J Pathol Transl Med.  2021 Mar;55(2):132-138. 10.4132/jptm.2020.12.11.

Adenocarcinoma of the minor salivary gland with concurrent MAML2 and EWSR1 alterations

• Choi S
• Cho J
• Lee SE
• Baek CH
• Kim YK
• Kim HJ
• Ko YH

• KMID: 2513899
• DOI: http://doi.org/10.4132/jptm.2020.12.11

Abstract

Salivary gland tumors are histologically diverse, and each entity has distinctive histopathological and molecular features. We report two cases of salivary gland tumors with unique histological and molecular findings, which have not been documented previously. The tumors were located in the base of the tongue in both patients. Most tumor cells were arranged in cords and nests, giving a trabecularlike appearance. Focally, glandular structures with intraluminal mucin and perivascular pseudorosette-like configurations were identified. Tumor cells had eosinophilic to clear cytoplasm, and showed mild nuclear atypia. They were positive for pancytokeratin and negative for S-100, p63, c-KIT, androgen receptor, and neuroendocrine markers. Multiple foci of capsular or lymphovascular invasion were identified, but the Ki-67 labeling index was low (< 5%). Fluorescence in situ hybridization revealed concurrent alterations of MAML2 and EWSR1 gene. Further investigations with a larger number of cases with similar histological and molecular features will accurately classify this tumor.

Keyword

Salivary gland; Neoplasm; gene; gene

Figure

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  Fig. 1 Histopathological findings and immunostaining results for case 1. (A) Low-power image shows cords and nests of tumor cells separated by fibrous septa. The tumor cells appear round to polygonal and contain bland-looking nuclei with fine chromatin and abundant eosinophilic granular cytoplasm. Mucinous cells are scattered throughout the tumor. (B) In some areas, tumor cell nuclei show peripheral palisading around blood vessels, which give a perivascular pseudorosette-like appearance. (C) Focally, tumor cells show glandular differentiation and intraluminal mucin secretion. (D) Endolymphatic tumor emboli are found in the peritumoral fibrous capsule. (E) Cytokeratin (AE1/AE3) staining is positive in both the trabecular and glandular components (left side), but focal staining is observed in the rosettoid area (right side). (F) Tumor cells around the hyalinized vasculatures (arrows) with pseudorosette-like arrangement exhibit positive CD99 immunoreactivity. (G) Immunohistochemical staining for p63 reveals the lack of myoepithelial differentiation of this tumor. (H) The Ki-67 labeling index in tumor cells is very low (< 1%).

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  Fig. 2 Histopathological findings and immunostaining results for case 2. (A) Low-power image shows the tumor cells arranged in nests and cords which are surrounded by thick fibrous septa, forming trabecular growth pattern. The tumor cells possess lightly eosinophilic to clear cytoplasm. (B) Glandular components with intraluminal and intracytoplasmic mucin secretion are found in multiple areas. (C) Cytokeratin (AE1/AE3) staining reveals diffuse strong positive reactivity. (D) Focal p63 expressions are found in only a few tumor cells.

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  Fig. 3 Representative image of fluorescence in situ hybridization (FISH) analysis for MAML2 and EWSR1 from case 1 (A, B) and 2 (C, D). (A, B) In case 1, FISH analysis for MAML2 reveal one fused signal and a single red signal (red arrows), suggesting partial deletion or unbalanced translocation of MAML1 (A). (B) EWSR1 shows one fused signal and separate red and green signal (yellow arrows), indicating translocation of EWSR1. (C, D) Case 2 shows several cells with split of red and green signals (yellow arrows) for MAML2 (C) and EWSR1 (D), indicating concurrent MAML1 and EWSR1 rearrangement.

Reference

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