Erroneous genetic sex determination of a newborn twin girl due to chimerism caused by foetal blood transfusion. A case report.

OBJECTIVE: We present a case of erroneous sex determination in a newborn twin girl (twin A) due to chimerism. CASE REPORT: Amniocentesis and ultrasound examination had pointed towards male sex of both twins. At birth, twin A presented as a phenotypically normal female with 46,XY karyotype, and 46,XY gonadal dysgenesis was suspected. Twin B was a normal male. RESULTS: In our department, further examinations of twin A included undetectable testosterone and inhibin-B and elevated FSH. Ultrasound suspected an infantile uterus, and sequencing of the SRY gene was normal. After gonadectomy, a 46,XX karyotype was demonstrated in both normal infantile ovaries and in the fibroblasts from a skin biopsy. Analysis of X-linked markers in DNA from blood lymphocytes in both twins was identical, consistent with 46,XY karyotypes. CONCLUSION: Twin A is a 46,XX female with a chimeric 46,XY blood cell line due to intrauterine transfusion from her twin brother.

Infertility despite surgery for cryptorchidism in childhood can be classified by patients with normal or elevated follicle-stimulating hormone and identified at orchidopexy.

OBJECTIVE: To analyse infertility despite orchidopexy in childhood. PATIENTS AND METHODS: The study comprised patients with cryptorchidism (70 bilateral and 65 unilateral) who had a simultaneous biopsy taken at orchidopexy in childhood, and in adulthood had analyses of semen and FSH. In adulthood 42 formerly bilateral cryptorchid boys had repeat testicular biopsies taken. Infertility was suspected in men with < 5 million sperm/mL in the best sample of semen and concomitant poor sperm motility, and who were classified by follicle-stimulating hormone (FSH) values. At orchidopexy the number of spermatogonia/tubule and the germ cell differentiation were measured. In adulthood the percentage of tubules with complete spermatogenesis, spermatogenic arrest and Sertoli-cell only status was assessed. RESULTS: Infertility was suspected in 38 of 70 (54%) of formerly bilateral and six of 65 (9%) formerly unilateral cryptorchid patients. High FSH values were expected in these suspected infertile patients, but 15 of 38 (59%) formerly bilateral and five of six formerly unilateral cryptorchid patients had normal FSH values. These patients were identified in childhood at orchidopexy; those with bilateral cryptorchidism generally presented with germ cells, but the mean number of spermatogonia per tubule was < 30% of the lowest normal value, and the germ cells were seldom normally differentiated, whereas those with unilateral cryptorchidism generally lacked germ cells in the biopsies. No patients had a decreased FSH value. CONCLUSION: Despite surgery for cryptorchidism, infertility was probable in a third (44 of 135) of the patients. We expected high FSH values in these patients, but in 45% (20/44) the FSH values were normal. These patients may have relative FSH deficiency. At orchidopexy these patients were identified to be bilaterally cryptorchid with few germ cells and those unilaterally cryptorchid had none in the biopsy. After orchidopexy in childhood, additional hormonal treatment, e.g. recombinant FSH or buserelin, may be indicated in these patients.

Cryptorchidism: aspects of fertility and neoplasms. A study including data of 1,335 consecutive boys who underwent testicular biopsy simultaneously with surgery for cryptorchidism.

