Adenosquamous carcinoma. A rare neoplasm with an aggressive course

Adenosquamous cell carcinoma of the head and neck: a retrospective single institution series

Objectives

Head and neck adenosquamous cell carcinoma (HN-ASCC) is a rare, aggressive neoplasm, with limited data reported in the literature. The aim of this study was to assess tumour behaviour and prognostic factors impacting overall survival (OS) in a retrospective, single institution series.

Methods

A retrospective study on patients affected by HN-ASCC who were treated surgically between 2002 and 2019 at the Department of Otorhinolaryngology - Head and Neck Surgery of the University of Brescia was conducted. Demographics, clinical data, OS, and relative prognostic factors were analysed.

Results

The study included 32 patients, with a median age of 66 years, mostly males (84.4%) and untreated (68.8%). Adjuvant treatments followed surgery in 28.1% of patients. Compared to conventional SCC, ASCC showed a higher proportion of cases arising in the larynx (40.6%); no difference was found in other features. Advanced (pT3-4) local stage at presentation (p = 0.023), perineural invasion (PNI, p = 0.01), and positive margins (p = 0.007) were independent negative prognostic factors for OS.

Conclusions

HN-ASCC is a rare, aggressive cancer, most frequently arising in the larynx of elderly males, usually diagnosed in an advanced local stage. OS is generally poor, affected by local advanced stage, PNI, and positive resection margins.

Adenosquamous Carcinoma with the Acantholytic Feature in the Oral Cavity: A Case Report and Comprehensive Literature Review

Adenosquamous carcinoma (ASC) is an aggressive subtype of squamous cell carcinoma (SCC). Due to its poor prognosis, a precise pathological diagnosis of ASC is essential but challenging because its pathological criteria are still unclear. Here, we present a rare case of oral ASC accompanied by acantholytic features. The tumor was raised in the mandibular gingiva and recurred locally approximately 13 months after the initial surgery with cervical lymph node metastasis. Pathological specimens of the primary lesion showed acantholysis in a large area of the SCC. Mucous cells, the characteristic finding indicating glandular differentiation, were imperceptible in the initial surgical specimen but increased in the locally recurrent and metastatic lymph node specimens. In a comprehensive literature review of oral ASC cases, the present case was the only case of ASC with acantholytic features. We reconfirmed that ASC has poor prognoses, such as low 5-year overall survival and disease-free survival, high locoregional recurrence, and high distant metastasis rates. A precise diagnosis of ASC is required for estimating prognosis and undergoing close follow-up, even if the adenocarcinomatous component is limited to a small area in the lesion.

A population-based analysis of adenosquamous carcinoma of the salivary gland

BACKGROUND

Adenosquamous carcinoma (ASC) of the salivary gland is a rare malignancy, and the characteristics and prognosis of this disease remain unclear. This study aimed to assess the clinicopathological characteristics of this rare disease and further determine the potential prognostic factors that affect its outcome.

METHODS

Data of patients with ASC of the salivary gland were extracted retrospectively from the Surveillance, Epidemiology, and End Results (SEER) database between 1973 and 2016. The clinicopathological characteristics of these patients were assessed, and prognostic factors were further determined using Cox regression analysis.

RESULTS

A total of 106 patients with ASC of the salivary gland were identified. The mean age at diagnosis was 66.1±14.9 years, with a male-to-female ratio of 1.47. The parotid gland was the most common primary site (N=91; 85.8%). The 1-, 2-, and 5-year overall survival (OS) rates were 71.5%, 55.0%, 41.5%, respectively. The 1-, 2-, and 5-year disease-specific survival (DSS) rates were 80.8%, 72.2%, and 59.2%, respectively. The OS and DSS shortened with increasing tumor stage, regardless of the American Joint Committee on Cancer tumor-node-metastasis stage or SEER historic stage. Surgery was the main treatment option to improve survival, and post-operative radiotherapy could also prolong OS and DSS (both P<0.01). A multivariate Cox regression analysis demonstrated that distant metastases and the use of surgery or radiation were independent prognostic factors for a favorable OS among patients with ASC of the salivary gland, and early stage (T1/T2) and the use of surgery were independent prognostic factors for favorable DSS among the patients with ASC of the salivary gland.

