O papel da ressonância magnética no diagnóstico do adenoma pleomórfico: revisão da literatura e relato de casos

Abstract

O diagnóstico precoce de lesões como o adenoma pleomórfico (AP) de glândulas salivares pode ser limitado pela localização profunda e difusa destas glândulas nos tecidos moles da região de cabeça e pescoço. Esta dificuldade agrava-se pelo fato de não se poder estabelecer os limites de tais lesões apenas pelo exame clínico. Das modalidades de exames por imagem, a ressonância magnética (RM) tem demonstrado papel de destaque no diagnóstico do AP por fornecer alta definição dos tecidos moles, sem a utilização de radiação ionizante, sendo uma das mais indicadas para esta finalidade. O objetivo deste estudo foi discutir, por meio de revisão da literatura, a importância dos vários métodos de diagnóstico por imagem, suas vantagens e desvantagens, enfocando a utilização da RM no diagnóstico e plano de tratamento do AP de glândulas salivares. O relato de dois casos ilustra as principais justificativas para a superioridade das imagens por RM no diagnóstico da referida lesão.

An unusual pleomorphic adenoma

“…Even though it has an origin which is exclusive to epithelial tissue, the variety of components accords it a mesenchymal appearance as a result of the production of secretions from the tumor cells themselves, which may be ductal or myoepithelial 7 . PA makes up approximately 90% of all benign lesions of the salivary glands 5,[8][9][10][11] . It represents between 53% and 77% of parotid tumors, 44% to 68% of tumors of the submandibular gland and 33% to 43% of tumors of the minor salivary glands…”

“…Another important characteristic is that they can present with incomplete encapsulation, particularly along the surface portion of those located in the palate, below the epithelial surface. Occasionally they may present neighboring, extracapsular lesions which, in cross-sectional images, show up as pedunculated areas of growth external to the principal neoplasm 6,10 . With the larger lesions, necrosis, hemorrhage and calcification or ossification may be present.…”

“…The presence of areas of necrosis, atypical mitoses, invasiveness and extensive hyalinization suggests the possibility of malignancy. On the other hand, calcifications inside the mass suggest a benign neoplasm or, less commonly, schwannoma or mucoepidermoid carcinoma 1,5,10,[13][14] . Even though it has well-known clinical and morphological characteristics, the malignancy of the pleomorphic adenoma is the holder of a pathogenesis which is still uncertain, as is the expression of oncogenes and the factors that influence its transformation 11 .…”

“…Malignant neoplasms in the minor salivary glands represent less than 2% of all cases of tumors 4 . However, neoplasms in these glands that go untreated may undergo a malignant transformation in between 5% and 25% of cases, resulting in carcinoma ex-pleomorphic adenoma (Ca-ex-PA) 10 . The treatment of choice is surgical removal.…”

“…The removal of bone is not generally required as the pleomorphic adenoma does not invade the bone tissue, although it may cause resorption from pressure. Given correct surgical removal, the prognosis is excellent [1][2][3]6,10,15 . itself in other areas of the head and neck.…”