Gunnlaugur P. Nielsen

CDKN2A Gene Deletions and Loss of p16 Expression Occur in Osteosarcomas That Lack RB Alterations

Osteosarcomas often suffer mutations of the RB (retinoblastoma) gene, with resultant inactivation of the pRb protein. pRb is one component in a cell-cycle control pathway that includes the p16 (encoded by the CDKN2A gene) and cyclin-dependent kinase 4 (cdk4, encoded by the CDK4 gene) proteins. We therefore sought to determine whether the CDKN2A and CDK4 genes were altered in those osteosarcomas that lacked RB inactivation. Twenty-one osteosarcomas (2 low-grade and 19 high-grade) were evaluated for homozygous deletion of the CDKN2A gene, CDK4 amplification, and allelic loss of the RB gene, as well as for expression of p16 and pRb proteins. Five high-grade osteosarcomas showed loss of p16 expression; four of these had homozygous CDKN2A deletions, and the fifth had a probable deletion obscured by numerous nonneoplastic, p16-immunopositive multinucleated giant cells. Thus, p16 immunohistochemistry may provide a sensitive means for assessing CDKN2A status. Twelve tumors (including the two low-grade osteosarcomas) were immunopositive for pRb, and nine tumors were immunonegative for pRb. Of the five cases with CDKN2A/p16 alterations, none had allelic loss of the RB gene and all expressed pRb, suggesting that each of these tumors had an intact RB gene. None of the tumors showed CDK4 amplification. No alterations were detected in the two low-grade osteosarcomas. This study suggests that CDKN2A is a tumor suppressor inactivated in osteosarcomas that lack RB mutations and that the p16-pRb cell-cycle control pathway is deregulated in a large number of high-grade osteosarcomas.

Tumor Induction of VEGF Promoter Activity in Stromal Cells

We have established a line of transgenic mice expressing the A. victoria green fluorescent protein (GFP) under the control of the promoter for vascular endothelial growth factor (VEGF). Mice bearing the transgene show green cellular fluorescence around the healing margins and throughout the granulation tissue of superficial ulcerative wounds. Implantation of solid tumors in the transgenic mice leads to an accumulation of green fluorescence resulting from tumor induction of host VEGF promoter activity. With time, the fluorescent cells invade the tumor and can be seen throughout the tumor mass. Spontaneous mammary tumors induced by oncogene expression in the VEGF-GFP mouse show strong stromal, but not tumor, expression of GFP. In both wound and tumor models the predominant GFP-positive cells are fibroblasts. The finding that the VEGF promoter of nontransformed cells is strongly activated by the tumor microenvironment points to a need to analyze and understand stromal cell collaboration in tumor angiogenesis.

Chondrosarcoma of the base of the skull : A clinicopathologic study of 200 cases with emphasis on its distinction from chordoma

