Reid A. Maclellan

Lymphatic and Other Vascular Malformative/Overgrowth Disorders Are Caused by Somatic Mutations in PIK3CA

OBJECTIVES To test the hypothesis that somatic phosphatidylinositol-4,5-bisphospate 3-kinase, catalytic subunit alpha (PIK3CA) mutations would be found in patients with more common disorders including isolated lymphatic malformation (LM) and Klippel-Trenaunay syndrome (KTS). STUDY DESIGN We used next generation sequencing, droplet digital polymerase chain reaction, and single molecule molecular inversion probes to search for somatic PIK3CA mutations in affected tissue from patients seen at Boston Childrens Hospital who had an isolated LM (n = 17), KTS (n = 21), fibro-adipose vascular anomaly (n = 8), or congenital lipomatous overgrowth with vascular, epidermal, and skeletal anomalies syndrome (n = 33), the disorder for which we first identified somatic PIK3CA mutations. We also screened 5 of the more common PIK3CA mutations in a second cohort of patients with LM (n = 31) from Seattle Childrens Hospital. RESULTS Most individuals from Boston Childrens Hospital who had isolated LM (16/17) or LM as part of a syndrome, such as KTS (19/21), fibro-adipose vascular anomaly (5/8), and congenital lipomatous overgrowth with vascular, epidermal, and skeletal anomalies syndrome (31/33) were somatic mosaic for PIK3CA mutations, with 5 specific PIK3CA mutations accounting for ∼ 80% of cases. Seventy-four percent of patients with LM from Seattle Childrens Hospital also were somatic mosaic for 1 of 5 specific PIK3CA mutations. Many affected tissue specimens from both cohorts contained fewer than 10% mutant cells. CONCLUSIONS Somatic PIK3CA mutations are the most common cause of isolated LMs and disorders in which LM is a component feature. Five PIK3CA mutations account for most cases. The search for causal mutations requires sampling of affected tissues and techniques that are capable of detecting low-level somatic mosaicism because the abundance of mutant cells in a malformed tissue can be low.

Infantile hemangioma: clinical assessment of the involuting phase and implications for management.

Background: Infantile hemangioma involutes during childhood; the tumor decreases in size and its color fades. Reconstructive procedures are often withheld until the lesion stops improving. The purpose of this study was to determine the age at which involution of infantile hemangioma ends, and factors that influence its regression. Methods: Consecutive patients with infantile hemangioma managed between 2007 and 2011 were studied retrospectively. The outcome variable was age at which the appearance of the infantile hemangioma ceased to improve. Predictive variables were sex, lesion size, location, tumor depth, ulceration, and history of treatment (local or systemic corticosteroid). Results: The study comprised 81 patients. Infantile hemangioma was located on the head/neck (79.0 percent), trunk (13.6 percent), or extremity (7.4 percent). Average tumor area was 9.3 ± 9.7 cm2. Twenty-six percent of the cohort was treated with a corticosteroid during the proliferative phase and 87.6 percent underwent reconstruction for a residual deformity. Kaplan-Meier analysis estimated that involution ceased at a median age of 36 months (interquartile range, 30 to 42 months), and 92 percent of tumors completed involution by 48 months. Multivariate Cox proportional hazards regression model showed that sex (p = 0.80), lesion size (p = 0.09), location (p = 0.77), tumor depth (p = 0.74), ulceration (p = 0.18), and previous local (p = 0.73) or systemic (p = 0.60) corticosteroid treatment did not influence regression. Conclusions: Most infantile hemangiomas do not improve significantly after 3.5 years of age. Reconstructive procedures should be considered at this age; the tumor has been allowed to regress and the deformity is improved before the development of long-term memory and psychosocial morbidity. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, IV.

PIK3CA activating mutations in facial infiltrating lipomatosis.

