Polymorphous low-grade adenocarcinoma: a study of 40 cases with long-term follow up and an evaluation of the importance of papillary areas

High-Grade Transformation and Carcinosarcoma: A Review of Two Forms of Advanced Progression in the Salivary Gland

CONTEXT.—

High-grade transformation, previously known as dedifferentiation, in salivary gland carcinoma and carcinosarcoma ex pleomorphic adenoma is a rare phenomenon. It is, however, clinically relevant and affects treatment and prognosis.

OBJECTIVE.—

To review the existing literature, describe the histologic and immunophenotypic features, and highlight the diagnostic criteria of high-grade transformation in various salivary gland carcinomas and carcinosarcomas; to review its effect on clinical presentation and prognosis; and to review relevant molecular characteristics and recent concepts and advances.

DATA SOURCES.—

Literature search in PubMed using key words such as "high-grade transformation," "dedifferentiation," and "carcinosarcoma" in salivary gland. Relevant articles were reviewed, and additional articles were curated from the references of these articles.

CONCLUSIONS.—

High-grade transformation occurs rarely but has a significant impact on prognosis and management. By microscopy, the high-grade area is usually a distinct nodule and shows solid and nested architecture, cellular atypia, high mitotic count, and necrosis. The molecular features are not well established. Carcinosarcoma almost always arises in a pleomorphic adenoma and likely follows an adenoma-carcinoma-sarcoma pathway.

Polymorphous adenocarcinoma of the buccal space-Rare, reported case from our institute

ABSTRACT

Polymorphous adenocarcinoma (PAC) of head and neck tumors is a rare salivary gland neoplasm of indolent course. We reported a 63-year-old female who presented as an asymptomatic mass in buccal space. The patient, after metastatic workup, underwent complete excision of the lesion with a negative margin. Postoperative histopathology and immunohistochemistry (IHC) were suggestive of PAC. Presently patient is on follow-up as per a multidisciplinary team decision. To conclude, PAC diagnosis is challenging due to morphological diversity, which necessities IHC. In addition, presently treatment of choice as per the literature review is complete excision.

Polymorphous adenocarcinoma of minor salivary gland: Case presentation and literature review

INTRODUCTION AND IMPORTANCE

Polymorphous low-grade adenocarcinoma (PLGA) is a rare neoplasm arising from minor salivary glands, representing approximately 3 % of head and neck tumors. The clinical presentation of PLGA is defined as a painless, slow-growing tumor, mostly occurring in the palate. We report a case of PLGA with a rare presentation.

CASE PRESENTATION

A 76-year-old male, known case of hepatitis B, diabetes, and hypertension, presented to the emergency department complaining of spitting blood and dysphagia. Imaging showed a heterogeneous enlarged left tonsil with hyperemia of the mucosa, and air foci. Biopsy with excisional biopsy confirmed the diagnosis of PLGA. The patient underwent completion tonsillectomy and selective neck dissection which yielded tonsillar tissue with underlying PLGA, and reactive lymph nodes with no malignant tissue respectively, margins were negative for malignancy.

CLINICAL DISCUSSION

Polymorphous low-grade adenocarcinoma is a rare lesion with clinical behavior resembling that of a benign neoplasm. Predominantly occurring in the oral cavity, especially on the hard palate, buccal mucosa, and retromolar region, with fewer cases in the upper lip. Occurrence in the nasopharynx and oropharynx is rare. PLGA presents as painless slow-growing masses, typically in females aged 50-60. Local excision with careful margin evaluation is the preferred treatment, with good prognosis compared to other carcinomas.

CONCLUSION

PLGA is rare, with limited reported case from around the world. It is mostly seen in adults between their fifth and sixth decades with female predominance. PLGA is diagnosed using imaging, immunohistochemistry. Owing to the limited cases there is no standard approach to treating PLGA. However, most cases are managed with local excision and showed an excellent response in terms of tumor nonrecurrence.

Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners

Polymorphous adenocarcinoma (PAC) is a common, usually low-grade salivary gland carcinoma. While conventional PACs are most associated with PRKD1 p.E710D hotspot mutations, the cribriform subtype is often associated with gene fusions in PRKD1, PRKD2, or PRKD3. These fusions have been primarily identified by fluorescence in situ hybridization (FISH) analysis, with a minority evaluated by next-generation sequencing (NGS). Many of the reported fusions were detected by break-apart FISH probes and therefore have unknown partners or were negative by FISH altogether. In this study, we aimed to further characterize the fusions associated with PAC with NGS. Fifty-four PACs (exclusively cribriform and mixed/intermediate types to enrich the study for fusion-positive cases) were identified and subjected to NGS. Fifty-one cases were successfully sequenced, 28 of which demonstrated gene fusions involving PRKD1, PRKD2, or PRKD3. There were 10 cases with the PRKD1 p.E710D mutation. We identified a diverse group of fusion partners, including 13 novel partners, 3 of which were recurrent. The most common partners for the PRKD genes were ARID1A and ARID1B. The wide variety of involved genes is unlike in other salivary gland malignancies and warrants a broader strategy of sequencing for molecular confirmation for particularly challenging cases, as our NGS study shows.

High-grade transformation of a polymorphous adenocarcinoma of the salivary gland: a case report and review of the literature

Background

Polymorphous adenocarcinoma (PAC) represents the second most widespread neoplasm of the minor salivary glands. These tumors rarely develop a histological progression from low-grade to high-grade malignancy, named "high-grade transformation" (HGT). Only nine cases are described in literature.

Case description

Here, we describe the case of a 76-year-old male patient with a PAC recurrence of the oral floor displaying HGT, and we explore the tumor cytomorphological features, genomic profiling, and the patient's clinical management. The tumor mass was characterized by poorly atypical cellular elements with vesicular nuclei and comedonecrosis foci. The growth pattern was predominantly solid, tubular, and cribriform. The lesion did not show microsatellite instability or targeted molecular alterations. The case was successfully treated with radical surgery followed by radiotherapy.

Conclusion

We report for the first time the recurrence of a PAC with HGT arising in the oral floor after 20 years from the primary lesion. These preliminary data and the literature analysis enhance the knowledge of this extremely rare disease.