CONCLUSIONS

This is the largest case series on ASC of the salivary gland. Advanced T stage, distant metastases, and the use of surgery and radiation were associated with OS or DSS of this disease.

Adenosquamous carcinoma, a rare and unknown tumor

Introduction: Adenosquamous carcinoma (ASC) of the head and neck is a rare malignant tumor, with one hundred cases diagnosed so far in the literature. Observation: A 66 years old female patient had a ASC of the right posterior floor of the mouth with a classification T1N0M0. Treatment consisted of surgical management and active surveillance. Discussion: Through this case report, we present this type of tumor and we discuss the main differential diagnosis from a clinical and histological point of view. Conclusion: This entity was described for the first time in 1968 by Gerughty. The CAS is defined by the World Health Organization as “a tumor of the upper respiratory tract, with two distinct squamous and glandular components.” The CAS is considered as an aggressive tumor with a redoubtable prognosis should not be ignored.

Importance of tumor extent in adenosquamous carcinoma of the head and neck: a retrospective cohort study

OBJECTIVE

The aim of this study was to determine the correlates of survival for patients diagnosed with adenosquamous carcinoma (ASC) of the head and neck.

STUDY DESIGN

Patients diagnosed with ASC of the head and neck between 1973 and 2012 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Kaplan-Meier and Cox proportional hazard regression analyses were conducted to investigate the prognostic factors and treatment modalities that determine overall survival (OS) and disease-specific survival (DSS).

RESULTS

In the analysis, of the 235 patients diagnosed with adenosquamous of the head and neck, 66.8% were male and 33.2% were female with a median age at diagnosis of 64 years. Kaplan-Meier analysis determined 5-year survival rates of 30% for OS and 50% for DSS. Univariate and multivariate analyses found that age at diagnosis, tumor size, tumor extent of disease, surgical resection, and radiation therapy were independent predictors of OS and DSS.

CONCLUSIONS

This study, to our knowledge, is the largest study, to date, determining the correlates of survival for ASC of the head and neck. Older age at diagnosis, larger tumor size, and further extent of disease were correlated with decreased survival. Surgical resection improves survival in patients with localized or regional disease, whereas radiation therapy confers survival benefit in patients with distant extent.

Adenosquamous carcinoma of the tongue: clinicopathologic study and review of the literature

Adenosquamous carcinoma (ASC) of the tongue is an uncommon malignant oral neoplasm with mixed glandular and squamous differentiation and a propensity for aggressive clinical behavior. Here, we report a rare case of ASC of the lateral border of the tongue in a 65-year-old Japanese man. The patient was treated by radical operation and remained well for 6 months before developing metastasis of the hilar and pretracheal lymph nodes. Subsequently, the patient was treated with combined chemotherapy (nedaplatin plus docetaxel and S-1 for two cycles, intravenously) and radiotherapy. Radiation therapy of metastatic lymph nodes was performed at a total dose of 60 Gy and was delivered in 2 Gy fractions 5 days/week. The patient is currently tumor free and is being followed up carefully. This article describes a rare case of ASC of the tongue and its conventional histologic, immunohistochemical, and electron microscopic findings, together with a review of the literature. The findings provide important information to better understand the possible clinical and therapeutic approaches for this uncommon tumor of the tongue.

