A New Hitherto Unreported Histopathologic Manifestation of Mammary Analogue Secretory Carcinoma: "Masked MASC" Associated With Low-grade Mucinous Adenocarcinoma and Low-grade In Situ Carcinoma Components

Mucin-rich salivary gland tumors

Salivary gland neoplasms characterized by abundant mucin production are rare but have long been recognized. Due to their scarcity, precise classification has long eluded these mucin-rich tumors. Recent molecular discoveries, however, have shed considerable light on the genetic underpinnings of mucin-rich salivary gland neoplasms. This manuscript will review the most up-to-date information on this fascinating group of salivary gland neoplasms.

NKX3.1 Expression and Molecular Characterization of Secretory Myoepithelial Carcinoma (SMCA): Advancing the Case for a Salivary Mucous Acinar Phenotype

BACKGROUND

Secretory myoepithelial carcinomas (SMCA) are rare, mucinous, signet ring predominant tumors with primitive myoepithelial features. While many mucinous salivary gland tumors have now been molecularly characterized, key drivers in SMCA have yet to be elucidated. Recently, NKX3.1, a homeodomain transcription factor implicated in salivary mucous acinar development was also shown in a subset of salivary mucinous neoplasms, salivary intraductal papillary mucinous neoplasms (SG-IPMN). To date, NKX3.1 expression has not been characterized in other mucinous salivary lesions. Here, we report molecular and extended immunophenotypic findings in SMCA and NKX3.1 expression in the context of other head and neck lesions.

METHODS

We retrieved 4 previously reported SMCA, performed additional immunohistochemical and targeted next-generation sequencing (NGS). We also investigated the use of NKX3.1 as a marker for SMCA in the context of its prevalence and extent (using H-score) in a mixed cohort of retrospectively and prospectively tested head and neck lesions (n = 223) and non-neoplastic tissues (n = 66).

RESULTS

NKX3.1 positivity was confirmed in normal mucous acini as well as in mucous acinar class of lesions (5/6, mean H-score: 136.7), including mucinous adenocarcinomas (3/4), SG-IPMN (1/1), and microsecretory adenocarcinoma (MSA) (1/1). All SMCA were positive. Fluorescence in situ hybridization for SS18 rearrangements were negative in all successfully tested cases (0/3). NGS was successful in two cases (cases 3 and 4). Case 3 demonstrated a PTEN c.655C>T p.Q219* mutation and a SEC16A::NOTCH1 fusion while case 4 (clinically aggressive) showed a PTEN c.1026+1G>A p.K342 splice site variant, aTP53 c.524G>A p.R175H mutation and a higher tumor mutation burden (29 per Mb). PTEN immunohistochemical loss was confirmed in both cases and a subset of tumor cells showed strong (extreme) staining for P53 in Case 4.

CONCLUSION

Despite a partial myoepithelial phenotype, SMCA, along with mucinous adenocarcinomas/SG-IPMN and MSA, provisionally constitute a mucous acinar class of tumors based on morphology and NKX3.1 expression. Like salivary mucinous adenocarcinomas/SG-IPMN, SMCA also show alterations of the PTEN/PI3K/AKT pathway and may show progressive molecular alterations. We document the first extramammary tumor with a SEC16A::NOTCH1 fusion.

Sinonasal mixed transitional epithelial-seromucinous papillary glandular neoplasms with BRAF p.V600E mutations - sinonasal analogues to the sialadenoma papilliferum family tumors

Sinonasal non-intestinal type adenocarcinoma (non-ITAC) is a heterogeneous category that may benefit from improved taxonomy. With the recognition that most non-ITAC are phenotypically seromucinous, stratification may be improved by applying salivary type morphologic criteria and molecular findings. We report two cases of papillary seromucinous adenocarcinoma with sinonasal papilloma-like surface components that show histologic and molecular features analogous to the salivary sialadenoma papilliferum family of tumors. Case 1 concerns a 50-year-old female who presented with a left anterior nasoethmoid polyp, while case 2 is that of a 74 year old female with nasal polyposis. Histologically, both cases demonstrated a surface transitional sinonasal papilloma-like component (more prominent in case 2) with a deeper bilayered glandular component showing papillary and tufted micropapillary growth of monomorphic columnar to cuboidal cells with eosinophilic cytoplasm. Case 1 also showed a deep cribriform/microcystic component. Immunostains showed a delimiting p63/p40 positive basal layer around the SOX-10 positive glandular elements, while the transitional sinonasal papilloma-like components were diffusely p63/p40 positive. Like sialadenoma papilliferum and related tumors, both cases demonstrated BRAF p.V600E mutations in both components and no other alterations. The patients remain disease free at 9 and 19 months respectively. Our cases illustrate a novel sinonasal lesion and suggest that improved morphologic and molecular categorization may refine and reduce the category of non-ITAC.

