A case of metastasizing pleomorphic adenoma

A case of initially metastasizing pleomorphic adenoma of parotid gland

Metastasis of pleomorphic adenoma (PA) is rare and usually presented as a locoregional recurrence developed many years after excision of the primary tumor although the PA is the most common neoplasm in the parotid gland. We described a case of a 48-year-old male with a parotid tumor with multiple enlarged ipsilateral lymph nodes which suggested a malignancy. The tumors had been neither evaluated nor excised and preoperative evaluation revealed benign PA in both lesions. After the complete surgical excision, the final pathology was notable for benign PA with metastasis to regional lymph nodes. At 1 year follow up he was clinically and radiographically free of disease. This implies that pleomorphic adenoma can occur as initially metastasis to regional lymph node even though benign neoplasm.

Metastasizing Pleomorphic Adenoma: Recurrent PLAG1/HMGA2 Rearrangements and Identification of a Novel HMGA2-TMTC2 Fusion

Pleomorphic adenoma (PA) is the most common salivary gland neoplasm. On a molecular level PA is characterized by a translocation involving PLAG1 or HMGA2. PA is considered to be a benign tumor although it can undergo malignant transformation. Alternatively, cases of histologically benign PA "metastasizing" to lymph nodes or distant body sites are well documented. Several theories have been proposed to explain this behavior. However, there is a lack of molecular data available to assess the relationship of metastasizing PA (MPA) and their benign counterparts. In this study we describe 4 cases of MPAs and perform the first molecular study linking them to conventional PA. The index case was identified in the course of routine clinical practice, while the other cases were retrieved from the archives of the authors. Slides were reviewed to confirm the diagnosis of both the primary/recurrent tumor and the metastasis. Fluorescence in situ hybridization (FISH) was performed in all cases and RNA sequencing was performed on the index case. In all cases there was a history of recurrent PA involving the parotid. Lymph node metastases were identified in 2 cases; non-lymph node metastases were identified in 3 cases. All the metastases were histologically benign. RNA sequencing performed on the index case demonstrated a novel HMGA2-TMTC2 translocation, which was confirmed by separate FISH break-apart assays for both genes. FISH performed on the remaining cases demonstrated rearrangement of PLAG1 in all 3 cases. This study demonstrates that MPA harbors the same disease-defining molecular hallmark as their benign counterparts.

Maxillofacial diagnostic features of the enigmatic metastasizing pleomorphic adenoma

Considering the confusion in the literature regarding local recurrence, spread, or metastases of pleomorphic adenoma (PA) in the head and neck region, the aim of this study was to enhance understanding of the characteristics of metastasizing pleomorphic adenoma (MPA) by reviewing the literature and presenting a case. English language articles with proof of metastases were included in the literature review. Of the 80 cases in the literature with MPA, 46 were female and 33 were male (sex missing for one case). Thirty-five percent of the neoplasms affected the bones; the maxilla was affected in five cases and the mandible in three. The parotid was the primary site in 72.5% of cases and the submandibular gland in 16.2% of cases. The local recurrence rate was 70%. The mean interval between primary PA and MPA was 15.52 years. The total mortality rate was 8.7%. A case of PA of the submandibular gland that recurred after surgical excision and metastasized (confirmed by the presence of intact cortical borders) to the ipsilateral mandibular body, upper lip, and neck is described. The high mortality rate in a histologically defined benign disease that metastasizes demands that management include careful primary excision and long-term clinical follow-up.

A case of metastasizing pleomorphic adenoma in the maxillary bone appearing twenty years after initial resection of pleomorphic adenoma of the hard palate

Metastasizing pleomorphic adenoma (MPA) is the inexplicable metastasis of a histologically benign pleomorphic adenoma (PA). Approximately 50 cases have been reported. A 62-year-old woman noticed pain in the upper molar area. Her medical history included an operation for PA in the hard palate that was performed 20 years previously. On imaging, four relatively well-defined lesions were demonstrated in the maxillary bone. She underwent an operation for these lesions. Each lesion revealed the same histological features. Morphological findings displayed typical features of PA. Immunohistochemical staining showed that tumor cells of both primary and metastasizing lesions were positive for pleomorphic adenoma gene (PLAG) 1, which is a sensitive marker for PA. Gene fusions involving PLAG1 were examined by reverse transcription-polymerase chain reaction. However, no gene rearrangements of PLAG1 were found. We report here on a case of MPA in the maxillary bone, which appeared 20 years after resection of the primary tumor and review the relevant literature.

Satellite tumors surrounding primary pleomorphic adenomas of the parotid gland

The occasional local recurrence of benign pleomorphic adenoma (PA) has generally been attributed to the vulnerability of the tumor capsule. Although some reports have also noted the presence of satellite tumors associated with PA recurrence, only few reports have focused on this issue. We paid special attention to the satellite lesions apart from the main tumors and discussed their frequency, origin, nature and the ways of treating them. A total of 108 specimens of primary parotid gland PA resected at the Okayama Saiseikai General Hospital from 1988 to 2008 were microscopically reviewed. Four (3.7%) patients displayed a main mass with satellite tumors in a single parotid gland. The immunohistochemical analysis of p53 and Ki-67 index showed no distinct difference between PAs with satellite tumors and those without. Satellite tumors surrounding the main mass of parotid PA is relatively rare. In most cases, such satellite tumors will arise from capsular perforation of the primary tumor cells. Preoperative evaluation to recognize the existence of satellite tumors would be important and capsular dissection should be discouraged. We could not find any evidence suggesting that primary PA with satellite tumors could be more biologically aggressive than those without.