PURPOSE: An attempt to make a rational strategy for treatment of cryptorchidism. MATERIALS AND METHODS: 1,335 cryptorchid boys with biopsy at surgery (1,638 specimens). We studied: frequency of no germ cells in biopsies from 698 patients <12 years at surgery; fertility potential of 140 patients who were now adults, and apperance of testicular neoplasia in all biopsies. RESULTS: Lack of germ cells appeared from 18 months. The frequency increased with increasing age. It appeared in 30% (61/202) bilateral, and 18% (88/496) unilateral cases. In men who had undergone bilateral or unilateral orchiopexy, respectively, there was normal sperm count in 19% (14/75) and 83% (54/65), and infertility was suspected in 56% (42/75) and 8% (5/65) (FE, p < 0.00005, p < 0.00005), respectively. The lowest, the mean, and the highest age-matched spermatogonia count per tubule at orchiopexy was associated with sperm count (Spearman test, p < 0.0001, p < 0.005, p < 0.05). Isolated, this was demonstrated for the 75 formerly bilateral (Spearman, p < 0.0001, p < 0.0001, p < 0.0001), but not the 65 formerly unilateral cases (Spearman, p = 1.0). No germ cells at orchiopexy was associated with suspected infertility. Risk was 78-100% in bilateral (dependent on one or both testes affected), and 33% in unilateral cryptorchidism. There was one invasive germ cell tumor, six cases of carcinoma in situ testis, and one Sertoli cell tumor. Three neoplasms were diagnosed in intra-abdominal testes, four in boys with abnormal external genitalia, and two in boys with known abnormal karyotype. Risk of neoplasia was 5% (7/150) in patients with intra-abdominal testis, abnormal external genitalia or diagnosed abnormal karyotype, versus 0% (0/1,185) in patients without these characteristics (FE, p < 0.00005). CONCLUSION: We recommend surgery for cryptorchidism before 15-18 months of age because: (a) lack of germ cells is very rare before, and (b) lack of germ cells is associated with subsequent risk of infertility. At primary surgery for cryptorchidism, we recommend examination for testicular neoplasia in cases of intra-abdominal testis, abnormal external genitalia or known abnormal karyotype.

Erythropoietin may reduce the risk of germ cell loss in boys with cryptorchidism.

PURPOSE: In boys with cryptorchidism older than 2 years a testicular biopsy at time of orchiopexy shows lack of germ cells in 10-40% of the cases. The number of spermatogonia per tubule is prognostic for subsequent fertility potential. A biopsy without germ cells is associated with 33-100% risk of infertility. In order to increase the number of germ cells, and thereby the fertility potential, additional hormonal therapy has been attempted before surgery. In a study, small doses of the gonadotropin-releasing hormone analogue buserelin before orchiopexy caused higher values. Others have found that hormonal treatment with human chorionic gonadotropin or gonadotropin releasing hormone analogue may harm the germ cells in cryptorchidism. The aim of the study is to demonstrate that additional hormonal therapy with erythropoietin has a positive effect on the number of germ cells. MATERIALS AND METHODS: Erythropoietin (Eprex) 100 IU/kg were administered subcutaneously weekly for 3 months prior to surgery in two cryptorchid boys, 6 months old and 1 year 9 months old, respectively, with renal function impairment. RESULTS: The number of spermatogonia per tubular cross-section in testicular biopsies was unusually high in both erythropoietin- treated cryptorchid cases compared to the control material of biopsies from the undescended testes of 698 cryptorchid patients and compared to the normal values. CONCLUSION: There are several hypothetic mechanisms that can explain the elevated number of spermatogonia seen in our erythropoietin treated cryptorchid patients. Erythropoietin may have a positive effect on germ cell proliferation in cryptorchidism.

[Age distribution of hospital autopsies 1977-1996. The relative frequency of autopsies on younger people has increased since the 1990 amendment]. / Aldersfordeling af hospitalsobducerede 1977-1996. Der obduceres nu forholdsvis flere unge siden indførelsen af den nye ligsynslov af 1990.

INTRODUCTION: Since the new law on autopsies was passed in 1990, the frequency of autopsy has fallen. We have carried out an analysis to illustrate the conditions/proportions for various age groups before and after the law came into force. METHOD: All the figures for deaths and autopsies during the period of 1977-1996 were reviewed. This includes the figures from the Danish Board of National Health and from the Department of Pathology at Rigshospitalet, Copenhagen. The frequency of autopsy was calculated for all groups, both before and after the amendment, and the results are discussed. RESULTS: The figures showed not only a significant decrease in the frequency of autopsy in almost all groups, but also a considerable decrease in the groups of the elderly as compared to the younger groups. DISCUSSION: The frequency of autopsy decreased during the period of 1977-1996. The most significant fall was seen around 1990, both in the general figures registered in connection with the cause of death and in the figures from the Department of Pathology at Rigshospitalet, Copenhagen. We also found that the decrease in the frequency of autopsies was greater in the groups of the elderly, when different age groups were examined. The percentage of autopsies performed on younger people has increased since the 1990 amendment.

Hormonal treatment may harm the germ cells in 1 to 3-year-old boys with cryptorchidism.

