Key Points
Question
What is the frequency of excessive scarring after surgery in patients with PIK3CA-related overgrowth?
Findings
In this observational study, 4 of 6 patients with PIK3CA-related overgrowth developed excessive scarring following surgery. All abnormal scars were located in phenotypically affected tissue.
Meaning
Excessive scarring is common in PIK3CA-related overgrowth, and patients should be counseled on this risk preoperatively.
This observational study examines the frequency of excessive scarring after surgery in patients with PIK3CA-related overgrowth.
Abstract
Importance
Patients with somatic overgrowth commonly require surgical intervention to preserve function and improve cosmesis. To our knowledge no observation of scarring outcomes in this population has been published to date.
Objective
To observe the frequency of abnormal scarring in patients with somatic overgrowth and sequencing-verified mutations in the PIK3CA gene.
Design, Setting, and Participants
This retrospective study evaluated scarring outcomes in patients with PIK3CA-related overgrowth. Samples of affected tissue were sequenced between July 2015 and October 2016. Medical records from multiple large academic tertiary care centers were reviewed for surgical history and scar descriptions, and clinical photographs were assessed by 2 surgeons (J.N.J. and D.M.K.) to confirm abnormal scarring. Analysis of medical records and photographs was performed between April 2017 and June 2017 by a multidisciplinary team from dermatology, plastic surgery, orthopedic surgery, radiology, and genetics departments. All patients considered for the study were diagnosed with somatic overgrowth and previously had affected tissue sent for next-generation sequencing. Those with pathogenic PIK3CA variants and 1 or more prior surgical procedures were reviewed.
Main Outcomes and Measures
Presence of excessive scarring in patients with PIK3CA overgrowth.
Results
A total of 57 patients with segmental overgrowth syndromes were sequenced. Of the 57 patients, 25 (44%) had pathogenic or likely pathogenic variants in PIK3CA. Of those with pathogenic PIK3CA variants, 6 (24%) had past surgical procedures, all with preoperative and postoperative photographs. Of 6 patients with PIK3CA-related overgrowth and a history of 1 or more surgical procedure, 4 (67%) developed excessive scarring. The cohort with abnormal scarring comprised 3 females and 1 male, with a median age of 8.5 years. All abnormal scarring occurred in affected overgrowth tissue. Three of the 4 patients developed the excessive scarring after debulking procedures for overgrowth and/or vascular malformations of the upper or lower extremity.
Conclusions and Relevance
Excessive scarring occurred frequently in patients with PIK3CA-related overgrowth syndromes. The risk of abnormal scarring should therefore be discussed preoperatively. Given the activating nature of these PIK3CA variants, we suggest that the excessive scarring may be owing in part to up-regulation of the PI3K-Akt-mTOR pathway. Additional studies are needed to assess scarring outcomes in patients with other types of overgrowth.
Introduction
Vascular anomalies comprise a diverse group of diseases ranging from simple birthmarks to complex lesions associated with extracutaneous abnormalities. When present in a segmental distribution, vascular anomalies are variably associated with regional soft tissue and skeletal overgrowth. Historically, this overgrowth was thought to result from increased perfusion, but next-generation sequencing has shown that vascular anomalies and associated overgrowth are caused by postzygotic genetic variants. A subset of syndromes characterized by vascular malformations and segmental overgrowth result from pathogenic variants in the PIK3CA gene, collectively termed the PIK3CA-related overgrowth spectrum (PROS). The PIK3CA gene encodes the p110α protein, a catalytic subunit of phosphatidylinositol 3-kinase (PI3K). PI3K is a component of the PI3K-Akt-mTOR signaling pathway, which has wide-ranging regulatory effects on cell proliferation, migration, and survival. Aberrant PI3K signaling also plays a role in tumorigenesis, as gain of function variants in PIK3CA have been implicated in a number of human cancers to date. Many of the PIK3CA variants observed in cancer, including E542K and E545K, have been identified as causative variants in PROS.
We report 4 patients with PROS (segmental overgrowth with sequencing-confirmed pathogenic PIK3CA variants) who developed excessive scarring in affected tissue following surgical procedures. We hypothesize that activation or dysregulation of cellular processes caused excessive and hypertrophic scarring in the affected tissue of these patients. Our results suggest that patients with vascular lesions and overgrowth caused by postzygotic PIK3CA variants may be at significant risk for abnormal scarring. In addition, our findings provide a clinical correlate to known underlying genetic variants, thus shedding light on the pathogenesis of excessive scarring.
Methods
This research was conducted as part of a multicenter study approved by the institutional review board at Children’s Hospital of Wisconsin. Written informed consent was obtained from all study patients. Affected tissue from 57 patients previously diagnosed with vascular lesions and segmental overgrowth underwent targeted next-generation sequencing using a panel enriched for 131 genes in cancer-related pathways, including PI3K-Akt-mTOR. Pathogenic or likely pathogenic PIK3CA variants with variant allele frequency of 1% or higher were identified as previously described. Medical records from sequenced patients were reviewed for surgical history and the presence of excessive scarring. Clinical photographs were obtained and reviewed by 2 surgeons (J.N.J. and D.M.K.) to visually confirm the diagnosis of abnormal scarring.
