Pleomorphic adenoma
The pleomorphic adenoma is a benign tumor that often, rarely occurs in the parotid gland in other salivary glands. With a share of 85 %, it is the most common benign neoplasm of the salivary glands and accounts for about half of all salivary gland tumors from a total.
Pleomorphic adenomas grow slowly and remain asymptomatic long. The treatment of choice is surgical removal of the tumor, with which a definitive cure can be achieved. Remain, however, residual tumor in the body so persistent recurrences can be the result. In addition, there may be the formation of a malignant tumor in a pleomorphic adenoma, wherein the risk is low in the beginning and only grows with time.
- 4.1 Differential Diagnosis
Epidemiology
The peak age is in the 4th - 6th Decade of life, the average age of onset is 43 years. Women are affected slightly more often than men ( 3:2 ). White ill more frequently than members of other races.
Etiology
The causes underlying tumorigenesis are unknown. Unlike the Warthin 's tumor, the second most common tumor of the parotid gland, there appears to be no association with cigarette smoking.
Molecular genetic table significant for the emergence pleomorphic adenoma is a translocation and overexpression of the coding for transcription factors genes PLAG (chromosome 8q ) and HMGA2 (chromosome 12q ).
Pathology
Main localization of the pleomorphic adenoma is the parotid gland ( 85 % ), followed by the small salivary glands (10 %) and submandibular gland ( 5%). Less common sites are the manifestation of the sublingual gland, lacrimal gland, the tracheobronchial system, the nasal cavity, skin, mammary gland or the soft tissue. Within the parotid gland tumor usually affects the superficial (75% ), rarely the deep (25 %) lobes.
Macroscopically, the tumor impresses as a few millimeters to several centimeters large, well-circumscribed, rubbery - elastic or fleshy, gray-white mass of tissue with mucoid or shiny sectional area. Recurrent tumors are often constructed mehrknotig.
Histologically, a commonly manifested by a thin connective tissue capsule limited tumor with multiform histoarchitecture, composed of epithelial and myoepithelial cells modified. This form cord-like, vein-like and solid associations or bee swarm-like within a changing extensive mucoid, myxoid or chondroid stroma distributed.
Immunohistochemistry
The epithelial components of the tumor is a positivity for carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), c-kit and in varying degrees for S -100. Reliable markers of myoepithelial component are particularly p63 and calponin; next to it there is a positivity for cytokeratins, S -100 or GFAP.
Helpful in differential diagnosis of adenoid cystic carcinoma is the expression of the markers Ki -67 and p53. While they are expressed in pleomorphic adenoma on average 1.6 and 1.2 percent of the tumor cells, 20-55 or 4-24 percent of the tumor cells are positive in the case of the adenoid cystic carcinoma. Moreover, adenoid cystic carcinomas show a much higher expression of the marker BCL -2.
Diagnosis
Pleomorphic adenomas are usually clinically apparent as a slow-growing, firm resistance. The tumors are otherwise largely asymptomatic and are often discovered incidentally during routine examinations. Often the lesions existed for a year or more before the patient visits the doctor.
The extent of the lesion can be determined by means of imaging techniques (magnetic resonance imaging, computed tomography or sonography). A definitive diagnosis is made by the pathologist by histological examination of the surgical specimen or sometimes already using reclaimed at a preoperatively performed fine needle aspiration cell material.
Differential Diagnosis
Clinical differential diagnoses include Warthin 's tumor and other salivary gland tumors, sarcoidosis, lymphoma or lymphadenopathy.
As part of the histological diagnosis to exclude tumors are particularly monomorphic adenomas ( adenoma, myoepithelioma ), adenoid cystic carcinoma, polymorphous low-grade adenocarcinoma of the, mucoepidermoid carcinoma, and various mesenchymal neoplasms.
Therapy
Treatment of choice is complete surgical removal of the lesion. When infection of the parotid gland, this usually means a partial removal (partial parotidectomy ) of the gland with preservation of the facial nerve, but at a safe distance in healthy tissue. Only rarely the radical parotidectomy is indicated with removal of the nerve. Merely skiving of the tumor by enucleation is no longer considered sufficient due to the high tendency of recurrence and the risk of the tumor tissue today.
Forecast
With conventional surgical procedure are described recurrence rates of 1-5 percent. If only one enucleation ( enucleation ) of the lesion, a tumor recurrence in up to 50 percent of cases can be observed. Stromareiche tumors appear to have an increased tendency to recur, presumably because it is more probable that under the operation to a spread of the often soft stroma. In contrast, cell-rich tumors may have an increased risk of malignancy. The risk of developing a malignant tumor in a pleomorphic adenoma ( carcinoma ex pleomorphic adenoma) is according to various studies with 2-23 per cent, indicated an average of 6 percent, with the degeneracy frequency is higher, the longer the findings there.
Even a benign tumor metastasis of actually observed. Since these are often observed only after long-term courses with multiple operations and let the metastases not detect malignancy frequently as well as the primary tumor, it is believed that the dissemination of tumor tissue under the operation, for example through opened vessels, may play a role. Tumor metastases are found in descending order of frequency in bone (50 percent), lung ( 30 percent) and lymph nodes ( 30 percent) and rarely in other locations such as the scalp, abdominal wall or liver.