An immunohistochemical study of keratin expression in ameloblastoma from a Kenyan population

Clinicopathologic study on a rare variant of ameloblastoma with basal cell features

OBJECTIVES

To investigate the clinical features, pathologic manifestations, and biologic behaviors of a variant of ameloblastoma with basal cell features (AM-BC).

MATERIALS AND METHODS

Following retrospective review of the clinical and pathological data of six cases of AM-BC, we described their histological and immunohistochemical (IHC) features and discussed the biologic behaviors, prognoses, pathogenesis, and clinical relevance of AM-BC. Direct sequencing of polymerase chain reaction products was also performed in all cases.

RESULTS

The six cases of AM-BC involved four women and two men, aged 22-82 years. Four lesions occurred in the maxilla and two in the mandible. Histologically, the basal cells tended to be arranged as unequally sized follicles, strands, or cords of odontogenic epithelium in the connective tissue stroma. Little or no stellate reticulum was present in the central portion of the nest. Expression of CKs was consistent with other histological variants of ameloblastoma (AM), but AM-BC had significantly higher p53 and Ki-67 (p < 0.05) labeling indices than other histological variants of AM. Two patients had BRAF gene mutations.

CONCLUSION

Ameloblastoma with basal cell features is a very rare variant of AM. Our study showed the differences and relationships that exist between AM-BC and other variants of AM, which could enhance understanding of AM-BC.

Immunohistochemical biomarkers in ameloblastomas

Ameloblastoma is an aggressive odontogenic tumour, which is locally invasive and highly recurrent. Studies show that ameloblastoma is a benign odontogenic neoplasia, being relatively rare and occasionally presenting behaviour of malignant lesions. In addition to these particularities, the histological diagnosis of ameloblastoma can be challenging when the tumour shows high rates of mitosis, absence of nuclear pleomorphism, basilar hyperplasia and neural invasion. In order to help in the diagnosis, prognosis and treatment of this neoplasia, some immunohistochemical markers were shown to be associated with tumoural epithelium. The identification of these markers as well as of their association with clinical signs can be useful to elaborate more efficient treatment strategies and to control this pathology, including improvement of the quality of life of patients affected by this neoplasia. This article aims to review some markers associated with specific molecular pathways, bone remodelling, cell proliferation, apoptosis, cell signalling and tumour suppression.

Immunohistochemical expression of K6, K8, K16, K17, K19, maspin, syndecan-1 (CD138), α-SMA, and Ki-67 in ameloblastoma and ameloblastic carcinoma: diagnostic and prognostic correlations

OBJECTIVE

To identify cutoff values of markers that correlate with the histopathologic diagnosis of ameloblastic carcinoma (AC) and/or the increased recurrence potential of ameloblastoma (AB).

STUDY DESIGN

Immunohistochemical expression (IHCE) of 9 selected markers were investigated in 18 non-recurrent ameloblastomas (NRABs), 6 recurrent ameloblastomas (RABs), and 5 ACs.

RESULTS

No significant difference in IHCE of K6, K8, K16, K17, K18, K19, maspin, or syndecan-1 was observed among study groups. α Smooth muscle actin (α-SMA)-positive area in central epithelial cells significantly differentiated between AB and AC (P = .017; t -test). Ki-67 score significantly differentiated between AB and AC (P < .005; t -test) and between AC and RAB (P = .015; ANOVA/post hoc).

CONCLUSIONS

Ki-67 score of 75 cells/HPF (ROC curve) is a potential indicator of AC. Clinical recurrence of AB may be predicted by α-SMA expression pattern. Syndecan-1 and α-SMA may indicate a higher aggressive potential of AB when expressed in the stroma.

Molecular biomarkers of cell proliferation in ameloblastomas

Cell proliferation is a vital biological process that is important for all living organisms because of its role in growth and the maintenance of tissue homeostasis. The control of this important process differs greatly among benign and malignant neoplasms, and the evaluation of cell proliferation in neoplasms has become a common tool used by pathologists to provide useful information pertaining to diagnosis, clinical behavior, and treatment. The usefulness of information regarding cell proliferation has led to numerous studies on the value of these methods for diagnosing different types of tumors and for clinical decision making. Ameloblastomas are no exception. This review discusses the use of several classical molecular proliferation markers, including Ki-67, proliferating cell nuclear antigen, cyclin D1 and DNA topoisomerase II alpha, to characterize ameloblastomas and proposes the use of new proliferation markers used previously to characterize other neoplasms. The use of these biomarkers offers valuable opportunities to evaluate the biological behavior of this type of odontogenic tumor.

