Immunohistochemical comparison of cutaneous lymphadenoma, trichoblastoma, and basal cell carcinoma: support for classification of lymphadenoma as a variant of trichoblastoma

Cutaneous Lymphadenoma: A Case Report and Literature Review

Cutaneous lymphadenoma (CL) is an uncommon epithelioid tumor that is usually present on the head and face. It was first described by Santa Cruz and Barr in 1987, as a lymphoepithelial tumor, and was renamed as CL in 1991. Although CL is considered as a benign tumor, there are cases of recurrence after shave excision and metastasis to regional lymph nodes. Correct diagnosis and complete resection are of great importance. Here, we report a typical case of CL and make a comprehensive review of this rare skin tumor.

Cutaneous Lymphadenoma Is a Distinct Trichoblastoma-like Lymphoepithelial Tumor With Diffuse Androgen Receptor Immunoreactivity, Notch1 Ligand in Reed-Sternberg-like Cells, and Common EGFR Somatic Mutations

The term "cutaneous lymphadenoma" was coined in this journal for an unusual lymphoepithelial cutaneous adnexal neoplasm, possibly with immature pilosebaceous differentiation. Some authors further proposed that cutaneous lymphadenoma was an adamantinoid trichoblastoma. However, although a hair follicle differentiation is widely accepted, the fact that this is a lymphoepithelial tumor is not appropriately explained by the trichoblastoma hypothesis. Our goal was to further clarify the phenotypic and genotypic features of cutaneous lymphadenoma in a series of 11 cases. Histologically, a lobular architecture surrounded by a dense fibrous stroma was present in all cases. The lobules were composed of epithelial cells admixtured with small lymphocytes and isolated or clustered large Reed-Sternberg-like (RS-L) cells. The epithelial cells were diffusely positive for the hair follicle stem cell markers CK15, PHLDA1, and for androgen receptor. No immunostaining for markers of sebaceous differentiation was found. Intraepithelial lymphocytes were predominantly CD3+, CD4+, FoxP3+ T cells. RS-L cells showed both strong Jagged-1 and Notch1 cytoplasmic immunostaining. Androgen-regulated NKX3.1 nuclear immunostaining was present in a subset of large intralobular cells in all cases. Double immunostaining showed coexpression of NKX3.1 and CD30 in a subset of RS-L cells. No immunostaining for lymphocytic or epithelial markers was present in RS-L cells. EGFR, PIK3CA, and FGFR3 somatic mutations were found by next-generation sequencing in 56% of the cases. We consider that cutaneous lymphadenoma is a distinct benign lymphoepithelial tumor with androgen receptor and hair follicle bulge stem cell marker expression, RS-L cell-derived Notch1 ligand, and common EGFR gene mutations.

The Multiple Faces of Nodular Trichoblastoma: Review of the Literature with Case Presentation

Trichoblastoma (TB) is a rare biphasic benign adnexal neoplasm originating from follicular germ cells but clinically, it can simulate basal cell carcinoma (BCC), making the diagnosis more difficult. There are several variants of Trichoblastoma and a good knowledge of these is essential for correct diagnosis and management. We report two new cases observed in the last year at our Pathological Anatomy Operative Unit, and conduct a careful review of the literature, from the first description of this lesion by Headington in 1970 to the most recent classifications.

A review of CD30 expression in cutaneous neoplasms

BACKGROUND

The surface protein CD30 is a therapeutic target of monoclonal antibody therapy. Knowledge of the frequency of CD30 expression and its prognostic relevance is therefore interesting, not only in lymphoproliferative disorders (LPD) but also in solid tumors of the skin.

METHODS

A review was completed in PubMed for all published reports of CD30 expression in cutaneous lymphomas, mastocytosis, epithelial tumors and sarcomas from 1982 to April 2019. Only accessible articles in English and German were considered. Entities with an expected CD30 expression, such as CD30-positive LPD, were not evaluated.

