Ductal adenomas of salivary gland showing features of striated duct differentiation (‘striated duct adenoma’): a report of six cases

Expanding the histological spectrum of salivary gland neoplasms with HMGA2::WIF1 fusion emphasising their malignant potential: a report of eight cases

AIMS

Recently, HMGA2::WIF1 fusion has been reported in pleomorphic adenoma (PAs) originating from the parotid gland with a characteristic canalicular adenoma (CAA)-like pattern. However, it is unclear whether HMGA2::WIF1 fusion may occur in salivary gland carcinoma or tumours originating from the minor salivary glands. We herein conducted a detailed clinicopathological review of eight salivary gland tumours harbouring HMGA2::WIF1 fusions.

METHODS AND RESULTS

The reviewed diagnoses of salivary gland neoplasms with HMGA2::WIF1 fusion were PA (n = four), myoepithelioma (n = one), myoepithelial carcinoma ex PA (n = two) and high-grade carcinoma with basaloid features (n = one). Two tumours originated from the minor salivary glands. Six tumours (80%) contained areas reminiscent of CAA characterised by interconnected trabeculae/canaliculi of monotonous oncocytic or cuboidal tumour cells associated with a hypocellular, hyalinised to myxoid stroma. Areas typical of PA were seen in four (50%) cases. All tumours showed diffuse S100 and CK7 immunopositivity. Adverse events were detected in two cases, including local recurrence in a patient with PA, and local and distant recurrences and disease-related death in a patient with a high-grade carcinoma of the minor salivary gland of the buccal space, showing tumour necrosis and perineural invasion.

CONCLUSION

Salivary gland neoplasms with HMGA2::WIF1 fusion are predominantly characterised by CAA/striated duct adenoma-like histology and a S100+/CK7+ immunoprofile. These tumours are not always benign, as among all reported cases approximately 20% showed malignancy (six of 28) and adverse outcome (three of 15), including recurrence, distant metastasis and disease-specific mortality.

Recurrent IDH2 Mutations in Salivary Gland Striated Duct Adenoma Define an Expanded Histologic Spectrum Distinct From Canalicular Adenoma

Striated duct adenoma (SDA) is a rare salivary gland neoplasm defined by histologic similarity to normal striated ducts. However, doubt persists about whether SDA represents a genuine entity distinct from canalicular adenoma and if a malignant counterpart exists. This study aims to evaluate the molecular underpinnings of SDA to clarify its pathogenesis and classification. We identified 10 SDA and 2 tumors called low-grade adenocarcinoma not otherwise specified that were retrospectively recognized to resemble SDA. All cases showed recurrent histologic features including (1) discrete monophasic tubules, (2) tall columnar eosinophilic cells, (3) monotonous oval nuclei, and (4) scant fibrous stroma, and most were positive for S100 protein (91%), SOX10 (80%), and CK7 (80%). Although 1 case was previously called adenocarcinoma based on interdigitation with normal acini, this pattern was also seen in some SDA, and likely does not indicate malignancy; the significance of growth surrounding nerve in 1 other case is less clear. Targeted sequencing identified IDH2 R172X mutations in all 8 cases with sufficient tissue, with positivity for IDH1/2 mutation-specific immunohistochemistry in 9 cases stained. In contrast, 5 canalicular adenomas lacked IDH2 mutations or other oncogenic alterations. Overall, IDH2 R172X mutations are a defining feature of SDA that, in combination with its recognizable pathologic profile, confirm it is a unique entity separate from canalicular adenoma. IDH1/2 mutation-specific immunohistochemistry may provide a convenient tool to facilitate diagnosis. Both morphology and IDH2 mutations raise parallels between SDA and breast tall cell carcinoma with reverse polarity.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Salivary Glands