Prognostic factors in mammary analogue secretory carcinomas of the parotid gland: Systematic review and meta-analysis

Mammary analogue secretory carcinomas (MASCs) of the parotid gland are considered as low-grade malignancies with good clinical outcome but lacking data regarding prognostic factors. We performed meta-analysis assessing prognostic factors for disease-free survival (DFS) and overall survival (OS) in 256 patients with MASCs of the parotid gland. A total of 73 studies have met the inclusion criteria and 76.3% of patients were seen with T1 and T2 tumors and negative neck nodes. Lymph node metastasis (57.4%) and distant recurrences (46.2%) were particularly found in T4 tumors (p < 0.001). DFS at 5 and 10 years was 77.9% and 47.2% compared to 88.1% and 77.2% for OS at the same time points. Male sex, T3-T4 tumors, and recurrent disease represented independent worse prognosticators for survival outcome. Altogether, parotid gland MASCs show good long-term outcome, but T4 tumors behave significantly more aggressive and require extended treatment strategies along with close follow-ups.

Secretory Carcinoma of the Skin: Report of 6 Cases, Including a Case With a Novel NFIX-PKN1 Translocation

Secretory carcinoma of the skin is a rare adnexal carcinoma, which is morphologically and immunohistochemically identical to secretory carcinoma of the breast and is associated with the presence of t (12;15) translocation, resulting in the ETV6-NTRK3 gene fusion. Nineteen cases of primary cutaneous secretory carcinoma have been previously published in the literature. In this study, we describe 6 new cases of secretory carcinoma of the skin. The study group consisted of 5 female patients and 1 male patient, ranging in age from 57 to 98 years (mean: 74.2, median: 74). Locations included the axilla (2), neck, eyelid, thigh, and nipple base, each one. Microscopically, all but 1 tumor were well circumscribed and nonencapsulated and exhibited characteristic abundant secretions within the microcystic and tubular spaces comprised by bland oval, round to cuboidal neoplastic cells. In addition, solid areas and focal pseudopapillae were seen, and, in 1 case, a focal mucinous component with small lakes of mucin containing small tumor nests or tubules of the neoplastic cells was present. The remaining neoplasm was mostly solid and papillary, with only few characteristic lumina containing secretions. Immunohistochemically, all cases expressed S-100 protein, mammaglobin, STAT5, GATA3, and NTRK. ETV6-NTRK3 gene fusion was detected in 5 cases, whereas, in the remaining tumor, a novel NFIX-PKN1 gene fusion was found.

What do we know about the cytological features of pure intraductal carcinomas of the salivary glands?

OBJECTIVE

Intraductal carcinomas (IDCs) are rare, poorly characterised salivary gland tumours. The cytological features of IDCs are even less known. In this paper, a systematic literature review of pure IDCs (without stromal invasion, not associated with other histotypes) of low-grade (LG-IDCs) and high-grade (HG-IDCs) was performed.

METHODS

The bibliographic research included multiple databases (PubMed, Scopus, Web of Science). Mild-moderate nuclear atypia favoured LG-IDCs, severe atypia favoured HG-IDCs.

RESULTS

Preoperative fine-needle aspiration cytology (FNAC) was performed in 13/94 published cases (14%): 10 parotid; two oral; one submandibular. All the cases were histologically LG-IDCs, except two parotid IDCs. FNAC results included: negative for malignancy (three of 13 cases, 23%); tumour of uncertain malignant potential (seven of 13, 54%); malignancy (three of 13, 23%). The ductal component was identified in two cases; mucoepidermoid carcinoma was suggested in two additional cases. The grade was underestimated on FNAC evaluation in one HG-IDC as focal high-grade features were present on subsequent histological examination. The cases diagnosed as malignant tumours or describing intermediate atypia resulted in LG-IDCs on subsequent histology. Occasional mitoses were described only in one HG-IDC; this feature may have not been considered in the remaining published cases.

CONCLUSIONS

FNAC and clinico-pathological correlation are important aids for clinicians and pathologists. FNAC could assist surgery even if an accurate diagnosis is sometimes impossible. Discrepancy in grading the nuclear atypia between the FNAC material and the resected specimen can occur, sometimes being unavoidable. Further studies are needed to better characterise this rare tumour.

