Different keratin profiles in craniopharyngioma subtypes and ameloblastomas

Single-cell RNA sequencing highlights intratumor heterogeneity and intercellular network featured in adamantinomatous craniopharyngioma

Despite improvements in microscopically neurosurgical techniques made in recent years, the prognosis of adamantinomatous craniopharyngioma (ACP) is still unsatisfactory. Little is known about cellular atlas and biological features of ACP. Here, we carried out integrative analysis of 44,038 single-cell transcriptome profiles to characterize the landscape of intratumoral heterogeneity and tumor microenvironment (TME) in ACP. Four major neoplastic cell states with distinctive expression signatures were defined, which further revealed the histopathological features and elucidated unknown cellular atlas of ACP. Pseudotime analyses suggested potential evolutionary trajectories between specific neoplastic cell states. Notably, a distinct oligodendrocyte lineage was identified in ACP, which was associated with immunological infiltration and neural damage. In addition, we described a tumor-centric regulatory network based on intercellular communication in TME. Together, our findings represent a unique resource for deciphering tumor heterogeneity of ACP, which will improve clinical diagnosis and treatment strategies.

Clinical, Radiographic and Histopathological Analysis of Craniopharyngiomas and Ameloblastomas: A Systematic Review

BACKGROUND

Craniopharyngiomas and ameloblastomas are tumors of epithelial origin, mostly characterized by a benign course, slow growth and for being locally invasive. Some studies highlight the similarity of these neoplasms, especially regarding histopathological aspects. In this context, the aim of the present study was to carry out a systematic literature review correlating the clinical, radiographic, and histopathological aspects of these two tumors.

METHODS

Searches were conducted at the Pubmed, Periódicos Capes, Scopus, Science Direct, Web of Science and Scielo databases, according to the following inclusion criteria: publications in English or Spanish, from the 2000s and 2021, comprising case report studies, case series and literature reviews.

RESULTS

Considering clinical and radiographic aspects, it is evident that craniopharyngiomas and ameloblastomas exhibit few similarities. Histopathologically, however, adamantinomatous craniopharyngiomas are the type of tumor that most resembles ameloblastomas, both concerning the formation of palisade epithelial cords and epithelial formations. Regarding to recurrences in cases of craniopharyngioma, it appears that a more radical surgical resection is more related to a lower recurrence rate for both craniopharyngiomas and ameloblastomas. As for the outcome, it was observed that craniopharyngiomas have a greater relationship with possible systemic disorders.

CONCLUSIONS

This histopathological similarity is related to their origin, since both craniopharyngiomas and ameloblastomas share a relationship with the oral cavity, either partially, as in the case of craniopharyngiomas, or totally, as in ameloblastomas, not comprising the same lesion in different locations. It is important to note that the differential morphogenetic evidence observed herein between these lesions opens up a new field of study aiming at better treatment alternatives in the future.

Adamantinomatous craniopharyngioma as a model to understand paracrine and senescence-induced tumourigenesis

Cellular senescence is a process that can prevent tumour development in a cell autonomous manner by imposing a stable cell cycle arrest after oncogene activation. Paradoxically, senescence can also promote tumour growth cell non-autonomously by creating a permissive tumour microenvironment that fuels tumour initiation, progression to malignancy and metastasis. In a pituitary tumour known as adamantinomatous craniopharyngioma (ACP), cells that carry oncogenic β-catenin mutations and overactivate the WNT signalling pathway form cell clusters that become senescent and activate a senescence-associated secretory phenotype (SASP). Research in mouse models of ACP has provided insights into the function of the senescent cell clusters and revealed a critical role for SASP-mediated activities in paracrine tumour initiation. In this review, we first discuss this research on ACP and subsequently explore the theme of paracrine tumourigenesis in other tumour models available in the literature. Evidence is accumulating supporting the notion that paracrine signalling brought about by senescent cells may underlie tumourigenesis across different tumours and cancer models.