PURPOSE: Hormonal treatment with human chorionic gonadotropin (HCG) or gonadotropin releasing hormone may be given initially for cryptorchidism. We evaluated whether hormonal treatment is safe for the germ cells in boys with cryptorchidism 1 to 3 years old in whom follicle-stimulating hormone, luteinizing hormone and testosterone values are normally low. MATERIALS AND METHODS: We measured the number of spermatogonia per tubule at orchiopexy in 72 consecutive boys with cryptorchidism who underwent simultaneous testicular biopsy. In 19 patients gonadotropin releasing hormone was unsuccessful, while 8 received HCG and 45 underwent orchiopexy without hormonal therapy. Groups were otherwise equal. RESULTS: Patients who underwent surgery only had a higher number of spermatogonia per tubule than those in whom hormonal treatment was unsuccessful (p<0.05). Spermatogonia per tubule values were normal only after surgery alone (p = 0.06). Gonadotropin releasing hormone and HCG influenced germ cells equally. CONCLUSIONS: In 1 to 3-year-old boys with cryptorchidism gonadotropin releasing hormone or HCG given for testicular descent may suppress the number of germ cells.

Germ cells may survive clipping and division of the spermatic vessels in surgery for intra-abdominal testes.

PURPOSE: Laparoscopy is a well described modality that provides an accurate visual diagnosis upon which further management of intra-abdominal testes may be based. Laparoscopic ligation of spermatic vessels as stage 1 of the procedure is a natural extension of laparoscopy. A staged approach provides adequate viability of the intra-abdominal testis. However, it is uncertain whether the more sensitive germ cells survive this procedure in addition to the Sertoli and interstitial cells of the human testis. Survival of germ cells is a prerequisite of later fertility potential. MATERIALS AND METHODS: We studied 17 nonpalpable testes in 10 patients 1 year and 7 months to 13(1/2) years old. Results of testicular biopsies of 13 intra-abdominal testes taken at stages 1 and 2 of surgery were available for histological comparison. RESULTS: Median number of spermatogonia per tubular cross section of the biopsies taken at stage 2 was slightly lower (0.03) compared to the median number at stage 1 (0.06) of the operation but this difference was not significant (p = 0.2031). CONCLUSIONS: Our study shows that the spermatogonia may survive clipping and division of the spermatic vessels, although the number of spermatogonia per tubular transverse section decreases slightly.

Anti-MIC2 as a tool in examination of testicular biopsies.

MIC2 is a pseudoautosomal gene localized on X and Y chromosomes. The MIC2 gene product is a glycoprotein expressed on the cell membranes of a number of somatic cells, including Sertoli cells of the testis, but not on the cell membranes of germ cells. In cases of cryptorchidism, a testicular biopsy is recommended in order to evaluate future fertility potential. The spermatogonia are identified on histological sections and the number per tubular transverse section is compared with normal values for age. The patient is at 33-100% risk of subsequent infertility when the number of spermatogonia per tubular transverse section is lower than 1% of the lowest normal age-matched value. Besides Sertoli cells the seminiferous tubules in undescended testes contain only a few germ cells, and it may be difficult to pinpoint the germ cells in small biopsies. Especially in nonpalpable testes their number may be heavily reduced. A reliable identification of germ cells may also be difficult in cultures of testicular biopsies from undescended testes. Against this background, we tried the use of an immunohistochemical method with DAKO antibody to the MIC2 gene product (MIC2, 12 E7, code no. M3601) in order to obtain a "negative reaction" of germ cells, contrasting with the stained Sertoli cells. The material comprised: 44 specimens of testicular parenchyma taken at time of surgery for cryptorchidism from 24 cryptorchid boys with nonpalpable testes and 14 testicular biopsies from 13 cryptorchid patients with palpable testes which had been cultured in vitro for 7, 14 or 21 days. In all cases the immunohistochemical method with DAKO antibody to the MIC2 gene product was helpful for identification of Sertoli cells and germ cells, and we therefore recommend the use of anti-MIC2 in all testicular biopsies where it is difficult to pinpoint the germ cells.

[Eosinophilic cystitis in children]. / Eosinofil cystitis hos børn.

Eosinophilic cystitis is an inflammatory disorder of the urinary bladder, characterised by irritative voiding symptoms, negative urine cultures, and eosinophilic infiltration of the bladder wall. Since 1960 only about 20 cases have been described in the English scientific reports, making it a rather rare entity. In children the disease appears to be shortlived and self-limited, requiring no specific treatment. We present a case with a 7.5-year-old boy, who experienced spontaneous remission of all symptoms, following an acute attack of eosinophilic cystitis.