RESULTS

The electronic research identified 1091 articles and a further 34 articles were obtained from manual bibliographic reference. Overall 91 articles were included that examined CD30 expression in various entities of cutaneous neoplasms and matched the inclusion criteria.

CONCLUSION

Apart from cutaneous CD30-positive LPD, the best-studied group for CD30 expression was mycosis fungoides (MF). CD30 positivity was found in 32% of classical (patch and plaque stage) and in 59.4% cases of transformed MF. CD30 was also frequently expressed in cutaneous mastocytosis (96.5%). In solid tumors, some single reports describe CD30 expression by tumor cells, but CD30-reactive lymphocytes were frequently observed in the tumor microenvironment (TME), especially in keratoacanthoma (KA).

Merkel Cell Polyomavirus T Antigens Induce Merkel Cell-Like Differentiation in GLI1-Expressing Epithelial Cells

Merkel cell carcinoma (MCC) is an aggressive skin cancer frequently caused by the Merkel cell polyomavirus (MCPyV). It is still under discussion, in which cells viral integration and MCC development occurs. Recently, we demonstrated that a virus-positive MCC derived from a trichoblastoma, an epithelial neoplasia bearing Merkel cell (MC) differentiation potential. Accordingly, we hypothesized that MC progenitors may represent an origin of MCPyV-positive MCC. To sustain this hypothesis, phenotypic comparison of trichoblastomas and physiologic human MC progenitors was conducted revealing GLI family zinc finger 1 (GLI1), Keratin 17 (KRT 17), and SRY-box transcription factor 9 (SOX9) expressions in both subsets. Furthermore, GLI1 expression in keratinocytes induced transcription of the MC marker SOX2 supporting a role of GLI1 in human MC differentiation. To assess a possible contribution of the MCPyV T antigens (TA) to the development of an MC-like phenotype, human keratinocytes were transduced with TA. While this led only to induction of KRT8, an early MC marker, combined GLI1 and TA expression gave rise to a more advanced MC phenotype with SOX2, KRT8, and KRT20 expression. Finally, we demonstrated MCPyV-large T antigens’ capacity to inhibit the degradation of the MC master regulator Atonal bHLH transcription factor 1 (ATOH1). In conclusion, our report suggests that MCPyV TA contribute to the acquisition of an MC-like phenotype in epithelial cells.

Differential diagnostic significance of epithelial and stromal CD10 expression in tumors of trichogenic origin

BACKGROUND AND OBJECTIVES

The histological differential diagnosis between benign trichogenic skin tumors and basal cell carcinoma may be challenging. We therefore set out to investigate whether expression of CD10, a cell surface protein with neutral endopeptidase activity, might be a suitable marker for the histological differential diagnosis of trichogenic skin tumors.

PATIENTS AND METHODS

We immunohistochemically analyzed 119 cases of benign trichogenic skin tumors and basal cell carcinoma. These included 28 nodular and 15 sclerosing basal cell carcinomas, 21 Pinkus tumors, 20 trichoblastomas, nine trichofolliculomas, eleven trichoepitheliomas, five desmoplastic trichoepitheliomas, and ten seborrheic keratoses.

RESULTS

The majority of nodular basal cell carcinomas expressed CD10 in tumor cells at the peripheral (22/28 [75 %]). On the other hand, trichoblastomas revealed peripheral CD10 expression in only 10 % (2/20) of cases, whereas 50 % showed central expression (10/20). Peripheral epithelial expression of CD10 was also found in Pinkus tumors (9/21 [42.9 %]) and trichoepithelioma (4/11 [36.4 %]). Desmoplastic trichoepithelioma showed no tumoral CD10 expression at all (0/5 [0 %]), while the majority of sclerosing basal cell carcinomas was positive for CD10 (13/15 [86.7 %]).

