Unicystic mucoepidermoid carcinoma (UC-MEC) is a rare MEC variant, and its diagnosis is frequently problematic. This study is aimed at summarizing its clinicopathologic characteristics, treatment, and prognosis and proposing key points to avoid missed diagnosis and misdiagnosis in clinical and pathological conditions. This retrospective study included 30 UC-MEC cases, and the clinical findings were collected from the clinical medical records. Radiographic features, histologic behaviors, MAML2 rearrangement by fluorescence in situ hybridization (FISH), and follow-up data were analyzed. Moreover, glandular odontogenic cyst (GOC) and cytadenoma (CA) were used as controls. In the UC-MEC group, 19 patients were female (63%), and 11 were male (37%). The mean patient age was 39.5 (range, 7–72 years). The affected locations included the jaw (8 maxillary, 3 mandibular) and salivary glands (7 parotid, 11 palates, and 1 floor of the mouth). The chief complaint was swelling; the lesions were all cystic, among which 66.7% were well circumscribed and 33.3% poorly defined. Microscopic examination showed two UC-MEC histologic subtypes. Type A presented as a single cyst with mural thickening (8/30, 27%) lined predominantly by epidermoid cells with interspersed intermediate and mucinous cells, and type B (22/30, 73%) showed infiltrative tumor islands in the cystic wall or the surrounding tissue. FISH analysis suggested that approximately 66.7% of UC-MEC harbored a MAML2 rearrangement. During the median follow-up period of 42 months (range, 6–120 months), all type A patients and 68% of type B patients who underwent complete surgical resection lived without relapse. Seven cases with type B cancer that underwent curettage initially had local recurrence. Clinicians and pathologists hardly recognize UC-MEC owing to its cystic architecture. Specific epidermoid, mucous, and intermediate tumor cells, and MAML2 fusion testing, are essential to avoid potential diagnostic pitfalls. Prompting and completing resection surgery with negative margins would have a favorable prognosis.
Three‐dimensional cultured salivary glands (SGs) microtissues hold great potentials for clinical research. However, most SGs microtissues still lack convincing structure and function due to poor supplementation of factors to maintain stem cell homeostasis. Extracellular matrix (ECM) plays a crucial role in regulating stem cell behavior. Thus, it is necessary to model stem cell microenvironment in vitro by supplementing culture medium with proteins derived from ECM. We prepared specific complexes from human SG ECM (s‐Ecx) and analyzed the components of the s‐Ecx. Human SG epithelial and mesenchymal cells were used to generate microtissues, and the optimum seeding cell number and ratio of two cell types were determined. Then, the s‐Ecx was introduced to the culture medium to assess its effect on stem cell behavior. Multiple specific factors were presented in s‐Ecx. s‐Ecx promoted maintenance of the stem cell and formation of specific structures resembling that of salivary glands and containing mucins, which suggested stem cell differentiation potential. Moreover, treatment of the microtissues with s‐Ecx increased their sensitivity to neurotransmitters. On the basis of the analysis of components, we believed that the presented growth factors are able to interact with stem cell they encountered in vivo, which promote the capacity to maintain stem cell homeostasis. This work provided foundations to study molecular mechanism of stem cell homeostasis in SGs and develop novel therapies for dry mouth through new drug discovery and disease modeling.
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