A Case Report of Mucoepidermoid Carcinoma With Extensive Keratinization in Parotid: Expanding the Morphologic Spectrum

Abstract

Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of salivary glands in children and young adults. Typically, it is composed of squamoid, mucin-producing and intermediate-types cells. However, overt keratinization is rare. To the best of our knowledge, extensive keratinization or keratin pearls in MEC has never been reported. Keratinization or keratin pearls are regard “practically never seen in low-grade MEC”. Herein, we report a case of a 34-year-old woman who presented with a tumor in right parotid gland for 2 months. Microscopically, the tumor was composed of extensive squamous cells with overt keratin pearls, intermediate cells and few scattered mucous cells. MAML2 gene break-apart and CRTC1-MAML2 gene fusion were detected by fluorescence in situ hybridization. This is the first report to describe a MEC case with extensive squamous metaplasia and overt keratin pearls formation, which expands the morphologic spectrum of MEC.

High-grade mucoepidermoid carcinoma of the salivary gland in a bull

“…8 Epidermoid cells may contain keratohyalin granules and can display keratin pearl formation histologically, resembling squamous cell carcinoma. 9 Accurate grading of MECs is clinically important given that the disease-free interval and therapeutic strategy are vastly different for low-grade versus high-grade MECs. In humans, low-grade MECs have reported 5-y survival rates of 92-100% after surgical removal, whereas the median 5-y survival rate for high-grade MECs drops to 0-43%.…”

“…8 Epidermoid cells may contain keratohyalin granules and can display keratin pearl formation histologically, resembling squamous cell carcinoma. 9…”

Aggressive Primary Thyroid Mucoepidermoid Carcinoma with Extensive Pulmonary Involvement

“…Microscopically, MECs exhibit a cystic or solid growth pattern, are composed of mucinous or squamous cells arranged in nest-like or cribriform structures which contain a variable degree of sclerotic stroma, and are stain-positive for p63 and CK5 and negative for thyroglobulin and calcitonin [16,17]. In contrast with salivary MECs, keratinization is seen in as many as one third of primary thyroid MECs [18]. Although concurrent papillary thyroid carcinoma may be detected in a number of cases, the cells of the MEC component are distinct and lack the papillary-like nuclear features of the papillary component [11,12].…”

“…Although concurrent papillary thyroid carcinoma may be detected in a number of cases, the cells of the MEC component are distinct and lack the papillary-like nuclear features of the papillary component [11,12]. As opposed to salivary gland MECs, those originating in the thyroid rarely express CRCT1/MAML2 gene rearrangements, which could be a useful tool in differentiating between primary thyroid MECs and metastases to the thyroid [18,19].…”