PMC4359867_01
(a) Tumor involving the right cheek area extending from the temporal area to the mandibular area (frontal view). (b) Semilateral view. (c) Lateral view. (d) CT scan: axial cut of the upper neck with IV contrast showing narrowing of the external auditory canal by the tumor. (e) CT scan: coronal cut of the upper neck with IV contrast showing erosion of the right zygomatic arch. (f) Intraoperative image showing an extended modified Blair incision. (g) Intraoperative image showing the parotid mass well circumscribed after elevation of the skin flap. (h) Tumor after "en bloc" excision. (i) Postoperative image of the patient.
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fig1
It is invading the lateral aspect of the masticator space, right temporomandibular joint, and external auditory canal causing narrowing of the latter and extending superiorly into the temporalis muscle and involving the masseter muscle (Figure 1).
(a) Epithelial-myoepithelial carcinoma. The ductal structures are composed of outer layer of polygonal, clear myoepithelial cells with variable sized and shaped nuclei. The central epithelial cells are smaller and have eosinophilic cytoplasm, round to oval nuclei, and a high nuclear to cytoplasmic ratio. (b) Focally, the epithelial-myoepithelial carcinoma component exhibits myxochondroid rich background with anastomosing stands of epithelial cells reminiscent of pleomorphic adenoma morphologically. (c) Basal cell adenocarcinoma: prominent eosinophilic hyaline material is seen around nodules of tumor composed of small cells with more chromatic nuclei around larger cells with paler nuclei. (d) Adenoid cystic carcinoma: tubular and cribriform and solid tumor nests. Basal lamina-containing cyst-like spaces are noted. The tumor cells show high grade cytology with markedly increased nuclear to cytoplasmic ratio. (e) Nests of tumor invading the peripheral portion of the nerve bundle in the areas dominated by adenoid cystic carcinoma. (f) The proliferative index by Ki-67 stain labeling showed significantly higher labeling index in the adenoid cystic component (lower left corner) in comparison to the epithelial-myoepithelial component (upper right corner).
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fig2
Mass is composed of multiple components, with epithelial-myoepithelial carcinoma being dominant (80% of the tumor mass) with a minor component of solid variant of adenoid cystic carcinoma and basal cell adenocarcinoma (Figure 2).