Anatoly Leytin

Twelve to 15% of sporadic colorectal cancers display defective DNA mismatch repair (MMR), manifested as microsatellite instability (MSI). In this group of cancers, promoter hypermethylation of the MMR gene hMLH1 is strongly associated with, and believed to be the cause of, MSI. A subset of colorectal neoplastic lesions arising in inflammatory bowel disease (IBD) is also characterized by MSI. We wished to determine whether hMLH1 hypermethylation was associated with diminished hMLH1 protein expression and MSI in IBD neoplasms. We studied 148 patients with IBD neoplasms, defined as carcinoma or dysplasia occurring in patients with ulcerative colitis or Crohn's disease. MSI was evaluated using multiplex fluorescent PCR to amplify loci D2S123, BAT-25, BAT-26, D5S346, and D17S250 in all cases. Lesions were characterized as high-frequency MSI (MSI-H) if they manifested instability at two or more loci, low-frequency MSI (MSI-L) if unstable at only one locus, or MS-stable (MSS) if showing no instability at any loci. Methylation-specific PCR was performed to determine the methylation status of the hMLH1 promoter region. hMLH1 protein expression was also evaluated by immunohistochemistry. Thirteen (9%) of 148 neoplasms arising in IBD were MSI-H, comprising 11 carcinomas and 2 dysplastic lesions. Sixteen additional lesions (11%) were MSI-L, comprising 11 carcinomas and 5 dysplastic lesions. The remaining 118 neoplasms (80%) were MSS. Six (46%) of 13 MSI-H, 1 (6%) of 16 MSI-L, and 4 (15%) of 27 MSS lesions showed hMLH1 hypermethylation (P = 0.013). Diminished hMLH1 protein expression in neoplastic cell nuclei relative to surrounding normal cell nuclei was demonstrated immunohistochemically in four of four (100%) hypermethylated lesions tested. In IBD neoplasia, hMLH1 promoter hypermethylation occurs frequently in the setting of MSI, particularly MSI-H. Furthermore, hMLH1 hypermethylation and MSI are strongly associated with diminished hMLH1 protein expression in IBD neoplasms. These findings suggest that hMLH1 hypermethylation causes defective DNA MMR in at least a subset of IBD neoplasms.

The p14(ARF) protein directly inhibits the MDM-2 oncoprotein, which mediates degradation of the p53 protein. It has been shown that p14(ARF) expression is frequently down-regulated by p14(ARF) gene hypermethylation in colorectal cancer. To determine whether p14(ARF) inactivation was involved in ulcerative colitis (UC)-associated carcinogenesis, the frequency and timing of p14(ARF) methylation was investigated in four different histological stages of UC-associated carcinogenesis. Methylation-specific PCR and bisulfite sequencing were used to determine the prevalence of p14(ARF) gene methylation. p14(ARF) methylation was observed in 19 of 38 (50%) adenocarcinomas, 4 of 12 (33%) dysplasias, and 3 of the 5 (60%) nonneoplastic UC mucosae. In contrast, 3 of 40 (3.7%) normal tissues showed p14(ARF) methylation (chi(2) test: P = 0.0003). Bisulfite sequencing was used to analyze 28 CpGs of p14(ARF) gene in 20 samples. The number of methylated CpGs ranged from 0 to 4, 0 to 20, and 0 to 28 in the normal, dysplastic, and carcinomatous samples, respectively (Kruskall-Wallis test: P = 0.0005). Densely methylated alleles were detected only in carcinomas by bisulfite sequencing. In conclusion, our data suggest that methylation of p14(ARF) is a relatively common early event in UC-associated carcinogenesis. p14(ARF) offers potential as a biomarker for the early detection of cancer or dysplasia in UC. Finally, analyses of p14(ARF) methylation in other organs should explore not only frank cancers but other premalignant lesions.

OBJECTIVE: We report six cases of myoid hamartoma of the breast, a rare benign lesion in which the characteristic smooth muscle cells may have epithelioid histology. We emphasize the importance of radiographic correlation and immunohistochemical studies to diagnosis, particularly on stereotactic core biopsies, to avoid potential confusion with infiltrating lobular carcinoma. DESIGN: Case studies. Prospective and retrospective analysis of six cases, including stereotactic biopsy of two. SETTING: Academic medical center-based pathology practice. PATIENTS: Six postmenopausal women, aged 50 to 59 years, with palpable or nonpalpable mammographically evident breast masses. RESULTS: All the lesions were radiographically well circumscribed, most showing heterogeneous radiodensity. Histologically variable amounts of glandular, fibrous, and adipose tissue were admixed with smooth muscle cells, which occasionally had prominent epithelioid features. All the lesions' myoid cells stained for smooth muscle markers as well as steroid receptor proteins. Stereotactic core biopsy was diagnostic in one case, making excision unnecessary. CONCLUSIONS: With proper radiographic correlation and immunohistochemical confirmation, myoid hamartoma can be confidently diagnosed even on the limited tissue samples yielded by stereotactic core biopsy.

A case of an osteogenic desmoplastic melanoma occurring on the sole of the foot of a 60-year-old African American man is described. The tumor measured 4.8 cm in greatest dimension, invaded to a thickness of 2.2 cm and metastasized to four of ten inguinal lymph nodes. The majority of the tumor had a classic desmoplastic phenotype with malignant spindle cells set in a sclerotic and myxoid matrix and foci of lymphocyte aggregation. In other areas, there were thick trabeculae of bone rimmed by malignant epithelioid melanocytes. There was a markedly atypical lentiginous hyperplasia in the overlying epidermis. Imaging showed no continuity with the underlying calcaneus. The tumor was characterized immunohistochemically by S100 positivity. Pathologists should be aware of this diagnosis and should differentiate it from osteosarcoma.