CONCLUSIONS

Our findings suggest that epithelial expression of CD10 - and not peritumoral stromal CD10 expression, as has been postulated - may well be of differential diagnostic significance. The pattern of distribution of CD10-positive neoplastic cells in particular can be useful in the diagnosis of trichogenic tumors.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma. Incidence of MCC continues to rise, and risk factors include advanced age, pale skin, chronic sun exposure, and immune suppression. Diagnosing MCC utilizes a combination of morphology and immunohistochemistry. Merkel cell polyomavirus (MCPyV) is present in approximately 70-80% of MCCs and represents a key pathogenic driver in those MCCs. In contrast, MCPyV-negative MCCs arise through progressive accumulation of ultraviolet-light induced somatic mutations. Staging of MCC proceeds according to the American Joint Commission on Cancer (AJCC) 8th Edition, which utilizes features of the primary tumor together with regional lymph node(s) (clinically and/or pathologically detected) and/or distant metastases. Many potentially useful biomarkers have been studied to refine risk stratification in MCC. In recent years, the host immune infiltrate has been leveraged as immune checkpoint blockade has emerged as an efficacious mode of treatment for patients with advanced MCC.

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Congenital cutaneous lymphadenoma

Cutaneous lymphadenoma is an uncommon benign neoplasm often considered to be an adamantinoid variant of trichoblastoma. Lesions present in both sexes, between 14 and 87 years of age, and are mainly located on the head and neck. Cases in children are rare and there is only 1 previous case of a congenital lymphadenoma. An 8-year-old Asian girl presented with a congenital lesion on her forehead comprising 4 pink papules, the largest 5 mm in diameter. Microscopy revealed a well-circumscribed tumor within the dermis and subcutis comprising well-demarcated epithelial lobules of basaloid and clear cells with subtle peripheral palisading, growing in a collagenous stroma but lacking retraction artefact. A relatively dense accompanying predominantly lymphocytic inflammatory cell infiltrate including both T-cells (CD3+) and B-cells (CD20+) permeated the nodules and spilled into the stroma. CD68+ histiocytes and CD1a+ Langerhans cells were moderately numerous. This is the second case of congenital lymphadenoma which-in spite of its rarity in childhood-widens the diagnostic possibilities of cutaneous lymphoepithelial tumors in children.

A Case of Trichogerminoma With Pilomatrical Differentiation and a Unique Immunohistochemical Profile

Trichogerminomas are rare adnexal neoplasms first described by Sau et al in 1992. Including the initial report, 20 cases have been reported, all with similar histological features, namely tumor nodules composed of basaloid cells that form densely packed, round nests or "cell balls" and which demonstrate variable degrees of pilosebaceous differentiation. In this study, the authors report a case of a trichogerminoma with pilomatrical differentiation and a unique immunohistochemical profile. The patient is a 71-year-old man with a well-delineated nodule on the top of the scalp. Histologically, the lesion measured 16 mm in greatest dimension and was composed of nodules of basaloid cells with central, compact, slightly eosinophilic cells nests. Immunohistochemically, the tumor nodules diffusely expressed cytokeratins 34βE12, AE1/3, and CK5/6. Diffuse expression of β-catenin and nuclear expression of p63 were also evident. The peripheral basaloid cells, but not the cell balls, expressed CD10, Ber-EP4, BCL-2, and CK7, the latter a previously unreported finding. The histological findings and immunohistochemical profile are compatible with a diagnosis of a trichogerminoma.

Basal-Cell Carcinoma Occurring in Cutaneous Infundibular Cysts: Report of 2 Cases and Review of the Literature

Cysts lined by stratified squamous epithelium indistinguishable from the epidermis, referred to as epidermoid cysts, epidermal inclusion cysts, and infundibular cysts, are the most common type of cyst occurring in the skin. They are invariably benign, and malignant neoplasms arising within the wall of such cysts are distinctly uncommon. Even basal-cell carcinoma, which is the most common cutaneous malignant neoplasm of the skin, has rarely been reported to occur in association with epidermoid cysts. The authors report their experience studying 2 patients with basal-cell carcinoma arising in association with an epidermoid cyst. These cases highlight the need to examine, histopathologically, tissue from this common and usually benign lesion. The authors also review the medical literature.