Cryptorchidism as a caudal developmental field defect. A new description of cryptorchidism associated with malformations and dysplasias of the kidneys, the ureters and the spine from T10 to S5.

Cryptorchidism is a feature of abnormalities in the hypothalamo-pituitary-testicular axis, and almost all disorders of sexual differentiation in which a testis is present. We found cryptorchidism to be associated with malformations and dysplasias of the kidneys, the ureters and the spine from T10 to S5. The description of this association is new. The association was seen in 18% of cryptorchid boys younger than 3 years of age in a department of paediatric surgery, in 34% of cryptorchid foetuses who died in the third trimester, in 65% of cryptorchid patients with imperforate anus, and in all individuals with tritonmelia, the male variant of sirenomelia. Sirenomelia/tritonmelia is an extreme degree of abnormal differentiation of the caudal developmental field, also called caudal dysplasia, the caudal regression syndrome and the caudal regression malformation sequence. Caudal developmental field defects were also the predominant abnormalities in the other groups of patients. Thus, cryptorchidism may be a feature of abnormal differentiation of the caudal developmental field. Position and histology of the undescended testes of the patients included in the association were similar to in cryptorchidism in general. In the literature the association was reported in 5-10% of boys considered to suffer from cryptorchidism only. Furthermore, our observations are concordant with recent theories about cryptorchidism. Consequently, we propose that cryptorchidism in general may be a caudal developmental field defect. Study of cryptorchid patients exhibiting malformations or dysplasias of the kidneys, the ureters or the spine from T10 to S5 is essential in order to isolate new genetic disorders and to spot environmental factors causing cryptorchidism.

Is infertility after surgery for cryptorchidism congenital or acquired?

We evaluated whether deletions of the DAZ (deleted in azoospermia) gene, abnormal karyotypes or hypogonadotropic hypogonadism (HH) were demonstrable in infertile men who had undergone surgery in childhood for cryptorchidism with a simultaneous testicular biopsy that demonstrated no or almost no germ cells. In six men with infertility after surgery for cryptorchidism, the adult karyotype and analyses for the DAZ gene, serum follicle-stimulating hormone, luteinizing hormone, and testosterone were performed from a peripheral blood sample. Testicular volume was also measured. All patients exhibited a 46,XY karyotype. There were no deletions of the DAZ-gene, no HH and no testicular atrophy. The infertility was thus not proved to be congenital, and consequently, surgical treatment is indicated before the germ cells disappear from undescended testes. This appears to be before 15 months of age.

Adenocarcinoma of the cervix and adenocarcinoma of the endometrium: distinction with PCR-mediated detection of HPV DNA.

The differential diagnosis between primary endocervical adenocarcinoma and adenocarcinoma originating in the endometrium may in some cases be difficult. The two cancer types have a different genesis, with human papillomavirus (HPV) as an important causal factor in the development of primary cervical carcinoma. In this study, the paraffin-embedded cervical tissues from 23 patients with stage II endometrial carcinoma and from 50 patients with primary cervical adenocarcinoma were examined for HPV DNA of types 16, 18, and 33. HPV DNA was demonstrated in 70% of the primary endocervical adenocarcinomas and in none of the endometrial carcinomas. It is concluded that HPV detection may be useful in the differential diagnosis of some cases of cervical and endometrial adenocarcinoma.

The pathogenesis of cryptorchidism and splenogonadal fusion: a new hypothesis.

OBJECTIVE: To obtain new information about the pathogenesis of cryptorchidism. MATERIALS AND METHODS: Published reports of 111 males with splenogonadal fusion were examined and the presence and type of cryptorchidism and the degree of continuity between the spleen and gonads determined. RESULTS: Of the 111 cases, 31% had cryptorchidism and of these 59% were bilaterally cryptorchid; 26% and 65% had right and left intra-abdominal testes, respectively. Of those with continuous splenogonadal fusion, 44% had cryptorchidism. Solely cryptorchid cases with splenogonadal fusion had reported bilateral absence of both legs, imperforate anus, spina bifida, diaphragmatic hernia and hypospadias. CONCLUSION: An hypothesis is proposed that the abnormal development of the diaphragmatic ligaments of the testes may lead to lack of their involution, with consequent cryptorchidism. In the case of splenogonadal fusion, the abnormal ligaments are colonized by splenic cells, possibly because of an abnormal proximity to the splenic anlage, with the resulting abnormal ligament persisting as the splenic cord and thus resulting in cryptorchidism. The basic abnormality may be in the connections of the diaphragmatic ligaments, caused by abnormal midline development in the third to fourth week of gestation.

