Carcinoma Ex-Pleomorphic Adenoma
Lester D. R. Thompson, MD
Key Facts
Terminology
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Presence of carcinoma arising from pleomorphic adenoma
Clinical Issues
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Usually 6th to 7th decades, about 10 years older than PA
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Parotid > > minor salivary glands
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Long clinical history of painless mass with recent rapid enlargement and nerve palsy
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Complete surgical resection
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Local recurrence is common (up to 50%)
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Local or distant metastases are common (up to 70%)
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Poor overall survival
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Prognostically significant factors include grade, stage, proportion of carcinoma, extent of invasion
Microscopic Pathology
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Carcinoma may be specific tumor type
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Carcinoma shows significant pleomorphism, increased mitoses, necrosis, destructive growth
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Relative proportions of carcinoma and adenoma vary widely
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Separated into low and high grade
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PA is very frequently extensively hyalinized (fibrotic, scarred)
Reporting Considerations
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Must report extent of invasion
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Noninvasive (encapsulated) carcinoma without evidence of capsular invasion
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Minimally invasive (≤ 1.5 mm)
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Invasive (> 1.5 mm)
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TERMINOLOGY
Abbreviations
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Carcinoma ex-pleomorphic adenoma (Ca ex-PA)
Synonyms
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Carcinoma ex benign mixed tumor
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Malignant mixed tumor
Definitions
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Presence of carcinoma arising from pleomorphic adenoma (PA)
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Requires concurrent pleomorphic adenoma histologically or history of pleomorphic adenoma at same site
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Carcinoma can be any epithelial neoplasm
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ETIOLOGY/PATHOGENESIS
Pathogenesis
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There is malignant transformation of epithelial component
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Areas of transition help to substantiate a continuum
CLINICAL ISSUES
Epidemiology
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Incidence
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Accounts for about 4% of all salivary tumors
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12% of all salivary malignancies
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7% of all pleomorphic adenomas
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Age
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Usually in 6th and 7th decades
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About 10-12 years older than age at presentation of pleomorphic adenoma
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Exceptional in children
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Gender
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Probably equal gender distribution
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Site
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Major salivary glands most often (80%)
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Parotid (80%) > submandibular (18%) > > sublingual gland (< 2%)
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May be due to large tumor size and increased recurrence rate for major gland location
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Minor glands (20%)
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Palate > > nasopharynx > nasal cavity > > larynx
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Presentation
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Long clinical history of pleomorphic adenoma
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The greater the length of time with tumor, the higher the risk of malignant transformation
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5 years: 1.6%; 15 years: 9.6%
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Symptoms/mass present for up to 44 years
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Need to have well-documented previous tumor in same anatomic site if there is no histologic evidence of benign PA
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Some tumors are slow growing and asymptomatic, so long history of mass by itself is insufficient
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May have had multiple surgeries
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About 20% have had previous surgery
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Usually, recent rapid enlargement
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Nerve palsies are common (40%)
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Majority are painless
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Rare: Skin ulceration, soft tissue attachment, bone invasion
Treatment
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Surgical approaches
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Complete surgical eradication
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Lymph node dissection often required (˜ 20%)
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Some recommend neck dissection for all major gland tumors
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Lymph node dissection may not be necessary for low-grade carcinomas or those with limited invasion
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Radiation
Prognosis
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Local recurrence can be seen (range of 25-50%)
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Majority are seen within 5 years of diagnosis
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Many patients experience more than 1 recurrence
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Recurrence rates tend to be lower for minor salivary gland primaries
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Higher percentage of patients die with disease if they have local recurrence
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Local or distant metastases are common (range of 50-70%)
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Local lymph node metastases: Up to 25%
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May be higher if there was previous surgery
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Distant sites: Lung, bone (spine), liver, brain, skin
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Most common in patients with local recurrence
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Poor overall survival
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Majority die of disease (60%)
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5-year survival (30%)
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Prognostically significant factors (order of importance)
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Grade
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Low grade: Tend not to die of tumor
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High grade: Majority die from tumor
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Stage
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Proportion of tumor that is carcinoma
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Extent of invasion
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Noninvasive (encapsulated): Excellent long-term outcome (identical to conventional PA)
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Minimally invasive tumors (≤ 1.5 mm): Good outcome (75-85% at 5 years)
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Widely invasive (> 1.5 mm): Poor outcome (25-65% at 5 years)
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Large tumor size
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Histologic subtype
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Polymorphous low-grade adenocarcinoma: 96% 5-year survival
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Salivary duct carcinoma: 62% 5-year survival
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Myoepithelial carcinoma: 50% 5-year survival
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Undifferentiated carcinoma: 30% 5-year survival
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High proliferation index
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Margin status
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Positive margins predict higher recurrence rate and higher death rate from tumor
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IMAGE FINDINGS
Radiographic Findings
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Location, extent, and lymph node status can be established
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Areas of benign PA may be identified
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Areas of calcification more common in PA
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Ill-defined margin or loss of sharp margin is often a clue to malignancy
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Low T2 MR signal in solid mass is worrisome for malignancy
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Perineural spread along CN VII in temporal bone
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Facial nerve plane separating superficial and deep lobes of parotid may be lost
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MACROSCOPIC FEATURES
General Features
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Circumscribed and encapsulated tumors may be seen
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Most tumors are poorly circumscribed with invasion easily identified
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Area of circumscription may represent residual PA
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Area of scarring may also represent residual PA
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Necrosis and hemorrhage may be present
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Benign areas: Translucent gray-blue
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Carcinoma areas: Firm, white, tan or gray
Sections To Be Submitted
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Must submit areas of transition between possible benign and malignant zones
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Must submit from periphery to be able to measure extent of invasion
Size
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Range: Up to 25 cm
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Mean: About 5 cm
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Average size is about 2x that of PA
MICROSCOPIC PATHOLOGY
Histologic Features
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Carcinomatous component may be part of specific tumor type
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Adenocarcinoma, NOS, salivary duct carcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, myoepithelial carcinoma, polymorphous low-grade adenocarcinoma, epithelial-myoepithelial carcinoma
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Epithelial and myoepithelial components together
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Epithelial component only
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Carcinoma shows
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Significant pleomorphism (enlarged pleomorphic cells with hyperchromatic nuclei, prominent nucleoli)
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Increased mitotic figures
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Areas of necrosis
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Destructive growth
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Relative proportions of carcinoma and adenoma vary widely
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Malignant and benign juxtaposed
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Malignant and benign blended
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Sclerotic nodule in malignant tumor suggests residual PA
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Multifocal, distinct and separate malignant nodules
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Carcinoma ranges from focal to diffuse
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In majority of cases, carcinoma represents > 50% of tumor volume
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