Cystic fibroepithelioma of Pinkus: two new cases and cystic changes in classical fibroepithelioma of Pinkus

We report two new cases of cystic fibroepithelioma of Pinkus together with immunohistochemical features and analyze the presence of cystic changes in a series of 16 classical fibroepitheliomas of Pinkus. Our findings show that the formation of cystic spaces is most probably caused by ischemic degeneration of stromal fenestrations, rather than by central tumor cell necrosis. This finding is supported by lack of CD34 positive blood vessels in edematous and hyalinized stromal fenestrations undergoing transformation into cystic spaces, as opposed to the uninvolved stromal fenestrations. Therefore, it is probably more accurate to refer to this process as pseudocystic stromal degeneration rather than true cyst formation. Also, two out of 16 classical Pinkus fibroepitheliomas exhibited focal pseudocystic changes in 50% and 10% of the tumor, respectively, demonstrating that this degenerative process can be found, rarely and focally, in classical cases as well.

Trichoblastic sarcoma with osteosarcomatous differentiation: evolution of one lesion with 3 histologic appearances over a 3-year period

Only one description of trichoblastic sarcoma exists in the literature. Here, we present the first case of trichoblastic sarcoma with heterologous osteosarcomatous differentiation. Biospy 1 demonstrated an intermediate-grade trichoblastic sarcoma with pleomorphic cells and atypical mitotic figures observed only in the stroma. The epithelium contained no malignant cells. The histologic morphology was reminiscent of an intermediate-grade phyllodes tumor of the breast. Biopsy 2, an excisional biopsy taken 7 months later, showed a high-grade sarcoma with osteosarcomatous differentiation. Immunohistochemistry performed on both specimens showed positive CD10 and bcl-2 staining in the sarcomatous component; p63 was positive in the benign epithelium only. p53 was negative in both the benign epithelium and the malignant stroma. Ki-67 labeling was approximately 10% in both components. Specimen 3, a complete rhinectomy performed 3 months later, showed a poorly differentiated sarcoma. Six months following his rhinectomy procedure, multiple pulmonary nodules consistent with metastatic disease were detected on chest computed tomography. This is the first case report documenting the evolution of an intermediate-grade trichoblastic sarcoma to a high-grade lesion with osteosarcomatous differentiation, to a poorly differentiated sarcoma. The tumor morphologically resembles malignant phyllodes tumor of the breast. Our case is the first to show negative p53 and positive bcl-2 staining in a trichoblastic sarcoma. We propose that cutaneous trichoblastic sarcoma is pathogenetically analogous to phyllodes tumors of the breast, adenosarcoma of the uterus, or ameloblastoma of the oral cavity.

Cutaneous lymphadenoma: a case report and immunohistochemical study

Cutaneous lymphadenoma is a rare neoplasm, and characterized by a florid mononuclear cell infiltration that appears to be an integral component of the tumor. Several reports suggested that these infiltrated lymphocytes mainly consist of T cells and Langerhans cells, but no detailed phenotypical analysis of these cells has been demonstrated yet. In this report, we describe a 70-year-old Japanese patient with cutaneous lymphadenoma. In the present case, we investigated the immunohistochemical profiles of tumor-infiltrating cells in cutaneous lymphadenoma, especially focusing on the profiles of T cell subsets. In addition, there are abundant mucin deposits within the tumor stroma, and tumor lobules are composed of BerEP4-positive cells. To the best of our knowledge, this is the first report that employed immunohistochemical staining of cutaneous lymphadenoma to verify the types of cells composing such tumors with special focus on the profiles of the T cell subsets.

