PMC10129378_01
Coronal MRI section in T1 sequence. (a). Right superficial parotid nodule with a heterogeneous signal, well-defined edges and an apparently fibrous capsule. (b and c): Axial MRI section in T1 FAT SAT sequence with and without gadolinium. This nodule shows a predominantly peripheral enhancement after gadolinium administration.
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It measured 29 x 27 x 27 mm and was first interpreted as a primary neoformative process (Figures 1 and 2).
MRI sections. (a): coronal, (b): axial and (c) sagittal in STIR sequence. Right superficial parotid nodule, with well-defined edges, a predominantly hyperintense, heterogeneous signal and papillary-like projections inside.
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It measured 29 x 27 x 27 mm and was first interpreted as a primary neoformative process (Figures 1 and 2).
FNA cytology: Bunches of atypical epithelial cells arranged in layers and papillary structures with notable macrokaryosis and scarce cytoplasm.
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Neoplastic cells were observed with moderate atypia, macrokaryosis, occasional nucleoli and scant cytoplasm arranged in three-dimensional strips, with nuclear superimposition in a haematic background in which few lymphocytes were identified (Milan Classification V) (Figure 3).
(a): Surgical procedure. Right superficial parotidectomy. Image shows a tumour lesion that affects nearly all the superficial lobe of the parotid gland. (b): Surgical site. This image shows anatomical integrity of the facial and great auricular nerves and the external jugular vein. This result features an ideal cleavage plane and separation from the tumour lesion.
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A right superficial parotidectomy was performed, with the facial nerve identified and preserved (Figure 4a and b).
Surgical specimen. Encapsulated lesion, hard, elastic to touch, approximately 25 x 22 mm.
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Intraoperative analysis of the surgical specimen identified low-grade monomorphic epithelial proliferation with margins free of tumour lesion (Figure 5).
(a): Haematoxylin-Eosin staining (10x) shows epithelial cells arranged in a papillary pattern with vacuoles in the cytoplasm that determine the formation of cystic units with eosinophilic interior content. (b): Epithelial cells with PAS-positive inclusions in the cytoplasm (40x).
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It was characterised by proliferation of neoplastic cells, with moderate atypia, macrokaryosis, occasional nucleoli and abundant cytoplasm with a vacuolated appearance arranged in a predominantly microcystic and follicular pattern, and with fine fibroconnective septa (Figure 6).
Immunohistochemical findings typical of MASC. (a): Tumour cells showed positive expression for the nuclear and membrane proteins mammaglobin, (b): GATA and (d): S100. (c): Phenotypic expression of mammaglobin, GATA 3 and S100 was also observed.
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Neoplastic cells were positive for S100, mammaglobin, periodic acid Schiff (PAS) and GATA 3 (Figure 7a-d).