Asian Cardiovasc Thorac Ann 2008;16:62-64
© 2008 Asia Publishing EXchange Ltd
Multiple Pulmonary Metastases from Benign Pleomorphic Adenoma
Ko Yung Sit, MRCS,
Wing Hung Chui, FRCS,
Elaine Wang, Dip Am Board (Path)1,
Shui Wah Chiu, FRCS
Division of Cardiothoracic Surgery, Department of Surgery, University of Hong Kong Medical Center
1 Department of Pathology, Grantham Hospital, Hong Kong, China
For reprint information contact: Shui Wah Chiu, FRCS, Tel: 852 2518 2639, Fax: 852 2553 3436, Email: chiusw{at}ha.hk, Division of Cardiothoracic Surgery, Department of Surgery, University of Hong Kong Medical Center, Grantham Hospital, Hong Kong, China.
 |
ABSTRACT
|
|---|
Metastasizing pleomorphic adenoma is a rare condition of metastasis from a histologically benign salivary gland tumor. We report a case of metastasizing pleomorphic adenoma presenting with multiple bilateral lung metastases, and discuss the clinical aspects of this disease.
|
INTRODUCTION
|
|---|
Pleomorphic adenoma is the most common neoplasm of the salivary gland. It is usually a benign, slow-growing and well-circumscribed tumor. However, there are rare reports of a subset of these tumors metastasizing to distant sites without undergoing malignant transformation.1 We report a rare case of multiple lung metastases originating from a histologically benign pleomorphic adenoma.
|
CASE REPORT
|
|---|
A 49-year-old man presented with an incidental finding of multiple bilateral lung shadows on his chest radiograph (Figure 1
). He had history of a left submandibular pleomorphic adenoma with benign histologic features, which was excised 11 years earlier. He had local recurrences of the tumor at 1 and 2 years after primary excision, and was treated with surgical excision and postoperative radiotherapy on both occasions. The patient had an otherwise unremarkable history and no incidence of pulmonary disease. He presented with another local recurrence in the left submandibular region. He had no respiratory symptoms. Computed tomography of the thorax demonstrated multiple nodular lesions in both lungs, with the largest measuring 4.1 x 3.0 cm (Figure 2). Fine-needle aspiration cytology was inconclusive. Video-assisted thoracoscopic wedge excisional biopsy of a representative peripheral mass was performed for histologic diagnosis. On gross examination, the lesion was a well-circumscribed spherical white tumor. Microscopically, it was composed of mixed tubular and ductal structures with dense eosinophilic luminal exudates and cells forming short trabeculae and aggregates (Figure 3). The ducts were lined with an inner layer of cuboidal cells and an outer layer of flat myoepithelial cells. A distinctive hyaline and fibromyxoid stroma was present. The histologic features were compatible with a diagnosis of benign metastatic pleomorphic adenoma. Comparison with the pathologic findings in the original salivary gland tumor confirmed that the histologic features of the lung lesion were identical. In view of the diffuse extent and slow-growing nature of the lung lesions, the patient is being managed conservatively. He remains asymptomatic on follow-up at 6 months.
View larger version (154K):
[in this window]
[in a new window]
|
Figure 2. Computed tomography of the thorax showing multiple bilateral lung metastases. The largest lesion in the left lung measured 4.1 x 3.0 cm.
|
|
View larger version (144K):
[in this window]
[in a new window]
|
Figure 3. Microscopy of the biopsied left lung lesion showing mixed tubular and ductal structures with dense eosinophilic luminal exudates in a background of distinct hyaline and fibromyxoid stroma. Hematoxylin and eosin stain, original magnification x100.
|
|
|
DISCUSSION
|
|---|
Metastasizing pleomorphic adenoma (MPA) was first described in 1942, and up to 80 cases have since been reported. Benign MPA is distinguished from truly malignant pleomorphic tumors (such as carcinomas arising from pleomorphic adenomas, and carcinosarcomas) by its benign histologic features. However, there are no agreed histopathologic parameters that can differentiate a nonmetastatic pleomorphic adenoma from MPA.
The mechanism underlying the metastatic behavior of MPA is still not certain. Hematogenous metastases are more prevalent than those to the regional lymph nodes. Bone, lung, and lymph nodes are the most common sites of metastatic disease, but kidney, liver, central nervous system, retroperitoneum, and skin have also been reported. Metastasizing pleomorphic adenoma is identical to primary pleomorphic adenoma both histologically and on chromosomal analysis, and even DNA flow cytometry is thus far unable to identify changes that may predict the development of MPA.2,3 As most reported cases occurred after surgical treatment of primary or recurrent lesions of the salivary gland, one hypothesis suggests that surgical manipulation may cause tumor cell dislodgement, hematogenous spread, and subsequent implantation at distant sites.4 Wermuth and colleagues5 suggested that pulmonary metastasis of pleomorphic adenomas may arise from aspiration of tumor cells shed from the salivary glands into the pharynx.
There is often a long interval between the occurrence of the primary pleomorphic adenoma and the later metastases. Metastases have been reported at 3 to 52 years after the occurrence of the primary lesion.3,6 In most cases, at least one prior episode of local recurrence of the primary pleomorphic adenoma is noted before the development of metastatic foci. Metastasizing pleomorphic adenoma without prior local recurrence is comparatively rare.1 The clinical significance of this observation is that adequate resection of the initial tumor to avoid local recurrence may preclude metastasis. A high index of suspicion of MPA should therefore be maintained in patients with a history of locally recurrent pleomorphic adenoma. The natural history of MPA remains to be clearly defined given its rarity. However, once MPA is diagnosed, an overall mortality rate of more than 20% has been reported.7 The role of radiotherapy or chemotherapy in the management of MPA, either as primary therapy or as an adjunct to surgery, is not yet established.4 Surgical excision is still regarded as the treatment of choice when feasible.
|
REFERENCES
|
|---|
- Schreibstein JM, Tronic B, Tarlov E, Hybels RL. Benign metastasizing pleomorphic adenoma [Review]. Otolaryngol Head Neck Surg 1995;112:612–5.[Medline]
- Jin Y, Jin C, Arheden K, Larsson O, Bauer HF, Mandahl N, et al. Unbalanced chromosomal rearrangements in a metastasizing salivary gland tumor with benign histology. Cancer Genet Cytogenet 1998;102:59–64.[Medline]
- Wenig BM, Hitchcock CL, Ellis GL, Gnepp DR. Metastasizing mixed tumor of salivary glands. A clinicopathologic and flow cytometric analysis. Am J Surg Pathol 1992;16:845–58.[Medline]
- Bradley PJ. ‘Metastasizing pleomorphic salivary adenoma’ should now be considered a low-grade malignancy with a lethal potential [Review]. Curr Opin Otolaryngol Head Neck Surg 2005;13:123–6.[Medline]
- Wermuth DJ, Mann CH, Odere F. Metastasizing pleomorphic adenoma arising in the soft palate. Otolaryngol Head Neck Surg 1988;99:505–8.[Medline]
- Chen KT. Metastasizing pleomorphic adenoma of the salivary gland. Cancer 1978;42:2407–11.[Medline]
- Klijanienko J, El-Naggar AK, Servois V, Rodriguez J, Validire P, Vielh P. Clinically aggressive metastasizing pleomorphic adenoma: report of two cases. Head Neck 1997;19:629–33.[Medline]
TOP
ABSTRACT
INTRODUCTION
