Trichilemmomas show loss of PTEN in Cowden syndrome but only rarely in sporadic tumors

Concurrent PTEN and PDGFRB Alterations Characterize Storiform Collagenoma

Storiform collagenoma is a rare mesenchymal skin tumor that is composed of thickened collagen bundles arranged in a characteristic storiform pattern with a relatively hypocellular CD34-positive spindle cell component. Storiform collagenoma is most often sporadic, but multiple lesions can occur in Cowden syndrome, which is characterized by germline alterations in PTEN (phosphatase and tensin homolog) on chromosome 10. Here, we investigated the molecular pathogenesis of storiform collagenoma using a targeted next-generation DNA sequencing platform, including 5 sporadic cases and one case associated with Cowden syndrome. Recurrent PTEN alterations were identified in all cases, with biallelic PTEN inactivation observed in the case associated with Cowden syndrome and one sporadic case. Unexpectedly, we also identified recurrent activating mutations in the platelet-derived growth factor receptor beta ( PDGFRB ) gene. This included a missense substitution in the D5 Ig-like domain of PDGFRB in the Cowden syndrome-associated case. In addition, we report missense alterations in the juxtamembrane domain of PDGFRB in 4 of 5 (80%) sporadic cases, including mutations that have been previously described in sporadic myofibroma and myopericytoma. Therefore, we confirm the neoplastic nature of storiform collagenoma, we expand the spectrum of reported PDGFRB alterations in mesenchymal tumors and we suggest a possible collaborative role for PTEN and PDGFRB in the pathogenesis of storiform collagenoma.

Molecular pathology of skin adnexal tumours

AIMS

Tumours of the cutaneous adnexa arise from, or differentiate towards, structures in normal skin such as hair follicles, sweat ducts/glands, sebaceous glands or a combination of these elements. This class of neoplasms includes benign tumours and highly aggressive carcinomas. Adnexal tumours often present as solitary sporadic lesions, but can herald the presence of an inherited tumour syndrome such as Muir-Torre syndrome, Cowden syndrome or CYLD cutaneous syndrome. In contrast to squamous cell carcinoma and basal cell carcinoma, molecular changes in adnexal neoplasia have been poorly characterised and there are few published reviews on the current state of knowledge.

METHODS AND RESULTS

We reviewed findings in peer-reviewed literature on molecular investigations of cutaneous adnexal tumours published to June 2021.

CONCLUSIONS

Recent discoveries have revealed diverse oncogenic drivers and tumour suppressor alterations in this class of tumours, implicating pathways including Ras/MAPK, PI3K, YAP/TAZ, beta-catenin and nuclear factor kappa B (NF-κB). These observations have identified novel markers, such as NUT for poroma and porocarcinoma and PLAG1 for mixed tumours. Here, we provide a comprehensive overview and update of the molecular findings associated with adnexal tumours of the skin.

Clear Cell Proliferations of the Skin: A Histopathologic Review

ABSTRACT

Cutaneous clear cell proliferations encompass a heterogenous group of several primary cutaneous neoplasms and metastatic tumors with different histogenesis. Many of these clear cell proliferations may seem strikingly similar under the microscope resulting in challenging diagnosis. In many of these clear cell lesions, the reason for the clear or pale appearance of proliferating cells is unknown, whereas in other ones, this clear cell appearance is due to intracytoplasmic accumulation of glycogen, mucin, or lipid. Artifacts of tissue processing and degenerative phenomenon may also be responsible for the clear cell appearance of proliferating cells. Awareness of the histopathologic findings as well as histochemical and immunohistochemical techniques are crucial to the accurate diagnosis. This review details the histopathologic features of clear cell cutaneous proliferations, classifying them according their type of differentiation and paying special attention to the histopathologic differential diagnosis among them.

The Skin in Cowden Syndrome

Cowden syndrome (CS) is an autosomal dominant condition caused by mutations in the phosphatase and tensin homolog (PTEN) gene, and is characterized by multiple hamartomas and a predisposition to malignant tumors. Characteristic skin lesions include trichilemmomas, acral keratosis, mucocutaneous neuromas, oral papillomas, and penile macules, and are often the first clues to the underlying diagnosis. Here, we discuss the mucocutaneous manifestations of CS, differential diagnoses of genetic causes of each cutaneous finding, genetic analyses for patients with skin manifestations, management of patients with CS, and potential new targeted therapies for CS.