Intraductal carcinomas of the salivary glands: systematic review and classification of 93 published cases

Intraductal carcinomas (IDCs) are rare, not well-characterized salivary gland tumors. A systematic literature review of pure IDCs (without stromal invasion) of low-grade (LG-IDCs) or high-grade (HG-IDCs) was performed: IDCs were classified using the apocrine (AR+/S100-) vs intercalated (S100+/AR-) classification. Eighty-two LG-IDCs and 11 HG-IDCs were identified (84% parotid; 11% oral; 3% submandibular; 1% lacrimal; and 1% unknown). Out of 11 HG-IDCs, 2 HG-IDCs (18%) recurred as HG-IDC or invasive carcinoma. IDCs were classified as follows: intercalated (30%); mixed apocrine and intercalated (27%); apocrine (11%); oncocytic (6%); intercalated with focal oncocytic features (1%); and unclassifiable (25%). Double AR/S100 expressors (4%) or discrepancies between morphology and immunophenotype (9%) were found. Apocrine features and necrosis were more frequent in HG-IDCs (55%; 45%). Pleomorphism favored HG-IDCs (especially when combined with >10 mitoses/10 HPFs and/or Ki67 index >10%), being associated with apocrine areas at least in 3 HG-IDCs (27%). IDCs were typically mammaglobin+/ER-/PR-/DOG1-. No immunomarker clearly distinguished HG-IDCs from LG-IDCs. About 57% IDCs (16 LG-IDCs, 1 HG-IDC) showed RET rearrangements, including NCOA4-RET (eight intercalated and two unclassifiable IDCs) and TRIM27-RET fusions (two mixed IDCs). No ETV6, ALK-1, ROS, NTRK3, MAML2, MAML3, or PLAG1 rearrangements were identified. Complete excision and total sampling should exclude invasive areas.

Synchronous Parotid (Mammary Analog) Secretory Carcinoma and Acinic Cell Carcinoma: Report of a Case

Mammary analogue secretory carcinoma (MASC) is a recently described low-grade salivary gland malignancy with histologic, immunohistochemical and molecular similarities to secretory carcinoma of the breast, including a specific t(12;15)(p13;q25) resulting in an ETV6-NTRK3 gene fusion. Ultrasound and magnetic resonance imaging frequently document a macrocystic structure. The main differential diagnosis of secretory carcinoma is with low grade acinic cell carcinoma (AciCC). The two can be differentiated with immunohistochemical stains for S100, mammaglobin, carbonic anhydrase VI and DOG-1; the identification of the specific translocation can help to characterize non-typical cases. We report a unique case of synchronous MASC and AciCC presenting in a parotid gland and discuss the implications of the correct identification of the two tumors.

Mammary analogue secretory carcinoma of salivary glands: diagnostic pitfall with distinct immunohistochemical profile and molecular features

Mammary analogue secretory carcinoma (MASC) is a newly defined entity among salivary gland malignancies which has just been established in the 4^th edition of the WHO classification of head and neck tumors. MASC (synonym: secretory carcinoma) are characterized by a specific rearangement of the ETV6 gene locus. Here, we present a series of 3 MASC cases including clinical data with follow-up for up to 26 months. All tumours immunhistochemically displayed strong positivity for cytokeratin 7, and mammaglobin, focal positivity for S100, cytokeratin 5/6 and muc-4. In contrast, immunhistochemical stainings against cytokeratin 14, hormon receptors, Her2/neu, androgen receptor and prostate-specific antigen were consistently negative. FISH analysis showed translocation of the ETV6 gene locus in the majority of tumour cell nuclei. During clinical follow-up, no local relapse or metastasis was detected. As these carcinomas are clinically and radiologically indistinguishable from other salivary gland tumours and as therapeutic approaches and prognosis might differ, we need to be able to diagnose MASC correctly.

Systematic review of mammary analog secretory carcinoma of salivary glands at 7 years after description

BACKGROUND

Mammary analog secretory carcinoma of the salivary glands (MASCSG ) is a newly introduced malignant tumor of the salivary glands. For decades, it has been confused with acinic cell carcinoma (ACC) of the salivary glands.

METHODS

All reported cases of MASCSG were surveyed from 2010 until January 2017. The collected data was compiled and computationally processed to describe the clinical parameters of MASCSG . Its epidemiology was also mapped. Moreover, inaccurate data was highlighted.

RESULTS

Clinically implicating, this article tackles simply the several clinical findings of MASCSG so that our contemporary nosology, at 7 years after description, can be updated. The cytogenetic, histologic, and immunohistochemical details are also defined.

CONCLUSION

The available data about MASCSG is sufficient enough to diagnose it with no need to investigate the ETV6-NTRK3 translocation. Although high-grade malignancy and distant metastases were rarely reported, a rapt attention should be paid both to the nature of this tumor and to the indicated close follow-up of such cases, especially when necrosis, increased mitotic activity, and other classic caveats are conspicuous. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1243-1248, 2017.