Lung carcinoma and malignant mesothelioma in patients exposed to Thorotrast: incidence, histology and p53 status.

In a previous registry-based survey of 999 patients injected with alpha-emitting 232ThO2 (Thorotrast), we identified elevated risks for lung carcinoma and malignant mesothelioma. Since injected Thorotrast is retained lifelong mostly in liver, spleen and lymph nodes, the mesothelial surfaces of these organs are constantly irradiated. Thorotrast-administered patients also perpetually exhale 220Rn, a 232Th-daughter. Study of Thorotrast-exposed patients may, therefore, provide data with regard to carcinogenicity of radon exposure, a current public health concern, as well as the pathogenesis of malignant mesothelioma. The incidence and histologic types of lung carcinoma and malignant mesothelioma within the cohort were examined by review of available histopathologic material and medical records. Further, mutations of the p53 gene were analyzed whenever possible as it has previously been suggested that radon-associated lung carcinomas exhibit specific mutational patterns. The cumulative risk for lung carcinoma reached 11.0% based on 20 confirmed cases. Nine were small cell lung cancer (SCLC), whereas the expected frequency was 18%. The risk for malignant mesothelioma reached 2.5% based on 7 cases. The actuarial risk of malignant mesothelioma for patients given more than 20 ml Thorotrast was 7.8% compared to 1.4% for patients administered smaller amounts. Seven lung carcinomas and 5 malignant mesotheliomas were analyzed for p53 mutations; only 1 (in a lung adenocarcinoma) was detected. A possible association between Thorotrast and SCLC is suggested. In addition, a possible dose-response gradient exists for Thorotrast and malignant mesothelioma.

Mutations in the tumor suppressor gene p53 in human liver cancer induced by alpha-particles.

The p53 tumor suppressor gene is mutated in varying fractions of almost all tumor types studied. The rate of mutations and the mutational spectrum in some tumors are specific for environmental mutagens assumed to be involved in the carcinogenic process. Thus, hepatocellular carcinomas supposedly induced by aflatoxin exposure often contain a specific point mutation in codon 249, and in lung cancers of miners with heavy radon exposure, another specific point mutation in codon 249 suggestive of an alpha-particle-specific mutation has been shown. The interpretation of studies linking the mutational spectrum with specific environmental exposures is complicated by the multifactorial or unknown genesis of most tumors. However, people given injections of the X-ray contrast medium Thorotrast (Th) in the past have experienced an enormous risk of liver tumors, and virtually all of these are supposedly induced by alpha-particles from the decay of 232Th. The examination of these tumors may provide evidence as to whether specific p53 point mutations are relevant in alpha-particle carcinogenesis. Therefore, we collected paraffin-embedded, formalin-fixed archival tissues from 18 hepatocellular carcinomas, 9 cholangiocarcinomas, and 9 hepatic angiosarcomas from Thorotrast-exposed patients. The tissues were analyzed for p53 protein expression by immunohistochemical staining by using the mAb DO-7 and for mutations of exons 5-8 by PCR and constant denaturant gel electrophoresis. G --> T transversions of the third base of codon 249 of the p53 gene were specifically screened for by restriction enzymes. No high score for p53 protein expression (i.e., positive staining of >20% of examined cells) was observed; lower scores were seen in 5 of 18 (28%) hepatocellular carcinomas, 1 of 9 (11%) cholangiocarcinomas, and 0 of 8 (0%) hepatic angiosarcomas. Only one p53 mutation, a heterozygous T --> G transversion of the first base codon 176, occurred in a hepatocellular carcinoma. The rate of p53 point mutations in alpha-particle-induced liver tumors seems to be lower than in European hepatocellular carcinomas in general. The study does not exclude the possibility that alpha-particle carcinogenesis may involve inactivation of p53 by gross deletions of the gene, but it speaks against the proposed specificity of point mutations of codon 249 in cancer supposedly induced by alpha-particles from radon progeny.