Basal cell carcinoma: cell of origin, cancer stem cell hypothesis and stem cell markers

Cancer stem cells have recently been described in several high-grade neoplasms. It is still unclear if they also occur in cutaneous malignancies. Cancer stem cells are not identical with somatic stem cells. The presence of tumour stem cells in a neoplasm does not in itself equal that the tumour derives from a somatic stem cell. A cell originally lacking stem cell characteristics could also acquire those features during the course of carcinogenesis and then becomes the clonal founder cell of a tumour. Basal cell carcinoma (BCC) is the most common cutaneous malignancy. A plethora of various stem cell markers has been applied to study its cellular origin. Intriguingly, the anatomical origin of BCC is still uncertain. This review will discuss the various stem cell markers used in BCC and the cellular origin of this tumour, and touches briefly on the possibility of cancer stem cells in BCC. If BCC or other skin cancers harbour tumour stem cells, these cells could be specifically targeted, making use of specific cell surface molecules such as receptor proteins. Novel drugs directed against those receptor proteins could replace currently available shotgun approaches including imiquimod.

Quantitative study of Langerhans cells in basal cell carcinoma with higher or lower potential of local aggressiveness

BACKGROUNDS

Basal cell carcinoma affects areas of the body that have been exposed to the sun, and this disorder has different clinical and histopathologic presentations. Some of these forms have a higher potential of local aggressiveness, while others have a lower potential. Langerhans cells actively participate in the skin immune system.

OBJECTIVES

To quantitatively evaluate the number of Langerhans cells on the epidermis of basal cell carcinoma with lower and higher potential of local aggressiveness and on adjacent normal epidermis.

METHODOLOGY

The authors divided the sample into two groups with 14 histological slides each: one with basal cell carcinoma with lower potential of local aggressiveness and the other with basal cell carcinoma with higher potential of local aggressiveness. Immunohistochemistry with S-100 protein was used in the identification of Langerhans Cells. Langerhans cells present in 7 microscopic fields were counted using optical microscopy (400X magnification) and Weibel's morphometric grade. The mean for each lamina was obtained. Wilcoxon's statistical test was employed.

RESULTS

In the group with lower potential of local aggressiveness, there was a significant increase in the number of Langerhans cells in the adjacent normal epidermis, as compared with the number of cells in the epidermis superposed to the basal cell carcinoma (pd 0.05). There was no significant statistical difference in the group with higher potential of local aggressiveness (p >0.05).

CONCLUSION

The higher number of Langerhans cells in the normal epidermis adjacent to the tumoral lesion with lower potential of local aggressiveness could indicate greater immunological resistance of the epidermis, thus limiting the aggressiveness of the neoplasm.

Does the panel of cytokeratin 20 and androgen receptor antibodies differentiate desmoplastic trichoepithelioma from morpheaform/infiltrative basal cell carcinoma?

BACKGROUND

Evaluation of androgen receptor (AR) and cytokeratin 20 (CK20) expression can aid in distinguishing between conventional basal cell carcinoma (characteristically AR+, CK20-) and trichoepithelioma (frequently AR-, CK20+). Within these two groups of tumors, morpheaform/infiltrative basal cell carcinoma (mBCC) and desmoplastic trichoepithelioma (DTE) are particularly challenging to differentiate both clinically and histologically. We investigated whether AR and CK20 immunostains may distinguish between mBCC and DTE.

METHODS

Immunohistochemistry for AR and CK20 was performed on 15 DTEs and 31 mBCCs. Any immunoreactivity within the tumor for AR or CK20 was considered positive.

RESULTS

AR expression was seen in 13% (2/15) of DTE and 65% (20/31) of mBCC cases (chi-square p = 0.0011). CK20-positive Mërkel cells were identified in 100% (15/15) of DTE and 3% (1/31) of mBCC (chi-square p < 0.0001). The expected pattern of AR-, CK20+ immunophenotype was present in 87% (13/15) of DTE cases. In mBCC, 61% (19/31) was AR+, CK20-. No DTE was AR+, CK20- and no mBCC was AR-, CK20+.

CONCLUSIONS

Immunohistochemical stains for AR and CK20 are useful to differentiate DTE from mBCC. The AR-, CK20+ immunophenotype is sensitive (87%) and specific for DTE (100%). The AR+, CK20- immunophenotype is specific (100%) and moderately sensitive (61%) for mBCC.

