Pleomorphic Adenoma

The terms "pleomorphic adenoma" and "mixed tumor" are equally satisfactory and interchangeable when describing this common minor salivary gland tumor. The designation "mixed" is based on the tumor's mixtures of neoplastic elements such that each mixed tumor has unique features (Melrose 1994). It has also been pointed out that the designation refers to the tumor showing combined features of epithelioid and connective tissuelike growth (Waldron 1991). There is universal agreement that the pleomorphic adenoma is the most common salivary gland tumor. The Armed Forces Institute of Pathology data of 13,749 salivary gland tumors showed 6,880 cases of pleomorphic adenoma, of which 4,359 were located in the parotid gland and 1,277 were located in minor salivary gland tissue (Auclair, Ellis, and Gnepp et al. 1991). The palate accounted for 711 of these 6,880 cases of pleomorphic adenoma (10.3%) and was the second most common site for this tumor in the AFIP data. The 711 cases in the palate represent 56% of cases located in the minor salivary glands. Interestingly, the AFIP data subclassified palatal pleomorphic adenomas into those occurring on the hard palate (118 cases) and those occurring in the soft palate (110 cases). There were 483 cases that were not specified as to location in the palate. The subclassification of specific anatomic location in the palate is of significance when working up these cases and planning surgical treatment for these patients. Those pleomorphic adenomas located primarily in the soft palate require investigation as to involvement of the para-pharyngeal space.

Treatment of the palatal pleomorphic adenoma is based on the realization that this tumor does not possess a capsule. This notwithstanding, the tumor does exhibit a "pseudocapsule" represented by a loose fibrillar network surrounding the tumor. In addition, the periosteum on the superior aspect of the tumor does serve as a very competent anatomic barrier such that palatal bone may be preserved in this tumor surgery, even when the bone has been "cupped out" clinically and radiographi-cally. Under such circumstances, the pleomorphic adenoma does not invade bone histologically such that bone resection is not warranted. In fact, it is reasonable to proceed with surgery without obtaining CT scans preoperatively. A periosteally sacrificing wide local excision is performed, observing a 5-10 mm linear margin surrounding the clinically apparent tumor (Figure 10.1). While these tumors are submucosal in nature, the mucosa must be sacrificed with the tumor due to the close proximity of the tumor and the overlying mucosa (Yih, Kratochvil, and Stewart 2005). The most appropriate linear margin of uninvolved soft tissue included at the periphery of the tumor seems to be a source of controversy (Carlson 1998; Ord 1994; Pogrel 1994). The soft palate musculature is dissected in a split thickness fashion so as to prevent an oralnasal communication. A preoperatively fabricated palatal stent protects the exposed bone in the postoperative period until granulation tissue appears on the bone surface of the palate. There is no need to provide reconstruction of this exposed bone surface, as mucosalization ultimately occurs predictably. Negative soft tissue margins in the specimen predict a curative surgery without recurrence

Figure 10.1a. The clinical appearance of a pleomorphic adenoma of the palate that has already undergone incisional biopsy.
Pleomorphic Adenoma Recurrence Pleomorphic Adenoma Histology

Figure 10.1b. An incisional biopsy was performed and showed an acanthomatous variant of the pleomorphic adenoma.

Figures 10.1d and 10.1e. In so doing, the periosteum serves as the superior anatomic barrier on the specimen.

Figure 10.1c. A periosteal sacrificing, bone-sparing wide local excision with split thickness sacrifice of the soft palate was performed with a 5-10 mm linear mucosal margin.

Figure 10.1f. The cut specimen shows the characteristic appearance of a pleomorphic adenoma.

Figure 10.1g. The histopathology of the tumor specimen shows the tumor approaching but well contained within the pseudocapsule.

Figure 10.1i. The tissue bed is noted at 3 months postoperatively.

Figure 10.1h. The remaining tissue bed is covered with a surgical stent and allowed to heal with tertiary intention. No tissue coverage of the palate is required.

Figure 10.1j. The tissue bed is noted at 12 months post-operatively. Effective mucosalization of the exposed bone surface of the hard palate and exposed muscle surface of the soft palate has occurred.

of the tumor (Beckhardt, Weber, and Zane et al. 1995).