Conventional chondrosarcoma (CSA) of the skull base is an uncommon neoplasm that can resemble chordoma, and indeed it is misdiagnosed frequently as such. This has important clinical implications, because when treated with similar aggressive treatment strategies, CSA has a much better prognosis than chordoma. In an effort to identify those morphologic and immunohistochemical features that help to identify conventional skull base CSA correctly and to understand its prognosis better, particularly compared with chordoma, when treated with surgery and proton beam irradiation, the authors performed a clinicopathologic analysis of 200 CSAs. The patients ranged in age from 10 to 79 years (mean, 39 years), 87 patients were male and 113 patients were female, and most presented with symptoms related to the central nervous system. Approximately 6% of the tumors arose in the sphenoethmoid complex, 28% originated in the clivus, and 66% developed in the temperooccipital junction. Histologically, 15 tumors (7.5%) were classified as hyaline CSA, 59 (29.5%) as myxoid CSA, and 126 (63%) as mixed hyaline and myxoid CSA. A total of 101 (50.5%) tumors were grade 1, 57 (28.5%) had areas of grades 1 and 2, and 42 (21%) were pure grade 2 neoplasms. The vast majority of patients originated from referring hospitals, and the diagnosis was changed prospectively at our institution to CSA from chordoma in 74 patients (37%). Of the tumors studied immunohistochemically, 96 of 97 (98.9%) stained for S-100 protein, 0 of 97 (0%) stained for keratin, and faint staining for epithelial membrane antigen was seen in 7 of 88 tumors (7.95%). All patients underwent high-dose postoperative fractionated precision conformal radiation therapy with a dose that ranged from 64.2 to 79.6 Cobalt-Gray-equivalents (median, 72.1 Cobalt-Gray-equivalents, given in 38 fractions. The 200 patients had a median follow-up of 63 months (range, 2.1 mos - 18.5 yrs). Tumor control was defined as lack of progression by clinical and radiographic assessment. Based on this definition, there were three local recurrences, and two of these patients died of tumor-related complications. The 5- and 10-year local control rates were 99% and 98% respectively, and the 5- and 10-year disease-specific survival rates were both 99%. In contrast to CSA, the 5- and 10-year survival rates of chordoma have been reported to be approximately 51 % and 35% respectively, and in our institution intensive treatment has resulted in 5- and 10-year progression-free survival rates of 70% and 45% respectively. CSA of the skull base can be distinguished reliably from chordoma, and this distinction is important because skull base CSA has an excellent prognosis when treated with surgery and proton beam irradiation, whereas chordomas have a substantially poorer clinical course despite similar aggressive management.

Malignant Transformation of Neurofibromas in Neurofibromatosis 1 Is Associated with CDKN2A/p16 Inactivation

Patients with neurofibromatosis 1 (NF1) are predisposed to develop multiple neurofibromas (NFs) and are at risk for transformation of NFs to malignant peripheral nerve sheath tumors (MPNSTs). Little is known, however, about the biological events involved in the malignant transformation of NFs. We examined the CDKN2A/p16 gene and p16 protein in NFs and MPNSTs from patients with NF1. On immunohistochemical analysis, all NFs expressed p16 protein. The MPNSTs, however, were essentially immunonegative for p16, with striking transitions in cases that contained both benign and malignant elements. None of the benign tumors had CDKN2A/p16 deletions, whereas three of six MPNSTs appeared to have homozygous CDKN2A/p16 deletions. Methylation analysis and mutation analysis of CDKN2A/p16 in MPNSTs did not reveal any abnormalities. These results show that malignant transformation of NF is associated with loss of p16 expression, which is often secondary to homozygous deletion of the CDKN2A/p16 gene. The findings suggest that CDKN2A/p16 inactivation occurs during the malignant transformation of NFs in NF1 patients and raises the possibility that p16 immunohistochemistry may provide ancillary information in the distinction of NF from MPNST.

Smooth-muscle tumors of the vulva: A clinicopathological study of 25 cases and review of the literature

The clinical and pathological features of 25 smooth-muscle tumors of the vulva were analyzed. The patients ranged in age from 17 to 67 (mean, 37.6) years; two were pregnant. Twenty-three tumors were 1.5 to 16 (mean, 5.2) cm in greatest dimension; the size of two tumors was unknown. Microscopic examination showed that 16 tumors were circumscribed, six had focally infiltrative margins, and the margins could not be evaluated in three tumors. Fourteen tumors were composed mainly of spindle cells; two of these tumors had prominent myxoid stroma. Seven tumors were predominantly epithelioid and had a prominent hyalinized or myxoid stroma; often the cells had a plexiform pattern. Four tumors contained an approximately equal number of epithelioid and spindle cells. Ten tumors had mild, nine moderate, and six severe cytologic atypia. Mitotic figures ranged from 0 to 10 (average, 1.8) per 10 high-power fields (hpf). Immunohistochemically, all the tumors stained for one or more muscle markers. Thirteen of 17 tumors were positive for estrogen receptors, and 16 of 18 were positive for progesterone receptors. Follow-up information ranging from 1 month to 19 years (average, 5 years) was available in 19 cases. Four tumors recurred locally, and one patient with recurrent tumor died of metastases 7 months after the initial operation. We propose an expanded criteria to distinguish between leiomyomas and leiomyosarcomas of the vulva. Tumors that manifest three or all of the four following features should be considered sarcomas: > or = 5 cm in greatest dimension, infiltrative margins, > or = 5 mitotic figures per 10 hpf, and moderate to severe cytologic atypia. Those that have only one of these characteristics should be diagnosed as leiomyoma, and those that exhibit only two of these features should be considered benign but atypical leiomyomas. The sarcomas should be excised with widely negative margins; the leiomyomas and the atypical leiomyomas should be excised conservatively, with long-term, careful follow-up.