The use of polymerase chain reaction to detect metastatic cancer cells within lymph nodes in stage I cervical carcinoma.

The aim of the study was to determine whether human papillomavirus (HPV) in lymph nodes is a useful marker for the risk of recurrence in patients with HPV-related cervical cancer. The polymerase chain reaction and DNA-DNA hybridization techniques were used to examine 149 formalin-fixed, paraffin-embedded lymph nodes that had been resected from 24 patients undergoing radical hysterectomy for stage IB cervical carcinoma. The lymph nodes were examined for the HPV type, which in each case was found in the cervical tumor. Of 18 patients with histologically negative nodes, HPV DNA was found in a lymph node in two of 10 patients who later experienced a recurrence and in three of eight patients who were alive and well for > or = 5 years after surgery. In addition, HPV was detected in the lymph nodes of two of four patients with nodal metastases at the primary surgery; four of nine histologically positive lymph nodes in these patients contained HPV. It is concluded that detection of HPV in resected lymph nodes is probably not a useful means of identifying the cervical cancer patients who might benefit from adjuvant postoperative therapy.

DNA content and expression of tumour markers in germ cells adjacent to germ cell tumours in childhood: probably a different origin for infantile and adolescent germ cell tumours.

The origin of testicular germ cell tumours occurring during childhood is poorly understood. In adults, the classical seminomas and non-seminomas originate from carcinoma in situ of the testis, which can usually also be detected in seminiferous tubules adjacent to the tumours. In order to contribute with information regarding a possible association between carcinoma in situ and the childhood group of germ cell tumours, we investigated seminiferous tubules adjacent to 13 infantile yolk sac tumours, five infantile teratomas, and six adolescent germ cell tumours of various types, using morphological evaluation, immunohistochemical staining with markers for carcinoma in situ cells, and densitometric DNA measurement of the germ cells. We detected clear differences between the germ cell populations adjacent to adolescent and infantile germ cell tumours. The former were associated with both normal germ cells and carcinoma in situ cells, like germ cell tumours occurring in adult men. Although we were in doubt in two cases, the infantile cell germ cell tumours were in general not associated with carcinoma in situ cells. The aetiology of infantile yolk sac tumours and teratomas may therefore be fundamentally different from that of adolescent and adult germ cell tumours. The origin of yolk sac tumours and teratomas remains to be elucidated.

Pathoanatomical aspects of malignant haematological disorders among Danish patients exposed to thorium dioxide.

The Danish Thorotrast Study was recently reestablished and improved. The cohort has been reidentified and followed up, and now comprises 1003 Thorotrast-exposed patients. For all suspected haematological cases, cytological and histological material has been revised and malignant diseases have been reclassified. The numbers of cases of leukemia and other related haematological disorders were as follows: 16 acute myeloid leukemia (AML); 8 myelodysplastic syndrome (MDS); 1 acute lymphatic leukemia (ALL); 3 chronic myeloid leukemia (CML); 4 non-Hodgkin's lymphoma (NHL); 2 multiple myeloma (MM); 2 myelofibrosis (MF); 2 chronic lymphatic leukemia (CLL). Except for CLL, all cases might be Thorotrast-induced. (Expected number of leukemias: < 2.5.) The findings in the German, Japanese, Portuguese and Danish studies are very similar. Some of the characteristic features include a high incidence of AML with several erythroleukemias, many cases of MDS, and a relatively low incidence of CML. In several studies of leukemia induced by alkylating agents, erythroleukemia is also described as a prominent feature. The possibility exists that a phase of relative predominance of erythroid elements in the bone marrow may be a common and not an unusual feature in the pathogenesis of these secondary leukemias. The findings are also compared with histopathological data from a Danish control group of de novo leukemia patients and from atomic bomb survivors with radiation-induced leukemia. The relative frequency of AML is higher among the Thorotrast-exposed patients than among the Danish control group and the A-bomb survivors. In contrast, low relative frequencies are seen for ALL and CML in Thorotrast cases in comparison with de novo leukemia cases and A-bomb survivors. It can be concluded that differences in relative and absolute frequency of leukemias and myelodysplastic syndrome exist not only between the irradiated populations and the unexposed control group, but even between groups exposed to low-LET (linear energy transfer) and high-LET radiation.