Simple epithelial cytokeratin-expression in seborrheic keratosis

Seborrheic keratosis: current concepts of pathogenesis

The article covers problems of seborrheic keratosis. The authors discuss current concepts of the etiology and pathogenesis of the disease paying special attention to the histology and immunohistochemistry of different forms and diverse clinical presentations. They describe Leser - Trelat syndrome as well as potential neoplastic transformation of seborrheic keratomas and their association with malignant skin neoplasms.

Epithelial keratin and filaggrin expression in seborrheic keratosis: evaluation based on histopathological classification

OBJECTIVES

Seborrheic keratosis (SK) is classified into six types: hyperkeratotic; acanthotic; irritated; clonal; reticulated; and adenoid. However, the origins of the respective types of SK remain unclear.

METHODS

To clarify the histogenetic origins of SK, we performed immunohistochemical studies of keratin (K) and filaggrin expression, taking into account the histopathological classifications of SK.

RESULTS

Hyperkeratotic SK mainly expressed K1, K10, and filaggrin. Acanthotic SK mainly expressed K14 with some K15. Irritated SK mainly expressed K14 and K17 in squamous eddies. Clonal SK, reticulated SK, and adenoid SK mainly expressed K14. The results show that hyperkeratotic SK differentiated towards squamoid terminal keratinization, whereas acanthotic, irritated, clonal, reticulated, and adenoid SK mainly differentiated towards basaloid undifferentiated cells. In addition, acanthotic SK differentiated towards the hair bulge, and irritated SK differentiated towards the follicular infrainfundibulum.

CONCLUSIONS

Based on the patterns of keratin and filaggrin expression demonstrated by the histopathological types, SK demonstrated diverse differentiation towards epidermal keratinization, basaloid cells, the infrainfundibulum and hair follicle bulges, which suggests that SK is in an undifferentiated and hyperproliferative state with heterogeneous differentiation. The immunohistochemical method of investigating patterns of keratin expression is useful in the differential diagnosis of cutaneous epithelial tumors.

Cytokeratin 10-negative nested pattern enables sure distinction of clonal seborrheic keratosis from pagetoid Bowen's disease

BACKGROUND

The histopathologic pattern of clonal seborrheic keratosis (SK) is quite similar to the nested pattern of pagetoid Bowen's disease [squamous cell carcinoma in situ (SCCIS)], and differentiation between the two can be challenging, especially when only small pieces are available for interpretation.

METHODS

Eleven examples of clonal SK and 13 examples of pagetoid SCCIS were examined histopathologically (tabulating necrotic keratinocytes, suprabasal mitoses, infiltrate, parakeratosis housing plump nuclei, crowding of nuclei) and immunohistochemically (using Ki-67, bcl-2, cytokeratin 7 and cytokeratin 10). Sensitivity, specificity, p-values (Fisher's exact test, two-tailed) and positive/negative likelihood ratios (+LR/-LR) were calculated.

RESULTS

Significant differences were seen with regard to crowding (p = 0.0009) and mitoses (p = 0.0006); however, only complete absence of necrotic keratinocytes or of crowding appeared to be diagnostically convincing for a diagnosis of clonal SK (-LR < 0.01). Significant differences were also seen with bcl-2 (p = 0.0005) and cytokeratin 10 antibodies (p < 0.00001). Both markers displayed a typical nested pattern in clonal SK, nests being bcl-2-positive and cytokeratin 10-negative. Cytokeratin 10-negative nests were the most convincing criterion for differentiation between clonal SK and pagetoid SCCIS (+LR > 10, -LR < 0.01).

CONCLUSIONS

The most reliable marker to distinguish clonal SK from pagetoid SCCIS is cytokeratin 10 when it spares nests. Other criteria that assist in the differential diagnosis are bcl-2 expression, absence of crowding and of mitoses.

