mobile scapula are prone to significant movement; for the LD donor site located at the dorsum, this movement can create shear stress in a spacious wound cavity.³ This shear stress potentially triggers pseudotumor formation of both hematomas and seromas.³ 

Albeit immediate postoperative seroma and hematomas are well-known sequelae, late-onset fluid collection that recurs several years after the initial procedure is a rare event.² In 2005, Öztürk et al¹¹ published a single case of late seroma at the LD donor site in a patient 4.5 years postoperatively; at the time of publication, the authors noted that, to the best of their knowledge, no reports of extremely late seroma formation existed in the English literature.¹¹ A possible correlation of seroma formation at the LD donor site with chemotherapeutic drugs has also been discussed.¹² 

Pseudotumors at the donor site of the LD flap still lack clear treatment guidelines due to their scarce occurrence. In the authors’ opinion, the termination of anticoagulant medication is not a plausible option for the prevention of such a rare complication due to associated life-threatening complications, such as a ischemic stroke or coronary perfusion problems. 

A few case reports showed individual treatment approaches usually trying to drain the hematoma at first.^1,3,9 Of note, aspiration is only possible if the mass has not solidified yet.³ Late solidified hematomas were usually treated with surgical excision of the mass followed by immediate wound closure.^2,3

Since pseudotumors at the flap donor site may indicate a secondary benign or malignant process or could be the result of a bacterial colonization within a solidified older hematoma, the time of onset is of relevance.² However, to the authors’ knowledge, an extremely delayed period of 29 years between flap transfer and pseudotumor formation has not been reported thus far. In addition, the application of NPWTi-d followed by secondary suture in patients with very late-onset pseudotumors has not been previously published as a treatment strategy to the authors’ knowledge. The current case reports support the awareness of pseudotumor as differential diagnosis to soft tissue tumors or late-onset bacterial infections, especially in cases with LD flap harvest. A new, palpable, solid tumor formation unrelated to a trauma in the dorsum requires meticulous examination and further clarification in order to distinguish it from other possible diseases such as malignant tumors.¹ In addition to preoperative diagnostic imaging (eg, magnetic resonance imaging), patients should be examined for anticoagulant medication and bleeding diathesis or hemophilia. 

The therapy regimen in the current report differs from previously published case reports.^2,3 After surgical removal of the mass, NPWTi-d was applied for several days, since bacterial contamination in the partially liquefied brown mass seemed probable in both cases. In addition, the time interval was used before closure to exclude any malignancy. In both cases, the wound at the back was subsequently closed by secondary sutures. In the postoperative course for both cases, no major complications occurred and no relapse of hematoma or seroma formation were detected in the last clinical control.

The removal of excess interstitial fluid and pathologic substances, the exertion of contractile forces, and beneficial blood flow alterations across the wound bed have various effects on a macro- and microscopic level.⁵ Moreover, NPWTi-d has been shown to decrease bacterial colonization within a wound, ultimately improving wound healing outcomes.^6,13,14 In the current cases, NPWTi-d was applied to clean the hollow space, which was susceptible to bacterial colonization; induce wound shrinkage; control postoperative bleeding; and bridge the time to the final pathological report. The occurrence of further bleeding or excessive wound drainage can be monitored during NPWTi-d therapy. In the authors’ opinion, continuous reduction of the foam size in the wound reduces the wound cavity and benefits the adherence of subcutaneous tissue with the underlying fascia. In addition, the authors believe the reduction of shear forces at the former donor site in the early phase of wound stabilization could decrease complication rates. 

This case report is limited because of its retrospective character and the analysis of only 2 patients. In addition, no control group could be included. The low incidence of this pathology impedes the ability to conduct studies with an appropriate sample size and statistical significance. The results represent the authors’ experience with this rare entity and are reflected in light of the current literature at the time of publication.

In conclusion, the occurrence of pseudotumors of the back is a very rare, late-onset complication after LD tissue transfer. Physicians should be aware of the differential diagnosis of pseudotumors, such as late-onset hematoma. To the authors’ knowledge, this is the first report of pseudotumor formation 29 years after the initial reconstruction with a latissimus dorsi flap. Negative pressure wound therapy with instillation and dwell time showed promising results in these 2 cases, ultimately reducing wound size and shear forces, which possibly led to an uneventful postoperative course (ie, without relapse of pseudotumors). These results may be helpful for future studies regarding late-onset pseudotumors resulting from LD flap transfer for reconstructive purposes. 

Authors: Maximilian C. Stumpfe, MD; Raymund E. Horch, MD; Alexander Geierlehner, MD; and Ingo Ludolph, MD

Affiliation: Department of Plastic and Hand Surgery, Laboratory for Tissue Engineering and Regenerative Medicine, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nuernberg FAU, Erlangen, Germany

Correspondence: Maximilian C. Stumpfe, MD, Department of Plastic and Hand Surgery, Laboratory for Tissue Engineering and Regenerative Medicine, University Hospital Erlangen, Friedrich Alexander University Erlangen-Nuernberg FAU, Erlangen, Germany; maximilian.stumpfe@uk-erlangen.de 

Disclosure: The authors disclose no financial or other conflicts of interest.