Glandular congenital lymphadenoma

Cutaneous lymphadenoma is known to occur over a broad age range, from 14 to 72 years of age. We report the unique clinical and histologic presentation of a cutaneous lymphadenoma from the suprapubic abdomen of a neonate which may represent a novel subtype, glandular congenital lymphadenoma. Cutaneous lymphadenoma is a rare tumor with a distinct histologic triad of epithelial nodules, dense fibrous stroma, and intense intranodular lymphocytic infiltrate. Typically, it is a slow growing, skin colored papule, nodule, or plaque, clinically resembling a basal cell carcinoma and often occurring in the head and neck region or lower extremities.

Merkel cell-poor trichoblastoma with basal cell carcinoma-like foci

We reexamined 11 cases of trichoblastoma, and two cases of trichoblastoma with basal cell carcinoma (BCC)-like foci were found. In these two trichoblastomas with BCC-like foci, the BCC-like foci were often localized in peripheral or deep areas of lesions extending out of the fibrocytic stroma. Immunohistochemistry was performed in five conventional trichoblastomas and in two trichoblastomas with BCC-like foci, using antibodies against CK20 and CK15. No CK20-positive Merkel cells and no expression of CK15 were seen in any neoplastic aggregations of the two trichoblastomas with BCC-like foci. In contrast, increased numbers of Merkel cells and positive staining for CK15 were observed in all five trichoblastomas without BCC-like foci. The five trichoblastomas without BCC-like foci included two trichoblastomas with a popped out or shelled out appearance, which characteristically had a thick fibrous capsule surrounding the fibrotic stroma, demonstrating numerous Merkel cells in the aggregations. Some trichoblastomas may undergo mutations, resulting in the development of foci of BCC and in the loss of the expression of CK15 as well as the disappearance of Merkel cells.

Lymphotropic adamantinoid trichoblastoma

We report a lymphotropic adamantinoid trichoblastoma in a 14-year-old girl. This is a rarely reported skin adnexal tumor in adolescent patients. The clinical, histologic, and immunohistochemical features of this tumor are described.

Expression of Androgen Receptor by Fibroepithelioma of Pinkus: Evidence Supporting Classification as a Basal Cell Carcinoma Variant?

The classification of fibroepithelioma of Pinkus as basal cell carcinoma or trichoblastoma remains controversial. Immunohistochemical stains for androgen receptor may be useful in differentiating basal cell carcinoma from trichoepithelioma or trichoblastoma. We studied androgen receptor expression in 13 fibroepitheliomas of Pinkus, 11 basal cell carcinomas, 12 trichoepitheliomas, and 3 trichoblastomas. Androgen receptor expression was present in 77% (10/13) of fibroepitheliomas of Pinkus, 73% (8/11) of basal cell carcinomas, 17% (2/12) of trichoepitheliomas, and 0% (0/3) of trichoblastomas. Androgen receptor expression was significantly higher in fibroepitheliomas of Pinkus compared with trichoepitheliomas and trichoblastomas (P = .0007), but not basal cell carcinoma (P = 1.00). Tumor-associated Merkel cells, a feature of benign follicular tumors, was identified by cytokeratin 20 stains. Merkel cells were identified in 85% (11/13) of fibroepitheliomas of Pinkus, 27% (3/11) of basal cell carcinoma cases, and 73% (11/15) of benign follicular tumors. Cytokeratin 20 expression was significantly higher in fibroepithelioma of Pinkus and benign follicular tumors compared with basal cell carcinomas (P = 0.0111 and P = 0.025, respectively). No significant difference was found between fibroepitheliomas of Pinkus and trichoepitheliomas and trichoblastomas (P = 1.00). Similar to basal cell carcinomas, fibroepitheliomas of Pinkus express androgen receptors, potentially supporting classification as a basal cell carcinoma. Conversely, fibroepithelioma of Pinkus demonstrates retention of Merkel cells, a feature of benign follicular tumors. Immunophenotypic evidence for the classification of fibroepithelioma of Pinkus remains inconclusive. In small, partial biopsy specimens, coexpression of androgen receptor and cytokeratin 20 may aid in the diagnosis of fibroepithelioma of Pinkus.