Update on Molecular Genetic Alterations of Cutaneous Adnexal Neoplasms

Cutaneous adnexal tumors recapitulate follicular, sweat gland, and/or sebaceous epithelia, and range from benign tumors to aggressive carcinomas. Adnexal tumors can be hallmarks for inherited tumor syndromes. Oncogenic drivers of adnexal neoplasms modulate intracellular pathways including mitogen-activated protein kinase, phosphoinositide-3-kinase, Wnt/β-catenin, Hedgehog, nuclear factor κB, and Hippo intracellular signaling pathways, representing potential therapeutic targets. Malignant progression can be associated with tumor suppressor loss, especially TP53. Molecular alterations drive expression of specific diagnostic markers, such as CDX2 and LEF1 in pilomatricomas/pilomatrical carcinomas, and NUT in poromas/porocarcinomas. In these ways, improved understanding of molecular alterations promises to advance diagnostic, prognostic, and therapeutic possibilities for adnexal tumors.

Validation of Immunohistochemical Assays for Integral Biomarkers in the NCI-MATCH EAY131 Clinical Trial

Biomarkers that guide therapy selection are gaining unprecedented importance as targeted therapy options increase in scope and complexity. In conjunction with high-throughput molecular techniques, therapy-guiding biomarker assays based upon immunohistochemistry (IHC) have a critical role in cancer care in that they inform about the expression status of a protein target. Here, we describe the validation procedures for four clinical IHC biomarker assays-PTEN, RB, MLH1, and MSH2-for use as integral biomarkers in the nationwide NCI-Molecular Analysis for Therapy Choice (NCI-MATCH) EAY131 clinical trial. Validation procedures were developed through an iterative process based on collective experience and adaptation of broad guidelines from the FDA. The steps included primary antibody selection; assay optimization; development of assay interpretation criteria incorporating biological considerations; and expected staining patterns, including indeterminate results, orthogonal validation, and tissue validation. Following assay lockdown, patient samples and cell lines were used for analytic and clinical validation. The assays were then approved as laboratory-developed tests and used for clinical trial decisions for treatment selection. Calculations of sensitivity and specificity were undertaken using various definitions of gold-standard references, and external validation was required for the PTEN IHC assay. In conclusion, validation of IHC biomarker assays critical for guiding therapy in clinical trials is feasible using comprehensive preanalytic, analytic, and postanalytic steps. Implementation of standardized guidelines provides a useful framework for validating IHC biomarker assays that allow for reproducibility across institutions for routine clinical use. Clin Cancer Res; 24(3); 521-31. ©2017 AACR.

Linear trichilemmomas on the ankle of a 28-year-old female

Trichilemmomas are benign cutaneous proliferations derived from the outer root sheath of the hair follicle. They most often occur on the head and neck region and show a female predominance. When multiple, they are associated with Cowden syndrome (CS), a rare disorder due to an autosomal dominant germline mutation in PTEN (phosphatase and tensin homolog on chromosome 10), a tumor suppressor gene. Trichilemmomas outside of the head and neck region are rare, and as such, the association with CS is not clear. A 28-year-old healthy female with no significant family history of cancer presented to her dermatologist with multiple erythematous papules on the left anterior ankle, starting at birth. A shave biopsy confirmed the diagnosis of trichilemmoma with focal desmoplastic features (or desmoplastic trichilemmoma). A PTEN immunohistochemical study showed patchy (but not complete) loss of staining of the lesional cells. After shave removal, the trichilemmomas recurred 1-2 months later.