The salivary gland section in the 5th edition of the World Health Organization Classification of Head and Neck Tumours features a description and inclusion of several new entities, including sclerosing polycystic adenoma, keratocystoma, intercalated duct adenoma, and striated duct adenoma among the benign neoplasms; and microsecretory adenocarcinoma and sclerosing microcystic adenocarcinoma as the new malignant entities. The new entry also includes mucinous adenocarcinoma subdivided into papillary, colloid, signet ring, and mixed subtypes with recurrent AKT1 E17K mutations across patterns suggesting that mucin-producing salivary adenocarcinomas represent a histologically diverse single entity that may be related to salivary intraductal papillary mucinous neoplasm (IPMN). Importantly, the number of entities in the salivary chapter has been reduced by omitting tumors or lesions if they do not occur exclusively or predominantly in salivary glands, including hemangioma, lipoma, nodular fasciitis and hematolymphoid tumors. They are now discussed in detail elsewhere in the book. Cribriform adenocarcinoma of salivary gland origin (CASG) now represents a distinctive subtype of polymorphous adenocarcinoma (PAC). PAC is defined as a clinically, histologically and molecularly heterogeneous disease group. Whether CASG is a different diagnostic category or a variant of PAC is still controversial. Poorly differentiated carcinomas and oncocytic carcinomas are discussed in the category "Salivary carcinoma not otherwise specified (NOS) and emerging entities". New defining genomic alterations have been characterized in many salivary gland tumors. In particular, they include gene fusions, which have shown to be tightly tumor-type specific, and thus valuable for use in diagnostically challenging cases. The recurrent molecular alterations were included in the definition of mucoepidermoid carcinoma, adenoid cystic carcinoma, secretory carcinoma, polymorphous adenocarcinoma, hyalinizing clear cell carcinoma, mucinous adenocarcinoma, and microsecretory adenocarcinoma.

The Decline of Salivary Adenocarcinoma Not Otherwise Specified as a Tumor Entity: Reclassification Using Contemporary Immunohistochemical Profiling and Diagnostic Criteria

The classification of salivary gland carcinomas has become increasingly specific over the last decade with the definition of new tumor types, documentation of novel molecular and immunohistochemical findings, and development of more refined diagnostic criteria. In this setting, it is unclear how many salivary tumors still cannot be easily categorized-and whether such tumors represent undifferentiated malignancies or include additional definable entities. Relying largely on current classification schemes and contemporary immunohistochemical panels, we reassessed salivary tumors previously diagnosed as adenocarcinoma, not otherwise specified (ACA NOS) from 2 large academic medical centers. Fifty-seven ACA NOS (72%) could be reclassified as more specific entities including 31 salivary duct carcinomas (39%), 7 polymorphous adenocarcinomas (9%), 5 epithelial-myoepithelial carcinomas (6%), 4 myoepithelial carcinomas (5%), 4 secretory carcinomas (5%), 1 acinic cell carcinoma (1%), 1 basal cell adenocarcinoma (1%), 1 intraductal carcinoma (1%), and 1 clear cell carcinoma (1%) as well as 2 metastatic squamous cell carcinomas (3%). Of reclassified cases, 21 (37%) represented variant histologies within these categories. ACA NOS comprised 11% of salivary malignancies before reclassification, but only 4% after reclassification. The remaining 22 ACA NOS demonstrated heterogeneous features, with an association between histologic grade and clinical outcome. In effect, ACA NOS is becoming a bygone entity as modern classification schemes and ancillary techniques now permit more specific typing of a majority of these tumors, potentially facilitating more specific prognostication and treatment. Additional distinctive entities such as mucinous adenocarcinoma may still be definable within the ACA NOS category.

ETV6 Gene Rearrangements Characterize a Morphologically Distinct Subset of Sinonasal Low-grade Non-intestinal-type Adenocarcinoma: A Novel Translocation-associated Carcinoma Restricted to the Sinonasal Tract

Low-grade sinonasal adenocarcinomas (low-grade SNACs) of the sinonasal tract comprise a poorly characterized and histologically heterogeneous group of tumors. We describe three cases of a histologically distinct variant of low-grade SNAC characterized by ETV6 gene rearrangements. The patients included 2 women (aged 32 and 88 y) and a man (aged 75 y); all were initially treated with surgery alone. Follow-up ranged from 9 to 170 months with one patient having 2 local recurrences and none experiencing distant or regional metastases. Tumors were composed of cytologically bland columnar and cuboidal eosinophilic tumor cells with basally located nuclei arranged in tubular and tubulotrabecular patterns. Immunohistochemically, CK7, DOG1, GCDFP-15, and SOX10 were positive in all cases, and vimentin was positive in 2 cases. Scattered single cells or small groups of tumor cells were S-100 positive. Only one case had weak, focal expression of GATA3, and mammaglobin was consistently negative. Two cases had ETV6-NTRK3 gene fusions, whereas ETV6 had an unknown fusion partner gene in one case. The highly similar morphology, immunohistochemical profile, and genetics of the presented cases are suggestive of a specific disease. Although translocation-associated adenocarcinomas in the sinonasal tract have previously been described exclusively as salivary-type carcinomas, we present the first type of carcinoma characterized by recurrent genetic rearrangements and distinct phenotype occurring exclusively in the sinonasal tract with no known major salivary gland counterpart. We provisionally designate this tumor ETV6-rearranged low-grade SNAC. Identification of additional cases is necessary to fully appreciate the morphologic and biological spectrum of this disease.

