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Background: The spectrum of conjunctival tumors in children and adolescents significantly differs from that of adults., Objective: The aim of this study was to show the distribution of histopathological diagnoses of pediatric conjunctival tumors., Material and Methods: Retrospective case series including all conjunctival tumors of children and adolescents under 18 years of age examined histologically over a period of 25 years (1990-2015) at the Eye Center in Freiburg, Germany., Results: Among the 262 conjunctival specimens, the most common diagnoses were conjunctival nevi (148, [56%]), most often with junctional activity (106/148, [72%]), pyogenic granulomas (26, [10%]), and dermolipomas (18, [7%]). In one case a malignant tumor (conjunctival melanoma) was detected (1, < 1%)., Conclusion: The results suggest that pediatric conjunctival tumors are benign in most cases. Most of them were of melanocytic origin, with a junctional conjunctival nevus being the most common diagnosis., (© 2023. The Author(s).)

It has been debated whether malignant transformation of trichoblastoma occurs. The concept was recently forwarded that basal cell carcinoma is as a malignant neoplasm of follicular germinative cells and should be named trichoblastic carcinoma to show its relationship to trichoblastoma. Almost all basal cell carcinomas are low-grade malignant neoplasms and develop metastases only very rarely, and if so, only after very long duration and untreated growth. Only rare basal cell carcinomas arise in trichoblastomas. Up to now there have only been two reports of high-grade trichoblastic carcinoma arising in trichoblastoma, showing systemic metastatic spread and death. We add two further cases of trichoblastic carcinoma with anaplastic nuclei, arising in trichoblastoma. One of the tumors arose in a small nodular trichoblastoma on the right forearm of an 84-year-old male patient. The other one was a trichoblastic carcinoma at the base of a trichoepithelioma on the right thigh of an 87-year-old woman with Brooke-Spiegler syndrome. Our cases emphasize that high-grade trichoblastic carcinoma develops via malignant transformation of trichoblastoma, and is very rare.

Cutaneous T cell lymphomas (CTCLs) are lymphoproliferative disorders involving the skin. Malignant cells have a CD4+ T-helper phenotype and are found in early stages of the disease in plaques and cutaneous tumors. MLV/HIV-pseudotyped retroviral vectors target gene transfer to CD4-positive T cells and are therefore well suited to be specific delivery vehicles to treat CTCLs. We established a mouse xenograft model for CTCL and generated MLV/HIV-pseudotyped vectors encoding the herpes simplex virus thymidine kinase (HSV-TK), a well-known suicide gene, to prove the efficacy of MLV/HIV vectors in CTCL treatment. Vector particles were intratumorally injected into CTCL nude mouse xenografts. Mice were systemically treated with ganciclovir (GCV) and the tumor tissue was analyzed. A significant delay in tumor growth was observed for HSV-TK-transduced and GCV-treated tumors. GFP expression could be detected exclusively in CD4+ cells of tumors after transduction with GFP-encoding control vectors. The data demonstrate a cell-specific in vivo gene delivery via MLV/HIV-pseudotyped vectors and open new avenues for the treatment of CTCL in humans.

The autosomal dominant Birt-Hogg-Dubé syndrome is a cutaneo-intestinal condition that manifests on the skin in the form of multiple, skin-colored small papules that, histologically, prove to be mantleomas (fibrofolliculomas and trichodiscomas). These cutaneous lesions usually appear in the region of the head, neck, and upper part of the trunk. To date, only a single report in the literature describes the localized occurrence of this syndrome. We now describe a localized form of the Birt-Hogg-Dubé syndrome in a man with multiple mantleomas that were confined to the left half of the face, and which, in part, were arranged in the form of plaques. Another striking finding in this patient was a conspicuous vascular component in the lesions, characterized by a pronounced, well-demarcated fibrosis in the region of cutaneous blood vessel proliferations. Because perivascular fibromas have already been observed in other patients with Birt-Hogg-Dubé-syndrome, the perivascular fibroma, with fibrofolliculoma and trichodiscoma, must be included within this syndrome's spectrum of skin changes.

Birt-Hogg-Dubé-syndrome, first described 20 years ago, is an autosomal dominant inherited disease, characterized by the occurrence of multiple cutaneous hamartomas with adnexal differentiation. An association with intestinal neoplasms has been mentioned repeatedly. Recently, the cutaneous lesions in this syndrome have been interpreted as different developmental stages of one single hamartoma with sebaceous differentiation, called mantleoma. Numerous dermatohistopathologic studies contribute to the certain diagnosis of Birt-Hogg-Dubé-syndrome. In contrast, little information is available on the therapy of the multiple skin lesions. A father and his daughter with Birt-Hogg-Dubé-syndrome were treated with the CO2 laser, producing satisfactory results.