Langerhans cells in cutaneous tumours: immunohistochemistry study using a computer image analysis system

Immunohistochemistry, based on antibody anti-S100 protein, was used to evaluate the Langerhans cells (LC) in benign and malign skin neoplasias. These cells were quantitatively estimated using a computer image analysis (OPTIMAS software system, Version 6.1) in skin biopsies diagnosed as basal cell carcinoma (BCC), epidermoid carcinoma (EpC), trichoepithelioma (TE), keratoacanthoma (KA), seborreic keratosis (SK) and actinic keratosis (AK). The antibody anti-S100 protein recognized them. No significant variations were observed in the number of LC among malignant tumour (BCC = 23.25 +/- 5.81 and EpC = 20.88 +/- 4.24). Benign lesions (AK = 33.04 +/- 7.11; TE = 55.74 +/- 9.35; SK = 42.38 +/- 9.92, and KA = 47.62 +/- 10.4) presented a higher number of LC when they were compared among them and to malignant and normal tissues. No significant differences were observed in LC area and volume between benign and malign neoplasias. These results indicate possibly differences in the immunogenicity between benign and malign epidermic tumours. In conclusion, the experimental computer assessment method was reliable and consistent to morphometric analysis of tumoural tissues.

Tubular adenoma of the skin with follicular and sebaceous differentiation: A report of two cases

The main controversies regarding tubular apocrine adenoma and papillary eccrine adenoma are whether they are two distinct entities or are the very same tumor, and if so, which lineage of differentiation (apocrine versus eccrine) it pursues. We report two cases of tubular adenoma with follicular and, in one case, additionally, sebaceous differentiation. The features in both cases indicated apocrine differentiation of the tubular component. One patient was a 60-year-old woman with a 1-year history of a solitary nodule on the scalp. The other patient was a 48-year-old woman with a solitary nodule of unknown duration located on the back. In both patients, the tumors were surgically removed. The patients were alive and well 2.5 and 2 years after surgery, respectively. The histologic features that both cases had in common included the combination of a tubular adenoma, foci of follicular differentiation, and areas of immature squamous metaplasia. In case 1, follicular differentiation was seen in the form of strands of basaloid cells surrounded by a stroma resembling the embryonic perifollicular sheath. Some aggregates of basaloid cells were juxtaposed with small collections of plump fibroblasts, imparting a resemblance to rudimentary follicular germs associated with follicular papillae. Many minute lumens surrounded by more eosinophilic cells were seen within the strands. In case 2, follicular differentiation was seen as several infundibulocystic structures surrounded by isthmic epithelium housing scattered mature sebocytes. In addition, there were areas reminiscent of desmoplastic trichoepithelioma (columnar trichoblastoma). In both cases, the areas with immature squamous metaplasia were represented by solid nodules that were mostly devoid of lumens and a peripheral basal/myoepithelial cell layer. In conclusion, these two cases of cutaneous tubular adenoma with accompanying follicular and sebaceous differentiation give further support to the proposition that the majority of these neoplasms have apocrine differentiation. Rare cases occurring in the sites normally devoid of apocrine glands may represent the eccrine counterpart.

Seborrheic keratosis with pseudorosettes and adamantinoid seborrheic keratosis: two new histopathologic variants

AIMS

Seborrheic keratoses are the most common benign cutaneous neoplasms in adult and middle-age patients. There are six distinctive histopathologic variants of seborrheic keratosis, namely, acanthotic or solid, reticulated or adenoid, hyperkeratotic or papillomatous, clonal or nested, irritated and inflamed.

METHODS

We report two additional histopathologic variants of seborrheic keratosis.

RESULTS

One lesion showed abundant intercellular mucin, closely resembling to adamantinoma, and therefore was named adamantinoid seborrheic keratosis. The other one exhibited a peculiar distribution of the basaloid keratinocytes, which were arranged radially around small central spaces, resulting in pseudorosette formation.