Canalicular adenoma: A systematic review

OBJECTIVE

Canalicular adenoma (CA) is an uncommon but unique benign tumor of salivary gland origin. It is the third most common benign tumor of minor salivary glands, representing less than 1% of all salivary neoplasms. A systematic review is presented of reported cases of CA, to determine trends in presentation, diagnostic features, treatment, and patient outcome.

METHODS

Searches of specific databases, as reported, were carried out to identify papers reporting CA. The variables were patient symptoms, tumor location, histopathological findings, demographics, treatment, follow-up, and recurrence.

RESULTS

430 cases were identified; the most common location was in the upper lip (66.3%), followed by hard palate (14.5%). The most common clinical presentation was a nodule (46.5%), followed by asymptomatic (29.5%), and discomfort (28.7%). CA was most frequently seen in females (64%). The average age was 66.3 years. 97% of cases were treated surgically. The average follow-up was 136.3 months, and recurrence was reported in 3% of the cases.

CONCLUSION

CA shows a strong predilection for the upper lip. CAs are frequently asymptomatic, but the principal symptom was pressure.

Striated duct adenoma presenting with intra-tumoral hematoma and papillary thyroid carcinoma-like histology

Striated duct adenoma of the salivary gland is a rare benign tumor characterized by unilayered duct epithelium and striations of the tumor cell membranes. To the best of our knowledge, only six cases have been reported in the literature. Here we report an additional case, which was complicated by an intra-tumoral hematoma on clinical presentation and by papillary thyroid carcinoma-like histology on intra-operative frozen section diagnosis. An asymptomatic 78-year-old male presented with a two-year-history of a painless tumor of the left parotid. An intra-tumoral hematoma, which is unusual for a salivary gland tumor, was suspected from results of pre-operative radiology. The patient then underwent a left parotidectomy. The intra-operative frozen section diagnosis indicated a benign tumor, although ectopic papillary thyroid carcinoma was raised as a differential diagnosis since the eosinophilic tumor cells occasionally possessed nuclear grooves and nuclear pseudo-inclusions. By precise histopathological examination using paraffin sections, the tumor was finally diagnosed as striated duct adenoma. This type of tumor has unique features of hypervascular stroma and papillary thyroid carcinoma-like nuclei. In our case, the former feature was associated with the intra-tumoral hematoma and the latter feature, with difficulty in frozen section tumor diagnosis.

Hybrid Intercalated Duct Lesion of the Parotid: Diagnostic Challenges of a Recently Described Entity with Fine Needle Aspiration Findings

Intercalated duct lesions (IDL) of the salivary glands are recently described, and encompass both hyperplasia and benign neoplasms that remain incompletely understood. IDLs have been linked to various benign and low-grade malignant salivary gland neoplasms. We herein present a case of a 77 year old woman with an IDL of the parotid composed of both a hyperplastic and an adenomatous component and report, for the first time, the fine needle aspiration findings of such a lesion. This case illustrates the morphologic spectrum of an IDL, as well as challenges in rendering an accurate cytological and histologic diagnosis. The potential diagnostic pitfalls presented by the hybrid pattern of this lesion are also discussed.

Functional Histology of Salivary Gland Pleomorphic Adenoma: An Appraisal

The complex microstructure of salivary gland pleomorphic adenoma is examined in relation to function. Events related to secretion of macromolecules and absorption, responses to the altered microenvironment and controversies concerning epithelial-mesenchymal transition versus modified myoepithelial differentiation are explored. Their effects on tumor cell phenotypes and arrangements are emphasized. Heterotopic differentiation and attempts at organogenesis are also considered. The approach allows interpreting microstructure independently of histogenetic perceptions, envisaging the tumor cells as a continuum, endorsing luminal structures as the principal components, and defining pleomorphic adenoma as a benign epithelial tumour characterized by variable epithelial-mesenchymal transition, secretion/differentiation and metaplasia.