Multiple clear cell acanthomas and a sebaceous lymphadenoma presenting in a patient with Cowden syndrome - a case report

Cowden syndrome (CS) is an uncommon autosomal dominant multiorgan/system genodermatosis. It is characterized by the development of multiple hamartomas of endodermal, mesodermal and ectodermal origin, an increased lifetime risk of breast, thyroid, endometrial and other cancers and an identifiable germline mutation. Mucocutaneous hamartomas are the most common lesions seen and mainly include facial trichilemmomas, oral mucosal papillomas and benign acral keratoses. Herein, we report a case of a 63-year-old Caucasian male with a long-established diagnosis of CS and history of thyroid cancer, colonic polyps, and innumerable trichilemmomas, seborrheic keratoses, squamous papillomas and non-melanoma skin cancers excised in the past. He presented in four separate occasions with small skin-colored papulonodular lesions that upon excision revealed to be clear cell acanthomas. He also developed a tumor in the preauricular area that was completely resected and was found to be a sebaceous lymphadenoma (SLA) of the parotid gland. This is to our knowledge, the second report of clear cell acanthoma and also the second reported case of SLA in a patient with CS.

Genodermatosis Affecting the Skin and Mucosa of the Head and Neck: Clinicopathologic, Genetic, and Molecular Aspect--PTEN-Hamartoma Tumor Syndrome/Cowden Syndrome

PTEN hamartoma tumor syndrome refers to a spectrum of disorders caused by mutations in the phosphatase and tensin homolog (PTEN) gene. Cowden syndrome, the principal PTEN-related disorder is characterized by multiple neoplasms and hamartomas, mucosal papillomatosis, and skin lesions, trichilemmomas. Trichilemmomas and mucocutaneous papillomatous papules are one of the first signs of the disease. Early recognition of these skin lesions may help on diagnosing an underlying malignancy and early cancer screening.

Somatic Copy Number Alterations at Oncogenic Loci Show Diverse Correlations with Gene Expression

Somatic copy number alterations (SCNAs) affecting oncogenic drivers have a firmly established role in promoting cancer. However, no agreed-upon standard exists for calling locus-specific amplifications and deletions in each patient sample. Here, we report the correlative analysis of copy number amplitude and length with gene expression across 6,109 samples from The Cancer Genome Atlas (TCGA) dataset across 16 cancer types. Using specificity, sensitivity, and precision-based scores, we assigned optimized amplitude and length cutoffs for nine recurrent SCNAs affecting known oncogenic drivers, using mRNA expression as a functional readout. These cutoffs captured the majority of SCNA-driven, highly-expression-altered samples. The majority of oncogenes required only amplitude cutoffs, as high amplitude samples were almost invariably focal; however, CDKN2A and PTEN uniquely required both amplitude and length cutoffs as primary predictors. For PTEN, these extended to downstream AKT activation. In contrast, SCNA genes located peri-telomerically or in fragile sites showed poor expression-copy number correlations. Overall, our analyses identify optimized amplitude and length cutoffs as efficient predictors of gene expression changes for specific oncogenic SCNAs, yet warn against one-size-fits-all interpretations across all loci. Our results have implications for cancer data analyses and the clinic, where copy number and mutation data are increasingly used to personalize cancer therapy.

Dermatofibrosarcoma Protuberans in a Patient With Cowden Syndrome: Revisiting the PTEN and PDGF Pathways

PTEN hamartoma tumor syndrome, of which Cowden syndrome (CS) is the most recognized variant, is characterized by multiple benign and malignant tumors of ectodermal, mesodermal, and endodermal origins, secondary to germline mutation in the phosphatase and tensin homolog (PTEN) gene. Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive malignant fibroblastic/myofibroblastic tumor of the skin, characterized by the t(17:22)(q22:q13) translocation resulting in fusion of the COL1A1 and PDGFB genes. An association between CS and DFSP has not been reported in the literature to date. The authors have encountered a male patient with CS and a history of DFSP that developed adjacent to a sclerotic fibroma on the parietal scalp, both excised at age 7. He presented at age 21 with an enlarging pink nodule at the same site on the parietal scalp. Excision revealed a dermal and subcutaneous storiform spindle cell proliferation with fat entrapment and positive staining for CD34, consistent with DFSP. Fluorescence in situ hybridization confirmed PDGFB gene rearrangement. PTEN expression in the patient's recurrent DFSP was nearly absent when compared with that of sporadic DFSP. To our knowledge, this is the first report of DFSP in a patient with CS. Although the association is likely to be coincidental, the authors revisited the PTEN and the PDGF pathways to speculate any possible interplay of the 2 conditions on a molecular level.

