MyPACS.net: Radiology Teaching Files > Case 53171420

Never visited PAROTID MASS
Contributed by: Nick Ludwig, Resident, SAMMC, Texas, USA.
Patient: 62 year old female
History: 62 year old female with enlarging post-auricular node per provided history.
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Findings: Slightly irregular, heterogenously enhancing mass in the deep left parotid space; ill defined margin inferomedially.  No evident effacement of the left parapharyngeal space.  No invasion of the left stylomastoid foramen.  No evident lymph node enlargement.
Diagnosis: Biopsy proven mucoepithelial pleomorphic adenoma
Discussion:

Benign mixed tumor; synonymous with pleomorphic adenoma

  • Benign heterogeneous tumor of parotid gland made up of an admixture of epithelial, myoepithelial & stromal components
  • Most common parotid space mass; large asymptomatic deep parotid lobes masses are almost always pleomorphic adenomas; infiltrative margins or multicentricity should suggest alternate diagnosis 
    • Most common parotid space tumor (80%)
    • 80% BMT arise in parotid glands
      • 8% in submandibular glands; 6.5% arise from minor salivary glands in nasopharyngeal mucosa
    • 80-90% of parotid BMTs involve superficial lobe
    • Multicentric BMT rare (< 1%)
    • Age
      • Most common > 40 years
      • Age range is 30-60 years
    • Gender: M:F = 1:2
    • Ethnicity: Most common in Caucasians, rare in African-Americans
  • Top differential
    • Warthin's tumor
    • Primary parotid carcinoma to include mucoepidermoid or adenoid cystic.
    • NHL of the parotid
    • Parotid nodal metastasis
  • Imaging
  • Small BMT: Sharply-marginated, intraparotid ovoid mass with uniform parenchymal enhancement
  • Large BMT (> 2 cm): Lobulated mass with inhomogeneous enhancement
  • Deep lobe BMT: Pear-shaped inhomogeneous mass pushing parapharyngeal space medially
  • Location: Parotid space
  • Size: Variable; may grow to 6-8 cm when in deep lobe
  • Morphology
    • Small BMT: Sharply-circumscribed mass surrounded on all sides by parotid with homogeneous parenchyma
    • Large BMT: Multilobular, inhomogeneous mass
    • Deep lobe lesions: Pear-shaped mass that widens stylomandibular notch & displaces parapharyngeal space anteromedially
  • CT findings
    • Small BMT
      • Smoothly marginated, homogeneously enhancing, ovoid mass
    • Large BMT
      • Inhomogeneously enhancing, lobulated mass with areas of lower attenuation representing foci of degenerative necrosis & old hemorrhage
      • Dystrophic calcification may be present, distinguishing from Warthin tumor
  • MRI findings
    • T1WI
      • Small BMT: Sharply marginated intraparotid mass with uniform hypointensity
      • Large BMT: Lobulated intraparotid mass with heterogeneous signal
      • Hyperintense signal can be seen in hemorrhagic lesion
    • T2WI
      • Small BMT: Well-circumscribed intraparotid mass with uniform intermediate to high signal
      • Large BMT: Lobulated intraparotid mass with heterogeneous high signal
      • May demonstrate low signal intensity capsule
      • STIR: Lesions more conspicuous
    • T1WI C+: Variable mild to moderate enhancement
  • Ultrasound
    • Well-demarcated homogeneous hypoechoic mass of superficial lobe of the parotid
    • Larger lesions may demonstrate heterogeneous hypoechogenicity
    • US may miss deep lobe BMT
  • Angiogaphically hypovascular; may help distinguish from a paragangionoma
  • Nuclear Medicine
  • 99mTc-Pertechnetate
    • Cold lesion
    • Helps differentiate from Warthin tumor (hot)
      • All other lesions, including malignancy, present as cold defect
  • Treatment: Surgical exisional biopsy
References: Statdx.com "Pleomorphic Adenoma" "Benign mixed parotid tumor" accessed via WWW on 3 July 2011.
Comments:
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Additional Details:

Case Number: 53171420Last Updated: 2011-07-04
Anatomy: Face and Neck   Pathology: Neoplasm
Modality: CTAccess Level: Readable by all users
Keywords: parotid mass, pleomorphic adenoma

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