Circumscribed salivary duct carcinoma of the palate: a non-threatening variant

Salivary Gland Intraductal Carcinoma: How Do 183 Reported Cases Fit Into a Developing Classification

Salivary gland intraductal carcinoma (IDC) is a very uncommon group of neoplasms. Many names, variations in diagnostic criteria, and newly observed molecular findings (including NCOA4 :: RET , TRIM27 :: RET , HRAS point mutations, and PIK3CA pathway alterations) have generated further confusion in being able to recognize and categorize this group of tumors. Different histologic appearances and patterns of growth suggest there is more than one tumor category, with intercalated duct, apocrine, oncocytic, and hybrid features seen. Frankly destructive invasion further complicates the category, as the name "intraductal" would suggest an "in situ" neoplasm. Recent evidence on fusion-positive IDC demonstrates the same molecular underpinnings in both the ductal and the myoepithelial cells, which aids in further separating these tumors. This article summarizes the historical group of 183 neoplasms classified under the umbrella of IDC and highlights the unique histologic, immunohistochemistry, and molecular features that may further guide nomenclature standardization and harmonization.

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.

Low-grade intraductal carcinoma of salivary glands: A systematic review of this rare entity

Background

Low-grade intraductal carcinomas are rare, malign tumors of salivary glands most commonly affecting parotid gland. It is a slow-growing tumor considered with a favourable prognosis after surgical excision.

Methods

To define the characteristics and management of low-grade intraductal carcinoma a systematic review was performed using the electronic databases Pubmed, Cochrane and Scopus. A new case report was also described.

Results

Including this case the review of literature identified only 54 cases reported thus far. Demographics, clinical presentation, diagnostic tools, treatment, follow-up and recurrence rate, histological and immunohistochemical patterns of this kind of tumor were summarized.

Conclusion

Low-grade intraductal carcinoma has already been well defined but is important to focus on the fact that in few cases component of high-grade infiltrations have been reported: this may modify surgical approach because a simple tumorectomy may not be enough.

Envisioning the next WHO head and neck classification

The next WHO classification should abandon "salivary duct carcinoma"; conventional salivary duct carcinoma should be classified as "high-grade salivary duct carcinoma". Low-grade salivary duct carcinoma should replace the current nosology of "low-grade cribriform cystadenocarcinoma". Cystadenocarcinoma should be classified with the descriptor "Not Otherwise Specified" and should be considered an exclusionary diagnostic category. On the other hand, "Not Otherwise Specified" does not fit for hyalinizing clear cell carcinoma (HCCC). The EWSR1-ATF1 fusion is specific for HCCC within the context of salivary neoplasia. We recommend adding "hyalinizing" even though this feature is not present in all cases; the benefit of which is the mental association with a salivary clear cell malignancy. Sinonasal Renal Cell-like Adenocarcinoma (SNRCLA) is a distinct clear cell neoplasm and should be added to the next WHO classification. Future studies will bear out whether SNRCLA is even a low-grade carcinoma, or may be reclassified as "adenoma". Lastly, the next WHO monograph should include the Risk Model in the general introductory statements on oral squamous cell carcinoma, under a subheading of "Histological Prognosticators". The positive predictive value for developing locoregional recurrence in patients with low-stage oral cavity squamous carcinoma (OSCC) and "worst pattern of invasion type-5" (WPOI-5) is 42 %. Low-stage high-risk OSCC with a combination of features other than WPOI-5 is associated with 32 % likelihood for locoregional progression. WPOI-5 also predicts occult metastatic disease (p = 0.0001, Chi squared, 2 DF). Thus the Risk Model can also be used to make decisions regarding staged elective neck dissections.

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.

Low-grade Intraductal Carcinoma of Salivary Gland

Low-grade intraductal carcinomas (LG-IDCs) of salivary gland are rare neoplasms that resemble atypical ductal hyperplasia or LG-IDCs of the breast. They have been referred to as "low-grade salivary duct carcinomas" or "low-grade cribriform cystadenocarcinomas." Herein, we describe 3 additional cases of LG-IDCs, 2 were pure intraductal carcinomas, although 1 demonstrated increasing cytologic atypia and progression to an invasive adenosquamous carcinoma. The latter had been present for 7 years before demonstrating clinical and pathologic progression to a widely invasive malignancy. The intraductal component in all cases exhibited a remarkable degree of apocrine differentiation. The tumor cells were positive for AE1:AE3, Cam 5.2, high molecular weight keratin, CK7, CK19, BRST-2, and androgen receptors (ARs). S-100 was positive in 2 cases and negative in 1 case. The intraductal neoplastic cells were surrounded by myoepithelial cells positive for CK14, actins, calponin, high molecular weight keratin, and p63. All the tumors were negative for CK20, estrogen and progesterone receptors, Her2Neu, and p53. Extensive apocrine differentiation, expression of ARs, CK7, and CK19, and progression to a widely invasive carcinoma after a long clinical latency have not been reported in LG-IDCs previously. These tumors share some histopathologic features with salivary duct carcinoma including apocrine differentiation, and expression of ARs and BRST-2. The terms "low-grade salivary duct carcinomas" and "low-grade cribriform cystadenocarcinomas" should be abandoned in favor of LG-IDC of salivary gland, which better reflects their predominantly noninvasive, intraductal nature.