Term Infant With a Large Red-Purple Mass in the Upper Thigh

A term female twin infant presents at birth with a large red-purple mass in the left upper thigh.Born to a 30-year-old gravida 3, para 1–0–1–1 woman with gestational hypertensionConception by in vitro fertilization resulting in a dichorionic diamniotic pregnancyPrenatal laboratory tests: blood type A negative, antibody negative, group B Streptococcus negative, hepatitis B surface antigen negative, rapid plasma reagin nonreactive, rubella equivocal, and HIV negativePrenatal course benign with normal fetal survey at 20 weeks’ gestation, low-risk cell-free DNA assessmentMaternal medications: prenatal vitamins, ferrous sulfate, baby aspirinGestational age: 37 weeks and 3 daysBorn by repeat cesarean birth; routine resuscitation; Apgar score of 9 and 9 at 1 and 5 minutes, respectively; a left upper thigh mass is noted (Figure 1)Birthweight: 2960 g (27%), birth length 48.5 (36%), birth head circumference 34 cm (54%)FIGURE 1.A large 8 cm × 4 cm firm, rubbery, nodular mass with a red-purple discoloration on the infant’s left anterior thigh was noted at birth.Heart rate: 123 beats per minuteRespiratory rate: 44 beats per minuteAxillary temperature: 36.7 °C (98.1 °F)General: well appearing infant in no distressHead, Eyes, Ears, Nose, Throat: Normocephalic; normal, open, flat fontanelles; no atypical facial features; patent nares; intact palate; no neck mass or crepitusLungs: Clear, equal breath sounds; no tachypnea, no chest retractionsCardiovascular: Normal heart sounds; regular rate and rhythm; no murmurs or gallop, femoral pulses 2+ bilaterallyAbdomen: Soft, no hepatomegaly or splenomegaly, bowel sounds present; patent anusGenitourinary: Normal female genitaliaExtremities: Hips with negative Barlow and Ortolani maneuver. Spine appears normal. There is a 8 cm × 4 cm firm, rubbery, nodular mass with a red-purple discoloration on the left anterior thighSkin: No icterus, no rash, no other lesions or masses besides mass on thighNeurologic: Rooting and sucking reflex present, symmetric Moro reflex, normal strength and tone. No abnormal movement, focal neurological deficit or cranial nerve palsyWhite blood cell count: 16.7 × 103/μL (16.7 × 109/L); hemoglobin 14.0 g/dL (8.7 mmol/L); hematocrit 40.3%; platelets 318 × 103/μL (318 × 109/L)Prothrombin time 12.6 seconds; partial thromboplastin time 39.4 seconds; international normalized ratio 1.2Fibrinogen: 356 mg/dL (10.4 μmol/L)D-dimer: 2223 (elevated)Total bilirubin: 5.8 mg/dL; direct bilirubin: 0.2 mg/dLReticulocyte count: 6%Congenital hemangiomaInfantile myofibromaInfantile hemangiomaInfantile fibrosarcomaRhabdomyoscarcomaInfantile myofibromaAn ultrasonography is obtained, and results show a uniform solid minimally vascular soft tissue with overall measurements of approximately 6 × 3 × 4 cm. There is likely a small feeding vessel coming from the adjacent left femoral artery.The surgical team is consulted, and the infant is transferred to the local children’s hospital for further evaluation. A magnetic resonance imaging of the pelvis (Figure 2) with and without contrast shows a well-circumscribed exophytic solid mass measuring 5.6 × 5.2 × 2.9 cm arising from the subcutaneous tissue of the left anterior thigh. There appears to be a vascular pedicle arising from the common femoral artery and vein. There does not appear to be any involvement of the underlying osseous structures or muscle. Chest radiograph is unremarkable with no mediastinal mass or lymph nodes. The infant continues to be hemodynamically stable.At 4 days of age, the mass is surgically removed with no complications. Pathology report showed a rubbery, nodular well-delineated neoplasm with biphasic morphology composed of immature appearing plump cells associated with branching vasculature. The periphery of the lesion consists of nodules of spindled cells. There are areas of necrosis and ulcerations seen. The lesion appears to be completely excised. Findings are consistent with an infantile myofibroma.The infant is admitted to the neonatal intensive care unit postoperatively and is discharged after 3 days with no complications, with follow-up appointments with general surgery and genetics.The infant continued to do well after surgical excision. At 6 weeks of age, a whole-body magnetic resonance imaging is performed to evaluate for other myofibromas with no evidence of other solid masses in the brain, torso, or extremities. The infant is referred for genetic testing. An oncopanel genetic test shows a mutation in the platelet-derived growth factor receptor beta (PDGFRB) variants within the mass, but germline testing is negative for PDGFRB variants. Despite the negative germline test, there was a potential risk of somatic mosaic pathogenic variant. As a result, the infant continues to have surveillance with abdominal and pelvic ultrasonography every 3 months for the first year of age with no current evidence of disease.Infantile myofibromas are the most common fibrous tumor of infancy, occurring in approximately 1 out of every 150 000 infants.1 It is more common in boys, with a 55∶1 male/female ratio.1,2 Infantile myofibroma is characterized by a firm, rubbery nodule that is flesh-colored, yellow, or blue-purplish in color, and