Cytokeratin expression in trichoblastic fibroma (small nodular type trichoblastoma), trichoepithelioma and basal cell carcinoma

An immunohistochemical and ultrastructural study of syringocystadenoma papilliferum

BACKGROUND

Syringocystadenoma papilliferum is a benign hamartomatous tumour of the skin. The histogenesis of this tumour is still controversial. There have been few reports regarding immunohistochemical investigations using only a limited range of antibodies and ultrastructural studies on this rare tumour.

OBJECTIVES

To elucidate the immunohistochemical and ultrastructural properties of this tumour.

METHODS

We investigated the immunohistological patterns of 12 different anticytokeratin (CK) antibodies and several other markers in five cases of this tumour, comparing them with the patterns in adult sweat glands. One of these cases was also evaluated ultrastructurally.

RESULTS

The luminal columnar cells of the tumour were mostly positive for CK7 and more than 70% were positive for CK19. These cells showed the heterogeneous expression of CK1/5/10/14, CK14 and CK5/8. These patterns were also observed in the luminal cells in the secretory or the ductal portion of the adult sweat glands. The basal cuboidal cells of the tumour almost constantly expressed CK1/5/10/14, CK5/8, CK14 and CK7 (except for one case), similar to the patterns of basal cells in the transitional portion and myoepithelial cells in the sweat glands. However, the basal tumour cells expressed CK19 and vimentin heterogeneously, and alpha-smooth muscle actin focally (three cases). Ultrastructurally, the constituent epithelial cells were mainly divided into three types: luminal cells, basal cells and clear cells. The luminal tumour cells bore features of the secretory or ductal luminal cells of sweat glands, although they were somewhat immature in appearance. The basal tumour cells were fundamentally basaloid in nature. The clear cells were undifferentiated or primitive in appearance, suggesting stem or progenitor cell properties. Transitional forms between the clear cells and the other two cell types were also identified.

CONCLUSIONS

The tumour epithelium was composed of several cell types demonstrating various developmental stages from the primitive clear cells to the basal cells demonstrating a tendency to differentiate toward basal cells in the apocrine transitional portion or myoepithelial lineage, or luminal cells toward the ductal or secretory epithelium. These results support the classical concept that syringocystadenoma papilliferum is a hamartomatous tumour that arises from pluripotent cells.

Carcinoma arising in a proliferating trichilemmal cyst expresses fetal and trichilemmal hair phenotype

Carcinomas that arise in a proliferating trichilemmal cyst (PTC) have been described under a variety of names. Monoclonal antibodies (mAbs) indicating follicular differentiation have become available and were used here in two rare tumors with uncommon biologic behavior. To further elucidate the histogenesis of carcinomas arising in a PTC, mAbs to hair follicle stem cells and to hair follicle differentiation-specific cytokeratins (mAbs to cytokeratin [CK] 7, CK8, CK18, and CK19 as well as mAbs to CD8/CK15 and CD34) were studied on paraffin-embedded sections of two cases of carcinoma arising in a PTC, one anaplastic carcinoma, and one poorly differentiated squamous cell carcinoma (SCC). For comparison, concurrent PTCs and trichilemmal cysts as well as four SCCs from controls were studied. The anaplastic carcinoma showed expression of CK7, indicating a fetal hair root phenotype, and expression of CD34, indicating trichilemmal differentiation. In contrast, the poorly differentiated SCCs as well as the control SCCs stained negative for most of the mAbs applied. Expression of fetal and trichilemmal hair follicle phenotypes suggests differentiation from hair stem cells and might explain differences in biologic behavior.

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.

Immunohistochemical and ultrastructural observations of desmoplastic trichoepithelioma with a special reference to a morphological comparison with normal apocrine acrosyringeum

BACKGROUND

Desmoplastic trichoepithelioma is a benign neoplasm considered to have follicular differentiation. Its sweat gland- or sebaceous-lines of differentiation have been also reported. There have been, however, only a few reports regarding extensive immunohistochemical and ultrastructural investigations of this neoplasm.