Mistaken identity of polymorphous low-grade adenocarcinoma treated as periapical lesion in anterior maxilla: A case report

This report presents a rare case of polymorphous low-grade adenocarcinoma (PLGA) in the anterior maxilla, mimicking a periapical lesion. A 56-year-old male reported with a painless swelling in the maxillary right canine-premolar region. The patient gave a history of root canal therapy for the same teeth one month ago. On intraoral examination, the involved teeth were restored with ceramic crowns. Radiographic examination revealed inadequate obturation with an ill-defined radiolucency in the periapical region. 3D cone beam computer tomography (CBCT) revealed erosion of the buccal cortical plate near the apices of the roots. Endodontic re-treatment was performed on both the teeth. Following this, the lesion was excised and submitted for histopathological analysis wherein it was identified as PLGA. Computerised tomographic (CT) scan and positron emission tomography scan (PET) results showed no regional or distant metastasis. Under general anaesthesia, the teeth were extracted, and wide surgical excision of the anterior maxilla was done till the healthy bone was exposed. Healing was uneventful during the follow-up period.

Salivary Gland Polymorphous Adenocarcinoma: Clinicopathological Features and Gene Alterations in 36 Japanese Patients

OBJECTIVES

Polymorphous adenocarcinoma (PAC) is a common intraoral minor salivary gland carcinoma in Western countries but is extremely rare in Japan. The current study aimed to characterize the clinicopathological features and status of molecular alterations of PAC-associated genes, such as (e.g., PRKD1/2/3, ARID1A, and DDX3X) in a large cohort of Japanese patients with PAC.

MATERIALS AND METHODS

We examined the cases of 36 Japanese patients with salivary gland PAC and 26 cases involving histopathological mimics. To detect gene splits, fluorescence in situ hybridization was carried out for PAC-associated genes. Additionally, we applied a SNaPshot multiplex assay to identify PRKD1 hotspot mutations.

RESULTS

This study revealed the indolent clinical course of PAC with a high 10-year overall survival rate (92.9%), accompanied by occasional local recurrences and cervical lymph node metastasis (both 23.3%). Twenty cases (55.6%) of PAC (but none of the mimics) exhibited alterations in at least one PAC-associated gene. Rearrangement of PAC-associated genes and PRKD1 E710D were identified in 17 (47.2%) and 4 (11.1%) cases, respectively; one case showed coexisting PRKD3 split and PRKD1 E710D. In the multivariate analysis, high clinical stage (P=0.0005), the presence of prominent nucleoli (P=0.0003), and ARID1A split positivity (P=0.004) were independent risk factors for disease-free survival.

CONCLUSION

Japanese patients with PAC showed clinicopathological features similar to those reported in Western countries. This study disclosed that PAC-associated genetic alterations were common and specific findings in PACs. The diagnostic role and possible prognostic significance of PAC-associated genetic alterations in PACs were suggested.

Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis

Polymorphous adenocarcinoma (PAC) is a rare variant of minor salivary gland tumors. Because of its architectural diversity, histological diagnosis of PAC can be difficult especially for small biopsies, and immunohistochemistry is of great help in differentiating it from its histologic mimics. The aim of this study is to conduct a systematic literature review to identify reliable immunohistochemical markers for PAC. We conducted an electronic literature search of the MEDLINE, ScienceDirect, SpringerLink, and Wiley Online Library databases, covering the literature published in the period between 1988 and 2021. The eligibility criteria included case reports and retrospective studies of PAC cases with details of immunohistochemical markers. Following the search and selection process, 32 studies with 409 cases were included in this systematic review. Overall, > 90% positivity was observed for pan-cytokeratin (CK) (97.3%), CK7 (96.8%), CK7/8 (97.4%), E-cadherin (90.0%), Vimentin (92.5%), S100 (97.0%), p63 (91.7%), and SOX10 (100%), while little to no positivity was observed for CK20 (0.0%), p40 (0.0%), and GFAP (5.0%). The average MIB-1 labeling index was 3.78%. The results of this systematic review indicate that CK7+/CK20-, p63+/p40-, S100+, Vimentin+, and GFAP- immunophenotype have diagnostic value for PAC. In addition, the use of S100, MSA, p40, and c-Kit provide additional layers of information helpful to differentiate PAC from adenoid cystic carcinoma, one of challenging differential diagnoses.

How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review

BACKGROUND

Recently, histologic grade was removed from salivary tumor nomenclature by the WHO to include disease of higher grade. One such entity, cribriform adenocarcinoma (CAC), is an aggressive group of polymorphous adenocarcinoma (PAC), with frequent nodal metastasis and locoregional recurrence. We aim to examine the biologic behavior of this disease as compared with the PAC general cohort inclusive of all subtypes.

METHODS

A systematic review of the literature on polymorphous adenocarcinoma and cribriform adenocarcinoma was completed. A descriptive analysis was performed for the following predictor variables: nodal and distant metastasis, in addition to recurrence. The outcome variables, disease free recurrence, and disease specific survival, where plotted using Kaplan-Meier curves.

RESULTS

PAC and CAC both show median age of diagnosis in the sixth decade of life and a female predominance. CAC occurs most frequently in the tongue and PAC in the palate. The 2 groups show a similar biologic behavior in regards to incidence of distant metastasis (4.1 vs 5.5%), recurrence (12.5 vs 17.8%), and death from disease (3 vs 2.7%). However, there was an increased incidence of nodal metastasis in CAC (53%) as compared with that in PAC of all subtypes (14%).

CONCLUSIONS

CAC exhibits more aggressive biologic behavior as compared with the PAC cohort. Although CAC is not an officially recognized entity, these tumors likely comprise a significant portion of the cases of PAC with poor outcomes and are deserving of attention and consideration for escalation in oncologic treatment.

The Evaluation and Management of Carcinoma of the Minor Salivary Glands

There are several hundred minor salivary glands throughout the upper aerodigestive tract, aiding in lubrication and protection of the system. Compared with all tumors of the head and neck and those of the six major glands, neoplasms of the minor glands are rare. However, more than half are found to be malignant, prompting a low threshold for further work-up. This review discusses the evaluation of patients who present with masses of the minor salivary glands, including strategies for tissue diagnosis and staging. Management options for and long-term survival outcomes of the most common malignancies affecting these glands are also discussed.