Immunohistochemistry in dermatopathology

CONTEXT

Immunohistochemistry is not a diagnostic test but a highly valuable tool that requires interpretation within a context.

OBJECTIVE

To review the current status and limitations of immunohistochemistry in dermatopathology.

DATA SOURCES

English-language literature published between 1980 and 2014.

CONCLUSIONS

Although immunohistochemistry is rarely completely specific or sensitive, it is an important adjunctive technique in dermatopathology and can be helpful in a series of diagnostic dilemmas.

Complete loss of PTEN protein expression correlates with shorter time to brain metastasis and survival in stage IIIB/C melanoma patients with BRAFV600 mutations

PURPOSE

Loss of function of PTEN is a frequent event in melanoma, particularly in tumors with BRAF(V600) mutations. The prevalence, pathologic features, and clinical outcomes associated with PTEN loss in patients with stage IIIB/C melanoma were interrogated to improve our understanding of the clinical significance of this molecular event.

EXPERIMENTAL DESIGN

Archival tissue from lymphadenectomy specimens among patients (n = 136) with stage IIIB or IIIC melanoma was assessed by DNA sequencing for activating BRAF and NRAS mutations, and by immunohistochemistry for the expression of PTEN protein. Associations of these molecular aberrations with demographics, tumor characteristics, and clinical outcomes were determined.

RESULTS

The prevalence of BRAF(V600) mutations (40% overall), NRAS mutations (10%), and PTEN loss (25%) did not vary by pathologic substage. BRAF/NRAS mutation status did not correlate with distant disease-free survival (DDFS) or overall survival (OS). Complete loss of PTEN expression correlated with shorter OS but not DDFS. When stratified by specific sites of distant metastasis, PTEN loss was associated with significantly shorter time to melanoma brain metastasis (MBM), but not to liver, lung, or bone metastasis. Analysis of PTEN in mutationally defined subsets showed that PTEN loss was significantly associated with OS and time to MBM in patients with BRAF(V600) mutations.

CONCLUSIONS

Loss of PTEN protein expression correlates significantly with decreased OS and time to MBM in stage IIIB/C melanoma patients with BRAF(V600) mutations. The findings add to evidence supporting a significant role for PTEN loss and the PI3K-AKT pathway in melanoma.

Frequent activating HRAS mutations in trichilemmoma

BACKGROUND

Trichilemmoma is a benign follicular epithelial tumour exhibiting outer root sheath differentiation. It is associated with Cowden syndrome and naevus sebaceus (NS), but the pathogenesis of sporadic tumours is poorly understood. Recently, NS was found to be caused by postzygotic HRAS or KRAS mutations.

OBJECTIVES

We sought to determine whether NS-related and NS-unrelated trichilemmomas harbour RAS mutations.

METHODS

Formalin-fixed and paraffin-embedded blocks of 12 NS-related and 15 NS-unrelated trichilemmomas from 26 individuals were retrieved and analysed to determine the presence of mutations in exons 1 and 2 of the HRAS, KRAS and NRAS genes by polymerase chain reaction and direct sequencing. Mutational hotspots of the FGFR3 and PIK3CA genes were also analysed for NS-unrelated cases.

RESULTS

Among the 27 cases, mutually exclusive HRAS c.37G>C and c.182A>G mutations were observed in 17 and three tumours, respectively. Of the 12 NS-related tumours, 11 (92%) harboured the HRAS c.37G>C substitution. Of the 15 sporadic tumours, nine (60%) harboured HRAS mutations, including six c.37G>C and three c.182A>G. An HRAS c.182A>G mutation was observed only in sporadic tumours. No mutations were observed in the other genes that were tested.