Adenosquamous Carcinoma of the Head and Neck: A Case-Control Study with Conventional Squamous Cell Carcinoma

Adenosquamous carcinoma (AdSC) is considered a rare variant of squamous cell carcinoma (SCC) which is considered to be more clinically aggressive. Data is very limited with very little case matched data on outcomes in the literature. It is also unknown whether the quantity of the adenocarcinoma component affects outcomes. A retrospective case-control study with 23 cases of AdSC and 1137 SCC controls was conducted. Cases were matched by anatomic subsite, treatment, and, for oropharynx, by p16 status. The following variables were adjusted for in the analysis: T classification (T1/T2 vs. T3/T4), N classification (N0-N2a vs. N2b-N3), age, and smoking. The adenocarcinoma component was quantified by the number of high power fields containing glands as low, moderate, or high. AdSCs had a significantly greater risk of disease recurrence but largely, the differences were not statistically significant. The quantity of adenocarcinoma did not correlate with disease recurrence or survival. This case-control study on AdSC shows modestly more clinically aggressive behavior than conventional SCC, even while controlling for p16 status for oropharyngeal cases. Further, it suggests the current definition of AdSC, with no minimum requirement for gland formation, is clinically accurate.

Squamous cell carcinoma variants of the upper aerodigestive tract: a comprehensive review with a focus on genetic alterations

CONTEXT

Squamous cell carcinoma of the upper aerodigestive tract is a heterogenous entity. Although conventional squamous cell carcinomas are easily recognized, the morphologic variants of squamous cell carcinoma can present a diagnostic challenge. Familiarity with these variants is necessary because many are associated with unique risk factors and are characterized by specific molecular alterations (eg, nuclear protein in testis midline carcinomas). Perhaps the most important distinction is in identifying viral-related from nonviral-related carcinomas. The accurate diagnosis of these variants is necessary for prognostic and therapeutic reasons.

OBJECTIVES

To provide a clinicopathologic overview and summary of the molecular alterations of the common squamous cell carcinoma variants, including verrucous, spindle cell, acantholytic, adenosquamous, basaloid, and papillary squamous cell carcinoma, as well as nuclear protein in testis midline carcinoma, and to discuss the distinguishing features of human papillomavirus- and Epstein-Barr virus-related squamous cell carcinomas.

DATA SOURCES

Published peer-reviewed literature.

CONCLUSIONS

Familiarity with squamous cell carcinoma variants is essential for proper diagnosis and to guide appropriate clinical management. Further insight into the molecular alterations underlying those variants may lead to alterations in existing treatment approaches and to evolution of novel treatment modalities.

Adenosquamous carcinoma of the head and neck: report of 20 cases and review of the literature

PURPOSE

To assess the clinical profile and prognostic factors in patients with adenosquamous carcinoma (ASC) of the head and neck treated by surgery and/or radiation therapy with or without chemotherapy.

METHODS

Data from 20 patients with stage I-II (n = 4), III (n = 5), or IVA (n = 11) head and neck ASC, treated between 1989 and 2010 were collected in a retrospective multicenter Rare Cancer Network study. Surgery was performed in 16 patients. Seventeen patients received combined modality treatment.

RESULTS

After a median follow-up of 15.5 months, 12 patients recurred. The 3-year and median overall survival, disease-free survival (DFS), and loco-regional control were 52% and 39 months, 32% and 12 months, and 47% and 33 months respectively. In multivariate analysis, DFS was negatively influenced by the presence of extracapsular extension and advanced stage.

CONCLUSION

Overall prognosis of locoregionally advanced ASC remains poor. However, early stage ASC patients managed with combined modality treatment may have prolonged DFS.

Adenosquamous carcinoma of the head and neck: relationship to human papillomavirus and review of the literature

