Lymphatic malformation (LM) is a low-flow vascular malformation composed of dysplastic lymphatic channels. It is congenital — present at birth or presents in early childhood, showing no spontaneous involution. US is the primary diagnostic modality and appears as a multiloculated cystic structure. Absence of internal vascularity on Doppler (completely avascular) is a pathognomonic finding and definitively distinguishes lymphatic malformation from venous malformation and hemangioma. Thin septae separate cystic spaces and septae may show vascularity.
Age Range
0-20
Peak Age
5
Gender
Equal
Prevalence
Uncommon
Lymphatic malformation results from a developmental anomaly of the lymphatic system during embryonic period. PIK3CA somatic mutations disrupt signaling pathways regulating lymphatic endothelial cell proliferation and lymphatic channel formation. Dysplastic lymphatic channels do not connect to the normal lymphatic system and lymph fluid cannot drain — resulting in cystic expansion. Cystic spaces are filled with lymph fluid (protein-poor transudate). The multiloculated cystic appearance on US reflects adjacent but separate dilated lymphatic channels — each cystic space contains anechoic fluid and is separated by thin septae (dysplastic lymphatic walls). Pathognomonic avascularity results from lymphatic channels not carrying blood — these structures contain only lymph fluid with no blood flow, therefore no Doppler signal is generated. This finding definitively differentiates from venous malformation (may have minimal venous flow) and hemangioma (intense arterial flow). Small blood vessels may exist within septae, and septae may show mild Doppler signal — but the cystic spaces themselves are completely avascular. In infection or hemorrhage complications, cystic content changes: fluid becomes echogenic with protein increase and fluid-debris level may be seen. On MRI, T2 hyperintense multiloculated cystic structure is characteristic; on T1, fluid is low signal but may be T1 hyperintense if hemorrhage is present.
Completely avascular (no flow) finding on Doppler within a multiloculated cystic structure is the pathognomonic finding of lymphatic malformation. This avascularity reflects lymphatic channels carrying lymph fluid not blood, definitively distinguishing from venous malformation (may have low venous flow) and hemangioma (high arterial flow).
On B-mode US, lymphatic malformation appears as a multiloculated cystic mass composed of multiple anechoic cystic spaces separated by thin septae. Cystic spaces are variable in size (mm-cm). Large cysts are dominant in macrocystic type, small cysts in microcystic type. Septae are thin (<2mm) with smooth contours. Posterior acoustic enhancement (fluid structure characteristic) is seen behind each cystic space.
Report Sentence
A multiloculated cystic mass separated by thin septae is seen, consistent with lymphatic malformation.
On color and power Doppler, the cystic spaces of lymphatic malformation are completely avascular — no flow is seen within any cyst. This pathognomonic avascularity finding definitively distinguishes lymphatic malformation from venous malformation (may have minimal venous flow) and infantile hemangioma (intense arterial flow). Minimal vascularity may be seen within septae — these are small blood vessels within septae and do not exclude lymphatic malformation diagnosis.
Report Sentence
No flow is identified within the cystic spaces on color and power Doppler, consistent with the pathognomonic avascularity finding of lymphatic malformation.
In infection or intralesional hemorrhage complications, cystic content changes: previously anechoic fluid becomes echogenic (protein/cell increase). Fluid-debris level may be seen — cell debris settles to the bottom due to gravity. Septae may thicken. These complication findings may require urgent treatment.
Report Sentence
Echogenic fluid and fluid-debris level are noted in the cystic spaces, suggesting infection/hemorrhage complication in lymphatic malformation.
On MRI T2, lymphatic malformation appears as a markedly hyperintense multiloculated cystic mass. Cystic spaces show fluid-bright signal. Septae show low signal. No flow voids — indicator of low-flow lesion. Hemorrhagic T1 hyperintense fluid-debris level may be seen in hemorrhagic complication.
Report Sentence
A markedly hyperintense multiloculated cystic mass without flow voids is seen on T2 — consistent with lymphatic malformation.
On contrast-enhanced MRI, only septae show enhancement in lymphatic malformation — cystic spaces do not enhance. This pattern confirms that cystic spaces are avascular and only septal vascular supply exists. In infection complication, septal thickening and increased peripheral enhancement may be seen.
Report Sentence
On post-contrast sequences, only septae show enhancement with no enhancement in cystic spaces — consistent with lymphatic malformation.
Criteria
Cystic spaces >1cm dominant, usually neck/axilla
Distinct Features
Best response to sclerotherapy. Large anechoic cysts prominent on US. 'Cystic hygroma' synonymous with old terminology.
Criteria
Cystic spaces <1cm dominant, diffuse infiltrative pattern, cutaneous vesicles may be present
Distinct Features
Lower sclerotherapy response. May appear heterogeneous solid on US (small cysts may be below US resolution). Surgical resection more difficult. Sirolimus treatment may be effective.
Criteria
Both >1cm and <1cm cystic spaces coexist, most common type
Distinct Features
Macrocystic component treated with sclerotherapy, microcystic component with sirolimus/surgery. Combined treatment approach usually necessary.
Distinguishing Feature
Venous malformation is compressible, fills with Valsalva, may have minimal venous Doppler flow, may contain phleboliths. Lymphatic malformation is completely avascular, no Valsalva response, no phleboliths.
Distinguishing Feature
Hemangioma is solid and intensely hypervascular (high-flow, low RI). Lymphatic malformation is cystic and completely avascular. Hemangioma shows postnatal proliferation, LM does not grow.
Distinguishing Feature
Hematoma is not multiloculated, shows time-dependent echogenicity change, associated with trauma history. LM is multiloculated cystic with septae and present from birth.
Urgency
routineManagement
interventionalBiopsy
Not NeededFollow-up
6-monthTreatment of lymphatic malformation depends on size, type, and symptom level. Macrocystic LM: percutaneous sclerotherapy (OK-432/picibanil, bleomycin, doxycycline) is first choice — response rate 70-90%. Microcystic LM: sclerotherapy response is low, sirolimus (mTOR inhibitor) may be effective. Surgical resection when complete removal is possible but incomplete resection risk is high in infiltrative lesions. Antibiotherapy and drainage in infection complication. US follow-up at 6-month intervals.
Lymphatic malformations do not involute. Macrocystic type responds well to sclerotherapy (OK-432/picibanil, doxycycline, bleomycin). Microcystic type is more resistant to treatment; sirolimus (mTOR inhibitor) is a newer treatment option. Infection and intralesional hemorrhage are the most common complications. Airway compression requires urgent intervention.