TSC2/PKD1 Contiguous Gene Syndrome: A Report of 2 Cases With Emphasis on Dermatopathologic Findings

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Multiple familial trichoepitheliomas (MFT) constitute an autosomally inherited syndrome possibly related to Brooke-Spiegler syndrome (BSS). Although some early studies suggested a role for the PTCH gene on chromosome 9q22.3 in the etiopathogenesis of MFT, recent studies of occasional patients with the MFT clinical phenotype identified mutations in the CYLD gene on chromosome 16q12-q13, a gene responsible for BSS. A systematic investigation of PTCH and CYLD mutations in patients with MFT has never been performed. Our main objective was to collect a reasonably large series of patients with MFT to (1) study the clinicopathological spectrum of the disease, (2) determine whether the PTCH gene is implicated in the pathogenesis of MFT, and if so (3) determine the relative frequency of CYLD and PTCH mutations, (4) establish if there may be any possible genotype-phenotype correlations, and (5) study the spectrum of somatic mutations. Clinical analysis including family histories, histopathological investigations, and molecular genetic studies were performed. There were 9 female and 7 male patients ranging in age from 11 to 63 years. They presented with multiple, small, discrete and sometimes confluent, skin-colored to pink, asymptomatic nodules preferentially located on the face, being especially prominent and confluent in the nasolabial folds and inner aspects of the eyebrows. A total of 66 conventional trichoepitheliomas (TEs) were studied microscopically. Aside from typical features of TE, some also exhibited variant morphological patterns including areas reminiscent of other benign adnexal neoplasms and melanocytic hyperplasia. In none of the 9 patients tested was a germline mutation of the PTCH gene identified. Germline CYLD mutations were detected in 6 of 13 patients tested (identical in 2 unrelated patients) including 2 novel mutations, whereas the remaining 7 individuals showed wild-type alleles. Two patients with germline wild-type CYLD showed, however, a somatic mutation in the gene (1 duplication, 1 substitution mutation). Neither CYLD nor PTCH germline mutations were found in the 5 patients in whom both genes were analyzed. MFT seems to be a phenotypic variant of BSS. The PTCH gene is rarely, if ever, involved in the pathogenesis of MFT. Absence of a germline mutation of the CYLD gene in cases harboring a somatic mutation may be explained by large deletions in the gene or by mutation in intronic sequences or in the promoter region. Considering our 5 patients with no mutation in either gene, the final possibility is that another, as yet undescribed gene (neither CYLD nor PTCH) is implicated in the pathogenesis of some patients with MFT.

Section: Discussionmentioning

confidence: 99%

Multiple (Familial) Trichoepitheliomas: A Clinicopathological and Molecular Biological Study, Including CYLD and PTCH Gene Analysis, of a Series of 16 Patients

Kazakov

Vaněček²,

Zelger³

et al. 2011

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“…The frequency of large rearrangements seems to be slightly lower when compared with other tumor suppressor genes affected in syndromes manifested by skin tumors, including Lynch syndrome/Muir-Torre syndrome and neurofibromatosis type 1 but comparable with tuberous sclerosis, Gorlin-Goltz, and Cowden syndromes. [50][51][52][53][54][55][56] In our cohort, there is still a relatively high percentage of patients without detectable germline mutation in the CYLD gene. Mutations in the coding region 36 and large rearrangements have been excluded leaving alterations in intronic 41 and regulatory regions, balanced translocations and, perhaps, epigenetic silencing, as possible explanations for BSS/MFT in our cohort.…”

Section: Discussionmentioning

confidence: 99%

Large Germline Deletions of the CYLD Gene in Patients With Brooke–Spiegler Syndrome and Multiple Familial Trichoepithelioma

Vaněček

Halbhuber

Kacerovská

et al. 2014

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Brooke-Spiegler syndrome (BSS) and its phenotypic variants, multiple familial trichoepithelioma (MFT) and familial cylindromatosis, are rare autosomal dominant hereditary diseases. They are characterized by the presence of multiple adnexal tumors, especially cylindromas, spiradenomas, spiradenocylindromas, and trichoepitheliomas. Implicated in the pathogenesis of the disease is the gene CYLD, which is localized on the long arm of chromosome 16. This gene encodes an evolutionarily conserved protein belonging to the deubiquitinating enzymes family, which plays a key role in many signaling pathways, especially in NF-κB, JNK, and Wnt. Less than 90 germline mutations of CYLD have been identified in patients with BSS/MFT. These mutations are mostly small alterations in the coding sequence and at exon-intron junction sites. One patient with an intronic mutation and another with a large CYLD deletion have also been recorded. In this study, the authors have analyzed a cohort of 14 patients with BSS/MFT from 13 families for large genome rearrangements by array comparative genome hybridization followed by confirmatory sequencing. We identified 2 large deletions, namely c.-34111_*297858del378779 and c.914-6398_1769del13642ins20 in patients with MFT and BSS, respectively. All other analyzable patients did not reveal any copy number alteration. It is concluded that the large rearrangements are relatively rare in patients without a germline CYLD mutation demonstrable by conventional sequencing. The pathogenetic mechanisms in patients with BSS/MFT lacking germline sequence alterations or large rearrangements in the CYLD gene remain to be clarified.

“…That epidermal melanocytic hyperplasia overlying trichoblastomas is not specific to this entity is evident by its occurrence in association with other epithelial and mesenchymal tumors; including fibrous papule, angiofibroma, plexiform neurofibroma, and Merkel cell carcinoma. [9][10][11] Epidermal melanocytic hyperplasia is distinct from melanocytic colonization, which is occasionally seen in various nonmelanocytic tumors [12][13][14][15][16] or maybe an essential component of the lesion as in melanocytic matricoma. 17 Melanocytic colonization was beyond the scope of this study but in a few cases for which staining for melanocytic markers was available, occasional intratumoral melanocytes were present.…”

Section: Discussionmentioning

confidence: 99%

Melanocytic Hyperplasia in the Epidermis Overlying Trichoblastomas in 100 Randomly Selected Cases

Omoush

Konstantinova²,

Michal³

et al. 2016

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One hundred cases of trichoblastomas (large nodular, small nodular, cribriform, lymphadenoma, and columnar) were randomly selected and studied for the presence of melanocytic hyperplasia in the epidermis overlying the tumors, which was defined as foci of increased melanocytes in the basal layer of the epidermis (more than 1 per 4 basal keratinocytes). Focal melanocytic hyperplasia was detected in a total of 22 cases of trichoblastoma (22%), and this phenomenon was most frequently seen in columnar trichoblastoma (7 cases), followed by large nodular trichoblastoma (5 cases). The mechanism of epidermal melanocytic hyperplasia overlying trichoblastoma is unclear. Ultraviolet may be a contributing factor, as focal melanocytic hyperplasia was also detected in one-third of cases in the epidermis overlying uninvolved skin, usually associated with solar elastosis. This is further corroborated by the occurrence of the lesions predominantly on the face. Melanocytic hyperplasia overlying trichoblastoma appears to have no impact on the clinical appearance of the lesion and is recognized only microscopically. In an adequate biopsy specimen containing at least part of trichoblastoma, it should not cause any diagnostic problems.