Trichilemmoma: an immunohistochemical study of cytokeratins

Use of Cytokeratin 17 in the Differentiation Between Desmoplastic Trichilemmoma and Cutaneous Basal Cell Carcinoma

ABSTRACT

Desmoplastic trichilemmoma (DTL) is a variant of trichilemmoma characterized by a prominent desmoplastic stroma that may mimic invasive carcinoma. These lesions typically show features of a conventional trichilemmoma at the periphery, surrounding dense hyalinized stroma with entrapped cords of tumor cells. On a small or superficial biopsy, DTL may pose a diagnostic challenge in distinguishing this benign adnexal neoplasm from invasive carcinoma, particularly basal cell carcinoma (BCC). We aimed to investigate whether the immunohistochemical expression of cytokeratin 17 (CK17) would be useful in the differentiation between DTL and BCC. CK17 is expressed in normal adnexal structures and has been shown to demonstrate strong staining in BCCs. Expression of CK17 was examined in 23 cases of DTL and 23 BCCs. An immunoreactivity score was assigned using the percentage of tumor cells staining with scoring as follows: 0, complete negativity; 1, < 15% tumor cells staining; 2, 15%-84% tumor cells staining; and 3, >85% staining. All cases of BCC scored as 3, whereas 18% of DTL scored as 3. The mean percent staining for CK17 was significantly higher for BCCs (97% of tumor cells) than DTLs (57% of tumor cells); P < 0.001 in the unpaired t test. The pattern of CK17 staining may also help differentiate between cases scoring 3. All BCCs showed strong diffuse staining throughout, whereas for those cases of DTL with a score of 3, the peripheral basaloid rim in the tumor lobules did not stain. CK17 is a useful adjunct in distinguishing DTL from BCC in small or superficial biopsy specimens.

Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation

Neoplasms derived from follicular tissue are extremely rare. Clinically, they are reported as non-symptomatic, slow-growing nodules. These lesions are mainly benign, but the malignant type can occur. Mainly middle-aged people (50-60 years of age) are affected. These carcinomas are mainly localized on the head and neck or torso. They can be locally aggressive and infiltrate surrounding tissue and metastasize to regional lymph nodes. In the minority of cases, distant metastases are diagnosed. Quick and relevant diagnosis is the basis of a treatment for all types of tumors. The patient's life expectancy depends on multiple prognostic factors, including the primary tumor size and its mitotic count. Patients should be referred to a specialized skin cancer center to receive optimal multidisciplinary treatment. This article tries to summarize all the information that is currently available about pathogenesis, diagnosis, and treatment methods of follicular tumors.

Lesions With an Epidermal Hyperplastic Pattern: Morphologic Clues in the Differential Diagnosis

In this report, we review the most common entities that show a epidermal hyperplastic pattern in the biopsy. These entities include inflammatory, reactive, infectious, hamartomatous, and tumoral conditions, each with a very different prognosis. Therefore, an approach based on the classic "patterns and clues" tools used in dermatopathology can bring a lot of information to the dermatopathologist or the general pathologist evaluating these lesions.

Keratinizing Squamous Epithelium Associated with Syringocystadenoma Papilliferum Differentiates towards Infrainfundibulum: Case Report with Immunohistochemical Study of Cytokeratins

We describe a case of Syringocystadenoma papilliferum (SCAP) with keratinizing squamous epithelium in a 26-year-old female presenting with a dark brown to black nodule on her forehead. After surgical excision, the specimen was examined immunohistochemically using antibodies against cytokeratin (CK) 1, 8, 10, 14, 17, 18 and 19. Within the keratinizing squamous epithelium, CK1, 10, 14 and 17 were present, whereas the other CKs were absent. Based on CK expression, keratinizing squamous epithelium in SCAP seems to differentiate towards the infrainfundibulum.

Cytokeratin Expression in Subungual Squamous Cell Carcinoma

Cytokeratin expression in subungual squamous cell carcinoma was investigated in order to evaluate the origin and state of differentiation of the tumour. The tumour nests contained cytokeratin 14, 16 and 17, which were also expressed in the nail bed. Therefore, cytokeratin expression in subungual squamous cell carcinoma may reflect its indolent clinical prognosis.

Keratin 19-positive cutaneous squamous cell carcinoma with elevated serum cytokeratin 19 fragment 21-1 level: A case report

cytokeratin 19 fragment 21-1 (CYFRA21-1) is a marker of lung cancer useful for evaluating clinical diagnosis and prognosis. To the best of our knowledge, there have been no reports of cutaneous squamous cell carcinoma (SCC) with high levels of CYFRA21-1 to date. We herein report a case of a 79-year-old man with a large subcutaneous tumor of the left shoulder, which was diagnosed as primary cutaneous poorly differentiated SCC. The tumor nests were composed of poorly differentiated atypical squamous cells exhibiting high-grade malignancy and mitotic figures; multinuclear cells were also identified inside lymph vessels. Keratin 19 (K19) was intensely expressed in tumor cells. A significantly elevated level of CYFRA21-1 (33 ng/ml) was observed preoperatively. After surgery, the level of CYFRA21-1 was significantly decreased (from 33 to 5.0 ng/ml). Our case demonstrated that K19-positive primary cutaneous undifferentiated SCC induced high levels of CYFRA21-1 in the serum. Thus, CYFRA 21-1 may be a marker indicative of poorly differentiated cutaneous SCC exhibiting K19 expression.

