UNASSIGNED: Mammary analogue secretory carcinoma (MASC) is a new disease among tumours affecting the salivary glands. It was first reported in 2010, and few cases have been reported worldwide. MASC is often incorrectly diagnosed as salivary gland acinic cell carcinoma. We present here the case of a patient with an asymptomatic parotid tumour who underwent a parotidectomy of the superficial lobe.
UNASSIGNED: A 78-year-old female patient came to the clinic for a tumour of approximately 2.5 × 2.5 cm and a hard, elastic consistency that had grown insidiously in the right preauricular region. Magnetic resonance imaging of the head and neck showed a heterogeneous ovoid lesion located in the lower part of the superficial lobe of the right parotid gland, measuring 29 × 27 × 27 mm. A superficial parotidectomy was performed with the facial nerve identified and preserved. Immunohistochemistry was positive for S100, mammaglobin, periodic acid Schiff (PAS) and GATA-3. Fluorescence in situ hybridisation analysis was subsequently performed and Translocation-ETS-Leukemia Virus (ETV6) gene rearrangement observed. These findings were consistent with diagnosis of a MASC. The patient then required no new interventions or adjuvant therapy. At publication, she was free of disease and continues in clinical follow-up.
UNASSIGNED: MASC is a tumour of the saliva glands that is recently described and rare. There are no studies that describe its biological behaviour or prognosis precisely.

This is a case of a 55-year-old female with past medical history of tobacco smoking, hypertension, and lupus who presented with a left lung nodule, found on computed tomographic scan of the chest during workup for a recently diagnosed squamous cell carcinoma in a cervical lymph node. Resection of the lung nodule showed a 2.3-cm well-defined pale-tan mass, and histologic examination showed a well-circumscribed lesion with papillary, solid, and gland-like architectural patterns, with eosinophilic secretions, areas of comedonecrosis, and increased mitotic activity. Immunohistochemical stains showed the lesion to be positive for cytokeratin 7, S100 protein, and focally positive for mammaglobin. Fluorescence in situ hybridization studies confirmed rearrangement of the ETV6 gene at 12p13.2. To date, our case is the second reported case of a primary mammary-analogue secretory carcinoma arising in the lung, and the first to show evidence of tumor necrosis: an unusual feature in an unusual location.

The present study aimed to investigate the histopathological and immunohistochemical characteristics of Mammary Analogue Secretory Carcinoma (MASC) of the Salivary Gland.
METHODS: Four cases of MASC were diagnosed after microscope images review, immunohistochemsitry (IHC) for Mammaglobin protein, Gata3 protein, S-100 protein, DOG1 protein, and break-apart ETV6 fluorescence in situ hybridization (FISH) in forty salivary gland tumors.
RESULTS: We have shown a t(12;15)(p13;q25) ETV6-NTRK3 translocation in all but one case of MASC suitable for analysis. This translocation was not found in any other salivary gland tumor types including acinic cell carcinoma (AciCC, 30 cases) and mucoepidermoid carcinoma (MEC, 6 cases). In IHC, all MASC showed diffuse positivity for Mammaglobin protein, Gata3 protein and S100 protein, as the DOG1 was negative.
CONCLUSIONS: MASC is rare tumor and often misdiagnosed as other salivary tumors, but whose specific histopathological, IHC and molecular genetic characteristics can help to identify it. ETV6-NTRK3 gene translocation is easily found in MASC, but may not occur in every case.

We present a case of a 63-year-old male with an 8-year history of a left-sided cystic facial mass which recurred despite multiple drainage procedures. Imaging findings showed a cystic mass in the left parotid gland and it was surgically resected. Pathology confirmed it to represent a mammary analogue secretory carcinoma, a relatively newly described entity. This case illustrates that mammary analogue secretory carcinoma can masquerade as a cyst within the parotid gland.

Mammary analogue secretory carcinoma is a recently recognized tumor of salivary gland with characteristic t(12;15)(q13;q25) that results in ETV6-NTRK3 fusion product. Distinguishing mammary analogue secretory carcinoma from other salivary gland tumors is important. Present study highlights cytologic findings in three cases of mammary analogue secretory carcinoma of parotid which facilitate preoperative diagnosis with the aid of ancillary diagnostic techniques. Fine needle aspiration cytology of parotid was performed on three cases after clinical examination. Immunocytochemistry for mammoglobin and S100 were performed. Parotidectomy was done in all cases. The corresponding hematoxylin and eosin stained slides and blocks of all cases were studied. Molecular analysis was done in one of the cases. Cases 1 and 3 revealed uniform atypical epithelial cells arranged in branching papillary pattern with few cells in microcystic pattern. Case 2 showed atypical cells arranged mainly in loose clusters and few singly dissociated. Individual cells revealed round nuclei, vesicular chromatin, prominent nucleoli and abundant finely vacuolated cytoplasm with metachromasia prominent in May-Grunwald-Giemsa smear (case 3). Characteristic hob-nail cells covering papillae were observed in cases 1 and 3. Immunocytochemistry showed strong positivity for mammoglobin and S100 thereby confirming the diagnosis of mammary analogue secretory carcinoma preoperatively. The diagnosis was in concordance with surgical specimen. Also, characteristic ETV6-NTRK3 translocation was confirmed in case 1. Increased awareness and high index of suspicion is necessary for the upfront diagnosis, more so for the papillary variant of mammary analogue secretory carcinoma. Immunocytochemistry aids in confirming this preoperative diagnosis, based on which treatment can be planned. Diagn. Cytopathol. 2016;44:519-525. © 2016 Wiley Periodicals, Inc.

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