A craniopharyngioma in a Wistar rat most likely originated in a Rathke's cleft cyst

We examined a 110-week-old RccHan^TM: WIST Wistar male rat from a carcinogenicity study. No clinical signs were observed, and the rat was sacrificed at the end of the study. Macroscopically, within the midline of the sphenoid bone, was a 10 mm, non-infiltrative, soft, heterogeneous mass. Microscopic evaluation showed an expansile, cystic proliferation, consisting of two patterns of epithelial lining: well-differentiated areas lined by a single layer to a pseudostratified, ciliated-cuboidal epithelia with Goblet cells compatible with Rathke’s cleft cyst; and poorly differentiated ones that formed irregular papillary projections, covered by atypical epithelia with squamous differentiation and hyperkeratosis compatible with areas of craniopharyngioma. Pleomorphisms were high in atypical areas with up to 2–3 mitotic figures per high power field. Within the cystic cavities, there was abrupt keratinization, mucus, cholesterol clefts, and foci of foamy macrophages. Immunohistochemistry revealed strong pancytokeratin immunolabelling of neoplastic cells confirming the epithelial origin. Well-differentiated epithelial lining showed cytokeratin-20 and cytokeratin-8 immunoreactivity, whereas the atypical squamous epithelium presented with a loss of cytokeratin-20 positive signal and weak to moderate positivity with cytokeratin-8. Areas compatible with a Rathke’s cleft cyst and craniopharyngioma were considered to co-exist in the same mass.

Current concepts and occurrence of epithelial odontogenic tumors: I. Ameloblastoma and adenomatoid odontogenic tumor

Ameloblastomas and adenomatoid odontogenic tumors (AOTs) are common epithelial tumors of odontogenic origin. Ameloblastomas are clinico-pathologically classified into solid/multicystic, unicystic, desmoplastic, and peripheral types, and also divided into follicular, plexiform, acanthomatous, granular types, etc., based on their histological features. Craniopharyngiomas, derived from the remnants of Rathke's pouch or a misplaced enamel organ, are also comparable to the odontogenic tumors. The malignant transformation of ameloblastomas results in the formation of ameloblastic carcinomas and malignant ameloblastomas depending on cytological dysplasia and metastasis, respectively. AOTs are classified into follicular, extrafollicular, and peripheral types. Ameloblastomas are common, have an aggressive behavior and recurrent course, and are rarely metastatic, while AOTs are hamartomatous benign lesions derived from the complex system of the dental lamina or its remnants. With advances in the elucidation of molecular signaling mechanisms in cells, the cytodifferentiation of epithelial tumor cells in ameloblastomas and AOTs can be identified using different biomarkers. Therefore, it is suggested that comprehensive pathological observation including molecular genetic information can provide a more reliable differential diagnosis for the propagation and prognosis of ameloblastomas and AOTs. This study aimed to review the current concepts of ameloblastomas and AOTs and to discuss their clinico-pathological features relevant to tumorigenesis and prognosis.

[Benign epithelial odontogenic tumors]

The group of benign epithelial odontogenic tumors consists of the four member types of the ameloblastoma family (solid/multicystic, extraosseous/peripheral, desmoplastic, unicystic), squamous odontogenic tumors, calcifying odontogenic tumors, adenomatoid odontogenic tumors, and keratocystic odontogenic tumors, the former "keratocysts" that were recently reclassified by the World Health Organization and are now regarded as tumors. The latter are by far the most frequent tumors in this group, followed by solid/multicystic ameloblastoma. Although the etiology of these lesions is still unknown, a close relationship to normal tooth development is obvious, which is partially imitated by some tumors. Despite some similarities to each other, at least in part, the biological behavior of these lesions is quite different, as are treatment modalities. The diagnosis is essentially based on localization (intraosseous vs. extraosseous/peripheral) and histology, whereupon the correlation of histological findings with radiographic morphology may be of additional diagnostic value. Because of the range of variation, immunohistochemical investigations are not helpful in diagnosing a particular case.

Presence of ghost cells and the Wnt signaling pathway in odontomas

BACKGROUND

Although it has been reported that ghost cells are present in odontomas, the generation mechanism of these cells is unclear. To evaluate the presence of ghost cells and involvement of the Wnt signaling pathway, we examined the expression of hard keratins, beta-catenin and Lef-1 in odontomas.

METHODS

Sixty-nine cases of odontoma were examined immunohistochemically with the use of antibodies against human hair proteins, beta-catenin and Lef-1.

RESULTS

Expression of hard keratins was found only in the cytoplasm of ghost cells in 46 (66.7%) of the 69 odontomas. Compound odontomas (78.8%) showed a higher incidence of ghost cells than complex odontomas (29.4%). Histopathologically, ghost cells were found within odontogenic epithelium adjacent to immature enamel and in the centre of Liesegang-ring-like calcified materials. Expression of beta-catenin and Lef-1 was observed in the cytoplasm and nucleus of odontogenic epithelial cells adjacent to the ghost cells in immature odontomas.