Challenges in the diagnosis of cutaneous adnexal tumours

The diagnosis of cutaneous adnexal neoplasms, a heterogeneous group of entities, is often perceived by practising pathologists as challenging. A systematic approach to diagnosis is necessary for classification of these lesions, which establishes the tumour differentiation (follicular, sebaceous, sweat gland or apocrine) and evaluates histological features differentiating between benign and malignant entities. Consideration of clinical history is a necessary adjunct in evaluation of the adnexal neoplasm, as characteristic anatomical sites are described for many adnexal lesions. In some instances, immunohistochemical studies may also be employed to aid the diagnosis. The differential diagnosis between primary cutaneous adnexal neoplasms and cutaneous metastases from visceral tumours may also be difficult. Clinical, radiological, histological and immunohistochemical characteristics will be further discussed, considering that the correct diagnosis has a significant impact on the patient's management and prognosis.

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.

Tricholemmoma and clear cell squamous cell carcinoma (associated with Bowen's disease): immunohistochemical profile in comparison to normal hair follicles

There have been only a few reported comparative immunohistochemical studies of normal hair follicles and tricholemmomas. Clear cell squamous cell carcinomas (SCCs), which are derived from Bowen's disease, histopathologically mimic or are difficult to distinguish from tricholemmal carcinoma. The purpose of and methods used in the present study are as follows: (1) evaluation of whether the immunohistochemical profile (cytokeratin (CK)1, CK10, CK17, CD34, and D2-40) in normal hair follicles is retained in tricholemmomas (11 lesions); and (2) a study of the immunohistochemical profile of in situ or superficially invasive clear cell SCCs (associated with Bowen's disease) (10 lesions) to investigate the presence or absence of tricholemmal differentiation markers in these lesions. The present study demonstrated that (1) the immunohistochemical profile of the normal outer root sheath cells was generally retained in tricholemmomas; (2) in contrast to the D2-40 expression in tricholemmomas (only a peripheral pattern, which is similar to that in the normal outer root sheath), the CD34 expression in tricholemmomas represented in a diffuse pattern, a peripheral pattern, and a combined diffuse and peripheral pattern; (3) tricholemmomas are benign neoplasms with outer root sheath (below the isthmus) differentiation, which characteristically show upregulation of CD34 expression with some functionally similar conditions to the terminal hair follicles in the anagen phase; and (4) there is no clear immunohistochemical evidence of tricholemmal differentiation in clear cell SCC (associated with Bowen's disease).

Immunohistochemical study of cytokeratin expression in nevus sebaceous

BACKGROUND

The histogenesis of nevus sebaceous (NS) is unclear.

METHODS

To elucidate the histogenesis of NS, cytokeratin (CK) profiles were examined immunohistochemically using 10 anti-keratin antibodies in the three stages of NS.

RESULTS

In the first stage, stratified differentiated keratins (CK1 and 10) were reduced, and basal keratin (CK14) was increased in the epidermis and primitive follicular structure (PFS). In the second stage, in addition to reduced CK1 and CK10 expressions and increased CK14 expression, CK17 expression was strongly expressed in the sebaceous ducts in proportion to the development of sebaceous gland. In the third stage, CK14, CK17 and CK19 were expressed in secondary tumors. CK16 was not detected throughout all stages of NS.

CONCLUSION

These results suggest that NS is not hyperproliferative but involves hamartomatous differentiation with undifferentiated keratins.

Squamous cell carcinoma with clear cells: how often is there evidence of tricholemmal differentiation?

Clear-cell carcinoma of the skin was described by Kuo in 1980 as a cutaneous tumor composed of clear cells that lacked cytoplasmic glycogen or evidence of tricholemmal keratinization. Tricholemmal carcinoma (TC) is conventionally considered to be a neoplasm derived from adnexal keratinocytes with glycogenated clear cells and evidence of outer root sheath or tricholemmal differentiation. The existence of TC has been questioned as it has been argued that without clear immunohistochemical evidence of outer root sheath differentiation, TC cannot be distinguished from clear-cell carcinoma of the skin. Our laboratory has not routinely stained the cases that appear to be carcinomas with clear keratinocytes to determine if glycogen is present and has not made the diagnosis of TC. We sought to test whether the presence of glycogen, light microscopic features said to be typical of TC, or immunohistochemical findings would delineate a group of "true" TC among the cases that we have been recording as squamous cell carcinomas with clear cells (SCC-C). 40 cases of SCC-C were evaluated for 7 histologic and histochemical criteria (a lobular arrangement, peripheral palisading, tricholemmal keratinization, folliculocentricity, evidence of a preexisting tricholemmoma, the presence of intracytoplasmic glycogen, and a thickened basement membrane) said to characterize TC. Selected cases were then stained for immunohistochemical markers (CD34, CK17, and NGFR/p75) that have been used as evidence for tricholemmal differentiation in some studies. Of the 40 cases, 38 (95%) SCC-C showed intracytoplasmic glycogen (periodic Schiff positivity abolished by diastase) and 55% of cases showed foci of tricholemmal keratinization. Overall, the carcinomas showed a spectrum of the above aggregated criteria ranging from 0 to 5. None possessed all the criteria expected in an ideal TC. In addition, the majority of the selected SCC-C in this study were negative (85%) for antigens typically found in the outer root sheath epithelium of the hair follicle. The glycogen-free clear-cell carcinoma described by Kuo seems uncommon in our patient population. Rare cases of SCC-C met the majority of Headington's criteria for TC or showed immunohistochemical evidence of tricholemmal differentiation. Thus, we also conclude that well-differentiated TC is rare and its description in the literature may overstate the case that it is a well-characterized cutaneous neoplasm.