The expression profiles of acidic epithelial keratins in ameloblastoma

OBJECTIVE

To characterize the subtypes of ameloblastoma by differentiation markers.

STUDY DESIGN

Expression of 9 major acidic epithelial keratins was immunohistochemically examined in 28 ameloblastomas.

RESULTS

Keratin 15 (K15) expression patterns corresponded to histological variants: follicular, plexiform and acanthomatous. Tumor nests comprising K15-expressing basal cells mimicked oral epithelium or dental lamina, and tumor nests comprising K15-negative basal cells mimicked outer enamel epithelium. Keratin 19 (K19) was consistently expressed in solid/multicystic ameloblastoma and unicystic ameloblastoma, while peripheral ameloblastoma and desmoplastic ameloblastoma contained K19-negative cells.

CONCLUSIONS

The 4 current subtypes had unvaried expression patterns within each group. However, they could be divided into 2 groups by K19 expression pattern: solid/multicystic and unicystic versus extraosseous/peripheral and desmoplastic. K15 expression pattern represented various types of differentiation for tumor nests mimicking tooth germ and oral epithelium. The results clarify the homogeneity and heterogeneity of ameloblastoma cell lineage and differentiation.

Comparative immunohistochemical study of ameloblastoma and ameloblastic carcinoma

OBJECTIVE

Ameloblastic carcinoma combines the histologic features of ameloblastoma with cytologic atypia, regardless of whether it has metastasized. Because of its rarity, there are few immunoprofile studies of ameloblastic carcinoma and few comparative studies of ameloblastic carcinoma and ameloblastoma. In this study, we compared the expression levels of cytokeratins (CKs), matrix metalloproteinases (MMPs), and Ki-67 between ameloblastoma and ameloblastic carcinoma, and assessed the usefulness of these markers for differentiating the tumors.

STUDY DESIGN

We assessed CK7, CK14, CK18, CK19, MMP-2, MMP-9, and Ki-67 expression by immunohistochemistry in 10 cases of ameloblastoma and 7 cases of ameloblastic carcinoma and then compared expression patterns between the 2 groups.

RESULTS

Immunostaining for CK14 and CK19 was diffuse and strongly positive in both tumor types, but staining for CK7 was focally positive in only 1 case of ameloblastoma and absent in all cases of ameloblastic carcinoma. However, there was a significant difference in CK18 expression between the 2 tumors (P = .000). Whereas 80% of ameloblastomas showed negative reactivity for CK18, most cases of ameloblastic carcinomas showed a moderate to strong intensity of immunostaining for CK18. Regarding the expression of MMPs, there were significant differences in parenchymal MMP-2 and stromal MMP-9 expression between the 2 tumors. Compared to ameloblastoma, ameloblastic carcinoma showed significantly strong expression of MMP-2 in parenchymal cells (P = .001) and MMP-9 in stromal cells (P = .013). However, there were no differences in MMP-2 expression of stromal cells and MMP-9 expression of parenchymal cells between ameloblastoma and ameloblastic carcinoma. The mean Ki-67 labeling index (LI) of ameloblastic carcinomas was 17.21%, which was significantly higher than that of ameloblastomas (3.57%; P = .002).

CONCLUSIONS

The significant expression of CK18, parenchymal MMP-2, stromal MMP-9, and Ki-67 could provide useful markers for differentiating ameloblastic carcinoma from ameloblastoma.