Adenosquamous carcinoma (ADSC) of the head and neck is an aggressive variant of squamous cell carcinoma (SCC). Certain variants of head and neck SCC are human papillomavirus (HPV)-related and have better prognosis. The relationship of HPV to head and neck ADSC has not been investigated. We searched our files for the term "adenosquamous" and head and neck subsites and found cases from 1998 to 2009. The requisite histologic criteria were the presence of SCC combined with distinct gland formation and/or intracellular mucin. DNA in situ hybridization for high-risk HPV, RNA in situ hybridization for high risk HPV E6 and E7 transcripts, and immunohistochemistry for p16 and p53 were performed. The existing literature on ADSC was also reviewed. Of the 18 cases, eight were from the larynx and hypopharynx, four from the oral cavity, three from the oropharynx, and three from the nasal cavity. Three cases (16%) showed both high risk HPV E6 and E7 and p16 expression, one from the nasal cavity and two from the oropharynx. Both oropharyngeal carcinoma patients were alive and disease free at 34 and 103 months, respectively. ADSCs of the head and neck are a heterogeneous group of tumors. A small minority of cases harbor HPV and most of these, particularly those occurring at sites with known high prevalence of HPV, show active viral transcription with detectable E6 and E7 and overexpression of p16. The HPV-related oropharyngeal cases, though rare, appear to do very well clinically, while the remaining cohort of ADSC patients do quite poorly. Head and neck ADSC appears to be a mixed variant that can be further classified according to its HPV status.

Determinants of outcome following surgery for oral squamous cell carcinoma

The recent changes in incidence and prevalence of oral squamous cell carcinoma in relation to gender and age mirror the changing patterns of exposure to tobacco and alcohol, the main etiological agents. Most cases of oral cancer are managed by surgery, often combined with radiotherapy. Histopathological assessment of the resection specimen provides information vital for postoperative management and prognosis. This review considers the full range of histological determinants of outcome in relation to the primary oral tumor and any metastatic involvement of the cervical lymphatic system, together with an outline of more general patient factors that may also impact on morbidity and mortality rates.

Adenosquamous carcinoma of maxillary sinus: case showing complete response to S-1

Background:

Adenosquamous carcinoma is a very rare tumour which is characterised pathologically by the simultaneous presence of distinct areas of adenocarcinoma and squamous cell carcinoma. Generally, adenosquamous carcinoma has an aggressive clinical course and is associated with a poor prognosis. Most cases have been treated by surgery alone or combined with radiotherapy. Chemotherapy is rarely used in treating adenosquamous carcinoma, and it has been difficult to establish treatment guidelines due to the paucity of cases.

Case:

We report a case of adenosquamous carcinoma which arose in the maxillary sinus of a 77-year-old man. Despite surgical treatment and chemoradiotherapy to the primary site, he developed bilateral neck metastases after the surgery. The patient was treated with S-1, a novel oral fluoropyrimidine anticancer agent, with a complete (albeit finite) response.

Conclusion:

This report presents the aggressive character of adenosquamous carcinoma and the possible role of S-1 in the treatment of this uncommon neoplasm.

Pitfalls and procedures in the histopathological diagnosis of oral and oropharyngeal squamous cell carcinoma and a review of the role of pathology in prognosis

Histopathological assessment of formalin-fixed biopsy tissue and surgical resection specimens remains the cornerstone of cancer diagnosis and pathological staging in routine clinical practice. In recent years, standard protocols for reporting head and neck cancer have been widely used and these have improved the general level of the pathological assessment. In this article, we look beyond the standard protocols and deal with potential difficulties and pitfalls in the assessment of incisional biopsy specimens, surgical resection specimens and neck dissections. We draw attention to possible shortcomings and issues requiring clarification. Emphasis is given to precise histopathological definitions, histopathological detection and differential diagnosis. The approach is a practical one--a consideration of common experiences and dilemmas faced by the reporting pathologist, and where possible, we offer guidance and practical tips. The article concludes with a brief consideration of the prognostic value of accurate histopathological staging.

Pathology of Malignant and Premalignant Oral Epithelial Lesions

Oral mucous membranes and the surrounding structures are largely composed of stratified squamous epithelium that is supported by a fibrous connective tissue lamina propria and a submucosa of fibroadipose tissue. Minor salivary glands, nerves, and capillaries course abundantly throughout the supporting collagen and fibro-fatty submucosa. Premalignant and malignant lesions arise most frequently from epithelium, and these epithelial lesions ultimately account for 95% of all cancers of the oral cavity. Malignant neoplasia of bone, cartilage, salivary glands, and connective tissue and those of lymphoproliferative derivatives are far less common occurrences in the oral cavity. Malignant neoplasms can and do arise from the tooth germ apparatus, but neoplasms of odontogenic elements are rare and are not included in this discussion.