Background: Facial infiltrating lipomatosis is a nonheritable disorder characterized by hemifacial soft-tissue and skeletal overgrowth, precocious dental development, macrodontia, hemimacroglossia, and mucosal neuromas. The authors tested the hypothesis that this condition is caused by a somatic mutation in the phosphatidylinositide-3 kinase (PI3K) signaling pathway, which has been indicted in other anomalies with overgrowth. Methods: The authors extracted DNA from abnormal tissue in six individuals, generated sequencing libraries, enriched the libraries for 26 genes involved in the PI3K pathway, and designed and applied a sequential filtering strategy to analyze the sequence data for mosaic mutations. Results: Unfiltered sequence data contained variant reads affecting ~12 percent of basepairs in the targeted genes. Filtering reduced the fraction of targeted basepairs containing variant reads to ~0.008 percent, allowing the authors to identify causal missense mutations in PIK3CA (p.E453K, p.E542K, p.H1047R, or p.H1047L) in each affected tissue sample. Conclusions: Affected tissue from individuals with facial infiltrating lipomatosis contains PIK3CA mutations that have previously been reported in cancers and in affected tissue from other nonheritable, overgrowth disorders, including congenital lipomatous overgrowth, vascular, epidermal, and skeletal anomalies syndrome, Klippel-Trenaunay syndrome, hemimegalencephaly, fibroadipose overgrowth, and macrodactyly. Because PIK3CA encodes a catalytic subunit of PI3K, and in vitro studies have shown that the overgrowth-associated mutations increase this enzyme’s activity, PI3K inhibitors currently in clinical trials for patients with cancer may have a therapeutic role in patients with facial infiltrating lipomatosis. The strategy used to identify somatic mutations in patients with facial infiltrating lipomatosis is applicable to other somatic mosaic disorders that have allelic heterogeneity.

Management of Primary and Secondary Lymphedema: Analysis of 225 Referrals to a Center.

BackgroundLymphedema is the chronic, progressive enlargement of tissue due to inadequate lymphatic function. Although lymphedema is a specific condition, patients with a large extremity are often labeled as having “lymphedema,” regardless of the underlying cause. The purpose of this study was to characterize referrals to a center to determine if lymphedema should be managed by specialists. MethodsPatients treated in our Lymphedema Program between 2009 and 2013 were reviewed. Diagnosis was determined based on history, physical examination, photographs, and imaging studies. Lymphedema type (primary or secondary), location of swelling, patient age, sex, and previous management were documented. The accuracy of referral diagnosis and the geographic origin of the patients also were analyzed. ResultsTwo hundred twenty-five patients were referred with a diagnosis of “lymphedema”; 71% were women and 29% were children. Lymphedema was confirmed in 75% of the cohort: primary (49%) and secondary (51%). Twenty-five percent of patients labeled with “lymphedema” had another condition. Before referral 34% of patients with lymphedema received tests that are nondiagnostic for the disease, and 8% were given a diuretic which does not improve the condition. One third of patients resided outside our local referral area. The average time between onset of lymphedema and referral to our Lymphedema Program was 7.7 years (range, 1–59 years). ConclusionsPatients presenting to a center with “lymphedema” often have another condition, and may be suboptimally managed before their referral. Patients with suspected lymphedema should be referred to specialists focused on this disease.

Endothelial Cells from Capillary Malformations Are Enriched for Somatic GNAQ Mutations.

Background: A somatic mutation in GNAQ (c.548G>A; p.R183Q), encoding G&agr;q, has been found in syndromic and sporadic capillary malformation tissue. However, the specific cell type containing the mutation is unknown. The purpose of this study was to determine which cells in capillary malformations have the GNAQ mutation. Methods: Human capillary malformation tissue was obtained from 13 patients during a clinically indicated procedure. Droplet digital polymerase chain reaction, capable of detecting mutant allelic frequencies as low as 0.1 percent, was used to quantify the abundance of GNAQ mutant cells in capillary malformation tissue. Six specimens were fractionated by fluorescence-activated cell sorting into hematopoietic, endothelial, perivascular, and stromal cells. The frequency of GNAQ mutant cells in these populations was quantified by droplet digital polymerase chain reaction. Results: Eight capillary malformations contained GNAQ p.R183Q mutant cells, two lesions had novel GNAQ mutations (p.R183L and p.R183G), and three capillary malformations did not have a detectable GNAQ p.R183 mutation. Mutant allelic frequencies ranged from 2 to 11 percent. Following fluorescence-activated cell sorting, the GNAQ mutation was found in the endothelial but not the platelet-derived growth factor receptor-&bgr;–positive cell population; mutant allelic frequencies were 3 to 43 percent. Conclusion: Endothelial cells in capillary malformations are enriched for GNAQ mutations and are likely responsible for the pathophysiology underlying capillary malformation.

Obesity-induced Upper Extremity Lymphedema

Summary: Obesity increases the risk of upper extremity lymphedema following treatment for breast cancer and can cause lower extremity lymphatic dysfunction in extremely obese individuals. We report the first patient with obesity-induced upper extremity lymphedema. A 62-year-old man with a previous body mass index (BMI) of 105.6, presented with a BMI 60.3 following weight loss. He complained of lymphedema of all 4 extremities, which was confirmed by lymphoscintigraphy. Because the upper limbs are more resistant to lymphedema than the lower extremities, a higher BMI threshold may be necessary to cause upper extremity lymphatic dysfunction.