Canalicular adenoma: a clinicopathologic and immunohistochemical analysis of 67 cases with a review of the literature

There is a lack of a comprehensive immunohistochemical (IHC) analysis of canalicular adenoma (CanAd), especially when combined with a description of the unique histologic features. Given the usual small biopsies, IHC may be useful in distinguishing CanAd from other tumors in the differential diagnosis. Retrospective. The patients included 54 females and 13 males (4.2:1), aged 43-90 years, with a mean age at presentation of 69.9 years. Clinical presentation was generally a mass (n = 61) slowly increasing in size (mean 38.5 months), affecting the upper lip (n = 46), buccal mucosa (n = 17) or palate (n = 4), involving the right (n = 29), left (n = 24) or midline (n = 9), without any major salivary gland tumors. The tumors ranged in size from 0.2 to 3 cm (mean 1.2 cm). Most tumors were multilobular or bosselated (76 %), often surrounded by a capsule. Histologically, the tumors were characterized by cystic spaces, tumor cords with beading, tubule formation, and by the presence of luminal squamous balls (n = 41). The cells were cuboidal to columnar with stippled chromatin. Mitoses were inconspicuous. A myxoid stroma (n = 64), sclerosis (n = 42), luminal hemorrhage (n = 51), and luminal microliths (calcifications) (n = 33) were characteristic. Nine (13.4 %) were multifocal. CanAd showed the following characteristic immunohistochemistry findings: CK-pan and S100 protein (strong, diffuse reaction); peripheral or luminal GFAP reaction; CK5/6 and p16 luminal squamous ball reaction; SOX10 nuclear reaction; cytoplasmic p63 reaction. CanAd are unique minor salivary gland tumors showing a distinct architecture and phenotype. They predilect to older women, with the majority multilobulated and affecting the upper lip, multifocal in 13 %; no major salivary gland tumors were identified. S100 protein, CK-pan, GFAP and SOX10 are positive, with luminal squamous balls highlighted by CK5/6 or p16.

Canalicular adenoma--search for the cell of origin: ultrastructural and immunohistochemical analysis of 7 cases and review of the literature

Canalicular adenoma (CA) is a rare, benign epithelial neoplasm of the salivary glands. Historically considered to be a variant of basal cell adenoma, this "monomorphic" adenoma has a distinct clinical, morphologic, and immunohistochemical profile. The putative cell of origin remains a topic of debate. A combination of morphology, immunohistochemistry, and ultrastructural analyses have been employed to determine histogenesis, but the interpretations of these studies have implicated multiple different cell types along the salivary gland duct as the cell of origin. The authors sought to further characterize CA using electron microscopy, immunohistochemistry, and special and immuno-stains on 7 cases. Their morphologic, immunohistochemical, and ultrastructural findings support a cell of origin demonstrating features of both the intercalated duct cells and the striated duct luminal epithelial cells.

Low-grade salivary duct carcinoma or low-grade intraductal carcinoma? Review of the literature

Low-grade salivary duct carcinoma (LG-SDC) is a rare neoplasm characterized by predominant intraductal growth, luminal ductal phenotype, bland microscopic features, and favorable clinical behavior with an appearance reminiscent of florid to atypical ductal hyperplasia to low grade intraductal breast carcinoma. LG-SDC is composed of multiple cysts, cribriform architecture with "Roman Bridges", "pseudocribriform" proliferations with floppy fenestrations or irregular slits, micropapillae with epithelial tufts, fibrovascular cores, and solid areas. Most of the tumor cells are small to medium sized with pale eosinophilic cytoplasm, and round to oval nuclei, which may contain finely dispersed or dark condensed chromatin. Foci of intermediate to high grade atypia, and invasive carcinoma or micro-invasion have been reported in up to 23 % of cases. The neoplastic cells have a ductal phenotype with coexpression of keratins and S100 protein and are surrounded by a layer of myoepithelial cells in non-invasive cases. The main differential diagnosis of LG-SDC includes cystadenoma, cystadenocarcinoma, sclerosing polycystic adenosis, salivary duct carcinoma in situ/high-grade intraductal carcinoma, and papillary-cystic variant of acinic cell carcinoma. There is no published data supporting the continuous classification of LG-SDC as a variant of cystadenocarcinoma. Given that most LG-SDC are non-invasive neoplasms; the terms "cribriform cystadenocarcinoma" and LG-SDC should be replaced by "low-grade intraductal carcinoma" (LG-IDC) of salivary gland or "low-grade intraductal carcinoma with areas of invasive carcinoma" in those cases with evidence of invasive carcinoma.