Histopathological prognosticators in oral and oropharyngeal squamous cell carcinoma

Histopathological assessment of the surgical resection specimen continues to provide information that is central to determining the post-operative treatment needs and prognosis for an individual patient with oral/oropharyngeal squamous cell carcinoma. This review describes the prognostic value of histopathological features related to the primary tumour and the cervical lymph nodes, and considers their relative merits. In addition, a brief overview of more general patient factors is included. Throughout the review, guidance is offered on practical aspects of the histopathological assessment together with brief mention of potential inaccuracies. Emphasis is given also to the importance of the partnership between the surgeon and the pathologist, the need for standardisation during all stages of the histopathological assessment, and the value of accurate documentation of the findings.

Clinicopathological features of head and neck adenosquamous carcinoma

Adenosquamous carcinoma is a rare tumour which is characterized pathologically by the simultaneous presence of distinct areas of squamous cell carcinoma and adenocarcinoma. The origin of adenosquamous carcinoma is controversial; however, it is generally considered to be aggressive and associated with a dismal prognosis. In the present study, the medical and pathological records of 4 patients with head and neck adenosquamous carcinoma are reviewed. In 1 patient, the tumour arose from an area of carcinoma in situ of surface epithelium. The origin from surface epithelium was not evident in any of the others. Perineural invasion was present in 3 patients. Three patients had evidence of cervical metastases. One patient died of postoperative complications, 1 suffered from local recurrence and developed distant metastases and 2 were alive with no evidence of disease over 30 months later. Adenosquamous carcinoma is an aggressive tumour; however, with appropriate treatment, some patients may remain well beyond 2 years.

The pathology of oral cancer

Oral cancer is a serious public health problem, with over 200,000 new cases reported annually worldwide, two-thirds of which occur in developing countries. The overall mortality rate for intra-oral cancer remains high at approximately 50%, even with modern medical services, probably due to the advanced stage of the disease at presentation. This review outlines recent advances in our understanding of the roles and interactions of major risk factors for oral cancer worldwide, notably tobacco, alcohol and betel quid and the genetic polymorphisms determining their metabolism that may predispose patients to oral carcinoma. Oral epithelial lesions with malignant potential are described. We discuss the histopathology of oral cancer, its grading and the staging of the disease at clinical, microscopic, immunohistological and molecular levels. A recommended minimum dataset for pathology reports is described. The available strategies and current prospects for controlling oral cancer in the community are summarised.

Adenosquamous carcinoma of the tongue in a 22-year-old female: report of a case with immunohistochemistry

Adenosquamous carcinoma is a very rare tumor that is characterized pathologically by the simultaneous presence of distinct areas of adenocarcinoma and squamous cell carcinoma. Only 15 cases in the oral cavity are reported in the literature, most occurring in middle-aged and elderly males. Pain is a commonly reported presenting symptom and may be related to the frequent presence of perineural invasion. Most cases have been treated surgically. However, early recurrence and death due to disease are common. We report an exceptional case occurring in a 22-year-old female. The tumor was associated with dysplasia of both minor salivary gland ductal epithelium and surface mucosal epithelium. Perineural invasion was also present. The patient was treated with combined surgery and radiotherapy and remained well for 9 months before developing locoregional recurrence and ultimately succumbing to the disease.

Adenosquamous carcinoma of the upper aerodigestive tract: a clinicopathologic study of 12 cases and review of the literature

PURPOSE

Adenosquamous carcinoma is an uncommon, controversial neoplasm. To further comprehend its natural history, the clinical and pathological features of 12 new cases were reviewed and analyzed collectively with those described in the English literature.

MATERIALS AND METHODS

Twelve cases of adenosquamous carcinoma of the upper aerodigestive tract with adequate follow-up and available microscopic slides and paraffin tissue blocks were identified in the anatomic pathology files of Presbyterian Hospital of the University of Pittsburgh Medical Center over the period 1983-2001.

