MAML2-rearrranged sclerosing mucoepidermoid carcinoma of submandibular gland: an incidental finding in a patient with history of recurrent sialadenitis and Sjögren's syndrome

The Sclerosing subtype of mucoepidermoid carcinoma is rare, with only 39 cases reported in literature. We present a new case of sclerosing mucoepidermoid carcinoma (SMEC) with MAML2 rearrangements. A 49-year-old woman with Sjögren's syndrome experienced recurrent submandibular sialadenitis and sialolithiasis, leading to the removal of her right gland. Postoperative imaging revealed a calcified mass in her left gland which was subsequently resected. The pathologic examination revealed a well-defined tumor with extensive fibrous stroma, predominantly epidermoid cells, and occasional mucinous components. There was a dense lymphocytic and plasma cell infiltrate at the tumor's periphery. Immunohistochemistry was positive for p40 and CK7, few IgG4+ plasma cells. No eosinophils were identified. Fluorescence in situ hybridization (FISH) revealed rearrangement of the MAML2 (11q21) region. Adjuvant radiation was not recommended because of the patient's history of autoimmune diseases and the fact that the tumor was small, localized, and had negative resection margins. The patient was advised to undergo a repeat CT scan of the neck, scheduled for 3 months later. This case highlights the importance of considering SMEC in the differential diagnosis of patients with sialolithiasis or Sjögren's syndrome.

Low-grade mucoepidermoid carcinoma mimicking benign cystic lesions in the salivary gland: A diagnostic dilemma

Mucoepidermoid carcinoma (MEC) is a common malignancy arising in the parotid gland. The diagnosis of MEC is typically based on its morphological features alone, characteristically containing mucocytes, intermediate cells and epidermoid cells. However, when cystic degeneration is diffuse, it is challenging to distinguish MEC from other benign cystic tumors. This is a case report of a 58-year-old Caucasian man who presented with a parotid mass. H&E sections of the mass reveal multiloculated cysts lined by bland-looking epithelium with only rare papillary architectures. The papillary proliferation contains mucocytes, and epidermoid cells highlighted by the p63 immunohistochemistry study. The diagnosis was confirmed by FISH result of positive MAML2 (11q21) rearrangement. Patient underwent parotidectomy and is disease-free 6 months post-surgery. MEC with cystic degeneration is a common diagnostic pitfall which can mimic many benign lesions in the salivary gland. We present a rare case with MEC with extensive cystic change, its molecular and pathologic findings and review the diagnostic features of MEC, its benign mimickers and useful tools for distinguishing these entities.

Salivary mucoepidermoid carcinoma: Histological variants, grading systems, CRTC1/3-MAML2 fusions, and clinicopathological features

AIM

To investigate the histological diversity of salivary mucoepidermoid carcinoma (MEC), its clinicopathological features, and its associations with CRTC1/3-MAML2 fusions.

METHODS

Salivary MEC cases (n=177) were examined for CRTC1/3-MAML2, histological variants were classified, and tumors were graded according to four different grading systems. Adverse histological features considered unusual in MEC were also investigated.

RESULTS

Of the 177 MEC cases, 110 were positive for CRTC1/3-MAML2. The classical variant was most frequent in the fusion-positive, fusion-negative, and all case groups. Clear/oncocytic variant was the second most frequent in the fusion-positive and total case groups. Oncocytic, Warthin-like, and spindle variants were recognized in the fusion-positive group only. Clear cell, sclerosing, mucinous, and central variants were recorded in both fusion-positive and fusion-negative groups. No case was classified as a ciliated variant, as a mucoacinar variant, or as a high-grade transformation. Compared with the classical variant, non-classical variants were characterized by frequent CRTC1/3-MAML2 fusions and a lower clinical stage in all cases. Of four histological features considered unusual in MEC, marked nuclear atypia, frequent mitoses (>10/10HPFs), and extensive necrosis were found independently of the fusion status, and accounted for 3-5% of all cases. However, none of the cases showed overt keratinization. On comparison, the AFIP and modified Healey grading systems downgraded tumors, the Brandwein system upgraded tumors, and the Memorial Sloan Kettering system provided a moderate means of assessment.

CONCLUSION

Recognition of the histological diversity of MEC, its clinicopathological features, and its associations with CRTC1/3-MAML2 fusions is helpful for an accurate diagnosis of this carcinoma.

Sclerosing mucoepidermoid carcinoma of the salivary glands: report of three cases with special concern to the counterpart accompanied by eosinophilia

Sclerosing mucoepidermoid carcinoma (SMC) is described as a "sclerosing variant" of mucoepidermoid carcinoma, and it is characterized by dense fibrosis and sclerosis of the stroma. SMC with eosinophilia (SMCE) is another and more rare subtype characterized by eosinophilia in addition to the sclerotic stroma common to SMC. However, unlike SMC, SMCE is not listed in the current 4th edition of WHO classification. Here, we describe three cases: one SMC in the parotid gland, one SMCE in the submandibular gland and one SMCE in the minor salivary gland of the oral cavity. The patients included a 71-year-old Japanese male, a 74-year-old Japanese female, and an 81-year-old Japanese female. They each complained of mass formation and underwent surgical resection. Histologically, the tumors mainly consisted of squamous cells with scarce keratinization that formed irregular large and small nests along with cystic structures containing mucous cells against the background of sclerotic stroma. One oral SMCE showed fine nesting and trabecular invasion. The two SMCEs included dense aggregates of eosinophils as well as more prominent lymphoid infiltration. Fluorescence in situ hybridization for MAML2 confirmed split signals in SMC, but not in SMCE.

Sclerosing variant of mucoepidermoid carcinoma: a diagnostic challenge

The sclerosing variant of mucoepidermoid salivary gland carcinoma is extremely rare. It is nearly impossible to diagnose this condition preoperatively. We present a case of a 23-year-old woman with a 1-year history of left parotid enlargement with inconclusive fine-needle aspiration cytology results. MRI showed an irregular parotid mass, and subsequent partial parotidectomy confirmed the diagnosis. We discuss the diagnostic pitfalls of this condition and provide a review of the literature surrounding its pathogenesis and management.