High-grade Transformation/Dedifferentiation in Salivary Gland Carcinomas: Occurrence Across Subtypes and Clinical Significance

High-grade transformation (HGT) or dedifferentiation has been described in a variety of salivary gland carcinomas, including acinic cell carcinoma, secretory carcinoma, adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, polymorphous adenocarcinoma, low-grade mucoepidermoid carcinoma, and hyalinizing clear cell carcinoma. High-grade (HG) transformed tumors are composed of a conventional low-grade component characterized by specific microscopic and immunohistochemical features for the given entity, intermingled with or juxtaposed to areas of HG morphology. This is usually either poorly differentiated adenocarcinoma, carcinoma not otherwise specified, or undifferentiated carcinoma, in which the original line of differentiation is lost. The HG component is composed of solid nests of anaplastic cells with large vesicular pleomorphic nuclei, prominent nucleoli, and abundant cytoplasm. Frequent mitoses and extensive necrosis may be present. The Ki-67 labeling index is consistently higher in the HG component. The molecular genetic mechanisms responsible for HGT of salivary gland carcinomas are largely unknown, though p53 inactivation and human epidermal growth factor receptor 2 overexpression and/or gene amplification have been demonstrated in the HG component in a few examples, the frequency varies for each histologic type. Salivary gland carcinomas with HGT are more aggressive than conventional carcinomas, with a higher local recurrence rate and a poorer prognosis. They have a high propensity for cervical lymph node metastasis suggesting a need for a wider resection and neck dissection. HGT of salivary gland carcinoma can occur either at initial presentation or less commonly at the time of recurrence, sometimes following postoperative radiotherapy. The potential for HGT in almost any type of salivary gland carcinoma warrants a thorough sampling of all salivary gland malignancies to prevent oversight of a HG component.

Polymorphous Adenocarcinoma

Polymorphous adenocarcinoma (PAC) is typically originated from the minor salivary glands and is characterized by cytology uniformity and architectural diversity. PAC commonly harbors PRKD1 E710D mutation. PAC has an excellent prognosis. However, greater than or equal to 10% papillary or greater than or equal to 30% cribriform pattern is an independent adverse prognostic factor. Cribriform adenocarcinoma of salivary gland (CASG) is a controversial entity that is considered within the same histologic spectrum of PAC in current classification schemes; however, it is regarded by some pathologists as a separate entity. CASG shows a propensity to base of tongue location, a lobulated growth pattern, a predominant solid/cribriform architecture, and a high frequency of PRKD1/2/3 fusion.

Role of elective neck dissection and adjuvant radiation therapy in patients with polymorphous adenocarcinoma

PURPOSE

To evaluate the role of elective neck dissection (END) and of adjuvant radiation (aRT) in polymorphous adenocarcinoma (PAC), previously known as polymorphous low-grade adenocarcinoma (PLGA).

METHODS

Retrospective cohort study of patients in the National Cancer Database with a histology of PAC (coded as PLGA) at a head and neck site diagnosed between 2004 and 2015. Multivariable Cox proportional hazard modeling was used to assess overall survival in the overall population, and in sub-analyses of clinically N0 disease, positive resection margins, and late stage disease.

RESULTS

A total of 922 patients [66.8% female; mean (SD) age, 60.9 (13.9) years] met inclusion criteria. 74.7% of patients received surgery alone, and 18.0% received surgery and aRT. Only 7.6% of patients with clinically N0 disease received an END, with 10.6% of these having at least one positive node. END did not have a survival benefit compared to no END [HR 1.28 (0.61-2.68)]. Compared to surgery alone, aRT did not have significantly increased survival in the overall population or in late stage [HR 0.68 (0.39-1.19) and HR 0.46 (0.18-1.22), respectively]. On sub-analysis of patients with positive resection margins, aRT had a significant survival benefit compared to surgery alone [HR 0.37 (0.14-0.99)].

CONCLUSION

PAC is a rare, slow-growing malignant tumor typically treated with surgical excision, with undefined indications for END or aRT. Our findings show END to not have a benefit to overall survival. In patients with positive resection margins, there was a survival benefit for aRT.

Histologic Classification and Molecular Signature of Polymorphous Adenocarcinoma (PAC) and Cribriform Adenocarcinoma of Salivary Gland (CASG): An International Interobserver Study

Polymorphous adenocarcinoma (PAC) shows histologic diversity with streaming and targetoid features whereas cribriform adenocarcinoma of salivary gland (CASG) demonstrates predominantly cribriform and solid patterns with glomeruloid structures and optically clear nuclei. Opinions diverge on whether CASG represents a separate entity or a variant of PAC. We aimed to assess the level of agreement among 25 expert Head and Neck pathologists in classifying these tumors. Digital slides of 48 cases were reviewed and classified as: PAC, CASG, tumors with ≥50% of papillary architecture (PAP), and tumors with indeterminate features (IND). The consensus diagnoses were correlated with a previously reported molecular alteration. The consensus diagnoses were PAC in 18/48, CASG in16/48, PAP in 3/48, and IND in 11/48. There was a fair interobserver agreement in classifying the tumors (κ=0.370). The full consensus was achieved in 3 (6%) cases, all of which were classified as PAC. A moderate agreement was reached for PAC (κ=0.504) and PAP (κ=0.561), and a fair agreement was reached for CASG (κ=0.390). IND had only slight diagnostic concordance (κ=0.091). PAC predominantly harbored PRKD1 hotspot mutation, whereas CASG was associated with fusion involving PRKD1, PRKD2, or PRKD3. However, such molecular events were not exclusive as 7% of PAC had fusion and 13% of CASG had mutation. In conclusion, a fair to moderate interobserver agreement can be achieved in classifying PAC and CASG. However, a subset (23%) showed indeterminate features and was difficult to place along the morphologic spectrum of PAC/CASG among expert pathologists. This may explain the controversy in classifying these tumors.