Fat-containing salivary gland tumors: a review

Fat-containing tumors of the salivary glands are uncommon. Their wide histological spectrum varies from pure lipomatous neoplasms similar to their cutaneous and soft tissue counterparts to mixed lipoepithelial lesions specific to the salivary glands. With few exceptions, these uncommon lesions affect mainly the elderly, with a mean age at presentation of ≥ 50 years and show a predilection for males. A few cases occur in childhood; some of them represent congenital lesions. In decreasing order of frequency, ordinary (soft-tissue type) lipoma, oncocytic lipoadenoma, non-oncocytic sialolipoma, and pleomorphic adenoma/myoepithelioma with extensive lipometaplasia are the main variants of fat containing tumors encountered in the salivary glands. While pleomorphic adenoma/myoepithelioma with lipometaplasia behave in the same way as their non-fat-containing counterparts, other lipomatous salivary gland tumors listed above are cured with simple excision and do not carry a risk of recurrence. Other lipoma variants (spindle cell lipoma, osteolipoma, fibrolipoma, angiolipoma, pleomorphic lipoma, lipoblastoma and hibernoma) are exceptionally rare in the salivary gland. Atypical lipomatous tumors/liposarcoma have been only rarely reported in the salivary gland and they behave in a similar fashion to their soft-tissue counterparts. Diffuse lipomatosis and lobular fatty atrophy are the two tumor-like lesions that might closely mimic sialolipoma, particularly in limited biopsy material without knowledge of the gross findings. This review summarizes the clinicopathological features of the main types of salivary fat-containing lesions and discusses their differential diagnoses.

Mammary analog secretory carcinoma of salivary glands: a report of 2 cases with expression of basal/myoepithelial markers (calponin, CD10 and p63 protein)

Mammary analog secretory carcinoma (MASC) of salivary glands is a recently described neoplasm with favorable outcome. We describe 2 cases of MASC occurring in a 34-year-old female and a 58-year-old male, both presenting with a swelling of upper lip and right parotid gland, measuring 15 and 20mm, respectively. Without adjuvant treatment, both patients have been free of disease for 15 months and 12 months since the operation. Microscopically, both tumors were cystic and showed tubular and cystopapillary architecture. The tumor cells had round to oval nuclei and eosinophilic cytoplasm. Presence of eosinophilic material was evident within cystic spaces. Immunohistochemically, both tumors expressed cytokeratins (CK), CK7, CK8, CK18, epithelial membrane antigen, vimentin, S-100 protein, mammaglobin, and STAT5a (signal transducer and activator of transcription 5a). Interestingly, both tumors showed variable expression of basal/myoepithelial markers. In one case, we observed diffuse expression of calponin and focal expression of p63 whereas expression of CD10 was absent. In the second case, the staining of calponin was negative, but there was focal expression of both p63 and CD10. Both neoplasms harbored the ETV6-NTRK3 fusion transcript as proved by RT-PCR. Although previously reported only rarely, we conclude that MASC may show expression of basal/myoepithelial markers.