CONCLUSION

These findings suggest that odontoma is a hard keratin-expressing tumor-like lesion, and that the Wnt signaling pathway may be involved in the formation of ghost cells in odontomas.

Nuclear beta-catenin accumulation associates with epithelial morphogenesis in craniopharyngiomas

Activation of the Wnt/wingless signalling cascade is a key mechanism in developmental morphogenesis, whereas aberrant nuclear accumulation of beta-catenin in adult tissues seems to be associated with neoplastic transformation and tumour progression. Adamantinomatous craniopharyngiomas carry activating mutations in exon 3 of the beta-catenin gene, which results in a distinct pattern of nuclear beta-catenin accumulation in up to 95% of respective tumour specimens. To better characterise the impact of nuclear beta-catenin aggregation in these neoplasms, we systematically examined epithelial differentiation and cell cycle-associated molecules in accumulating compared to non-accumulating tumour cell clusters using a cohort of 65 adamantinomatous craniopharyngiomas. Monoclonal antibodies directed against cytokeratins 5/6 (CK5/6) were utilised to differentiate squamous from simple epithelium, the latter being identified by immunoreactivity for cytokeratins 8 and 18 (CK8/CK18). Intriguingly, nuclear beta-catenin accumulation in whorl-like tumour cell clusters was always associated with a distinct CK8 and CK18 immunoreactivity, whereas surrounding non-accumulating tumour cells showed exclusively squamous differentiation indicated by CK5/6 expression. In addition, a low proliferation activity combined with an increased expression of p21(WAF1/CIP1), a key control protein of the cell cycle, was observed in beta-catenin accumulating cells. Our data support an impact of nuclear beta-catenin on different cytoarchitectural and epithelial differentiation patterns in adamantinomatous craniopharyngiomas.

Comparative immunohistochemical assessment of craniopharyngioma and related lesions

Craniopharyngiomas (CP), Rathke's cleft cysts (RCC), and sellar xanthogranulomas (XG) are closely related lesions. As expression of cytokeratins 8 (CK8) and 20 (CK20) was reported in RCC but not in CP, the present study investigates the reproducibility of immunohistochemical distinction between CP and RCC, attempting to identify the relationship of XG to these lesions. A comparative study of 55 patient specimens (25 CP, 28 RCC, and 2 XG) was analyzed for the histological features of xanthomatous changes and squamous metaplasia, and expression of CK8 and CK20. In the 25 CP cases, xanthomatous changes were seen in 5 (20%), with CK8 reactivity demonstrated in all 25 cases. A prominent xanthomatous component was identified in 13 of 28 RCC (46%), and squamous metaplasia was seen in 11 (39%), 9 of which also contained xanthomatous features. CK8 reactivity was demonstrated in all 28 RCC cases, whereas CK20 was seen only in 9 cases (32%). Of the two cases diagnosed as XG, none contained epithelium, and immunohistochemistry for cytokeratins was not observed. Overall, differential expression of cytokeratins cannot reliably distinguish CP from RCC. Furthermore, expression of CK20 in RCC is generally seen within a background of prominent squamous metaplasia and reactive xanthomatous changes.

Expression and growth dependency of the insulin-like growth factor I receptor in craniopharyngioma cells: a novel therapeutic approach

Craniopharyngioma is a rare benign intracranial epithelial tumor that, however, often recurs and sometimes kills the affected patients, one-third of which are children. In many cases, the patients acquire growth hormone deficiency and postoperatively need substitution. Generally, growth hormone promotes local release of insulin-like growth factor I (IGF-I), which in turn activates the IGF-I receptor (IGF-IR) if present. Together, these circumstances raise the question whether IGF-IR may be involved in craniopharyngioma growth. To address this issue, we analyzed phenotypically well-characterized primary low-passage craniopharyngioma cell lines from nine different patients for IGF-IR expression and IGF-I dependency. Two of the cell lines showed no/very low expression of the receptor and was independent on IGF-I, whereas five cell lines exhibited a strong expression and was clearly contingent on IGF-I. The two remaining cell lines had low receptor expression and IGF-I dependency. Upon treatment with an IGF-IR inhibitor, cells with high IGF-IR expression responded promptly with decreased Akt phosphorylation followed by growth arrest. These responses were not seen in cells with no/very low receptor expression. Growth of cell lines with low IGF-IR expression was only slightly affected by IGF-IR inhibition. Taken together, our data suggest that IGF-IR may be involved in the growth of a subset of craniopharyngiomas and points to the possibility of the involvement of IGF-IR inhibitors as a treatment modality to obtain complete tumor-free conditions before growth hormone substitution.