Base of skull chordomas in children and adolescents : A clinicopathologic study of 73 cases

Chordomas in children and adolescents comprise <5% of all chordomas and most frequently develop in the skull base. These tumors are believed to behave more aggressively than chordomas in adults and may have unusual morphology. This study examines a large series of pediatric skull base chordomas treated with a standardized protocol to characterize the behavior and morphology of these tumors. There were 31 males and 42 females ranging from 1 to 18 (mean 9.7) years. Forty-two cases (58%) were conventional chordomas, some of which had unusual histopathologic features. Chondroid chordomas comprised 23% of cases. Fourteen tumors (19%) were highly cellular and had a solid growth pattern with no myxoid matrix or lobular architecture. Eight of these had cytologic features of conventional chordoma cells including physaliferous cells (cellular chordoma). The remaining cellular tumors were composed of poorly differentiated epithelioid cells set in a fibrous stroma and lacked physaliferous cells (poorly differentiated chordoma). All variants studied by immunohistochemistry showed positive staining for cytokeratin, epithelial membrane antigen, S100 protein, and vimentin. Mitoses and necrosis were seen in all variants. Follow-up data were available for all patients and ranged from 1 to 21 (mean 7.25) years. The survival rate was 81%. All but 1 patient with poorly differentiated chordoma died of disease. Overall, base of skull chordomas in children and adolescents treated with proton beam radiation have better survival than chordomas in adults. However, poorly differentiated chordomas are highly aggressive tumors.

Lipomatous hemangiopericytoma. A histologic, ultrastructural and immunohistochemical study of a unique variant of hemangiopericytoma.

We report three cases of a unique, previously undescribed soft tissue tumor composed of mature adipocytes and hemangiopericytomatous areas, for which we propose the term lipomatous hemangiopericytoma. The tumors occurred in adults and were located in the sinonasal area, the soft tissue of the shoulder, and the retroperitoneum. The tumors ranged in size from 4 to 10 cm in greatest diameter and grossly were solid and ranged from tan to yellow. Histologically, they were composed of a variable admixture of benign lipomatous and hemangiopericytomatous components. Immunohistochemically, they stained with antibodies to vimentin and not to alpha-smooth-muscle actin, muscle-specific actin, desmin, S-100 protein, glial fibrillary acidic protein, epithelial membrane antigen, or keratin. Ultrastructurally, the cells constituting the hemangiopericytomatous areas had the features of pericytes, and no lipoblasts or transitional forms between lipocytes and pericytes were found. The histologic differential diagnosis of this neoplasm includes spindle-cell lipoma, angiolipoma, liposarcomas, tumors showing smooth muscle and adipocytic differentiation, and hemangiopericytoma infiltrating fat. Because of the small number of cases and the limited follow-up, we cannot be certain of their biologic behavior, although we expect that they are benign. Lipomatous hemangiopericytoma represents a distinctive pathologic entity that should be recognized and studied further.

Eosinophilic angiocentric fibrosis is a form of IgG4-related systemic disease.