The morphologic features of trichofolliculoma are variable, reminiscent of the anagen, catagen, and telogen phases of a normal hair follicle in its cycle. We recently described an early, fully developed stage and late stages of trichofolliculoma. Using immunohistochemical examination, we sought to demonstrate hyperplasia of Merkel cells in all three stages of trichofolliculoma. We found this to be the most striking in small lesions of the late stage. The distribution of the Merkel cells in several stages of trichofolliculoma coincided with the known arrangement of normal follicular Merkel cells during the follicular cycle. However, antibodies against neurofilaments failed to detect innervated Merkel cells, in contrast to normal follicular Merkel cells. Antibodies against Ki67 did not reveal proliferative Merkel cells in any of the trichofolliculomas, but for unknown reasons, a distinct cytoplasmic staining of Merkel cell processes sometimes occurred. Nuclear Ki67 was strongly expressed in the nuclei of follicular keratinocytes of the fully developed trichofollicullomas, whereas those at a late stage showed a markedly decreased staining pattern. Our finding of Merkel cells in all trichofolliculomas underlines their classification as hamartomas with follicular differentiation. Hyperplasia of Merkel cells, even in trichofolliculomas at a late stage, as regressing lesions might implicate hitherto unknown regulatory functions of this neuroendocrine cell.

Kaposi's sarcoma (KS) has been reported after solid organ transplantation mostly in recipients of renal, liver, heart, and bone allografts. We describe the first case of a patient with lung transplantation who developed KS of the skin, but also of the lung graft. The tumors were localized to places of previous trauma, implying the involvement of a Koebner phenomenon. Moreover, a polymerase chain reaction assay revealed the presence of DNA sequences of herpesvirus 8 (HHV-8) on tissue of the cutaneous KS. Serological tests showed HHV-8 seronegativity of the graft donor and HHV-8 seropositivity of the patient before lung transplantation suggesting that the latter was already infected before the surgery and that immunosuppression resulted in the development of KS. This case report raises the question of the prevalence of HHV-8 in candidates for transplantation and organ donors, and of the value of an antiviral prophylaxis to lower the risk of KS.

The autosomal dominant inherited syndromes of Hornstein and Knickenberg (HKS), and Birt, Hogg and Dube (BHDS) are both characterized clinically by the overall spread of multiple flesh coloured papules of the skin. However, it is a matter of debate if colonic neoplasms (adenomas as well as adenocarcinomas) are associated findings in the HKS or rather in the BHDS. Furthermore, histological differences are said to exist between the skin lesions in the two syndromes: whereas perifollicular fibromas were described in the HKS, fibrofolliculomas and trichodiscomas were found in the BHDS. In the present study, we report on a father and his daughter in whom we initially diagnosed a BHDS. We then examined a greater number of the papular lesions in histologic sections cut vertically as well as horizontally to the epidermis. Our results indicate that the histologic differences between the skin lesions in the two syndromes are artificial ones, caused by interpretation of different sectioning planes, and that consequently HKS and BHDS are the same. Therefore, it is necessary to look for colonic polyps in the syndrome in question, regardless if one prefers the name HKS or BHDS for it.

The trichofolliculoma is a follicularly differentiated hamartoma, usually described as showing many vellus follicles, spreading from a central infundibular cyst. In spite of the well known regressive changes of normal hair follicles during catagen and telogen, the possibility of corresponding changes in the trichofolliculoma has not yet been discussed in the literature. By examining a total of 31 cases of trichofolliculoma it is demonstrated that this hamartoma undergoes an evolutionary process with great morphological changes, which can be attributed to the anagen, catagen, and telogen phase of the follicular cycle.

Association between mycosis fungoides (MF), its leukaemic variant Sezary syndrome (SS) and the human T-cell lymphotropic virus type-I (HTLV-I) has been controversial, with the reported incidence of infection varying between 0% and nearly 100%. We studied 127 patients (85 MF, 28 SS, five Sezary cell leukaemia, four lymphomatoid papulosis, and five unspecified cutaneous T-cell lymphomas (CTCL)) originating from Europe (France, Spain, U.K., Portugal) or from U.S.A. (California) for the presence of HTLV-I infection markers. HTLV-I and -II serology were performed on 78 patients using standard immunological methods. Reverse transcriptase (RT) assay was also performed in 26 cases using an RT-PCR-based method of high sensitivity. Molecular analyses were performed on 215 DNA samples (121 from fresh PBMCs, 26 from PBMCs after short-term culture and 68 from skin lesions) by PCR amplification using HTLV-I and -II gag, pol, env, pX and LTR specific primers. Immunological tests were negative except for two sera which were indeterminate. PCR with all HTLV-I and -II primer pairs showed negative results in all 215 samples investigated. No RT activity was detected in short-term PBMC cultures of any of the 26 cases studied. The results of this large study from five different countries clearly indicate that MF and SS are not associated with HTLV-I infection.