Primary sinonasal ameloblastoma

A case of primary ameloblastoma of the right sinonasal tract in a 66-year-old man is reported. The tumour presented as a radiographically solid mass filling the right nasal cavity and sinuses and without continuity with maxillary alveola. After radical surgery plus postoperative radiotherapy, the patient has pursued a non-aggressive clinical course after nine months of follow-up. The paper reviews the clinico-pathological features of this rare tumour and supports the theory of its sinonasal epithelium origin.

Ameloblastoma in the Hong Kong Chinese. Part 1: systematic review and clinical presentation

OBJECTIVES

The aim of Part 1 of this study was to determine the clinical presentation of central ameloblastomas in the Hong Kong Chinese and to compare them with other reported series by a systematic review (SR).

METHODS

The study had two elements, that of a complete series of all ameloblastomas presenting at a major Chinese maxillofacial surgical unit as well as a SR. The files of the Department of Oral and Maxillofacial Surgery of the University of Hong Kong between 1989 and 2000 were reviewed for ameloblastoma cases. The relevant literature was identified by electronic databases, review of citation lists and hand searching of key journals. The principal selection criterion was that the study should represent a complete collection of cases.

RESULTS

Fifty-three published series of cases were included in the SR. They generally reported little more than sex, mean age and range, and affected jaw. Only 16 studies considered recurrence. Sixty-one cases of ameloblastoma were identified in the present study. There were 30 males and 31 females, contrary to the predilection for males in other reports. Eighty-four percent of cases were found in the mandible, agreeing with the SR. The mean age at first presentation was 30.5 years, lower than that of the SR; only a Korean report and a small Bangladeshi report showed younger presentation. The present report had the shortest period between first becoming aware of the lesion and seeking treatment; this period was significantly shorter for younger patients. Although the present study was in agreement with the SR with regard to swelling, this study reported a significantly higher proportion of patients presenting with pain.

CONCLUSION

Although the presentation of ameloblastoma within this Chinese community was broadly similar to that observed in other populations, it differed in a number of important respects. It had a younger age at first presentation than many other communities, including other Orientals; it was associated with a shorter period between first becoming aware of the lesion and seeking treatment, particularly in the young; and it was more frequently associated with pain than in the SR.

Differential Expression of Cytokeratins 8 and 20 Distinguishes Craniopharyngioma From Rathke Cleft Cyst

Background.—Craniopharyngiomas are epithelial neoplasms usually located in the sellar and suprasellar regions. Distinguishing craniopharyngioma from Rathke cleft cyst is sometimes difficult, and the distinction is clinically significant because Rathke cleft cysts have a better prognosis than craniopharyngiomas.

Design.—We retrieved 10 cases with a primary diagnosis of craniopharyngioma and 5 cases with a diagnosis of Rathke cleft cyst for analysis. Five cases of normal pars intermedia of pituitary glands from autopsy served as controls. We evaluated the expression patterns of a broad range of low– to intermediate–molecular weight cytokeratins (CK7, CK8, CK10, CK17, CK18, CK19, and CK20) and high–molecular weight cytokeratins (K903: a combination of CK1, CK5, CK10, and CK14; and CK5/6) in these cases.

Results.—Craniopharyngiomas had a cytokeratin expression pattern distinct from that of Rathke cleft cysts and pituitary gland pars intermedia: craniopharyngiomas did not express cytokeratins 8 and 20, whereas Rathke cleft cysts and pars intermedia of pituitary glands both expressed cytokeratins 8 and 20.

Conclusion.—The differential expression of cytokeratins distinguishes between craniopharyngioma and Rathke cleft cyst, and this difference could be useful for identifying craniopharyngioma in difficult cases in which only a small biopsy is available. The different cytokeratin profiles of craniopharyngioma and Rathke cleft cyst suggest that these lesions do not come from the same origin, or that they come from a different developmental stage of the pouch epithelium.