Biphasic Thyroid-Like Low-Grade Nasopharyngeal Papillary Adenocarcinoma with a Prominent Spindle Cell Component: A Case Report

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TLLG-NPPA) is a distinctly rare malignancy of the nasopharynx. Morphologically and immunophenotypically, TLLG-NPPA resembles papillary thyroid carcinoma (PTC) and is characterized by a papillary architecture with PTC-like nuclear features and thyroid transcription factor-1 expression. Recently, some cases of TLLG-NPPA with a spindle cell component have been reported. In this study, we report a very interesting case of biphasic TLLG-NPPA that was predominantly composed of spindle cells, with comprehensive analyses of its clinical, pathological, and immunophenotypical features. A 50-year-old woman presented with a sensation of a foreign body in the nasopharynx. Nasopharyngoscopy and computed tomography demonstrated a pedunculated mass arising from the nasopharyngeal roof. Based on the clinical impression of a nasopharyngeal tumor, an excisional biopsy was performed. At low-power magnification, the nasopharyngeal mass consisted of papillary tumor tissue, the growth pattern and architecture of which resembled those of PTC. The papillae were complex and packed tightly with fibrovascular cores. At high-power magnification, each papillary structure was lined with a pseudostratified cuboidal-to-columnar epithelium. The tumor cell nuclei frequently showed a ground-glass appearance, intranuclear grooves, pseudoinclusions, and membrane thickening and irregularity, resembling the characteristic nuclear morphology of PTC. These histological features were compatible with TLLG-NPPA. Intriguingly, in between the papillary components were spindle cells that appeared very similar to the glandular epithelial cells that imperceptibly merged with the papillary component. This spindle cell component comprised two-thirds of the entire tumor volume. The nuclear morphology of the spindle cell component was similar to that of the papillary component. On immunostaining, both the papillary and spindle cell components were diffusely and strongly positive for thyroid transcription factor-1, cytokeratin 7, cytokeratin 19, vimentin, and Hector Battifora mesothelial-1. In contrast, the tumor cells tested negative for p63, p40, smooth muscle actin, S-100, cytokeratin 5/6, thyroglobulin, BRAF V600E, and Epstein–Barr virus-encoded small RNAs. Only two cases of biphasic TLLG-NPPA exhibiting a prominent spindle cell component had been reported previously in the English literature. When the pathologist receives a primary nasopharyngeal mass with the aforementioned histological features, particularly biopsy specimens with predominant spindle cells, biphasic TLLG-NPPA should be considered in the differential diagnosis. By describing its detailed clinicopathological characteristics, we anticipate that this report will expand the existing knowledge on the spindle cell component associated with TLLG-NPPA.

Major and minor salivary gland tumours

Salivary glands carcinomas are very rare epithelial malignant tumors. In 2013 in Europe, 7800 new diagnoses were estimated, 8.5 % of all head and neck cancer. The last WHO classification (2017) counts more than 20 malignant histotypes, this variety as well as the rarity of some of them needs a skilled pathologist for diagnosis. Surgery remains the mainstay of management followed by radiation in high-grade and high-risk pathological features cases. The intensity modulated radiotherapy (IMRT) should be preferred over conformational radiotherapy techniques as adjuvant and exclusive treatment in advanced cases. Particle radiotherapy (i.e. protons, carbon ions) can have a role in advanced/unresectable disease since it was proved to have better results over photons in loco-regional control both in adenoid cystic carcinoma and in other histotypes. Although chemotherapy is still the most frequent treatment for metastatic patients, several new compounds (i.e. anti-angiogenic agents, tailored agents, checkpoint inhibitors) are under investigation.

Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes

Polymorphous adenocarcinoma (PAC) and cribriform adenocarcinoma of (minor) salivary gland (CASG) are salivary gland tumors with overlapping spectrum of morphology. Whether these represent distinct entities or a histologic spectrum of the same tumor remains contentious. PACs harbor recurrent PRKD1 E710D hotspot mutations in >70% of cases, whereas 80% of CASGs display rearrangements involving PRKD1, PRKD2, or PRKD3 (PRKD1/2/3). We studied the molecular and morphologic features of 37 PACs/CASGs, seeking to identify the associations among genotype, histologic phenotype, and classification. DNA was subjected to Sanger sequencing analysis of the PRKD1 hotspot locus. Fluorescence in situ hybridization (FISH) analysis for PRKD1/2/3 was performed using dual-color break-apart probes. Tumors were classified into four categories as described previously: PAC, CASG, tumor with indeterminate features (TIF), and tumor with a predominant papillary pattern (TPPP). PRKD1 E710D hotspot mutations were identified in 56%, 20%, 43% and 0% of PACs, CASGs, TIFs, and TPPPs, respectively. FISH demonstrated PRKD1/2/3 rearrangements in 13%, 78%, 36%, and 75% of PACs, CASGs, TIFs, and TPPPs, respectively. Histologically, fusion-positive tumors were associated with a high percentage of papillary growth, low percentage of single filing arrangement, a propensity of base of tongue location, and frequent (50%) lymph node metastasis, compared with the mutation-related tumors which had negligible nodal metastasis risk. Our results demonstrated that (1) PACs/CASGs are underpinned by genetic alterations affecting PRKD genes; (2) despite the associations between PAC and PRKD1 hotspot mutations and CASG and PRKD1/2/3 fusion, such distinction is not absolute; and (3) there is of a novel genotypic-phenotypic association whereby fusion-positive tumors are usually located in the base of the tongue, show papillary architecture and have a high risk of nodal metastasis. Genetic analysis of PRKD genes appears to be useful characterizing this spectrum of tumors, not only histologically but also clinically identifying those tumors with high risk of nodal metastasis.

Polymorphous adenocarcinoma of salivary glands

OBJECTIVE

Polymorphous adenocarcinoma of salivary gland (PAC) is rare. Despite being described as a low risk histology, some patients develop regional and distant metastasis. More aggressive behavior has been attributed to a PAC subcategory called cribriform adenocarcinoma of minor salivary glands (CAMSG). We examined oncological outcomes of PAC.

PATIENTS AND METHODS

Fifty-seven patients with PAC were identified from an institutional database of 884 patients surgically treated for salivary gland malignancies from 1985 to 2015. Detailed histopathological analysis was performed. Survival outcomes were calculated using the Kaplan-Meier method. Factors predictive of recurrence were identified using the Cox proportional hazard method.