it can present in 3 different forms: solitary form, single cutaneous nodule;multicentric form, involving skin, subcutaneous tissues, muscle and bone; andgeneralized form, with visceral involvement.2Solitary lesions are more common, representing 70% to 80% of cases, and have a good prognosis.3–5 Multicentric lesions are rarer (20% 30% of all cases), more common in girls (63% of female cases), and are generally benign.2–5 The generalized form has poor prognosis and can be fatal due to visceral involvement.2,6 Patients with suspected infantile myofibroma should have additional radiographic evaluation to evaluate for visceral involvement.2 Although most cases arise spontaneously, mutations in PDGFRB and NOTCH3 have been identified in the development of infantile myofibroma.3Infantile myofibroma is diagnosed by the distinct histopathology of a biphasic pattern of dark-stained round small spindle cells with enlarged hyperchromatic nuclei located in the center and light-stained spindle-shaped myofibroblasts arranged along the periphery.5,7 Immunohistochemistry can be used to confirm an infantile myofibroma diagnosis with strong positivity for α-smooth muscle actin and vimentin and negativity for S100, a marker for neurofibroma, and glucose transporter 1, a marker for infantile hemangioma.5,8A solitary or multicentric infantile myofibromas can resolve spontaneously, but treatment is often surgical excision, especially with visceral involvement or if symptomatic due to compression of other organs. Patients with solitary and multicentric lesions have a good prognosis. Visceral involvement, particularly pulmonary involvement, has a poor prognosis with mortality rate as high as 33% to 75%.2,5 Chemotherapy has been used in patients with visceral involvement but with little success.2Recurrence is possible with multicentric and generalized forms, and therefore, surveillance is recommended every 6 months for 2 years.2Congenital hemangioma (CH) is a benign vascular tumor fully formed at birth and often detected on prenatal ultrasonography due to its high vascularity. These lesions typically present as red-purple lesions but can also present as a solitary tumor.9 They are divided into 3 subgroups: rapidly involuting CH, which regresses once the infant is born and typically disappears within 1 to 1.5 years;noninvoluting CH, which remains stable and continues to grow; andpartially involuting CH, which initially regresses but eventually stabilizes around 1 year.9For this infant, ultrasonography of the lesion did not show significant vascularity outside of a single vessel feeding the mass.Infantile hemangiomas are the most common benign tumor of infancy, resulting from abnormal endothelial proliferation and are commonly referred to as “strawberry marks.”10 These lesions present as precursor lesions at birth and typically proliferate within the first few weeks after birth.9 Infantile hemangiomas are more common in female infants and those who are white, preterm, or born from multiple gestations.11 They can be identified by specific markers such as glucose transporter 1 overexpression, as well as positivity for Lewis Y antigen, merosin, and FcRII.10 Most infantile hemangiomas resolve on their own and can be treated with beta-blockers (topical or oral), corticosteroids, or surgical excision.10 Because infantile hemangiomas typically present as smaller lesions that then grown postnatally, the infant’s skin lesion is not consistent with an infantile hemangioma.Infantile fibrosarcoma is the most common nonrhabdomyosarcoma soft tissue tumor in infants. It typically presents within the first 2 years of age, with about 40% of cases evident at birth.12 This tumor is characterized by rapid growth and is often poorly circumscribed, potentially involving subcutaneous fat, fascia, and tendons, particularly in the distal extremities.13 Histologically, infantile fibrosarcoma is characterized by spindle cells with fusiform oval nuclei and lance-shaped, tapered cells.12,14 The management of infantile fibrosacrcoma generally involves surgical excision, and the prognosis is typically favorable.13 Like infantile hemangioma, in this case, the size of the mass at birth makes infantile fibrosarcoma less likely.Rhabdomyosarcoma is the most common soft tissue sarcoma in childhood, originating from rhabdomyoblasts, which are primitive mesenchymal cells with varying degrees of skeletal muscle differentiation. This type of sarcoma accounts for approximately 50% of pediatric soft tissue sarcomas.14 Rhabdomyosarcomas can occur in various locations, with those arising from the genitourinary tract, such as the vagina or bladder wall, being particularly common in infants.14 Head and neck rhabdomyosarcomas are also frequently observed in young children. Tumors in the extremities are less common in newborns but can appear in adolescents.15A large, red-purple nodular lesion in a healthy newborn may be a scenario that a pediatrician will encounter in the newborn nursery. An accurate diagnosis can begin with ultrasound imaging to determine vascularity of the lesion, biopsy or excision with histologic stains, possible imaging of other organs to assess for systemic disease, and consultation with pediatric surgery or pediatric dermatology.