Results
A total of 57 patients with segmental overgrowth syndromes were sequenced. Of the 57 patients, 25 (44%) had pathogenic or likely pathogenic variants in PIK3CA. Of those with pathogenic PIK3CA variants, 6 (24%) had past surgical procedures, all with preoperative and postoperative photographs. Four (67%) of these surgical patients developed abnormal scarring (Figure). Patients with abnormal scarring tended to be younger (median age, 8.5 years) than those with normal scarring outcomes (median age, 46 years). None of the study patients were taking sirolimus, a drug that has been used for the treatment of complicated vascular malformations and is known to impair wound healing. Procedures associated with abnormal scarring were mainly for debulking of overgrowth tissue and/or vascular malformation (3 of 4 patients); however, 1 patient developed a keloid at the site of ventriculoperitoneal shunt placement. In all cases, abnormal scars were located in tissue affected by overgrowth. One patient had a surgical incision that extended into unaffected tissue; this portion of the scar demonstrated normal healing. Clinical descriptions and genotyping results are presented in the Table.
Figure. Scarring in Patients With PIK3CA-Related Segmental Overgrowth.
Representative photographs of excessive scarring in this cohort.
Table. Demographic Information, Genotypes, and Phenotypic Features of Patients With PIK3CA-Related Overgrowth and Abnormal Scarring.
| Patient | Sex | Approximate Age, y | PIK3CA Variant | VAF, % | Procedure | Scarring Outcome |
|---|---|---|---|---|---|---|
| 1 | Female | 50s | p.E110del | 2.1 | Leg length shortening and total knee replacement | Normal |
| 2 | Female | <10 | p.E453K | 34.9 | Ventriculoperitoneal shunt placement | Excessive |
| 3 | Female | <10 | p.E542K | 5.0 | Debulking of overgrowth tissue | Excessive |
| 4 | Male | 10s | p.E542K | 4.9 | Debulking of overgrowth tissue | Excessive |
| 5 | Female | 10s | p.E545K | 4.0 | Debulking of overgrowth tissue and vascular malformation | Excessive |
| 6 | Male | 30s | p.E545K | 1.0 | Open carpal tunnel release and proximal row carpectomy | Normal |
Abbreviation: VAF, variant allele frequency.
Discussion
We describe a series of patients carrying pathogenic postzygotic PIK3CA variants detected by next-generation sequencing who developed excessive scarring following surgical intervention.
Excessive scarring encompasses keloids and hypertrophic scars (HTS), which are benign fibrous growths that develop secondary to an exaggerated wound healing response. Histologically, keloids and HTS demonstrate fibroblast hyperproliferation and increased collagen deposition. Significant overlap exists between keloids and HTS, and it has been suggested that these entities represent different stages of the same abnormal scarring process. The etiopathogenesis of keloids and HTS is not fully understood. However, numerous in vitro studies have demonstrated the role of the PI3K-Akt-mTOR pathway in keloid development. Antagonism of this pathway has been shown to decrease collagen and fibronectin production, inhibit proliferation, and induce apoptosis in keloid-derived fibroblasts. Despite these experimental findings, to our knowledge no patients with excessive scarring and known variants in PI3K-Akt-mTOR pathway genes have been described.
Clinical reports of keloids or HTS in patients with overgrowth syndromes are scarce. Muzaffar and colleagues reported a patient with proteus syndrome and right-sided hemihypertrophy who, after undergoing syndactyly separations of the bilateral feet and right hand, developed keloidal scarring only in the overgrowth tissue (right hand and foot) but not on the normal-sized left foot. Keloidal scarring confined to the distribution of a scalp/neck capillary malformation was also described in a patient with Klippel-Trenaunay syndrome. Both Proteus (AKT1) and Klippel-Trenaunay syndromes (PIK3CA) result from postzygotic gain of function variants in PI3K-Akt-mTOR pathway genes.
Although evaluation of scarring outcomes was not the original objective of this cohort, we noted an unusual frequency of excessive scarring in our patients who had undergone surgical procedures. In this study, 4 of 6 patients (67%) with PIK3CA-related overgrowth developed abnormal scarring at surgical incision sites. These results suggest that in addition to overgrowth of bone and soft tissue, gain of function variants in PIK3CA may predispose to overgrowth of scar tissue, resulting in the formation of abnormal scars such as keloids or HTS. Given the postzygotic nature of these variants, we hypothesize that phenotypically affected tissue (a portion of which harbors the causative PIK3CA variant) is more likely to develop abnormal scarring than unaffected tissue. This is evidenced by the fact that a single surgical incision in patient 3 demonstrated both excessive scarring in overgrowth tissue as well as normal scarring in an unaffected region. From a clinical standpoint, our results suggest that patients with segmental overgrowth and documented or presumed pathogenic variants in PIK3CA should be counseled on the possible increased risk of keloids and/or HTS prior to surgery.
Limitations
The retrospective and observational nature of this study poses several limitations. Keloids and HTS likely develop as a result of numerous systemic and local factors in addition to genetic predisposition. For example, increased tension at the wound site has been demonstrated to increase the risk of keloidal scarring. Skin excision during debulking procedures can necessitate tight closures, thus increased tension could have contributed to abnormal scarring in these patients. The patients in this study had procedures performed by different surgeons across multiple surgical specialties, thus reflecting a wide variety of techniques and expertise. Many patients with PROS have co-occurring vascular malformations, and it has been suggested that underlying endothelial dysfunction might predispose to keloid formation. However, excessive scarring also appeared in overgrowth tissue without vascular lesions in 2 of 4 patients in our cohort. It is possible that local tissue hypoxia, postoperative infection, or other aspects of the surgical site environment played a role in the development of excessive scarring, though we were unable to control for or assess the relative contribution of these factors.
Conclusions
Additional studies are needed to assess for the presence of PIK3CA variants in the abnormal scar tissue itself, and to delineate which cell type (endothelial, fibroblast, etc) harbors the variant. Furthermore, gain of function variants in a number of other genes are known to cause overgrowth syndromes, and it is possible that patients with these variants may have a similar predilection to developing excessive scarring.
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