RESULTS

Fifty-four (95%) had tumors of minor salivary gland origin; the most frequent location was the oral cavity in 41 (76%), specifically the hard palate in 32 (55%). Forty-six patients (81%) were clinical T1-T2; 3 (5%) had a clinically positive neck. Thirty-two patients (56%) were classified as PAC and 14 (25%) as CAMSG. Forty-four patients (77%) had surgery alone; 13 (23%) had surgery and postoperative radiotherapy. The 5- and 10-year overall survival and disease-specific survival were 88% and 79% and 98% and 94%, respectively (median follow up 84 [1-159] months); 5- and 10-year recurrence-free survival were 93% and 88%, respectively. Univariate analysis showed male sex, III/IV stage, and CASMG variant had increased incidence of recurrence but were not statistically significant.

CONCLUSION

PAC of the salivary glands is an indolent disease with good survival outcomes. Recurrence is uncommon and tends to occur late. Long-term follow-up is indicated in patients with this disease.

Salivary Gland Malignancies

Salivary gland tumors are rare pathologic entities that are derived from major and minor salivary gland tissue located throughout the head and neck region. These tumors are distinctly heterogenous, comprising numerous cell types, especially those deemed malignant. The incidence of malignant salivary gland tumors is widely distributed in both adult and pediatric patient populations. Accurate diagnosis and optimal treatment of these tumors pose challenges to both interpreting pathologists and ablative surgeons. This article examines the epidemiology and pathology of malignant tumors of the major and minor salivary glands and provides recommendations for the most successful treatment approaches.

Historical Evolution of the Polymorphous Adenocarcinoma

The 2017 World Health Organization Classification of Head and Neck Tumors introduced for the first time the diagnostic terminology "cribriform variant of polymorphous adenocarcinoma". This nomenclature attempts to reconciliate the ongoing taxonomical controversy related to cribriform adenocarcinoma of tongue. In order to better understand this classification conundrum, it is imperative for pathologist to comprehend the historical evolution of polymorphous adenocarcinoma formerly known as polymorphous "low grade" adenocarcinoma. This review highlights our understanding of these tumors since their origins.

Polymorphous adenocarcinoma of the salivary glands: reappraisal and update

Although relatively rare, polymorphous adenocarcinoma (PAC) is likely the second most common malignancy of the minor salivary glands (MiSG). The diagnosis is mainly based on an incisional biopsy. The optimal treatment comprises wide surgical excision, often with adjuvant radiotherapy. In general, PAC has a good prognosis. Previously, PAC was referred to as polymorphous low-grade adenocarcinoma (PLGA), but the new WHO classification of salivary gland tumours has also included under the PAC subheading, the so-called cribriform adenocarcinoma of minor salivary glands (CAMSG). This approach raised controversy, predominantly because of possible differences in clinical behaviour. For example, PLGA (PAC, classical variant) only rarely metastasizes, whereas CAMSG  often shows metastases to the neck lymph nodes. Given the controversy, this review reappraises the definition, epidemiology, clinical presentation, diagnostic work-up, genetics, treatment modalities, and prognosis of PAC of the salivary glands with a particular focus on contrasting differences with CAMSG.

Palatal Polymorphous Adenocarcinoma with High-Grade Transformation: A Case Report and Literature Review

Polymorphous adenocarcinoma (PAC) is the second most common intraoral malignant neoplasm of the minor salivary glands. However, it is very rare for PAC to show high-grade transformation (HGT) and to our knowledge, the English literature only seven reported cases. HGT tends to be observed when PAC recurs, and it is extremely rare to be seen at initial presentation. Here we report a 43-year-old Japanese male patient with PAC of the right palate showing HGT at initial presentation. Histopathologically, the tumor was characterized by a prominent solid and papillary-cystic growth pattern, with nuclear atypia and necrosis in area of HGT. The immunohistochemical staining pattern was consistent with PAC, as the tumor cells showed diffuse positivity for cytokeratin, vimentin and S-100, and focal positivity for bcl-2, ɑ-SMA and EMA. The tumor cells in HGT areas were markedly positive for AR and Ki-67 (about 40%/HPF), and also focally positive for cyclin D1 and p53, whereas HER2/neu, ER, PgR, p63, D2-40, GCDFP-15, and mitochondria were negative. Here we present a very rare case of palatal PAC with HGT at initial presentation.

Predictors of Outcome in the Phenotypic Spectrum of Polymorphous Low-grade Adenocarcinoma (PLGA) and Cribriform Adenocarcinoma of Salivary Gland (CASG): A Retrospective Study of 69 Patients

Polymorphous low-grade adenocarcinoma (PLGA) shows histologic diversity with fascicular and targetoid features while cribriform adenocarcinoma of salivary gland (CASG) demonstrates predominant cribriform and solid patterns with glomeruloid appearance and optical clear nuclei. The current study is designed to identify pathologic features that may predict clinical outcome in 69 PLGA/CASG. Seven patients had recurrences or distant metastasis, including 3 local recurrences, 2 nodal metastases, and 2 distant metastases. The following histologic factors predicted disease-free survival on univariate analysis: tumor size, bone invasion, lymphovascular invasion, tumor necrosis, ≥10% papillary pattern, and ≥30% cribriform pattern. On multivariate analysis, 10% of papillary pattern and 30% cribriform pattern were independent prognostic factors of disease-free survival. Histologic classification of the 69 tumors (based on the prior reported definition of CASG) showed 21 CASGs (30%), 23 PLGAs (33%), and 22 (32%) with indeterminate features of PLGA and CASG. In addition, 3 (4%) tumors demonstrated a predominant papillary pattern (≥50%). Interestingly, not all CASGs were located in the minor salivary gland and 2 tumors were identified in the parotid. One patient died from her disease and she harbored a CASG with >30% cribriform pattern. In conclusion, tumor size, bone invasion, and lymphovascular invasion are significant parameters that can predict adverse clinical behaviors in PLGA/CASG on univariate analysis. Using the prior reported definition, an overlapping histology between PLGA and CASG was noted in over a third of the cases. Regardless of tumor subclassification, the percentage of cribriform and papillary patterns seems to be prognostically relevant and should be documented.

Salivary Gland Tumors: Current Concepts and Controversies

This current review focuses on current concepts and controversies for select key salivary gland epithelial neoplasms. Rather than the traditional organization of benign and malignant tumors, this review is structured around select key topics: biphasic tumors, mammary analogue secretory carcinoma, and the controversy surrounding polymorphous low-grade adenocarcinoma and cribriform adenocarcinoma of (minor) salivary gland origin.

Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumors of the Salivary Gland

The salivary gland section in the 4th edition of the World Health Organization classification of head and neck tumors features the description and inclusion of several entities, the most significant of which is represented by (mammary analogue) secretory carcinoma. This entity was extracted mainly from acinic cell carcinoma based on recapitulation of breast secretory carcinoma and a shared ETV6-NTRK3 gene fusion. Also new is the subsection of "Other epithelial lesions," for which key entities include sclerosing polycystic adenosis and intercalated duct hyperplasia. Many entities have been compressed into their broader categories given clinical and morphologic similarities, or transitioned to a different grouping as was the case with low-grade cribriform cystadenocarcinoma reclassified as intraductal carcinoma (with the applied qualifier of low-grade). Specific grade has been removed from the names of the salivary gland entities such as polymorphous adenocarcinoma, providing pathologists flexibility in assigning grade and allowing for recognition of a broader spectrum within an entity. Cribriform adenocarcinoma of (minor) salivary gland origin continues to be divisive in terms of whether it should be recognized as a distinct category. This chapter also features new key concepts such as high-grade transformation. The new paradigm of translocations and gene fusions being common in salivary gland tumors is featured heavily in this chapter.

Basaloid/blue salivary gland tumors

Basaloid tumors are a common diagnostic problem in salivary gland pathology. However, delineating each of these tumor types is facilitated by an algorithmic approach incorporated by tumor border and cell types. This approach greatly diminishes the challenge of separating polymorphous low-grade adenocarcinoma (PLGA) from adenoid cystic carcinoma (ACC). Despite the overlap in growth pattern, ACC is biphasic while PLGA is not. More relevant challenges, namely differentiation of the biphasic basaloid neoplasms including: epithelial-myoepithelial carcinoma (EMCA), cellular pleomorphic adenoma (PA), basal cell adenoma (BCA), and basal cell adenocarcinoma (BCAC), are resolved by a combination of morphologic, immunophenotypic, and to a limited extent, molecular features. Among the most challenging scenarios is high-grade transformation of any of the aforementioned entities. Here, the diagnosis requires recognition of a conventional component and exclusion of metastatic (or in some cases primary) SCC and even select neuroendocrine carcinomas and sarcomas in some cases.

Cribriform adenocarcinoma of the soft palate with multiple lymph node metastasis and long-term follow-up

INTRODUCTION

Cribriform adenocarcinoma of the tongue and minor salivary glands (CATMSG) is a recently described entity, with most cases previously published as polymorphous low-grade adenocarcinoma (PLGA). Typical cases share some main characteristics, such as oral sites (mainly tongue), regional lymph node metastasis, and morphology resembling solid and follicular variants of papillary thyroid carcinoma.

OBJECTIVE

To present a CATMSG and emphasize the importance of reclassifying PLGAs with unusual behavior.

CASE REPORT

A 78-year-old male presented with an ulcerated mass in the soft palate treated as PLGA. The patient developed 5 regional metastases over 11 years of follow-up, all diagnosed as PLGA. He died due to the disease, and because of the very aggressive behavior of PLGA, all histopathologic slides were revised and the tumor was reclassified as CATMSG.

CONCLUSION

This report emphasizes the importance of reevaluating aggressive PLGA and contributes to a better understanding of CATMSG.

Polymorphous low-grade adenocarcinoma: A Danish national study

OBJECTIVES

To present a national series of polymorphous low-grade adenocarcinoma (PLGA) patients, including survival rates and an analysis of prognostic factors.

MATERIALS AND METHODS

By merging three Danish nationwide registries, 73 patients diagnosed with PLGA from 1990 to 2005 were identified. Histological slides were reviewed and data concerning demographics, tumour site, clinical stage, treatment profiles and follow-up were retrieved. Survival estimates and prognostic factors were evaluated by comparing Kaplan-Meier plots using the Mantel-Haenszel log-rank test.

RESULTS

Of the 73 patients, 47 (64%) were female. Median age was 58years. The most common location was the palate (73%). Median latency was five months. Recurrence was seen in 13% of patients. Overall survival (OS), disease-specific survival (DSS) and recurrence-free survival (RFS) rates after 10years were 73%, 99% and 83%, respectively. Univariate analyses suggested that free resection margins significantly improve RFS.

CONCLUSION

PLGA usually has an excellent survival outcome even in cases of advanced stage disease and locoregional recurrence. Primary choice of treatment should be complete surgical excision. Although there is no convincing evidence for the efficacy of adjuvant radiotherapy, it should still be considered, particularly in cases of involved resection margins and advanced stage disease. Late recurrences are common and respond well to salvage therapy.

Plasmacytoid-Type Cellular Differentiation in Polymorphous Low-Grade Adenocarcinoma

INTRODUCTION

Polymorphous low-grade adenocarcinoma (PLGA) occurs more frequently in minor salivary glands. The diagnosis of PLGA, in general, is not difficult but in occasional tumors showing limited invasion or in small biopsy specimens, PLGA may be confused with cellular pleomorphic adenoma (PA). Plasmacytoid cells, a usual component of PAs, have been considered helpful for correct tumor identification.

OBJECTIVE

The aim of this study was to verify the frequency (if any) of plasmacytoid-type cellular differentiation (PD) in PLGA.

MATERIALS AND METHODS

Thirty-two cases of PLGA were reviewed. PD was recognized in 2 cases (6.25%), in which immunohistochemical expression of AE1/AE3, CK7, CK14, vimentin, α-SMA, p63, S-100, calponin, GFAP, and Ki-67 was evaluated.

RESULTS

The 2 cases presented conventional areas of PLGA and variable quantities of cells with PD forming aggregates in the stroma and lining ductal structures. Cells with PD showed positivity for AE1/AE3, CK7, S-100, and vimentin and were negative for CK14, calponin, and GFAP in both cases. In case 1, cells with PD did not present α-SMA and p63 positivity whereas in case 2 they were positive, but for α-SMA such reactivity was restricted to cells forming solid aggregates.