BackgroundEosinophilic angiocentric fibrosis (EAF) is an uncommon tumefactive lesion of the orbit and upper respiratory tract of unknown etiology. The condition is characterized histologically by concentric layers of fibrosis around small-caliber arteries and a mixed inflammatory infiltrate dominated by eosinophils. After the serendipitous observation of an elevated serum concentration of IgG4 in 1 patient with EAF, we investigated the hypothesis that EAF is an IgG4-related systemic disease. MethodsWe retrospectively identified 5 EAF cases from our files. Demographic, clinical, and serological data were reviewed, and the histologic features and tissue IgG4 staining patterns were examined on biopsies from each case. ResultsPatients (2 male, 3 female) ranged in age from 31 to 82 years (mean, 56 y). The extent of disease varied from isolated involvement of the nasal cavity or the lacrimal gland to multicentric disease affecting the sinuses, nasal tract, and lower respiratory tract. The duration of symptoms ranged from 6 months to >20 years. The demographic features of the patients and disease extent were consistent with previously published reports of EAF, except for involvement of the lower respiratory tract in 1 case. Four of the 5 cases showed concentric perivascular fibrosis surrounding small-caliber vascular channels, embedded in an inflammatory infiltrate composed of lymphocytes, plasma cells, and eosinophils. One lacrimal gland biopsy showed a periductal inflammatory infiltrate, and 2 cases showed a storiform pattern of fibrosis. The index case had a serum IgG4 concentration of 1490 mg/dL (normal, 8 to 140 mg/dL). IgG4-positive plasma cells were identified in biopsies from 4 of the 5 cases. The numbers of IgG4-positive plasma cells ranged from 43 to 118 per high-power field, and the IgG4:IgG ratios ranged from 0.68 to 0.97. Neither IgG4-bearing nor IgG-bearing plasma cells were identified in 1 patient, whose longstanding disease was characterized principally by concentric perivascular fibrosis. ConclusionOur data suggest that EAF is part of the spectrum of IgG4-related systemic disease.

Comparative Pathology of Nerve Sheath Tumors in Mouse Models and Humans

Despite the progress made in our understanding of the biology of neurofibromatosis (NF), the long-term clinical outcome for affected patients has not changed significantly in the past decades, and both NF1 and NF2 are still associated with a significant morbidity and a decreased life span. A number of NF1 and NF2 murine models have been generated to aid in the study of NF tumor biology and in the development of targeted therapies for NF patients. A single, universal pathological classification of the lesions generated in these murine models is essential for the validation of the models, for their analysis and comparison with other models, and for their future effective use in preclinical treatment trials. For the formulation of a pathological classification of these lesions, the WHO classification of human tumors was used as a reference. However, it was not adopted for the classification of the GEM lesions because of some important differences between the human and murine lesions. A novel classification scheme for peripheral nerve sheath tumors in murine models was therefore devised.

Long-term results of combined modality therapy in primary bone lymphomas

PURPOSE To report the Massachusetts General Hospital experience in the management of patients with primary bone lymphoma (PBL) treated with combined modality therapy (CMT). METHODS AND MATERIALS Records from 37 eligible patients were reviewed. Two patients were treated with complete resection of the tumor, while 35 patients underwent radiation therapy with a median total dose of 54 Gy (range 38.35-66.5). All patients received combination chemotherapy, which contained doxorubicin in 33 cases. We compared the current data with our previous experience in patients treated with local measures only. RESULTS Actuarial disease-free survival (DFS) at 5 and 10 years is 78% and 73%, respectively, while overall survival (OS) is 91% and 87%, respectively. No local failures were seen. Pathologic fracture at presentation influenced DFS (p = 0.005) and OS (p = 0.017) adversely. OS was compromised in patients older than 60 years (p = 0.059) and DFS in patients with pelvic primaries (p = 0.015). CMT was associated with improved DFS (p = 0.0008) and OS p = 0.0001) compared to our historical controls. Ten patients (27%) developed complications requiring orthopedic procedures following completion of therapy at a median of 25.5 months (range 4-228). CONCLUSION Patients with PBL have a favorable outcome with CMT, which appears superior to radiation therapy alone. Late complications can be seen, especially in weight-bearing bones.