METHODS

Histopathological and immunohistochemical studies were performed on three cases of desmoplastic trichoepithelioma, comparing it with normal skin. One of these cases was ultrastructurally investigated.

RESULTS

The cord-like basaloid nests were reacted with the anti-cytokeratin (CK)1/5/10/14, -CK5/8, -CK14 and -CK15 antibodies, but not with the anti-CK6 antibody. Similar findings were observed in the outer layers of the normal follicular outer root sheath. Basaloid cell nests in one case, which showed ductal structures in the nests, also expressed CK7, CK8/18 and CK19. These keratins were also detected in the normal sweat glands. In addition, CK8/18 and CK19 were expressed in the basal cells of the outer root sheath. Keratinous cysts had inner reactions with the anti-CK10/11 and -CK6 antibodies, and outer reactions with anti-CK5/8 and -CK14 antibodies. Ultrastructurally, the cells in the cord-like nests were basically immature and basaloid in appearance. A few cells contained Odland bodies, which were also observed in the normal apocrine acrosyringeum. The ductal structure was lined by the cells which bore numerous microvilli in the luminal surface.

CONCLUSION

The cells in desmoplastic trichoepithelioma are suggested to be in close association with the basal cells in the outer root sheath, which can differentiate into various parts of the folliculosebaceous apocrine unit.

Cytokeratins as markers of follicular differentiation: an immunohistochemical study of trichoblastoma and basal cell carcinoma

Trichoblastoma(s) (TB) are benign neoplasms of follicular differentiation frequently found in nevus sebaceus. Many morphologic features are shared with nodular basal cell carcinoma(s) (BCC), sometimes rendering the differential diagnosis difficult. Because both neoplasms can simulate components of mature hair follicles histologically, we attempted to corroborate this by immunohistochemical examination of cytokeratins and hair keratins differentially expressed in the hair follicle. Trichoblastoma(s) and BCC showed homogenous expression of CK14 and CK17. The innermost cells of the tumor nodules in all TB and in 72% of BCC were positive for CK6hf. Using a specific CK15 antibody, 38% of TB showed a focal labeling and all BCC remained negative; 70% of TB and 22% of BCC expressed CK19. CK8 was expressed by numerous Merkel cells present in all TB but in none of the BCC examined. All type I and II hair keratins tested, (especially hHa1, hHa5, and hHa8) remained negative in all tumors examined. Trichoblastoma(s) and BCC show consistent expression of CK6hf, CK14, and CK17; variable expression of CK15 and CK19; and absence of hair keratins. This indicates a differentiation toward the outer root sheath epithelium or the companion layer and not toward the inner root sheath, matrix, or cortex.

Expression of Basigin in human fetal, infantile and adult skin and in basal cell carcinoma

BACKGROUND

Basigin is a glycosylated transmembrane protein belonging to the immunoglobulin superfamily and is thought to be associated with cell development and differentiation. We investigated the relation between Basigin expression and epidermal development in this study.

METHODS

Basigin expression was immunohistochemically investigated during organogenesis of human skin and in human basal cell carcinoma (BCC).

RESULTS

Human fetal skin showed negative staining at 10 weeks of gestation. At 20 weeks, the cytoplasm and membranes of adnexal germ and hair follicular cells were strongly positive, while epidermal basal cells showed weakly positive staining. After birth, basal cells, suprabasal cells, anagen hair follicular cells and eccrine glandular cells showed positive staining. Membranes of basal cells expressed more Basigin compared to other cell components. Basigin was not detectable in granular cells and telogen hair follicular cells. Sixteen of 30 BCCs were entirely negative for Basigin. However, cells at budding areas of tumor masses were positive in 14 of the 30 BCCs.

CONCLUSIONS

These findings suggest that 1) Basigin is associated with epidermal proliferation and differentiation, 2) most parts of BCCs might be derived from early fetal epidermal basal cells, and 3) that a part, only the budding area of BCCs, has the characteristics of epithelial germ cells.

