Case of the Week # 519

Case of the Week # 519

Javier Cortejoso
 on 03/06/2023
 on Monday, March 6th, 2023
The ultrasound images show the following:
• Images 1-4: different sections of the posterolateral side of the neck show a hyperechoic and well-delineated, homogeneous, solid mass. With color Doppler, the tumor contains large feeding vessels with blood flow coursing peripherally, and pulsed duplex Doppler interrogation demonstrates low-resistance arterial waveforms
• Images 5-12: sagittal, coronal and axial MRI sections of the neck characterize the lesion as hyperintense on T2-weighted images, and hypointense on T1-weighted MRI

Tumors are considered congenital when detected during pregnancy or in the first 3 months of life. Congenital tumors represent 1.5–2% of all pediatric tumors, with a prevalence of 1 in 12,500 to 27,500 live births. The soft tissues give rise to a diverse group of tumors. Although relatively common in pathologic series, representing 12%–22% of all congenital tumors, soft-tissue tumors are less commonly reported in the radiology literature.

Posterior solid fetal neck masses are rare anomalies. The differential diagnosis in this case includes hemangioma, which is the most likely diagnosis, and teratoma. Rare etiologies of cervical masses include fibrous connective tissue tumors, kaposiform hemangioendothelioma, neuroblastoma, and rhabdomyoma.

Vascular lesions may produce tumor-like masses with potentially serious consequences for the fetus. The International Society for the Study of Vascular Anomalies (ISSVA) differentiates between vascular tumors (which are proliferative endothelial lesions with high flow) and vascular malformations (arterial, venous, capillary, lymphatic or mixed), which are developmental malformations of hematic or lymphatic vessels. The most common types of vascular tumors of childhood are infantile hemangioma, congenital hemangioma, kaposiform hemangioendothelioma, and angiosarcoma. The notion of congenital hemangiomas has been introduced recently, differentiating between non-involuting congenital hemangiomas (NICH), and rapidly involuting congenital hemangiomas (RICH). Hemangiomas account for a significant number of prenatally diagnosed neoplasms, but because most of them are small or absent at birth, they are often not included in the register of congenital tumors. The most frequent location is the head and neck (60%). On ultrasound, they appear as a well-defined homogenous, echogenic mass arising in the subcutaneous tissues of the neck, although they can be mixed cystic and solid lesions. They can present with calcifications, although this finding is more common in teratoma. Color Doppler demonstrates increased flow to the mass with decreased arterial resistance and increased venous drainage. On MR images, they usually demonstrate intermediate signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and high flow vessels. Additionally, areas of fatty replacement can be seen. Sequestration of platelets in the lesion may lead to thrombocytopenia, consumptive coagulopathy, and microangiopathic hemolytic anemia, also known as Kasabach-Merritt syndrome.

Fibrous connective tissue tumors are the largest group of congenital soft-tissue tumors and include fibromatosis, myofibromatosis, inflammatory myofibroblastic tumor, digital fibroma, fibrous hamartoma, and infantile fibrosarcoma which is the most common soft-tissue malignancy in newborns. Ultrasound of fibrous connective tissue tumors shows a soft-tissue mass with variable echogenicity. They most commonly have a low signal intensity on both T1-weighted and T2-weighted images, with infiltration of the fat and muscle. There are cases with intermediate or high signal intensity on T2 images. Infantile fibrosarcoma is located in the head and neck region in 10% of cases and their appearance may be similar to that of benign vascular lesions. Inflammatory myofibroblastic tumors are uncommon lesions primarily affecting children and young adults. They have rarely been described in infants, with a very small number described prenatally and in neonates. Cases of prenatally diagnosed inflammatory myofibroblastic tumors include tumors in the paravertebral space, at the skull base, the neck, in the thoracic cavity and chest wall. Ultrasonographic and magnetic resonance imaging of the fetus demonstrates a solid, homogenous mass.