DISCUSSION

To our knowledge, these two histopathologic variants of seborrheic keratosis have been not previously described in the literature.

Congenital subcutaneous dendritic cell rich lymphoepithelial hamartoma

We present the clinical, radiologic, histologic, immunohistochemical, and ultrastructural characteristics of a congenital pretibial subcutaneous lesion composed of a mixture of T and B cells, epithelial cells, and dendritic cells, probably representing a hamartoma. After total removal, there has been no recurrence. The prominent dendritic component of this lesion, demonstrated immunohistochemically and ultrastructurally, separates the lesion from cutaneous lymphadenoma and other adnexal tumors.

CD117, CK20, TTF-1, and DNA topoisomerase II-alpha antigen expression in small cell tumors

BACKGROUND

Distinguishing merkel cell carcinoma (MCC), small cell lung carcinoma (SCLC) metastatic to the skin, and atypical basal cell carcinoma (BCC) can be problematic in some cases. Significant differences in the biology of these tumors necessitate that they need to be distinguished from one another.

METHODS

We evaluated the immunophenotypic characteristics of 22 MCCs, nine SCLCs, and 19 BCCs using antibodies to cytokeratin 20 (CK20), thyroid transcription factor-1 (TTF-1), CD117, and DNA topoisomerase II-alpha (topo II).

RESULTS

Nineteen of 22 MCCs stained with the antibody to CK20, none stained with anti-TTF-1, and 13 stained with anti-CD117. No SCLC stained with anti-CK20, all stained with anti-TTF-1, and eight stained with anti-CD117. No BCC stained with any of the three markers. The proliferative index (PI), determined by the expression of topo II, was similar for SLCLs (mean 58.5 +/- 9.0%) and MCCs (mean 45.2 +/- 12.4%) and was lowest in BCCs (mean 25.0 +/- 8.7%).

CONCLUSIONS

CK20 and TTF-1 appear to be reliable in distinguishing MCC from SCLC. CD117 is expressed in both MCC and SCLC, limiting its diagnostic utility. CK20, TTF-1, and CD117 are not expressed in BCC. The high PI seen in MCCs suggests a role for topoisomerase II inhibitors in their treatment.

Cutaneous lymphadenoma

Cutaneous lymphadenoma is a rare tumor with distinctive histologic features. This entity was originally described as lymphoepithelial tumor by Santa Cruz and Barr in 1987. It was renamed cutaneous lymphadenoma in 1991. To date, at least 31 cases of this entity have been reported. The literature did not contain a clinical photograph of this lesion. A case of this rare tumor is described that includes clinical and histologic features. The literature regarding the unclear histogenesis of this distinctive tumor is reviewed. This report is one of a only few clinical illustrations of cutaneous lymphadenoma. Consistent with previous reports, the histologic findings in this case include basaloid proliferation and intraepithelial lymphocytes. The usual initial clinical diagnosis is basal cell carcinoma localized mainly to the head and neck area. The incidence is approximately equal in male and female patients. Excision of this benign neoplasm is curative. Controversy exists regarding the histogenesis of this tumor.

Melanotrichoblastoma: immunohistochemical study of a variant of pigmented trichoblastoma

Trichoblastomas (TBs) are benign skin tumors recapitulating the differentiation of hair follicles. Several pathologic variants have been described, including the rare pigmented TB. We report a deeply pigmented nodular tumor excised on the scalp of a 32-year-old African woman, which was clinically suggestive of blue nevus or melanoma. Histologically, the tumor presented features of TB, remarkable by virtue of heavy melanin deposits found within and around tumor nests. By immunohistochemistry, abundant dendritic melanocytes with features of hair follicle melanocytes (expression of S100 protein, tyrosinase, and, most importantly, gp100/HMB-45) were found within the tumor masses. By analogy with melanoacanthoma, a tumor consisting of a combined proliferation of epidermal keratinocytes and melanocytes, we called this tumor "melanotrichoblastoma" and view it as a peculiar variant of (pigmented) TB.

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.