CONCLUSION

Although PD in PLGA is rare, it is necessary to be aware of this possibility, particularly in small incisional biopsies and in PLGA with limited invasion, to avoid confusion with cellular PA.

Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland

AIMS

Polymorphous low-grade adenocarcinoma (PLGA) is the second most common intra-oral salivary gland malignancy. The vast majority of PLGAs harbour a PRKD1 E710D hot-spot somatic mutation or somatic rearrangements of PRKD1, PRKD2 or PRKD3. Given the kinase domain homology among PRKD1, PRKD2 and PRKD3, we sought to define whether PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements would be driven by somatic mutations affecting the kinase domains of PRKD2 or PRKD3.

METHODS AND RESULTS

DNA was extracted from eight microdissected PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements. Samples were thoroughly centrally reviewed, microdissected and subjected to Sanger sequencing of the kinase domains of the PRKD2 and PRKD3 genes. None of the PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements harboured somatic mutations in the kinase domains of the PRKD2 or PRKD3 genes.

CONCLUSION

PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements are unlikely to harbour somatic mutations in the kinase domains of PRKD2 or PRKD3. Further studies are warranted to define the driver genetic events in this subgroup of PLGAs.

Histopathological spectrum of polymorphous low-grade adenocarcinoma

Polymorphous low-grade adenocarcinomas (PLGA) are distinctive salivary gland neoplasms, with an almost exclusive propensity to arise from the minor salivary glands. PLGA frequently manifests as an asymptomatic, slow-growing mass within the oral cavity, which must be separated from adenoid cystic carcinoma and benign mixed tumor for therapeutic and prognostic considerations. We report a case of a 67-year-old male, who presented with a long-standing mass in the palate. This lesion was diagnosed as PLGA based on histopathological findings, which was further confirmed by the immunohistochemical marker.

Cystadenocarcinoma of the salivary glands with potential lymph node metastasis

Cystadenocarcinoma derived from the salivary gland in the head and neck region is an extremely rare malignancy. Therefore, the clinicopathological characteristics is not well understood. The purpose of this study was to clarify the clinicopathological characteristics, and present a total of four patients who were treated at the National Cancer Center Hospital East during the period between 1995 and 2012. The patients were all male, with ages ranging from 47 to 74 years old. The primary sites were the parotid glands, submandibular gland and minor salivary gland of the tongue. Within the follow-up period from 19 to 54 months, lymph node metastases were observed in three of the four patients. However, all the patients were salvaged by additional resection, including neck dissection, and remain alive to date without distant metastases. Cystadenocarcinoma is classified as a low-grade histological subtype of salivary gland tumors. Although the tumor has the potential to produce lymph node metastases, as shown in our patients, it is generally an indolent tumor with a good prognosis as compared with high-grade subtypes. This study suggests that a long-term follow up paying close attention to lymph node metastases is necessary for cystadenocarcinoma.

Polymorphous low grade adenocarcinoma

Polymorphous low-grade adenocarcinoma (PLGA), is a rare, salivary gland intraoral tumor with complexities in diagnosis and this review highlights the difficulties.

Cribriform adenocarcinoma of the minor salivary glands arising in the epiglottis--a previously undocumented occurrence

A 39-year-old female was referred to her local Ear, Nose, and Throat department with tonsillar hypertrophy. During intubation for a tonsillectomy, a mass was also noted on the epiglottis. Histopathologic examination showed this mass to be a cribriform adenocarcinoma of the minor salivary glands (CAMSG). As far as the authors are aware, a CAMSG has never been documented in the larynx.

Not just another paediatric neck lump: metastatic cribriform adenocarcinoma of the palate in an adolescent

Objective:

This paper reports the case of a 13-year-old girl with a 2-year history of left cervical lymph node swelling that was diagnosed as metastatic cribriform adenocarcinoma of the tongue and minor salivary gland.

Case report:

A 13-year-old girl with a left, level II cervical lymph node underwent excisional biopsy after an ultrasound suggested suspicious features. The histology indicated polymorphous low-grade adenocarcinoma, and a primary lesion in the left palate was identified. The patient underwent left maxillectomy, neck dissection and reconstruction. Histological analysis of resection specimens led to a revised diagnosis of cribriform adenocarcinoma of the tongue and minor salivary gland.

Conclusion:

Cribriform adenocarcinoma of the tongue and minor salivary gland has recently been described as a separate entity to polymorphous low-grade adenocarcinoma in light of histological and behavioural differences, including higher rates of metastasis at presentation. This is the first report in the world literature of an adolescent with this entity. It is possible that some previous reports of polymorphous low-grade adenocarcinoma in childhood would have been more accurately described as cribriform adenocarcinoma of the tongue and minor salivary gland.

Polymorphous low-grade adenocarcinoma of the head and neck

Polymorphous low-grade adenocarcinomas are rare tumors that can arise from many areas of the head and neck. We reviewed the pertinent literature pertaining to the incidence, diagnostic evaluation, and treatment strategies for this malignancy. Histopathologic diagnosis always involves careful analysis of tissue and especially characteristic immunohistochemical staining patterns. Common differential diagnoses include adenoid cystic carcinoma, pleomorphic adenoma, and other benign or malignant salivary gland neoplasms. Although the ideal treatment is debated, surgical resection at times combined with adjuvant radiation therapy is preferred by many physicians. Further research will be needed to delineate optimal management.

Surface Papillary Epithelial Hyperplasia (Rough Mucosa) is a Helpful Clue for Identification of Polymorphous Low-Grade Adenocarcinoma

The purpose of this study is to evaluate surface papillary epithelial hyperplasia, a microscopic finding that corresponds to the clinical finding of rough or stippled mucosa, as a predictor of polymorphous low-grade adenocarcinoma (PLGA). We conducted a retrospective review of minor salivary gland neoplasms submitted to our biopsy service from 1991 to 2013. Our review was limited to lesions involving the oral cavity/soft palate with the following diagnoses: PLGA, pleomorphic adenoma (PA), mucoepidermoid carcinoma (MEC), and adenoid cystic carcinoma (ACC). A total of 202 minor salivary gland neoplasms were included in the study. Among cases in which surface epithelium was present for evaluation (n = 112), surface papillary epithelial hyperplasia was evident in 30 % of PLGA and 1 % of non-PLGA (i.e., MEC, ACC, PA). The greater frequency of surface papillary epithelial hyperplasia in the PLGA versus non-PLGA cases and in the benign versus malignant cases was significant (p = .0001 and p = .041, respectively). The sensitivity and specificity of papillary epithelial hyperplasia for PLGA were 30 % (95 % confidence interval (CI) 11.97-54.27 %) and 99 % (95 % CI 94-99.82 %), respectively. The clinical presentation of PLGA appeared relatively nonspecific, with all analyzed tumor types exhibiting a predilection for females, middle-aged to older adults, palatal location, pink/tan/normal color, and firm consistency. In conclusion, papillary epithelial hyperplasia was evident in only a minority of PLGA. However, when present within the context of a palatal salivary gland neoplasm, it appears to indicate a high probability of PLGA. Accordingly, rough mucosa may be a useful clinical pearl for identification of PLGA.

Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands

Polymorphous low-grade adenocarcinoma (PLGA) is the second most frequent type of malignant tumor of the minor salivary glands. We identified PRKD1 hotspot mutations encoding p.Glu710Asp in 72.9% of PLGAs but not in other salivary gland tumors. Functional studies demonstrated that this kinase-activating alteration likely constitutes a driver of PLGA.

Polymorphous low-grade adenocarcinoma: a case series and determination of recurrence

OBJECTIVES/HYPOTHESIS

Information on polymorphous low-grade adenocarcinoma (PLGA) consists primarily of case reports and small institutional series with varying recurrence rates. In this report, we describe our institutional experience and conduct a review of the literature to assess the overall incidence of PLGA among oral salivary gland tumors and determine recurrence rates.

STUDY DESIGN

A retrospective case series and literature-based review was performed.

METHODS

Retrospective case series at an academic tertiary referral center. Review of clinical records and pathological analysis of tissue specimens from 20 patients treated for PLGA from July 1, 1990 to July 1, 2011. A literature-based review on PLGA was also performed.

RESULTS

Twenty patients (mean age, 54 years; eight males) with PLGA based on pathologic diagnosis were included. The most common initial presentation was an asymptomatic mass (45%), and the most frequent site was the palate (60%). Our literature review identified 54 case reports, eight case series, and 17 large series. In total, 456 cases of PLGA were identified, with an overall recurrence rate of 19%. Half of the recurrences occurred by 36 months; however, recurrences were reported up to 24 years after initial resection.

CONCLUSIONS

PLGA arises from minor salivary glands and is characteristically slow growing and indolent. Although these tumors may be histologically low-grade, our review highlights the high rates of recurrence of these tumors as well as the ability to metastasize to local lymph nodes and distant organs. The mainstay of treatment should be wide surgical excision with long-term oncologic follow-up.

LEVEL OF EVIDENCE

4.

Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin

Polymorphous low-grade adenocarcinoma (PLGA) and cribriform adenocarcinoma of minor salivary gland (CAMSG) are low-grade carcinomas arising most often in oral cavity and oropharynx, respectively. Controversy exists as to whether these tumors represent separate entities or variants of one spectrum, as they appear to have significant overlap, but also clinicopathologic differences. As many salivary carcinomas harbor recurrent translocations, paired-end RNA sequencing and FusionSeq data analysis was applied for novel fusion discovery on two CAMSGs and two PLGAs. Validated rearrangements were then screened by fluorescence in situ hybridization (FISH) in 60 cases. Histologic classification was performed without knowledge of fusion status and included: 21 CAMSG, 18 classic PLGA, and 21 with "mixed/indeterminate" features. The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions, respectively, while no fusion candidates were identified in two PLGAs. FISH for PRKD1 rearrangements identified 11 additional cases (22%), two more showing ARID1A-PRKD1 fusions. As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol and protein kinase C signal transduction pathway, we expanded the investigation for these genes by FISH. Six additional cases each showed PRKD2 and PRKD3 rearrangements. Of the 26 (43%) fusion-positive tumors, there were 16 (80%) CAMSGs and 9 (45%) indeterminate cases. A PRKD2 rearrangement was detected in one PLGA (6%). We describe novel and recurrent gene rearrangements in PRKD1-3 primarily in CAMSG, suggesting a possible pathogenetic dichotomy from "classic" PLGA. However, the presence of similar genetic findings in half of the indeterminate cases and a single PLGA suggests a possible shared pathogenesis for these tumor types.

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.

Immunohistochemical clue for the histological overlap of salivary adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

It remains difficult to distinguish adenoid cystic carcinoma (ACC) from polymorphous low-grade adenocarcinoma (PLGA). Although these neoplasms exhibit nearly similar histologic patterns, their biologic behavior is significantly different. This study was carried out in an attempt to overcome the histological overlap between these tumors using immunohistochemical method for c-kit and galectin-3 proteins on twenty cases of salivary gland tumors including twelve ACC and eight PLGA. Results revealed positive cytoplasmic reactivity for c-kit in 100% of ACC cases and only in 25% of PLGA. On the other hand, galectin-3 expression was observed in 100% of both ACC and PLGA cases. Moreover, solid variant of ACC showed overexpression of both proteins than cribriform and tubular subtypes. Significant positive correlation between the two studied proteins in ACC and PLGA was also observed (p < 0.05). Upon these results, over expression of c-kit and galectin-3 in ACC cases supports the concept of solid variant as a high-grade tumor. Moreover, c-kit may be used as a helpful marker to distinguish ACC from PLGA in cases where the diagnosis can be challenging.

Polymorphous low-grade adenocarcinoma: a 17 patient case series

Polymorphous low-grade adenocarcinoma (PLGA) is a rare malignancy most commonly seen in the minor salivary glands. First described in 1983, this entity has been recognized to have an indolent course with rare metastases or deaths. We describe our experience with 17 patients treated at our institution for PLGA from 1984 to 2012. All tumors were located in the oral cavity or soft palate. All patients were treated surgically, with the exception of one patient who declined therapy. No deaths or metastases have been identified in subsequent follow-up. Three patients in this series had undergone prior surgery up to 20 years previously and were treated for recurrences at our institution; no other recurrences have been noted. In summary, PLGA is best treated with wide excision to negative margins with excellent prognosis, but long-term follow-up is recommended given the propensity for late recurrences.