RESULTS

The 8 men and 4 women ranged in age from 34 to 81 years (mean, 62.8 years). The larynx (5 cases) and the floor of the mouth (4 cases) were the most common sites of origin. Nine patients had cervical lymph nodes positive for carcinoma (8 at diagnosis), 7 experienced local recurrences, and 2 developed distant metastases. Four of 10 (40%) patients with follow-up died of disease. Combining our cases with those in the literature (total of 58 cases) revealed similar findings: 64.7% were associated with positive cervical lymph nodes, 46.7% experienced local recurrences, 23.1% developed distant metastases, and 42.9% died of their disease at a mean follow-up period of 24.7 months.

CONCLUSIONS

Adenosquamous carcinoma is an aggressive neoplasm with a tendency for early lymph node metastasis, frequent local recurrence, occasional distant metastasis, and death from disease, usually within 2-3 years. Surgery with neck dissection is the treatment of choice.

Adenosquamous carcinoma: a case report with immunohistochemical evaluation

The histogenetic origin of adenosquamous carcinoma, a high-grade variant of malignant epithelial neoplasm, has long been debated. We report a case that clearly demonstrated a mucosal surface epithelial origin. This concept was supported through histologic analysis of hematoxylin- and eosin-stained sections, as well as by the pattern of immunohistochemical reactivity with antibodies directed against low and high molecular weight cytokeratins, cell adhesion molecules (CAM 5.2), and carcinoembryonic antigens. The histologic differential diagnosis, biological behavior, and prognosis of adenosquamous carcinoma are also examined.

Adenosquamous carcinoma of the tongue: report of a case with histochemical, immunohistochemical, and ultrastructural study and review of the literature

A rare case of oral adenosquamous carcinoma in a 78-year-old woman is reported. The tumor occurred in her tongue and metastasized to the submandibular and cervical lymph nodes. Histologically, the tumor showed invasive growth involving the submucosal and muscle layers. Its solid carcinomatous nests exhibited ductal differentiation in the deeper aspects and squamous differentiation toward the surface. Histochemical examination revealed an accumulation of acid mucopolysaccharide in the ductal lumina, and the ductal cells were immunohistochemically positive for carcinoembryonic antigen, epithelial membrane antigen, cancer antigen 15-3 and Ulex europaeus agglutinin I. Ultrastructurally, tonofibrils, desmosomes and numerous cytoplasmic processes were common features of the tumor cells. In addition, true glandular structures and pseudocysts were seen in areas. Clinical features of 13 adenosquamous carcinomas in the literature were analyzed.

Adenoid squamous carcinoma of the conjunctiva--a clinicopathological study of 14 cases

AIMS

In order to determine the clinicopathological features and optimum management of a series of patients with adenoid squamous cell carcinoma of the conjunctiva, all cases of squamous cell carcinoma (SCC) of the conjunctiva and cornea on file in the registry of the ophthalmic pathology at the Armed Forces Institute of Pathology were reviewed.

METHODS

On histopathological examination, a predominant adenoid or pseudoglandular pattern due to islands of neoplastic squamous or epidermoid cells surrounded by acantholytic cells was necessary for inclusion in the study. Histochemical and transmission electron microscopic studies (TEM) were performed. Clinical features of all the patients were extracted from the charts.

RESULTS

The anatomical location of the 14 tumours was corneoscleral limbus (seven patients) and bulbar conjunctiva (seven patients). Eight patients presented with inflammatory signs and irritation (red eye, tearing, foreign body sensation), while six patients developed a slowly growing, painless mass. Histochemical and TEM studies showed extracellular hyaluronic acid and no intracellular mucin. Of the two patients initially treated by enucleation, one was free of disease after 2 years while the second patient had recurrence in the socket and died of brain metastases despite wide orbital excision and radiotherapy. All five patients with recurrent tumours initially had irritated red eyes and two required enucleation. One such patient, after orbital exenteration and radiotherapy, died of unrelated disease.

