Tumors of the nasal cavity and paranasal sinuses comprise of the 1% of all cat neoplasia. Recent studies show this rate to be around 8.4%. Approximately 90% of these rare tumors are malignant and invasive. Most of these tumors are non-epithelial in origin and the most common neoplasia are malignant lymphomas and the second most common are carcinomas. Studies exist showing this rate to be higher for tumors that are epithelial in origin. Acinic cell carcinoma of the nasal cavity has been reported in only one cat until now.
Material ve Method
16 year old mixed breed male cat was taken to a private clinic 1,5 year ago with a progressive swelling of the paranasal sinus area, nasal bleeding and loss of appetite. Magnetic resonance imaging (MRI) showed a solid mass, 5 cm in diameter with irregular borders, pressuring the globe, extending to the orbital area and the upper oral cavity in the nasal cavity. Tumoral mass was surgically removed but relapsed in 6 months. Incisional biopsy sample was taken for histopathological and immunochemical examination and after acinic cell carcinoma diagnosis, mass was excised again. VENTANA-BENCHMARK XT system was used for immunochemical marking and smooth muscle actin (SMA) was used as immune marker. Ki-67 antibodies were used to determine p63 and the proliferation index. Periodic Acid (PAS) and PAS diastase (DPAS) stains were used for mucin.
MRI. Mass infiltrating the right paranasal area starting from left lateral and covering paranasal sinuses and reaching right paranasal area from the midline.
No immune response was observed with SMA and p63 antibodies and ki-67 proliferation index was determined as 5-6% (Image 2).
Image 2. A. Ki-67 positivity in a few neoplastic cells. B. Negative reaction in neoplastic cells with p63 antibodies. Basal cells positive.
Histopathologically, the mass was observed to consist of well differentiated neoplastic cells with a lot of clear and partially granular mucinous cytoplasm, hyperchromatic centrally located nuclei in the salivary gland epithelia morphology, acinous and follicular structure separated by a thin fibrous stroma. In addition, tumoral mass had no capsule and had stromal invasion. DPAS did not reveal any distinguishable color change in the tissues.
Image 3. A. Acinar cells forming a lobular structure separated by thin fibrous stroma. B. Well differentiated round neoplastic cells with a lot of clear cytoplasm and centrally located nuclei.
Image 4. A. PAS stain. B. PAS-diastase stain
Acinic cell carcinomas are carcinomas with low histological grade and they are closely similar to serous cells of salivary glands. Its presence in the sinonasal cavity is quite rare in both humans and in animals. Salivary gland tumors in cats mostly are of submandibular origin and are reported to spread to surrounding lymph nodes and to a lesser extent to other organs. In our case, low proliferation index shows that the tumor has a slow growth rate and is a neoplasm of a low histological grade. P63 negativity is also congruent with immunohistochemical qualities of other adenocarcinomas. Tumor relapsed in this case but there was no distant metastasis. Patient is alive after 9 months following the second operation and his overall health is reported to be good.
Acinic cell carcinoma, rarely encountered in veterinary pathology, despite being a neoplasm with low histological grade has a bad prognosis because the lesion is space occupying and has relapse potential. Therefore, although it is encountered rarely, acinic cell carcinoma should be taken into consideration in nasal area pathologies in animals.
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