As previously mentioned, the pleomorphic adenoma that develops in the soft palate may be different from the pleomorphic adenoma of the hard palate, insofar as its anatomic progression is concerned. Tumors located on the hard palate will grow into the oral cavity (Figure 10.2), whereas tumors of the soft palate (Figure 10.3) may descend into the parapharyngeal space (Carlson 1998). As such, when considering the surgical treatment for a pleomorphic adenoma of the soft palate, the surgeon should obtain CT scans preoperatively so as to determine possible involvement of the para-pharyngeal space. When dissection of the parapha-ryngeal space by the tumor is noted, a combined transoral/transcutaneous approach to tumor extirpation is indicated. A mandibular osteotomy for

Figure 10.2. A large pleomorphic adenoma that is primarily located over the hard palate. As such, it is permitted to grow in an exophytic fashion, with cupping out of the palatal bone but no involvement of the parapharyngeal space. Reprinted with permission from Carlson ER. 1995. Salivary gland pathology—clinical perspectives and differential diagnosis. In: The Comprehensive Management of Salivary Gland Pathology, Oral and Maxillofacial Surgery Clinics of North America 7. Philadelphia: W.B. Saunders, pp. 361-386.

Figure 10.2. A large pleomorphic adenoma that is primarily located over the hard palate. As such, it is permitted to grow in an exophytic fashion, with cupping out of the palatal bone but no involvement of the parapharyngeal space. Reprinted with permission from Carlson ER. 1995. Salivary gland pathology—clinical perspectives and differential diagnosis. In: The Comprehensive Management of Salivary Gland Pathology, Oral and Maxillofacial Surgery Clinics of North America 7. Philadelphia: W.B. Saunders, pp. 361-386.

Figures 10.3b and 10.3c. Its chronic growth permitted entry into the parapharyngeal space, as noted on CT scans.

Figure 10.3a. The clinical appearance of a pleomorphic adenoma that is located primarily in the soft palate.

Figures 10.3b and 10.3c. Its chronic growth permitted entry into the parapharyngeal space, as noted on CT scans.

Figure 10.3d. Due to the relative inability to dissect this tumor bed entirely transorally, a decision was made to perform a combined transcutaneous and transoral approach to the tumor ablation with an Attia double osteotomy of the mandible. Wide transcutaneous access was accomplished for this tumor surgery.

Figure 10.3d. Due to the relative inability to dissect this tumor bed entirely transorally, a decision was made to perform a combined transcutaneous and transoral approach to the tumor ablation with an Attia double osteotomy of the mandible. Wide transcutaneous access was accomplished for this tumor surgery.

Figure 10.3f. Bone plates were placed on the mandible in preparation for the osteotomy. The plates were then removed and an Attia double osteotomy of the mandible was performed that involved a horizontal resection of the mandible superior to the mandibular foramen and a vertical resection of the mandible anterior to the mental foramen.

Figure 10.3e. Dissection of the mandible was performed in a subperiosteal fashion, while maintaining as much periosteum and muscle as possible on the lateral surface of the mandible.

Figure 10.3g. Superior reflection of the mandibular segment was then able to be accomplished.

Figure 10.3h. Reflection of the medial surface of the medial pterygoid muscle permitted entry into the parapharyngeal space with identification of the tumor.

Figure 10.3j. The combination of transcutaneous access and transoral access permitted safe delivery of the specimen.

Figure 10.3i. With the great vessels of the neck protected, Figure 10.3k. Histopathology identified a pleomorphic the tumor ablation continued intraorally with development adenoma with tumor present in the pseudocapsule, but of the tumor dissection surrounding the pseudocapsule. with negative margins.

Figure 10.3i. With the great vessels of the neck protected, Figure 10.3k. Histopathology identified a pleomorphic the tumor ablation continued intraorally with development adenoma with tumor present in the pseudocapsule, but of the tumor dissection surrounding the pseudocapsule. with negative margins.

Figure 10.31. Following delivery of the specimen, the plates are replaced on the mandible and closure occurred.

effective dissection of the tumor bed and protection of the great vessels in the neck may be indicated.

