Carcinoma Ex-Pleomorphic Adenoma

Carcinoma Ex-Pleomorphic Adenoma
Lester D. R. Thompson, MD
There is a well-circumscribed tumor, with areas of residual pleomorphic adenoma image and calcifications image. However, even at low power, the areas of carcinoma image are more cellular, with a glandular architecture.
There is a remarkable degree of cytologic pleomorphism with a sclerotic background stroma. Areas suggestive of residual pleomorphic adenoma image are seen, although limited by this high-power view.
TERMINOLOGY
Abbreviations
  • Carcinoma ex-pleomorphic adenoma (Ca ex-PA)
Synonyms
  • Carcinoma ex benign mixed tumor
  • Malignant mixed tumor
Definitions
  • Presence of carcinoma arising from pleomorphic adenoma (PA)
    • Requires concurrent pleomorphic adenoma histologically or history of pleomorphic adenoma at same site
    • Carcinoma can be any epithelial neoplasm
ETIOLOGY/PATHOGENESIS
Pathogenesis
  • There is malignant transformation of epithelial component
  • Areas of transition help to substantiate a continuum
CLINICAL ISSUES
Epidemiology
  • Incidence
    • Accounts for about 4% of all salivary tumors
      • 12% of all salivary malignancies
      • 7% of all pleomorphic adenomas
  • Age
    • Usually in 6th and 7th decades
      • About 10-12 years older than age at presentation of pleomorphic adenoma
      • Exceptional in children
  • Gender
    • Probably equal gender distribution
Site
  • Major salivary glands most often (80%)
    • Parotid (80%) > submandibular (18%) > > sublingual gland (< 2%)
    • May be due to large tumor size and increased recurrence rate for major gland location
  • Minor glands (20%)
    • Palate > > nasopharynx > nasal cavity > > larynx
Presentation
  • Long clinical history of pleomorphic adenoma
    • The greater the length of time with tumor, the higher the risk of malignant transformation
      • 5 years: 1.6%; 15 years: 9.6%
      • Symptoms/mass present for up to 44 years
    • Need to have well-documented previous tumor in same anatomic site if there is no histologic evidence of benign PA
      • Some tumors are slow growing and asymptomatic, so long history of mass by itself is insufficient
  • May have had multiple surgeries
    • About 20% have had previous surgery
  • Usually, recent rapid enlargement
  • Nerve palsies are common (40%)
  • Majority are painless
  • Rare: Skin ulceration, soft tissue attachment, bone invasion
Treatment
  • Surgical approaches
    • Complete surgical eradication
    • Lymph node dissection often required (˜ 20%)
      • Some recommend neck dissection for all major gland tumors
      • Lymph node dissection may not be necessary for low-grade carcinomas or those with limited invasion
  • Radiation
    • Majority receive postoperative radiation therapy
      • Especially used for widely invasive &/or high-grade tumors
      • May be useful in controlling local disease
Prognosis
  • Local recurrence can be seen (range of 25-50%)
    • Majority are seen within 5 years of diagnosis
    • Many patients experience more than 1 recurrence
    • Recurrence rates tend to be lower for minor salivary gland primaries
    • Higher percentage of patients die with disease if they have local recurrence
  • Local or distant metastases are common (range of 50-70%)
    • Local lymph node metastases: Up to 25%
      • May be higher if there was previous surgery
    • Distant sites: Lung, bone (spine), liver, brain, skin
      • Most common in patients with local recurrence
  • Poor overall survival
    • Majority die of disease (60%)
    • 5-year survival (30%)
  • Prognostically significant factors (order of importance)
    • Grade
      • Low grade: Tend not to die of tumor
      • High grade: Majority die from tumor
    • Stage
    • Proportion of tumor that is carcinoma
    • Extent of invasion
      • Noninvasive (encapsulated): Excellent long-term outcome (identical to conventional PA)
      • Minimally invasive tumors (≤ 1.5 mm): Good outcome (75-85% at 5 years)
      • Widely invasive (> 1.5 mm): Poor outcome (25-65% at 5 years)
    • Large tumor size
    • Histologic subtype
      • Polymorphous low-grade adenocarcinoma: 96% 5-year survival
      • Salivary duct carcinoma: 62% 5-year survival
      • Myoepithelial carcinoma: 50% 5-year survival
      • Undifferentiated carcinoma: 30% 5-year survival
    • High proliferation index
    • Margin status
      • Positive margins predict higher recurrence rate and higher death rate from tumor
IMAGE FINDINGS
Radiographic Findings
  • Location, extent, and lymph node status can be established
  • Areas of benign PA may be identified
    • Areas of calcification more common in PA
  • Ill-defined margin or loss of sharp margin is often a clue to malignancy
  • Low T2 MR signal in solid mass is worrisome for malignancy
  • Perineural spread along CN VII in temporal bone
    • Facial nerve plane separating superficial and deep lobes of parotid may be lost
MACROSCOPIC FEATURES
General Features
  • Circumscribed and encapsulated tumors may be seen
  • Most tumors are poorly circumscribed with invasion easily identified
    • Area of circumscription may represent residual PA
    • Area of scarring may also represent residual PA
  • Necrosis and hemorrhage may be present
  • Benign areas: Translucent gray-blue
  • Carcinoma areas: Firm, white, tan or gray
Sections To Be Submitted
  • Must submit areas of transition between possible benign and malignant zones
  • Must submit from periphery to be able to measure extent of invasion
Size
  • Range: Up to 25 cm
  • Mean: About 5 cm
  • Average size is about 2x that of PA
MICROSCOPIC PATHOLOGY
Histologic Features
Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Carcinoma Ex-Pleomorphic Adenoma

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