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Aims: Hybrid tumours (HTs) of the parotid gland (PG) are extremely uncommon. A review of the literature revealed that most reported cases were either a combination of two distinct benign neoplasms or a benign neoplasm and another malignant tumour. The limited number of reported HTs cases makes the prognostic evaluation and treatment selection difficult. Here, we report the literature review and our experience with HTs in the PG.
Methods and Material: The present study evaluated retrospectively 450 cases of the PG tumours, which were treated in our hospital. Out of 450 parotidectomies performed in 5 cases (1.1%) HTs were diagnosed on postoperative histopathology examination. Moreover the article includes a short review of the literature on hybrid neoplasms of the PG.
Results: Based on the literature review HTs have been described in less than 0.1% of all the PG tumours. Only 21 cases of hybrid malignant neoplasms (with our 2 cases) have been reported thus far in the literature. Three of 5 our HTs cases were diagnosed as benign HTs and 2 cases as malignant HTs. The most common component of tumours was a pleomorphic adenoma. In two cases it was combined with Warthin tumour and in one case with basal cell adenoma. Malignant HTs were composed of squamous cells carcinoma (SCC) and Burkitt lymphoma in the first case and polymorphous carcinoma and low grade lymphoma malignum lymphociticum in the second case. Thus we paid a special attention to these cases in the article and we present detailed medical history of these two cases.
Conclusions: The histogenesis of HTs is largely unknown. Recognition of HT is important particularly when the component tumours have different biological behaviour. However, the limited number of reported cases makes the prognostic evaluation and treatment selection difficult.
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