Trans-Spatial Mass
Bernadette L. Koch, MD
DIFFERENTIAL DIAGNOSIS
Common
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Abscess
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Lymphatic Malformation
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Venous Malformation
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Infantile Hemangioma
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Neurofibromatosis Type 1
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Rhabdomyosarcoma
Less Common
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Lipoma
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Thymic Cyst
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4th Branchial Anomaly
Rare but Important
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Teratoma
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Fibromatosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
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Trans-spatial: Multiple contiguous spaces
Helpful Clues for Common Diagnoses
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Abscess
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Key facts
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Signs and symptoms of infection
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May be in deep soft tissues of neck
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May present with airway impingement
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75% drainable pus; 25% phlegmonous, nondrainable inflammatory tissue
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Imaging
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Low-attenuation, rim-enhancing mass
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Retropharyngeal edema common
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May extend via danger space into mediastinum
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Lymphatic Malformation
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Key facts
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Most common cystic neck mass with spontaneous hemorrhage
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Sudden increase in size secondary to hemorrhage or viral respiratory infection
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Imaging
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Unilocular or multilocular; macrocystic or microcystic; 1 space or trans-spatial
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Insinuates morphology
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Only septations enhance, unless associated with venous malformation
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Lack high-flow vessels on flow-sensitive MR sequences and angiography
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Fluid-fluid levels secondary to intralesional hemorrhage common
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Venous Malformation
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Key facts
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Lobulated soft tissue mass; variably sized venous channels with phleboliths
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Mass increases in size with Valsalva, crying, or bending over
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Imaging
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Intermediate attenuation/hyperintense T2 with variable contrast enhancement
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No high flow vessels
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Infantile Hemangioma
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Key facts
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Neoplasm with spontaneous proliferation and involution
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Present within 1st few weeks of life; usually not present at birth
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May be multiple (PHACES syndrome)
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Imaging
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Lobulated mass, intense enhancement
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High-flow intralesional vessels
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Neurofibromatosis Type 1
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Key facts
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Localized neurofibroma (NF), diffuse NF, plexiform NF (PNF), or malignant peripheral nerve sheath tumor (PNST)
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If multiple or plexiform, think NF1
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Imaging
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May be hypoattenuating on CT
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Localized: Well-circumscribed, fusiform, solid masses and moderate enhancement ± dumbbell-shaped extension into neural foramina
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Diffuse NF: Plaque-like subcutaneous lesion with poorly defined infiltrating margins, moderate enhancement
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Plexiform NF: Lobulated, tortuous, rope-like enlargement in major nerve distribution; resembles “tangle of worms”
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Malignant PNST: Benign vs. malignant difficult to differentiate on imaging; consider malignant if ≥ 5 cm, intensely enhancing with infiltrative margins
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Rhabdomyosarcoma
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Key facts
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Sites: Orbit, nasopharynx, temporal bone, sinonasal, cervical neck
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Imaging
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Soft tissue mass with variable contrast enhancement ± bone erosion
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Coronal post-contrast fat-saturated T1 images best for intracranial extension
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Helpful Clues for Less Common Diagnoses
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Lipoma
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Key facts
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Benign neoplasm, mature fat
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Imaging
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Well-circumscribed homogeneous mass of fat attenuation and signal intensity
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Small minority of lesions will have a nonfatty soft tissue component
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Any space of neck
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Single space or trans-spatial
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Imaging cannot differentiate between lipoma and low-grade liposarcoma
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Thymic Cyst
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Key facts
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Remnant of thymopharyngeal duct, 3rd branchial pouch remnant
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Wall contains Hassall corpuscles
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Imaging
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Cystic neck mass along course of thymopharyngeal duct ± solid enhancing thymic tissue
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Close association with carotid sheath
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May be connected to mediastinal thymus directly or by fibrous cord
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Rarely extends to skull base; may rupture into parapharyngeal space
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4th Branchial Anomaly
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Key facts
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Presents with recurrent thyroiditis or anterior neck abscess secondary to sinus tract extending from apex of pyriform sinus to lower anterior neck
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Imaging
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Cyst or abscess anterior to left thyroid lobe with associated thyroiditis
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Barium swallow or post barium swallow CT may show sinus tract extending from apex of pyriform sinus to anterior lower neck
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Helpful Clues for Rare Diagnoses
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Teratoma
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Key facts
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All 3 germ cell lines
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Mature, immature, and malignant
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Imaging
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Fat, calcium, cyst, and solid components
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Fibromatosis
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Key facts
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Synonyms: Desmoid fibromatosis, extraabdominal desmoid fibromatosis, infantile fibromatosis
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Histologically benign fibroproliferative disorder with potentially aggressive clinical course and invasive growth
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Associated with Gardner syndrome
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Imaging
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Poorly marginated trans-spatial mass
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Moderate post-contrast enhancement
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± bone erosion or invasion
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Image Gallery
![]() Axial CECT shows a large, multilobulated, rim-enhancing abscess arising from the left palatine tonsil
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