Moderate hyperplasia of Merkel cells (MC) in chronic sun-damaged skin and hypertrophic actinic keratoses is well known. In the present study we investigated the number of MC in 24 samples of chronic radiation dermatitis and 19 cases of fibroepithelioma of Pinkus (FP), which is known to arise preferably in radiation-damaged skin. Using antibodies against the low molecular weight cytokeratins 8, 18, and 20 and chromogranin A to visualize MC, we found hyperplasia of MC in chronic radiation dermatitis. Additionally, in all FPs we could detect many MC, especially in areas with a pronounced fenestrated pattern. Recently, regulative functions of MC on the growth of follicular epithelium under various conditions were discussed. Thus, MC hyperplasia suggests a causal role also in the development of FP. In this context, hyperplasia of MC in chronic radiation dermatitis could explain the frequent occurrence of FP due to radiation exposure. As we recently found MC also in trichoblastomas but not in basal-cell carcinomas, the MC in FP may indicate its relationship to the benign trichoblastoma rather than to the basal-cell carcinoma. It is possible that regulative influences of the MC are important for the clinically rather benign course of FP.

The possibility of a neuroendocrine differentiation in basal cell carcinomas (BCCs) has been a matter of debate for many years. In the present immunohistochemical study, applying the cytokeratins 8, 18 and 20 as the most established markers for Merkel cells (MCs), we did not find elevated numbers of MCs in any of 205 BCCs. This speaks against a neuroendocrine line of differentiation in BCCs. In contrast, we found various amounts of MCs in 15 of 36 trichoblastomas, which are the main benign differential diagnosis of BCC. In 4 trichoblastomas abundant MCs were spread over the whole epithelial tumor area. Additionally, the trichoblastomas' overlying epidermis exhibited significantly much higher numbers of MCs than the uninvolved adjacent skin or the epidermis overlying the BCCs. These findings might be an additional aid in the distinction between trichoblastomas and BCCs. Furthermore, concerning the recent discussion about the role of MC in growth and development of follicular germ, our observations are another sign of regulative influences of the MC, also in follicular germ under pathological conditions. Trichoblastomas with high numbers of MCs could be characterized as showing advanced differentiation toward the neuroendocrine component of the hair follicle, i.e., the MCs.

We analyzed three Merkel cell carcinomas (MCC), applying comparative genomic hybridization (CGH) with DNA from paraffin-embedded and cultured tumor material as the probes. By this method, numerous changes in chromosome copy numbers were observed in each tumor investigated. Recurrent gains of chromosomes 1, 6, 18q and 20 were detected in two tumors. A third tumor showed complex chromosomal copy number changes, including gain of chromosome 8 and 9. These gains, as well as gain of chromosome 1 in the first two tumors, were confirmed by fluorescence in situ hybridization to paraffin tissue sections. Our results support the view that important genes for MCC development may be located on chromosomes 1, 6, 18q and 20.

Kaposi's sarcoma (KS), a vascular tumour that contains characteristic spindle cells forming slit-like spaces, may have an infectious aetiology. Recently, sequences of a new human herpesvirus, KSHV/HHV-8, have been identified in both HIV-associated and classical KS. We sought to identify the target cell of this virus in KS tumour tissue. Using PCR in situ hybridization (PCR-ISH) we show that KSHV/HHV-8 is present in the flat endothelial cells lining vascular spaces of KS lesions as well as in typical KS spindle cells. These findings show that KSHV/HHV-8 is present in the cell types thought to represent neoplastic cells in these lesions.

The incidence of Merkel cells has previously been investigated in a number of inflammatory and tumorous lesions of the skin. Special attention was given to tumors with follicular differentiation. In the present study we examined the localization of Merkel cells in another adnexal tumor, the desmoplastic trichoepithelioma (n = 15), as well as in its main differential diagnosis, the morpheiform basal-cell carcinoma (n = 30). Using immunohistochemical methods, we found Merkel cells as a stable constituent in desmoplastic trichoepitheliomas, but failed to detect them in morpheiform basal-cell carcinomas. These findings might therefore be an important tool in the sometimes very difficult but clinically imperative distinction between these two conditions. Furthermore, our study may be of interest in the discussion about the origin of desmoplastic trichoepitheliomas. High numbers of Merkel cells in desmoplastic trichoepitheliomas indicate a bulge-derived origin of this adnexal tumor, since high numbers of Merkel cells, especially in the bulge, were recently discovered. Although the significance of Merkel cell hyperplasia in desmoplastic trichoepithelioma is not presently understood, a regulatory role of the Merkel cell in growth and development of this adnexal tumor is suggested.