CONCLUSION

The study demonstrates that adenoid SCC of the conjunctiva often presents with inflammatory signs. The tumour is locally aggressive and may metastasize and should, therefore, be histopathologically differentiated from the less aggressive conventional squamous cell carcinoma. Optimum treatment includes wide excision with documented histological clear margins of resection on permanent sections and frequent follow up.

Hybrid tumours of salivary glands. Definition and classification of five rare cases

Hybrid tumours are very rare tumour entities which are composed of two different tumour entities, each of which conforms with an exactly defined tumour category. The tumour entities of a hybrid tumour are not separated but have an identical origin within the same topographical area. In contrast, biphasically differentiated tumours are a mixture of two cellular patterns with a corresponding term in the tumour classification. Examples of a biphasic differentiation are: basaloid-squamous carcinoma, adeno-squamous carcinoma or sarcomatoid carcinoma, and epithelial-myoepithelial carcinoma, mucoepidermoid carcinoma or adenoid cystic carcinoma. Hybrid tumours must also be distinguished from the multiple occurrence of salivary gland tumours which can develop syn- or metachronously. In the tissue samples of more than 6600 salivary gland tumours covered by the Salivary Gland Register (Institute of Pathology, University of Hamburg, Germany) only 5 cases of hybrid tumours were recorded between 1965 and 1994. This means less than 0.1% of all registered tumours. Case 1 was a very rare example of a hybrid adenoma with differentiation as a basal cell adenoma and a canalicular adenoma of the parotid gland. The similar cellular origin of both types of adenoma may be an explanation for its development in a hybrid adenoma. Case 2 is a hybrid tumour with a composition of basal cell adenoma and a glandular type of adenoid cystic carcinoma. In both types of tumours the two cell types (duct-lining cells and modified myoepithelial cells) have a similar histogenetic origin. Therefore, the development of the both cell types in a hybrid tumour with two trends of differentiation is possible. Case 3 represents a hybrid adenoma as a mixture of a Warthin tumour and a sebaceous adenoma. Although inclusions of sebaceous cells are observed in Warthin tumours, this hybrid tumour shows a composition of two different epithelial structures in a varied mixture. Case 4 is a very rare and unique hybrid carcinoma with two absolutely different components: acinic cell carcinoma and salivary duct carcinoma. The poor prognosis of this hybrid carcinoma is determined by the salivary duct carcinoma. Case 5 represents a hybrid carcinoma whose two components have a similar histogenetical basis: epithelial-myoepithelial carcinoma and a glandular type of adenoid cystic carcinoma. Both carcinomas are composed of variable proportions of ductlining cells and myoepithelial cells.

Multiple tumours of the salivary glands--terminology and nomenclature

Multiple tumours of the salivary glands are very rare and their combinations according to histological classification of the tumours, localisation and origin (origin in independent topographical areas or in the same tissue) are diverse. The following two categories can be distinguished: common occurrence of multiple salivary gland tumours with identical histology, or with different histology. In either group the tumours can be unilateral or bilateral, synchronous or metachronous. The most common multiple tumours with an identical histology are Warthin tumours and pleomorphic adenomas. Bilateral occurrence has been observed especially in oncocytomas, acinic cell carcinomas and basal cell adenomas. In the group of multiple tumours with differing histology, Warthin tumours and pleomorphic adenomas show a number of combinations with other adenomas or carcinomas of the salivary glands. Notable also is the simultaneous occurrence of salivary gland tumours with other oral tumours or extraglandular tumours, especially thyroid carcinomas and breast carcinomas. Multiple salivary gland tumours must be distinguished by nomenclature from tumours with biphasic differentiation and hybrid tumours. Tumours with biphasic differentiation are defined as regular, recurring mixtures of two cellular components in the same tumour and have a corresponding term in the tumour classification. Hybrid tumours are very rare and are composed of two different tumour entities within the same topographical area. Each of the tumour entities conforms with an exactly defined tumour category.