Hui C. Tsou

Clinical and pathological features of breast disease in Cowden's syndrome: An underrecognized syndrome with an increased risk of breast cancer☆

Cowdens syndrome (CS), or multiple hamartoma syndrome, is an autosomal dominant disorder associated with benign skin tumors and an increased risk of breast cancer. In an effort to understand the basic mechanisms regulating the development of breast cancer in this patient population, as well as to define diagnostic aspects of the disorder, we describe for the first time the clinical and pathological spectrum of breast disease in CS. We obtained the clinical histories and examined the histopathology of 59 cases from 19 women with CS sent to us from a variety of institutions. The 19 women showed a spectrum of benign histopathological findings, including ductal hyperplasia, intraductal papillomatosis, adenosis, lobular atrophy, fibroadenomas, and fibrocystic change. Seventeen (89%) showed features suggestive of a breast hamartoma. Fourteen women (74%) showed malignant disease, most of which was ductal carcinoma. Twelve patients (86%) showed ductal carcinoma in situ (DCIS), and 12 (86%) showed infiltrating ductal carcinoma. One patient had only DCIS and another patient showed both infiltrating tubular carcinoma and lobular carcinoma in situ. Ten patients (71%) actually showed foci of tumor involving densely fibrotic, hamartomatous areas. In summary, we show that women with CS have a spectrum of exuberant benign and malignant breast pathology. A common benign breast lesion in CS is a densely fibrotic hyalinized nodule, whereas the most frequent breast malignancy is ductal carcinoma.

PTEN/MMAC1 mutations in hepatocellular carcinomas

Mutations in the PTEN/MMAC1 gene have been identified in several types of human cancers and cancer cell lines, including brain, endometrial, prostate, breast, thyroid, and melanoma. In this study, we screened a total of 96 hepatocellular carcinoma (HCC) samples from Taiwan, where HCC is the leading cancer in males and third leading cancer in females, for mutations in the PTEN/MMAC1 gene. Complete sequence analysis of these samples demonstrated a missense mutation in exon 5 (K144I) and exon 7 (V255A) from HCC samples B6-21 and B6-2, respectively. A putative splice site mutation was also detected in intron 3 from sample B6-2. Both B6-21 and B6-2 were previously shown to contain missense mutations in the coding sequences of the p53 gene. Functional studies with the two missense mutations demonstrated that while mutation V255A in exon 7 resulted in a loss of phosphatase activity, mutation K144I in exon 5 retained its phosphatase activity. Additionally, we identified a silent mutation (P96P) in exon 5 of the PTEN/MMAC1 gene from HCC sample B6-22. These data provide the first evidence that the PTEN/MMAC1 gene is mutated in a subset of HCC samples.

Role of PTCH and p53 Genes in Early-Onset Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common skin cancer in the Western world. Ultraviolet (UV) exposure, race, age, gender, and decreased DNA repair capacity are known risk factors for the development of BCC. Of these, UVB irradiation from sunlight is the most significant risk factor. The incidence of sporadic BCC increases in individuals older than age 55, with the greatest incidence reported in individuals who are older than 70, and is rare in individuals who are younger than 30. In this study, we analyzed 24 BCC samples from individuals who had BCC diagnosed by the age of 30. Fifteen single-stranded conformation polymorphism variants in the PTCH gene were identified in 13 BCC samples. Sequence analysis of these single-stranded conformation polymorphism variants revealed 13 single nucleotide changes, one AT insertion, and one 15-bp deletion. Most of these nucleotide changes (nine of 15) were predicted to result in truncated PTCH proteins. Fifteen p53 mutations were also found in 11 of the 24 BCC samples. Thirty-three percent (five of 15) and 60% (nine of 15) of the nucleotide changes in the PTCH and p53 genes, respectively, were UV-specific C-->T and CC-->TT nucleotide changes. Our data demonstrate that the p53 and PTCH genes are both implicated in the development of early-onset BCC. The identification of UV-specific nucleotide changes in both tumor suppressor genes suggests that UV exposure is an important risk factor in early onset of BCC.

Phenotypic findings of Cowden syndrome and Bannayan-Zonana syndrome in a family associated with a single germline mutation in PTEN

Cowden syndrome (CS) and Bannayan-Zonana syndrome (BZS) are two hamartoma syndromes with distinct phenotypic features. Although partial clinical overlap exists between CS and BZS, they are considered to be separate entities. PTEN has been identified as the susceptibility gene for both disorders, suggesting allelism. We have identified a germline mutation, R335X, in PTEN in a family consisting of two female members with the phenotypic findings of CS and two male members with the phenotypic findings of BZS. To our knowledge, this is the first report that shows the presence of separate subjects with CS and with BZS in a single family associated with a single germline PTEN mutation.

The genetic basis of Cowden’s syndrome: three novel mutations in PTEN/MMAC1/TEP1

Cowden’s syndrome (CS) is an autosomal dominant disorder associated with an increased risk of developing benign and malignant tumors in a variety of tissues, including the skin, thyroid, breast and brain. Women with CS are felt to have an increased risk of developing breast cancer, and virtually all women with CS develop bilateral fibrocystic disease of the breast. Recently, a series of germline mutations have been identified from CS families in a gene known as PTEN/MMAC1/TEP1. In this study, we used heteroduplex analysis and direct sequencing analysis and identified three novel germline mutations in the PTEN/MMAC1/TEP1 coding sequence from unrelated individuals with CS. We report a de novo transition (T→C) at nucleotide 335 in exon 5. This missense mutation resulted in a leucine to proline (CTA to CCA) change at codon 112. We also describe a novel splice site mutation (801+2T→G) in intron 7 that caused exon skipping in PTEN/MMAC1/TEP1 mRNA. The third mutation we report is a missense mutation, consisting of a transition (T→C) at nucleotide 202 in exon 3, resulting in a tyrosine to histidine (TAC to CAC) change at codon 68. Finally, we also detected a rare polymorphism in exon 7 of the PTEN/MMAC1/TEP1 coding sequence. These data confirm the observation that mutations of the PTEN/MMAC1/ TEP1 coding sequence are responsible for at least some cases of CS, and further define the spectrum of mutations in this autosomal dominant disorder.