Use of a keratolytic agent with occlusion for topical treatment of hyperkeratotic seborrheic keratoses

BACKGROUND

Seborrheic keratoses are the most common benign tumors in adults. Despite their negative cosmetic appearance, no topical treatment is commonly recommended for these lesions.

OBJECTIVE

Our objective was to assess whether clinical benefit could be achieved by using a keratolytic topical agent and superficial scraping for this condition.

METHODS

A topical 50% urea-containing product under occlusion was applied daily to large and/or thick hyperkeratotic seborrheic keratoses on the truck and extremities. The patients were instructed to digitally scrape the surface of the lesions in an attempt to reduce the thickness of the lesions.

RESULTS

In a pilot nonrandomized open-label survey, patients expressed satisfaction with using this topical therapeutic technique.

CONCLUSIONS

Hyperkeratotic seborrheic keratoses can be satisfactorily managed with topical agents and scraping with reasonable patient satisfaction. Further studies with various keratolytic agents using other delivery systems are warranted.

Seborrheic keratosis with basal clear cells: A distinctive microscopic mimic of melanoma in situ

BACKGROUND

We observed seborrheic keratoses with many basilar clear cells, creating a microscopic pattern that mimicked a seborrheic keratosis involved by melanoma in situ.

OBJECTIVE

We sought to report a series of these seborrheic keratoses and the immunohistochemical stains used to reach a proper diagnosis.

METHODS

We reviewed 9 cases of seborrheic keratosis that had a distinctive pattern of basal clear cells with ample cytoplasm. All cases were evaluated by conventional microscopy, and Melan-A, S-100, and high molecular weight keratin 903 immunostains.

RESULTS

The basal clear cells failed to react with Melan-A and S-100 protein antisera. In contrast, these cells labeled with an antikeratin antibody in all cases. In all, 7/9 (78%) showed immunopositivity only at the peripheries of cells, creating a pattern that could be mistaken for a negative stain if not examined at high magnification.

LIMITATIONS

This is a retrospective review of cases limited to a large referral dermatopathology service.

CONCLUSIONS

We describe a previously uncharacterized pattern of seborrheic keratosis that can microscopically mimic melanoma in situ. Careful conventional microscopy coupled with a panel of immunostains can allow the proper diagnosis to be reached.

An immunohistochemical and histochemical study of cytokeratin, involucrin and transglutaminase in seborrhoeic keratosis

The mode of differentiation of seborrhoeic keratoses was investigated by immunohistochemical staining using cytokeratin (CK) polypeptide-specific monoclonal antibodies and an antibody specific for the particulate form of epidermal transglutaminase (ETgase), and by applying an anti-human involucrin serum. The role played by (E)Tgase was further evaluated using an activity assay based on the covalent attachment of monodansylcadaverine. Samples of uninvolved epidermis served as reference tissue. CK reactivities suggested that seborrhoeic keratoses is a hyperproliferative disease with an epidermal CK composition. CK5 and CK14 were prominent markers of basal and basaloid keratinocytes, whereas a decrease in staining occurred in advanced maturation stages and areas of terminal keratinization. In contrast, CK1 and CK10 were prominent markers of suprabasaloid differentiation stages and produced complementary stainings to those of CK5 and 14. Generally, CK10 staining was more impressive than CK1 staining and seemed to start before CK1 staining. In contrast to CK10 staining, cornified areas lost CK1 reactivity. These staining patterns were similar to those observed in uninvolved reference tissues. The epidermal CK subset was further supplemented with the 'hyperproliferative' CK6 and 16 which occur sequentially. Positive staining for CK6 was noted from basal and proximal basaloid cells onwards, whereas distal basaloid cells additionally showed CK16 staining. The presence of other non-epidermal CK polypeptides could not be shown. The competence for other differentiation markers belonging to the group of (E)Tgase and cornifying cell membranes also evolved with a typical epidermal pattern. (E)Tgase activity was restricted to advanced and terminal stages of keratinization and was dual in nature, i.e. a diffuse cytoplasmic staining occurred together with a prominent staining of cornifying cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)