Carcinoma Ex-Pleomorphic Adenoma



Carcinoma Ex-Pleomorphic Adenoma


Lester D. R. Thompson, MD





Key Facts


Terminology



  • Presence of carcinoma arising from pleomorphic adenoma


Clinical Issues



  • Usually 6th to 7th decades, about 10 years older than PA


  • Parotid > > minor salivary glands


  • Long clinical history of painless mass with recent rapid enlargement and nerve palsy


  • Complete surgical resection


  • Local recurrence is common (up to 50%)


  • Local or distant metastases are common (up to 70%)


  • Poor overall survival


  • Prognostically significant factors include grade, stage, proportion of carcinoma, extent of invasion


Microscopic Pathology



  • Carcinoma may be specific tumor type


  • Carcinoma shows significant pleomorphism, increased mitoses, necrosis, destructive growth


  • Relative proportions of carcinoma and adenoma vary widely


  • Separated into low and high grade


  • PA is very frequently extensively hyalinized (fibrotic, scarred)


Reporting Considerations



  • Must report extent of invasion



    • Noninvasive (encapsulated) carcinoma without evidence of capsular invasion


    • Minimally invasive (≤ 1.5 mm)


    • Invasive (> 1.5 mm)







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

Tags:
Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Carcinoma Ex-Pleomorphic Adenoma

Full access? Get Clinical Tree
Get Clinical Tree app for offline access