Molecular basis of variegate porphyria: a de novo insertion mutation in the protoporphyrinogen oxidase gene

Abstract The porphyrias are disorders that result from the inherited or acquired dysregulation of one of the eight enzymes in the heme biosynthetic pathway. Variegate porphyria (VP) is characterized by deficiencies in protoporphyrinogen oxidase (PPO) and has recently been genetically linked (Z = 6.62) to the PPO gene on chromosome 1q21. In this study, we have identified two sequence variants in the PPO gene in a family with VP. The first is a neutral polymorphism at the -47 position of intron 2; this polymorphism is present in the general population and is unlikely to underlie the VP phenotype. The second is a mutation in the PPO gene in a patient with VP; the mutation consists of an apparently de novo 2-bp insertion in exon 3 of PPO and results in a frameshift and downstream premature termination codon. These data establish that a frameshift mutation in PPO is the underlying mutation in this patient with VP and explain the sporadic occurrence of the phenotype in this family.

Identification of PTEN mutations in five families with Bannayan-Zonana syndrome

Abstract: Germline mutations in PTEN, a putative tumor suppressor gene, has been identified in 2 autosomal dominant inherited hamartoma syndromes, Cowden syndrome (CS) and Bannayan‐Zonana syndrome (BZS). While both diseases exhibit distinct phenotypic features. there seems to be a partial clinical overlap between the 2 diseases. To date, 9 families with BZS have been screened for PTEN mutations, of which 5 were found to exhibit mutations in this gene. We report 5 novel germline mutations in the PTEN coding sequence from 5 unrelated families with the BZS phenotype. While all the mutations we identified are novel in BZS, 1003C‐T (nonsense mutation) and 209+5G‐A (putative splice site mutation) have been previously reported in unrelated families with CS and Lhermitte‐Duclos disease. Interestingly, 1 of the families has an individual with BZS and 1 with CS phenotype, associated with a single PTEN mutation, 885insA. These data support the notion that CS and BZS may be within the spectrum of the same primary disorder.

Similarities of cutaneous and breats pathology in Cowden's Syndrome

Abstract: Cowdens Syndrome (CS), or multiple hamartoma syndrome, is an autosomal dominant disorder characterized by mucocutaneous lesions, multiple benign tumors of internal organs and an increased risk of breast cancer. Here, we describe and illustrate in detail the benign breast pathology of 59 breast cases from 19 women with CS. Fibrosis is a significant characteristic of the breasts of patients with CS. Fibroaden‐ omas appear to hyalinize at an early age and are frequently complex. The specimens demonstrate a spectrum of dense hyalinization of both the lobule and the stroma, and hyaline nodules appear to be the most charac‐ teristic lesion. This hyalinization process shares striking similarities with keloids, as well as the sclerotic nodules seen in the skin of CS individuals. Ductal carcinoma in CS was common, and it appeared to be associated with stromal hyalinization. Other frequently found benign features are adenosis and cysts. Of interest, the features of the benign breast disease in CS show certain similarities with senescent lobules, fibrous mastopathy of diabetes mellitus, and mammary hamartomas. These observations provide a framework for pathologists to identify this underrecognized syndrome.

Patterns of X chromosome inactivation in sporadic basal cell carcinomas: Evidence for clonality

BACKGROUND Some basal cell carcinomas (BCCs) contain genetic mutations, suggesting that the lesion is composed of a monoclonal population of cells. Clonality, a distinguishing feature of neoplasia, can be inferred by referencing clonal markers such as the pattern of X chromosome inactivation. The X-linked human androgen receptor gene (HUMARA; GenBank) contains a polymorphic DNA marker that reliably illustrates the pattern of X chromosome inactivation in a tissue. OBJECTIVE Our purpose was to determine the clonality of sporadic BCCs by examining patterns of X chromosome inactivation. METHODS The patterns of X chromosome inactivation in paired samples of normal skin and sporadic BCCs from 24 women were compared by means of the HUMARA gene assay. RESULTS All samples from normal skin displayed random X chromosome inactivation, consistent with lyonization. In 15 of 25 tumor samples (60%), nonrandom X chromosome inactivation was detected, consistent with monoclonality. CONCLUSION At least some sporadic BCCs are composed of a monoclonal population of cells, strengthening the contention that a collection of mutations confers a growth advantage to this epithelial lesion.

Germline PTEN mutations in three families with Cowden syndrome

Abstract: Cowden syndrome (CS) is an autosomal dominant inherited disorder characterized by hamartomas in a variety of tissues including the skin, thyroid, breast, endometrium, and the brain. Individuals with CS are predisposed to development of malignancy in these organs, especially the breast and the thyroid. We describe 3 unrelated individuals with CS associated with germline PTEN mutations. While the frameshift (375insTTTA) and the missense (Gly69Arg) mutations reported herein are novel in CS, the nonsense (Arg130stop) mutation has been described in 2 families with CS and in a single family exhibiting both CS and Bannayan–Zonana phenotype.