A Case of Trichilemmal Carcinoma Treated with Mohs Micrographic Surgery

Trichilemmal carcinoma is a cutaneous adnexal tumor originating from the outer root sheath of hair follicle, and it was first described by Headington in 1976. Clinically, it usually occurs as an asymptomatic solitary papule, nodule or mass on the face or scalp. This neoplasm is a malignant counterpart of trichilemmoma, and it has been reported in the literature as trichilemmal carcinoma, tricholemmal carcinoma, malignant trichilemmoma, and tricholemmocarcinoma. Although histologically, trichilemmal carcinoma frequently has maliganant features, it has a relatively benign clinical behavior. We think Mohs micrographic surgery is a useful treatment modality in trichilemmal carcinoma because the final skin defect is smaller than a wide excision. We report a case of primary trichilemmal carcinoma which had developed on the face, treated with Mohs micrographic surgery.

SOX9 expression is a general marker of basal cell carcinoma and adnexal-related neoplasms

BACKGROUND

SOX9 is a transcription factor that fulfills multiple functions during development. In the hair follicle SOX9 is expressed in the outer layer of the epithelial sheath, and the hair stem cell compartment. Recent data suggest that Sox9 acts as a downstream target of the Sonic hedgehog (Shh) pathway. Activation of the Shh pathway is a major cause of cutaneous basal cell carcinoma (BCC). Here we test whether activation of SOX9 is a general feature of BCC, or whether it could be used as a biomarker to better define subtypes of these skin tumors. In addition we investigated SOX9 expression in other skin epidermal tumors.

METHODS

Tumors sections were stained with hematoxylin & eosin (H&E). SOX9 activation was determined by immunofluorescence.

RESULTS

SOX9 activation was observed in all subtypes of BCC tested. Staining was heterogeneous and could be detected among the basaloid cells of the palisading cell layer as well as in the tumour nest. SOX9 expression was detected in all adnexal tumors analyzed and absent in Bowen's disease and Merkel tumor.

CONCLUSIONS

SOX9 expression is a general feature of BCC and adnexal skin neoplasms, suggesting a contribution of SOX9 to the pathogenesis of these tumors.

Cytokeratin and filaggrin expression in nevus comedonicus

To elucidate the pathogenesis of abnormal keratinization in nevus comedonicus, we performed an immunohistochemical study using antikeratin and antifilaggrin (filament-aggregating protein) antibodies. There were no significant differences between nevus comedonicus and normal skin in cytokeratin expression. Although filaggrin was only detected in the granular layer in open comedones, filaggrin was detected in both superficial cells and also intermediate cells in closed comedones, suggesting that filaggrin is involved in the formation of closed comedones. The disorder of terminal differentiation related to filaggrin may play a role in the pathogenesis of abnormal keratinization in nevus comedonicus.

Cytokeratin, filaggrin, and p63 expression in reepithelialization during human cutaneous wound healing

Cytokeratin (CK), filaggrin (filament aggregating protein), and p63 expression and cellular distribution during reepithelialization has not been systemically studied in the healing stage of human cutaneous wounds. We examined these proteins by immunohistochemical methods in 12 cases of skin ulcer, using seven anti-keratin antibodies, anti-filaggrin, and anti-p63 antibody. At the edge of the wound in skin ulcers, CK1 and 10 expression was reduced, while CK14, 16, and 17 expression was raised. Beneath the wound bed, all layers of the epidermal tongue, deriving from sweat ducts, were positive for CK14 and 17. Both cytokeratins were also found in basal and luminal cells of the dermal duct. CK expression by epithelia continuous with hair follicles showed that, CK14, 16, and 17 were present, and CK1 and 10 were absent. Filaggrin expression was elevated in reepithelialized epithelium. Expression of p63 expression was verified in the suprabasal layer in reepithelialized epithelia. CK, filaggrin, and p63 expression in the reepithelialization stage at the wound edge and at epidermal appendages remaining in the wound bed is undifferentiated and hyperproliferative. The presence of CK14 and 17 in the remaining epidermal appendages in the pathological wound may be important in epidermal replacement.