Pleomorphic adenomas are known to occur in other minor salivary gland sites, including the lip, buccal mucosa, and tongue. Lip tumors accounted for 297 cases in the AFIP files, of which a majority occurred in the upper lip. Lower lip pleomorphic adenomas are very rare. The buccal mucosa accounted for 126 cases in the AFIP series. The surgery required for removal of pleomorphic adenomas in the lip and buccal mucosa involves an excision of the tumor and associated minor salivary gland tissue. The plane of dissection is "peri-pseudocapsular" in nature. This ensures an anatomic barrier of fascia surrounding the tumor. These tumor surgeries are curative as long as tumor spillage does not occur intraoperatively. Subtherapeutic ablation of these tumors in the form of an enucleation will certainly predispose the patient to persistent disease. Such recurrences are noted to be multifocal in nature as originally described in the major salivary glands (Foote and Frazell 1953).

Malignant pleomorphic adenomas of salivary gland origin are uncommon neoplasms. The broad heading, malignant mixed tumor, includes three different clinical and pathologic entities: carcinoma ex-pleomorphic adenoma, carcinosarcoma, and metastasizing pleomorphic adenoma. Carcinoma ex-pleomorphic adenoma, perhaps the most commonly referenced malignant pleomorphic adenoma, is a pleomorphic adenoma in which a second neo-

Figure 10.3m. The 6-month postoperative view of the palate is noted. This surgery was curative for this patient's tumor. Reprinted with permission from Carlson ER, Schimmele SR. 1998. The management of minor salivary gland tumors of the oral cavity. In: Surgical Management of Salivary Gland Disease, The Atlas of the Oral and Maxillofacial Surgery Clinics of North America 6. Philadelphia: W.B. Saunders, pp. 75-98.

Figure 10.3m. The 6-month postoperative view of the palate is noted. This surgery was curative for this patient's tumor. Reprinted with permission from Carlson ER, Schimmele SR. 1998. The management of minor salivary gland tumors of the oral cavity. In: Surgical Management of Salivary Gland Disease, The Atlas of the Oral and Maxillofacial Surgery Clinics of North America 6. Philadelphia: W.B. Saunders, pp. 75-98.

plasm develops from the epithelial component that fulfills the criteria for malignancy. These features include invasiveness, destruction of normal tissues, cellular anaplasia, cellular pleomorphism, atypical mitoses, and abnormal architectural patterns (Wenig and Gnepp 1991). The AFIP data showed 326 cases of carcinoma ex-pleomorphic adenoma, which accounted for 2.4% of their 13,749 cases. A significant majority of these were located in the parotid gland (64.4%); however, these malignancies occurred in the minor salivary glands, as well. The palate accounted for 36 of 57 cases in the minor glands, with the upper lip (6 cases), tongue (4 cases), and cheek (4 cases) also represented. A review of this tumor shows that preoperative duration of a benign pleomorphic adenoma is the main determining factor regarding malignant transformation. Specifically, the incidence of malignancy progressively increases from 1.6% for tumors present for less than 5 years to 9.4% for tumors present for periods longer than 15 years (Wenig and Gnepp 1991). The other predisposing condition for the development of this malignancy is recurrence of a benign pleomorphic adenoma. This fact supports a curative approach to the pleomor-phic adenoma from the outset, with abandonment of the subtherapeutic enucleation of these tumors in the parotid gland or minor salivary gland tissues.

The prognosis for this malignancy is generally considered dismal, with 71% of patients exhibiting metastatic disease during the course of their disease.

Carcinosarcoma, also known as true malignant pleomorphic adenoma, is a tumor defined by histologic evidence of malignancy in both the epithelial and stromal elements of the tumor. These tumors are more rare than the carcinoma ex-pleo-morphic adenoma, accounting for only 8 cases in the AFIP registry, and none occurred in the minor salivary glands. Other cases presented in the literature do identify the existence of this diagnosis in the minor salivary glands.

Metastasizing mixed tumor is a histologically benign pleomorphic adenoma, but located in distant sites. The pleomorphic adenomas are known to arise in major as well as minor salivary glands, and the metastatic foci have been identified in the cervical lymph nodes, spine, and liver (Wenig and Gnepp 1991). Data on the interval from removal of the primary tumor to the identification of the first metastasis is 1.5-51 years, with an average of 16.6 years.

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