Diagnostic Accuracy of Lymphoscintigraphy for Lymphedema and Analysis of False-negative Tests

Background: Lymphedema is the chronic enlargement of tissue due to inadequate lymphatic function. Diagnosis is made by history and physical examination and confirmed with lymphoscintigraphy. The purpose of this study was to assess the accuracy of lymphoscintigraphy for the diagnosis of lymphedema and to determine characteristics of patients with false-negative tests. Methods: Individuals referred to our lymphedema program with “lymphedema” between 2009 and 2016 were analyzed. Subjects were assessed by history, physical examination, and lymphoscintigraphy. Patient age at presentation, duration of lymphedema, location of disease, gender, previous infections, and lymphedema type were analyzed. Results: The study included 227 patients (454 limbs); lymphedema was diagnosed clinically in 169 subjects and confirmed by lymphoscintigraphy in 162 (117 primary, 45 secondary; 96% sensitivity). Fifty-eight patients were thought to have a condition other than lymphedema, and all had negative lymphoscintigrams (100% specificity). A subgroup analysis of the 7 individuals with lymphedema clinically, but normal lymphoscintigrams, showed that all had primary lymphedema; duration of disease and infection history were not different between true-positive and false-negative lymphoscintigram results (P = 0.5). Two patients with a false-negative test underwent repeat lymphoscintigraphy, which then showed lymphatic dysfunction consistent with lymphedema. Conclusion: Lymphoscintigraphy is very sensitive and specific for lymphedema. All patients with false-negative studies had primary lymphedema. A patient with a high clinical suspicion of lymphedema and a normal lymphoscintigram should be treated conservatively for the disease and undergo repeat lymphoscintigraphy.

Operative Treatment of Lymphedema Using Suction-Assisted Lipectomy.

BackgroundSurgical management of lymphedema includes removal of affected tissues (excisional procedures), or operations that create new lymphatic connections (physiologic procedures). The purpose of this study was to determine the efficacy of one type of excisional procedure, suction-assisted lipectomy, for extremity lymphedema. MethodsPatients treated in our Lymphedema Program between 2007 and 2015 with liposuction that had postoperative follow-up were reviewed. The diagnosis of lymphedema was made by history/physical examination and confirmed with lymphoscintigraphy. Patient sex, age, type of lymphedema (primary or secondary), location of disease, infection history, volume of lipoaspirate, and reduction of extremity volume were recorded. ResultsFifteen patients were included, mean age was 45 years (range, 17–71). Six patients had secondary upper extremity lymphedema, and 9 patients had lower limb disease. Eight patients had a history of repeated cellulitis involving the lymphedematous extremity. Mean lipoaspirate volume was 1612 mL (range, 1200–2800) for the upper extremity and 2902 mL (range, 2000–4800) for the lower limb. Postoperative follow-up averaged 3.1 years. The mean reduction in excess extremity volume was 73% (range, 48% to 94%), and patients reported improvement in their quality of life. ConclusionsSuction-assisted lipectomy is an effective technique to reduce extremity volume for patients with lymphedema.

Management of Vascular Anomalies and Related Conditions Using Suction-Assisted Tissue Removal.

Summary: Vascular anomalies and related conditions cause overgrowth of tissues. The purpose of this study was to determine the efficacy and safety of liposuction techniques for pediatric overgrowth diseases. Patients treated between 2007 and 2015 who had follow-up were reviewed. Seventeen patients were included; the median age was 12.7 years. The causes of overgrowth included infiltrating lipomatosis (n = 7), capillary malformation (n = 6), hemihypertrophy (n = 1), infantile hemangioma (n = 1), lipedema (n = 1), and macrocephaly-capillary malformation (n = 1). Forty-seven percent had enlargement of an extremity, 41 percent had facial hypertrophy, and 12 percent had expansion of the trunk. All subjects had a reduction in the size of the overgrown area and improved quality of life. Suction-assisted tissue removal is an effective technique for reducing the volume of the subcutaneous compartment for patients with pediatric overgrowth diseases. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Liposuction for Swelling in Patients with Lymphedema

Lymphedema is frequently a disabling consequence of cancer staging. Liposuction can considerably reduce swelling and may improve lymphatic drainage in an affected limb. This intervention is worthy of additional study.