Sub-populations of melanocytes in pigmented basal cell carcinoma: a quantitative, ultrastructural investigation

BACKGROUND

Pigmentation is a characteristic clinical feature of basal cell carcinomas (BCCs) in Japanese patients. The pathogenesis of melanin pigment in pigmented BCCs is poorly understood.

METHODS

We have combined the techniques of morphometric analysis and electron microscopy to assess accurately the morphologic aspects of melanocytes that occurred in pigmented and non-pigmented areas of pigmented BCCs.

RESULTS

In the pigmented areas melanocytes were not only located along the basal membrane but also interspersed between tumor cells in the central parts of the tumor nest, and had large and numerous dendrites. Those in a supra-basal location displayed some degree of degeneration due to mitochondrion and melanosome swelling. In the non-pigmented areas melanocytes were only basally located, showed fewer dendrites, and frequently showed abortive melanosomes. However, melanocytes in these two different portions were in the active state of melanogenesis and proliferation. Ultrastructural cytomorphometric analysis also showed significant differences in most of the nuclear and cell parameters including nuclear and cell area, the nuclear/cell area ratio, cell perimeter and cell form factor between these two types of melanocytes. Particularly melanocytes in the pigmented areas were twice the cell size of the latter. In addition, the melanosomes remained almost completely in the apoptotic tumor cells, and the phagocytosis of the melanosome-containing apoptotic cells by the neighboring tumor cells appeared to be followed by the formation of the melanosome complexes.

CONCLUSIONS

These findings suggest that different populations of melanocytes are probably present in pigmented BCCs, and repeated cycles of phagocytosis of melanosome-containing apoptotic cells may represent the predominant way of forming large melanosome complexes. The present morphological observation and quantitative analysis provide a morphological basis for further studies to interpret other pathologic changes in pigmented BCCs.

Induction of basal cell carcinomas and trichoepitheliomas in mice overexpressing GLI-1

Basal cell carcinoma is the most prevalent cancer in the western world, showing a rapid increase in incidence. Activation of the Sonic hedgehog/Patched (PTCH) signaling pathway because of PTCH1 inactivation is a key event in sporadic and familial basal cell carcinoma development in humans and is associated with transcriptional activation of specific target genes, including PTCH1 itself. These changes are analogous to the situation in Drosophila where hedgehog activates the zinc-finger transcription factor Cubitus interruptus, leading to increased transcription of target genes. In the present study, we show that mice ectopically expressing the human Cubitus interruptus homolog GLI-1 in the skin develop tumors closely resembling human BCCs as well as other hair follicle-derived neoplasias, such as trichoepitheliomas, cylindromas, and trichoblastomas. Furthermore, examination of the tumors revealed wild-type p53 and Ha ras genes. These findings firmly establish that increased GLI-1 expression is central and probably sufficient for tumor development and suggest that GLI-1-induced tumor development does not depend on additional p53 or Ha ras mutations.

Induction of basal cell carcinomas and trichoepitheliomas in mice overexpressing GLI-1

Basal cell carcinoma is the most prevalent cancer in the western world, showing a rapid increase in incidence. Activation of the Sonic hedgehog/Patched (PTCH) signaling pathway because of PTCH1 inactivation is a key event in sporadic and familial basal cell carcinoma development in humans and is associated with transcriptional activation of specific target genes, including PTCH1 itself. These changes are analogous to the situation in Drosophila where hedgehog activates the zinc-finger transcription factor Cubitus interruptus, leading to increased transcription of target genes. In the present study, we show that mice ectopically expressing the human Cubitus interruptus homolog GLI-1 in the skin develop tumors closely resembling human BCCs as well as other hair follicle-derived neoplasias, such as trichoepitheliomas, cylindromas, and trichoblastomas. Furthermore, examination of the tumors revealed wild-type p53 and Ha ras genes. These findings firmly establish that increased GLI-1 expression is central and probably sufficient for tumor development and suggest that GLI-1-induced tumor development does not depend on additional p53 or Ha ras mutations.