Other soft tissue masses include rhabdomyomas, lipoblastomas, neuroblastoma, and teratoma. Rhabdomyomas are rare, benign tumors arising from striated muscle. Cardiac rhabdomyomas are the most common type, while the head and neck are the most common extracardiac site. Rhabdomyosarcoma represents >50% of all soft tissue sarcomas in children, but its congenital presentation is extremely rare. Ultrasound shows a soft tissue mass, similar to muscle. MRI reveals a mass isointense to muscle on T1-weighted and hyperintense on T2-weighted images. Lipoblastomas are rare, usually encapsulated, benign neoplasms of the embryonal fat. Ninety percent arise before the age of 3 years. Most lipoblastomas arise in the extremities, although some originate in the trunk, head, or neck. Lipoblastomas can be heterogeneous and have intermediate to high signal intensity on T1-weighted images depending on the quantity of immature lipoblasts. Neuroblastoma, with its typical adrenal location, is well recognized in the newborn. Cervical location of neuroblastoma has been described in children, but seldom in the fetus. The typical sonographic appearance is solid with variable echogenicity including microcalcifications with acoustic shadowing. Finally, teratomas are benign tumors containing cells from ectodermal, mesodermal and endodermal layers. They typically arise from the sacrococcygeal region, with the head and neck being the second most frequent location (6–10% of all teratomas). Located anterior in the neck, they are mixed cystic and solid lesions containing color Doppler flow and calcifications.

The differential diagnoses of fetal neck masses include hemangioma, lymphangioma, cystic hygroma, teratoma, goiter, sarcomas, neuroblastoma, rhabdomyoma/rhabdomyosarcoma, myofibroma, cervical myelomeningocele, and occipital encephalocele. The location and/or the ultrasound characteristics exclude some of these diagnoses in our case. The most common solid mass arising in the anterior compartment of the neck is cervical teratoma, while cystic hygroma (a lymphatic malformation predominately cystic and multilocular) is the most frequently diagnosed posterior neck mass in fetuses. Color Doppler flow imaging provides additional information that can supplement routine gray-scale imaging. The peripheral flow pattern on color Doppler imaging is characteristic of inflammatory processes. Central vascularity or a combination of central and peripheral vascularity are seen in hemangioma and malignant tumor. Hemangiomas can have large feeding vessels with documented arterial waveforms, which coincides with the vascular nature of the lesion demonstrated in this case.

Suggested readings:
• Alamo L, Beck-Popovic M, Gudinchet F, et al. Congenital tumors: imaging when life just begins. Insights Imaging. 2011;2(3):297-308.
• Calvo-Garcia MA, Kline-Fath BM, Adams DM, et al. Imaging evaluation of fetal vascular anomalies. Pediatr Radiol. 2015;45(8):1218-1229.
• Gorincour G, Dugougeat-Pilleul F, Bouvier R, et al. Prenatal presentation of cervical congenital neuroblastoma. Prenat Diagn. 2003;23(8):690-693.
• Kaplan MC, Coleman BG, Shaylor SD, et al. Sonographic features of rare posterior fetal neck masses of vascular origin. J Ultrasound Med. 2013;32(5):873-880.
• Kornacki J, Skrzypczak J. Fetal neck tumors - antenatal and intrapartum management. Ginekol Pol. 2017;88(5):266-269.
• Latifi HR, Siegel MJ. Color Doppler flow imaging of pediatric soft tissue masses. J Ultrasound Med. 1994;13(3):165-169.
• O'Callaghan MG, House M, Ebay S, et al. Rhabdomyoma of the head and neck demonstrated by prenatal magnetic resonance imaging. J Comput Assist Tomogr. 2005;29(1):130-132.
• Tsukimori K, Hojo S, Kawarabayashi Y, et al. Fetal neck capillary hemangioma associated with Kasabach-Merritt syndrome. J Ultrasound Med. 2007;26(3):397-401.
• Valdez TA, Desai U, Volk MS. Recurrent fetal rhabdomyoma of the head and neck. Int J Pediatr Otorhinolaryngol. 2006;70(6):1115-1118.
• Woodward PJ, Sohaey R, Kennedy A, et al. From the archives of the AFIP: a comprehensive review of fetal tumors with pathologic correlation. Radiographics. 2005;25(1):215‐242.
• Zieliński R, Respondek-Liberska M. The role of prenatal ultrasound assessment in management of fetal cervicofacial tumors. Arch Med Sci. 2016;12(4):850-855.

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