Clinicopathological and immunohistochemical study of 39 cases of Adenomatoid Odontogenic Tumour: a multicentric study

Adenomatoid Odontogenic Tumour (AOT) is a relatively uncommon odontogenic lesion and few studies describing its cytokeratin profile have been reported in the English-language literature. Thirty-nine cases of AOT from three Oral Diagnosis services (Brazil, Mexico and Guatemala) were studied, considering their clinical, radiographic, and histological features and immunohistochemical expression of cytokeratins (AE1/AE3, 34betaE12, CK1, CK5, CK6, CK7, CK8, CK10, CK13, CK14, CK16, CK18, and CK19), vimentin and Ki-67. Sixty five percent of cases affected women, anterior maxilla was the preferred site and radiographically most cases showed unilocular radiolucency with well defined sclerotic borders. Calcifying epithelial odontogenic tumour (CEOT)-like areas were found in 36 out of 39 cases, and 10 cases showed positivity for Congo red in polarized light. All cases were positive for AE1/AE3, 34betaE12, CK5, CK14 and CK19. CEOT-like areas were negative for CK 19. Vimentin was also expressed in 27 cases and this profile may indicate the existence of a variable phenotype in certain areas of the tumour. There were no recurrences after surgical treatment, and this can be related to the low proliferative activity observed in all cases with Ki-67 marker.

Keratin 16 Expression in Epidermal Melanocytes of Normal Human Skin

Although the prevailing dogma states that keratin filaments are the hallmark of keratinocytes and other epithelial cells, recent publications suggest that they may be expressed by a variety of normal and malignant cells of different embryonic origin. Keratin expression has been reported in fibroblasts and endothelial cells as well as in various sarcomas. Also, some human melanomas express keratins in addition to the traditional diagnostic markers of differentiation, such as S-100 and melanocyte-specific antigens. Many studies have shown that cultured cells obtained from various melanomas express keratin. Most recently, keratin expression has also been shown in cultured melanocytes of normal skin. We now report that normal human melanocytes in vivo express keratin 16 (K16) but not keratins 1, 5, 8, 10, 14, or even keratin 6, the type II partner that is normally expressed with K16 in keratinocytes. Similarly, melanocytes in vitro express K16 but not K6. Keratin 16 expression in vivo was present in basal melanocytes in specimens derived from donors (0-77 years) and from different anatomic locations, suggesting that keratin 16 is constitutively expressed by all melanocytes. It appears that keratin expression may be more prevalent than previously assumed, and that these cytoskeletal filaments may play important roles in tissues and cells other than epithelia.

Cytokeratin expression in central mucoepidermoid carcinoma and glandular odontogenic cyst

Central mucoepidermoid carcinoma (MEC) is an entity whose origin is still controversial. Glandular odontogenic cyst (GOC) is a recently described lesion whose relationship to low-grade central MEC has been reported in the literature. Our aim was to assess the cytokeratin (CK) profile of central MEC and GOC, and compare the results with CK expression in salivary gland MEC and odontogenic cysts and tumors. Eighty-five cases, including 6 central MECs, 23 salivary gland MECs, 10 GOCs, 34 odontogenic cysts and 12 ameloblastomas, were studied through immunohistochemistry using eleven monoclonal anti-CK antibodies. All central MECs expressed CKs 5, 7, 8, 14, and 18 and all GOCs expressed CKs 5, 7, 8, 13, 14, and 19. Comparing CK expression from GOC and central MEC we found differences in CKs 18 (30% vs 100%) and 19 (100% vs 50%). Central MEC and GOC are probably distinct entities with CK profiles similar to lesions of glandular and odontogenic origins, respectively, and expression of CKs 18 and 19 could be useful in their differential diagnosis.

Keratin expression in human tissues and neoplasms

Keratin expression in human tissues and neoplasms Keratin filaments constitute type I and type II intermediate filaments (IFs), with at least 20 subtypes named keratin 1-20. Since certain keratin subtypes are only expressed in some normal human tissues but not others, and vice versa, various tissues have been subclassified according to the pattern of keratin staining. Simple epithelia generally express the simple epithelial keratins 7, 18, 19, and 20, while complex epithelia express complex epithelial keratins 5/6, 10, 14, and 15. When an epithelium undergoes malignant transformation, its keratin profile usually remains constant. The constitution and expression patterns of keratin filaments in human epithelial neoplasms are complex and often distinctive. In this article, we first briefly review the molecular and cell biology of keratin filaments. We then focus on the expression patterns of keratin filaments in various human neoplasms.