Lipomatous salivary gland tumors: a series of 31 cases spanning their morphologic spectrum with emphasis on sialolipoma and oncocytic lipoadenoma

Lipomatous neoplasms of the salivary glands are rare. Their wide histologic spectrum has not been sufficiently studied. We collected 31 fat-containing salivary gland lesions excluding pleomorphic adenoma and myoepithelioma with lipometaplasia. There were 19 male and 12 female patients aged 7 to 89 years (mean, 53 y). Tumors originated in the parotid (n=29) and the submandibular (n=2) gland. On the basis of the proportion and distribution of adipose tissue and the epithelial type, tumors could be categorized into 3 main groups: ordinary lipoma (n=20) identical to soft tissue lipoma but located within the salivary gland, oncocytic lipoadenoma (n=6) composed predominantly of oncocytes with variable fatty component, nononcocytic sialolipoma (n=4) composed of lobular fatty tissue (≥70%) with evenly distributed normal salivary tissue recapitulating the composition of normal salivary glands and microcystic lipoadenoma (n=1) composed of cystic ducts admixed with adipose tissue. The mean tumor size was 3.3, 3.8, and 2.9 cm for lipoma, oncocytic lipoadenoma, and nononcocytic sialolipoma, respectively. Associated diseases included Madelung disease with bilateral atypical lipomatous tumors of the neck and bilateral parotid lipoma (1), oncocytic lipoadenoma after irradiation for sinonasal adenocarcinoma (1), and periparotideal lipoma excised years before oncocytic lipoadenoma (1) and nononcocytic sialolipoma (1). No recurrence was recorded at a mean follow-up of 72 months (range, 6 to 184 mo). Sebaceous islands were seen in 5/6 oncocytic lipoadenomas and in 2/4 sialolipomas. Periductal inflammation/fibrosis was common in sialolipoma and oncocytic lipoadenoma. This study demonstrates the wide morphologic spectrum of fatty salivary gland lesions. Oncocytic lipoadenoma is an epithelial-predominant tumor that is distinct from the fat-dominated nononcocytic sialolipoma, but the 2 types seem to merge in some cases.

Intercalated duct lesion of the parotid

Intercalated duct lesions of the salivary glands are rare tumors that were only recently described. However, their resemblance to other salivary gland tumors as well as their association with malignant neoplasms makes their detection, treatment, and follow-up paramount. We present the case of a 63-year-old woman diagnosed with an intercalated duct lesion of the parotid. Her case is illustrative of the difficulty and importance of an accurate pathologic diagnosis in the management of patients with these lesions.

Mammary analog secretory carcinoma of salivary gland origin with the ETV6 gene rearrangement by FISH: expanded morphologic and immunohistochemical spectrum of a recently described entity

Mammary analog secretory carcinoma (MASC) is a recently described tumor predominantly arising in the parotid gland. These tumors represent locally invasive malignancies with microcystic architecture, low-grade nuclei, and granular pink vacuolated cytoplasm. They display strong vimentin and S100 positivity and harbor an identical t(12;15)(p13;q25) to their breast counterpart, leading to a ETV6-NTRK3 fusion oncogene. These features help exclude the most important differential diagnostic considerations, namely, acinic cell carcinoma (AciCC) and low-grade cystadenocarcinoma, not otherwise specified. Here we present a series of 7 recent examples of MASC, which showed features not previously described. These 7 cases were observed in patients ranging in age from 14 to 77 years (mean, 40 y), occurred almost exclusively in male patients (6:1), and showed >50% (4 of 7 cases) involvement of the oral cavity, with only 2 arising in the parotid. The remaining case is the first reported in the submandibular gland. The tumors showed a variety of patterns including single macrocysts, combined macrocystic and microcystic spaces, and solid architecture. They showed prominent hobnailing in the cystic areas. Secretions within the cysts and tubular areas tended to be positive for periodic acid schiff, periodic acid schiff diastage and mucicarmine, the latter also showing occasional intracytoplasmic mucin droplets, a feature not previously recognized. One case showed prominent mucinous differentiation, which, coupled with high-molecular-weight keratins (HMWK) positivity, mimicked mucoepidermoid carcinoma (MEC). The tumors were generally positive for HMWK (6 of 7), S100 (5 of 7), vimentin, CK19, and other epithelial markers. The finding of duct involvement, proven with an incomplete p63-positive basal layer surrounding a minority of tumor cell nests and cysts, raised the possibility of a ductal epithelial origin for MASC. Alternatively, this could represent secondary ductal involvement by tumor. All cases showed rearrangement of the ETV6 gene by fluorescence in situ hybridization, confirming the diagnosis of MASC. These findings reinforce MASC as a unique low-grade salivary gland tumor entity with morphologic overlap with AciCC, MEC, and cystadenocarcinoma.