A case of pleomorphic adenoma of the parotid gland metastasizing to a mediastinal lymph node

OBJECTIVE

Pleomorphic adenomas are the most common salivary gland tumors and are typically cured with complete surgical excision. There are rare reports, however, in which these histologically benign tumors have inexplicably metastasized to distant sites. We present a case of a patient who presented, 27 years after excision of a parotid pleomorphic adenoma, with a recurrence in the parotid bed and a mediastinal metastasis.

STUDY DESIGN

Case report.

METHODS

A 43-year-old woman presented with a mass in the right parotid bed 27 years after excision of a pleomorphic adenoma of the parotid. The patient's presentation, workup, and final diagnosis of benign metastasizing pleomorphic adenoma will be discussed, along with a pertinent review of the literature.

RESULTS

A diagnosis of recurrent pleomorphic adenoma was made from a fine needle aspiration biopsy of the right parotid mass. On subsequent computed tomographic scan, chest images revealed an incidental left mediastinal mass, which also proved to be a pleomorphic adenoma on computed tomography-guided fine needle aspiration biopsy. The patient underwent a completion parotidectomy and sternotomy with excision of the mediastinal mass. Examination of the pathology specimens confirmed a diagnosis of pleomorphic adenoma in both the parotid bed and the mediastinum. No histologic characteristics of malignancy were seen in either specimen; therefore, a diagnosis of benign metastasizing mixed tumor was rendered.

CONCLUSION

Benign metastasizing pleomorphic adenoma is a rare and controversial but distinct clinical entity. Although the definition of the term benign precludes metastatic disease, these tumors do not demonstrate any malignant features yet metastasize to distant sites. It remains to be determined whether these benign metastasizing pleomorphic adenomas are really low-grade salivary malignancies.

'Metastasizing pleomorphic salivary adenoma' should now be considered a low-grade malignancy with a lethal potential

PURPOSE OF REVIEW

To review the current knowledge on the clinical entity of metastasizing pleomorphic adenoma.

RECENT FINDINGS

Using case studies, the literature continues to explore the potential to identify a chromosomal abnormality that might explain the clinical entity, and may constitute a submicroscopic malignant transformation with molecular genetic alterations. Presently there are no agreed histopathological parameters that can identify or confirm a difference in behavior between the 'common' pleomorphic adenoma from the metastasizing pleomorphic adenoma.

SUMMARY

The evidence supports that metastasizing pleomorphic adenoma is most likely to be an unrecognized and as yet unclassified malignant neoplasm and as such must be considered a low-grade, potentially lethal malignant disease when it presents, which may constitute a submicroscopic malignant transformation with molecular genetic alterations. Further research is required to answer the many questions.

Mucoepidermoid carcinoma expleomorphic adenoma of the submandibular gland

We described a rare case of carcinoma expleomorphic adenoma in which mucoepidermoid carcinoma arise from a previous incompletely excised pleomorphic adenoma of the submandibular gland. The tumor was surgically resected along with a modified radical neck dissection and postoperative radiotherapy. The patient remained disease free 3 years after the last operation. The pathology showed concurrent presence of Warthin's tumor in the specimen. The concurrent presence of mucoepidermoid carcinoma, pleomorphic adenoma, and synchronous Warthin's tumor make this case unique, and such a combination associated with the submandibular gland has not been documented in the literature before.

Neutron radiotherapy for recurrent pleomorphic adenomas of major salivary glands

INTRODUCTION

Pleomorphic adenoma is the most common neoplasm arising in the salivary glands. Surgical management is the primary therapeutic modality. With the use of modern surgical techniques, recurrence is infrequent, and facial nerve sparing is the norm. However, for patients with recurrent disease, the risk of further relapses is increased with surgical resection alone, particularly for those patients in whom multiple recurrences have already occurred. The role of adjuvant radiotherapy in this setting remains uncertain. Although neutron radiotherapy is superior to conventional radiotherapy for malignant salivary gland tumors, its role in the treatment of pleomorphic adenomas is less well defined. We report our experience using this modality for high-risk, recurrent pleomorphic adenomas.

METHODS

Sixteen patients were treated with neutron radiotherapy for recurrent pleomorphic adenomas of major salivary glands from 1986 through 1993. The median age at diagnosis was 33 years (range, 11-77 years); median age at the time of neutron radiotherapy was 52 years (range, 22-77 years); median number of prior surgical procedures was 3 (range, 1-6); median duration from initial diagnosis to radiotherapy was 14.5 years (range, 3 months-30 years); median follow-up was 83 months (range, 9-144 months). The median period at risk for survivors was 96 months (defined as the interval from completion of neutron radiotherapy to last follow-up). Ten patients had evidence of gross residual disease at the time of treatment as determined by imaging studies, with nine patients having multinodular disease.

RESULTS

The 10-year actuarial survival was 79%. One patient died from lung metastases 9 months after treatment; one patient died from a liver tumor of uncertain origin, but the histology could not rule out a metastasis from the previous pleomorphic adenoma; and one patient died from recurrent disease at the base of skull. The 15-year actuarial locoregional control rate was 85%. One of the two patients with locoregional recurrence had a malignant transformation into an adenocarcinoma. No statistical difference in 15-year actuarial survival (75% vs 83%, p =.82) was found comparing patients with gross residual disease vs microscopic residual disease. The actuarial 15-year locoregional control was 76% for patients with gross residual disease vs 100% for those with microscopic disease. The 15-year actuarial risk of RTOG/ESTRO nonaudiologic grade III/IV complications was 21%. No facial nerve injuries were observed as a direct consequence of neutron radiotherapy.

CONCLUSIONS

Neutron radiotherapy offers both excellent local control rates and survival rates in patients with multiply recurrent pleomorphic adenomas that are not candidates for surgical resection, even in the presence of gross residual disease. The treatment-related morbidity is acceptable. Malignant transformations and metastases, although uncommon, may be observed in this tumor.