Development and optimization of tissue preparative methodology for DNA content analysis of soft tissue neoplasms

Cytogenetic aberrations and DNA ploidy in soft tissue sarcoma. A Southwest Oncology Group Study

We performed cytogenetic analysis and determined DNA content by flow cytometry (FCM) on freshly disaggregated tumor biopsies from 45 patients with soft tissue sarcomas (STS). Cytogenetically aberrant clones characterized 30 (67%) tumors, with the remaining 15 yielding normal karyotypes with or without nonclonal aberrations. No tumors with multiple unrelated clones were observed. Among the 30 tumors with clonally abnormal karyotypes, 21 (70%) had near-diploid stemlines, six were near-triploid and three were near-tetraploid. Ten of the clonally aberrant tumors contained nonrandom chromosomal translocations characteristic of histologic subtypes. Overrepresentation of chromosomes 7 and 8 were common numerical aberrations. Structural aberrations most often involved chromosomes 1, 7, 9, 12, and 14. Clustering of breaks in 9p resulting in partial loss of the short arm was frequent. Unstable aberrations including rings, dicentrics, large markers, small numbers of double minutes, and telomeric associations were seen in nine tumors. With FCM, 27 (60%) tumors had aneuploid DNA content and 18 (40%) were DNA diploid. Of those 18 DNA diploid tumors, 11 showed clonal karyotypic aberrations. In addition, apparent discrepancies between the results of the cytogenetics and FCM with respect to ploidy pattern were seen in 13 samples; 11 had DNA content in the peritriploid to peritetraploid range but the corresponding karyotype was normal or near-diploid. When the findings of the cytogenetics and DNA content analyses were combined, an abnormal cell population by one or both methods was detected in 38 (84%) tumors. The concurrent application of standard cytogenetics and DNA ploidy by FCM provide complementary information confirming a high incidence of genetic alterations in STS.

Flow cytometric DNA content analysis of 185 soft tissue neoplasms indicates that S-phase fraction is a prognostic factor for sarcomas. French Federation of Cancer Centers (FNCLCC) Sarcoma Group

BACKGROUND

The authors determined the flow cytometric (FCM) DNA characteristics of 53 benign tumors and 132 malignant (71 primary, 61 recurrent) soft tissue sarcomas to investigate their heterogeneity and to evaluate the prognostic values of DNA ploidy status and S-phase fraction (SPF).

METHODS

One to 11 frozen samples were collected from 185 tumors at 10 participating centers of the French Federation of Cancer Centers (FNCLCC). All FCM analyses were performed in the same laboratory. Histologic diagnoses were collegially reviewed, and grade was assessed by the pathologists of the FNCLCC Sarcoma Group. Relationships between FCM, clinical, and pathologic data were investigated using univariate and multivariate analyses for risks of mortality and metastasis.

RESULTS

All except 2 of the 53 benign lesions were DNA diploid. One schwannoma and one desmoid tumor exhibited small abnormal DNA peaks. SPF was low in all benign lesions. One-third of the sarcomas were DNA diploid, whereas two-thirds were DNA aneuploid. Relationships were found between aneuploidy and mitotic count, grade, and histologic subtype of malignant fibrous histiocytoma. DNA ploidy status did not influence the clinical outcome. Multiple sampling performed in 32 sarcomas showed both diploid and aneuploid samples in 6 tumors. Heterogeneity was related to tumor size. SPF evaluated in 85 sarcomas was related to DNA ploidy status, mitotic count, and grade. SPF > or = 4% was significantly associated with a low overall survival rate. In a multivariate analysis performed for the whole group of 132 patients, the single factors with independent prognostic value for patient mortality were disease free status after the treatment course (P < 0.0001) and SPF (P = 0.03). In the subgroup of patients who were initially free of metastases and free of tumor after the treatment course, SPF remained the only factor that significantly influenced the overall survival rate (P = 0.021).

CONCLUSIONS

Despite its high failure rate, SPF is an independent factor in the prognosis of soft tissue sarcoma and should be considered when patients with a high mortality risk need to be selected for adjuvant chemotherapy.

DNA image cytometry on sections as compared with image cytometry on smears and flow cytometry in melanoma

DNA measurements of 130 melanomas were carried out by flow cytometry (FCM) and image cytometry (ICM). ICM was applied to cytological preparations of fresh material (cICM) and to sections of formalin-fixed paraffin embedded tissue (sICM). The DNA ploidy, the DNA index of G0/G1 peaks (DI), and the proliferation index (PI) were used to compare all the methods. The following parameters reflecting malignancy were calculated only from ICM histograms: the 5c exceeding rate (5cER) and the malignancy grade (MG). In cases found to be DNA aneuploid by FCM, the PI values (FCM versus cICM) and the DIs (between all methods) showed a high correlation, and the concordance in relation to the DNA ploidy status was 96% (FCM versus cICM) and 94% (FCM versus sICM). However, we ascertained essential differences between FCM and ICM in melanomas classified as DNA diploid by FCM. The concordance in DNA ploidy was only 66% (FCM versus cICM) and 64% (FCM versus sICM). In contrast, cICM and sICM yielded similar results in most cases. With the exception of the near diploid range, ICM is superior to FCM in detecting DNA aneuploidy. In particular, DNA tetraploid stem lines can easily be overlooked by FCM. Therefore, DNA measurements of tumours judged to be DNA diploid by FCM must be verified by ICM. ICM on sections proved to be applicable and yielded reliable results provided that a suitable thickness was used, and the measuring of sectioned and overlapping nuclei was largely avoided by careful focusing in either direction.

S-phase fraction of 155 soft tissue sarcomas: correlation with clinical outcome

BACKGROUND

Traditionally, grade is considered the most important prognostic factor for soft tissue sarcomas (STS). However, because of the alleged difficulties in reproducibility of grading, new, objectively determined prognostic factors would be of value. The aim of our study was to establish if S-phase fraction (SPF) measured with flow cytometry was of prognostic significance for STS.

METHODS

In this study, we included all 193 adult STS patients with superficial trunk or limb tumors who were treated by the Helsinki University Central Hospital (HUCH) STS group between January 1987 and May 1993. One hundred and seventy-two formalin fixed paraffin embedded tumor samples were available. SPF measurement was successful in 155 cases.

RESULTS

Eighty-six cases were diploid. Ploidy was found to have no effect on overall survival. The median SPF was 6.8% (diploid tumors, 4% and nondiploid tumors, 12.9%). A high SPF predicted a shorter survival in patients with diploid tumors (P=0.003). The prognostic value was even stronger when we studied disease specific survival and excluded from analysis samples that contained less than 50% tumor cells (P=0.011). However, no prognostic value could be detected in nondiploid tumors or in the material as a whole.

CONCLUSIONS

Our results suggest that high SPF is an adverse prognostic factor for survival of patients with diploid STS. However, further studies are needed to confirm these results.

Primary embryonal rhabdomyosarcoma of long bone. Case report and review of the literature

We report a case of primary embryonal rhabdomyosarcoma of long bone, presenting as a lytic destructive bone tumor in the right femoral diaphysis of a 7-year-old girl. To our knowledge, this is only the third report of this entity. The neoplasm was a pure embryonal rhabdomyosarcoma with numerous rhabdomyoblasts. Immunohistochemistry confirmed the diagnosis: The cells were reactive with antibodies directed against desmin, muscle-specific actin, and myoglobin. No other neoplastic mesenchymal component was present within the tumor. Although rare, primary rhabdomyosarcoma, along with Ewing's tumor and osteosarcoma, should be considered in the differential diagnosis of malignant bone tumors in childhood.