CONCLUSIONS

The high frequency of HRAS activating mutations, including the c.182A>G substitution, which was rather rare in NS, suggests that most trichilemmomas are authentic neoplasms.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Stem cell quiescence acts as a tumour suppressor in squamous tumours

In some organs, adult stem cells are uniquely poised to serve as cancer cells of origin. It is unclear, however, whether tumorigenesis is influenced by the activation state of the adult stem cell. Hair follicle stem cells (HFSCs) act as cancer cells of origin for cutaneous squamous cell carcinoma (SCC) and undergo defined cycles of quiescence and activation. The data presented here show that HFSCs are unable to initiate tumors during the quiescent phase of the hair cycle, indicating that the mechanisms that keep HFSCs dormant are dominant to the gain of oncogenes (Ras) or the loss of tumor suppressors (p53). Furthermore, Pten activity is necessary for quiescence based tumor suppression, as its deletion alleviates tumor suppression without affecting proliferation. These data demonstrate that stem cell quiescence is a form of tumor suppression in HFSCs, and that Pten plays a role in maintaining quiescence in the presence of tumorigenic stimuli.

Phosphatase and tensin homolog immunohistochemical staining and clinical criteria for Cowden syndrome in patients with trichilemmoma or associated lesions

Trichilemmomas and mucocutaneous papillomatous papules are associated with Cowden syndrome (CS). Germline Phosphatase and tensin homolog (PTEN) mutations have been identified in 34% to 80% of those meeting clinical criteria for CS. PTEN expression has not been well evaluated in large numbers of trichilemmoma. We investigated clinical criteria for CS in trichilemmoma patients and studied PTEN staining to determine how often patients with trichilemmoma have CS and whether PTEN staining is useful. About 102 cases of trichilemmoma or associated lesions from 95 patients were collected. Clinical histories were reviewed to investigate the incidence of CS using International Cowden Consortium operational criteria for diagnosis of CS, version 2000. PTEN staining was performed and graded for intensity and percentage. Although 1 patient had 3 trichilemmoma or associated lesions, and 5 had 2 trichilemmoma or associated lesions, none of 95 patients met clinical criteria for a diagnosis of CS. Twelve of the 89 cases available for staining (13.5%) showed decreased PTEN. Of these, the demographic, clinical, and pathological features were not significantly different compared with PTEN intact cases. None of the cases from the 6 patients with more than 1 trichilemmoma or associated lesions showed decreased PTEN staining. We thus conclude that the likelihood of a clinical diagnosis of CS among patients with a solitary or only a few trichilemmoma is extremely low. PTEN expression is decreased in some sporadic trichilemmomas or associated lesions. This is the largest study investigating clinical history and PTEN staining in patients with trichilemmoma or associated lesions. Because none of our patients met clinical diagnostic criteria for CS, the direct correlation of PTEN in CS and sporadic trichilemmoma remains unclear.

A multicenter phase 1 study of PX-866 in combination with docetaxel in patients with advanced solid tumours

Background:

This phase I, dose-finding study determined the safety, maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D), pharmacokinetics, and antitumour activity of PX-866, a phosphatidylinositol 3-kinase inhibitor, combined with docetaxel in patients with incurable solid tumours.

Methods:

PX-866 was administered at escalating doses (4–8 mg daily) with docetaxel 75 mg m⁻² intravenously every 21 days. Archived tumour tissue was assessed for potential predictive biomarkers.

Results:

Forty-three patients were enrolled. Most adverse events (AEs) were grade 1 or 2. The most frequent study drug-related AE was diarrhoea (76.7%), with gastrointestinal disorders occurring in 79.1% (docetaxel-related) and 83.7% (PX-866-related). No dose-limiting toxicities were observed. The RP2D was 8 mg, the same as the single-agent MTD. Co-administration of PX-866 and docetaxel did not affect either drug's PKs. Best responses in 35 evaluable patients were: 2 partial responses (6%), 22 stable disease (63%), and 11 disease progression (31%). Eleven patients remained on study for >180 days, including 8 who maintained disease control on single-agent PX-866. Overall median progression-free survival (PFS) was 73.5 days (range: 1–569). A non-significant association between longer PFS for PIK3CA-MUT/KRAS-WT vs PIK3CA-WT/KRAS-WT was observed.

Conclusion:

Treatment with PX-866 and docetaxel was well tolerated, without evidence of overlapping/cumulative toxicity. Further investigation with this combination is justified.