Tumor Size of Invasive Breast Cancer on Magnetic Resonance Imaging and Conventional Imaging (Mammogram/Ultrasound): Comparison with Pathological Size and Clinical Implications.

BACKGROUND AND AIM: In Landspitali University Hospital, magnetic resonance imaging is used non-selectively in addition to mammogram and ultrasound in the preoperative assessment of breast cancer patients. The aim of this study was to assess invasive tumor size on imaging, compare with pathological size and evaluate the impact of magnetic resonance imaging on the type of surgery performed. MATERIAL AND METHODS: All women with invasive breast cancer, diagnosed in Iceland, between 2007 and 2009 were reviewed retrospectively. In all, 438 of 641 (68%) patients diagnosed had preoperative magnetic resonance imaging. Twelve patients treated with neoadjuvant chemotherapy were excluded and 65 patients with multifocal or contralateral disease were assessed separately. RESULTS: Correlations between microscopic and radiologic tumor sizes were relatively weak. All imaging methods were inaccurate especially for large tumors, resulting in an overall underestimation of tumor size for these tumors. Magnetic resonance imaging under- and overestimated pathological tumor size by more than 10 mm in 16/348 (4.6%) and 26/348 patients (7.5%), respectively. In 19 patients (73%), overestimation of size was seen exclusively on magnetic resonance imaging. For tumors under- or overestimated by magnetic resonance imaging, the mastectomy rates were 56% and 65%, respectively, compared to an overall mastectomy rate of 43%. Of 51 patients diagnosed with multifocal disease on pathology, 19 (37%) were diagnosed by mammogram or ultrasound and 40 (78%) by magnetic resonance imaging resulting in a total detection rate of 84% (43 patients). Fourteen (3%) patients were diagnosed preoperatively with contralateral disease. Of those tumors, all were detected on magnetic resonance imaging but seven (50%) were also detected on mammogram or ultrasound or both. CONCLUSION: Our results suggest that routine use of magnetic resonance imaging may result in both under- and overestimation of tumor size and increase mastectomy rates in a small proportion of patients. Magnetic resonance imaging aids in the diagnosis of contralateral and multifocal disease.

Prolonged chemotherapy impairs liver regeneration after portal vein occlusion - an audit of 26 patients.

AIM: The aim of the present retrospective study was to investigate the influence of neoadjuvant chemotherapy on liver regeneration after portal vein occlusion before major hepatectomy. METHOD: Between 2003 and 2007, 26 patients underwent portal vein occlusion, of whom 22 had portal vein embolisation and 4 portal vein ligation. 15 of 23 patients with colorectal liver metastases had neoadjuvant chemotherapy. RESULTS: After portal vein occlusion, the ratio of the future liver remnant volume to total parenchymal liver volume (FLR%) was reduced in patients receiving neoadjuvant chemotherapy (27 +/- 1% vs 32 +/- 1%, p = 0.03). A smaller future liver remnant before portal vein occlusion resulted in a greater degree of hypertrophy (r(2) = 0.18, p = 0.04). Patients with tumour size greater than 60 mm showed a decreased degree of hypertrophy (7 +/- 1)% as compared to patients with smaller tumours (13 +/- 1%, p = 0.01). There was one death shortly after portal vein embolisation. 19/26 patients were resected with zero operative mortality. CONCLUSION: Prolonged neoadjuvant chemotherapy has a small negative effect on liver regeneration induced by portal vein occlusion. Liver regeneration induced by portal vein occlusion is relatively large when tumour burden is small.

Interstitial laser thermotherapy (ILT) of breast cancer.

AIM: To find out if ILT can be used as radical treatment of breast cancer. METHOD: Twenty-four patients, aged 39-84 (mean 61), with invasive breast cancer were treated with ILT. All underwent mammography, ultrasound and core biopsy before treatment. The tumour was an invasive ductal carcinoma in 15 patients, a lobular carcinoma in eight and lobular-ductal cancer in one. Average tumour diameter was 14 mm on ultrasound (5-35). Patients were treated in the outpatient clinics under local anaesthesia. Probes were placed under ultrasound guidance, in 19 patients, and ILT was performed with a diode laser at a steady-state temperature of 48 degrees C for 30 min using temperature feedback control. Standard surgical excision was performed 12 (4-23) days after ILT and was preceded by Doppler ultrasound. RESULTS: Treatment-induced necrosis of invasive cancer was 33% (range 0-100) and was complete in three patients. At follow-up before surgery, the extent of laser damage could not be judged with ultrasound, although abolished tumour blood flow was demonstrated after treatment resulting in large necroses. Efficacy of treatment varied negatively with tumour size. The inefficacy of ILT was mainly due to the underestimation of tumour size by mammography and ultrasound and the shortcomings of these methods to demonstrate tumour borders, tumour irregularity and carcinoma in situ (CIS). ILT was well tolerated. Five patients had breast tenderness, and three patients had pain, during the first day after treatment. Small skin necroses were observed in two patients. CONCLUSION: Small breast cancers can be treated radically with ILT. The method may become useful in the treatment of breast cancer but needs further refinement, even for small well-defined breast cancers, if it is going to be employed for radical treatment.

DNA of Helicobacter spp. and common gut bacteria in primary liver carcinoma.

BACKGROUND AND AIM: Gastric and enteric Helicobacter species have been associated with the pathogenesis of some extragastric diseases. METHODS: We retrospectively investigated the presence of DNA of Helicobacter species in samples of the cancer and the surrounding tumour-free liver tissues of patients with hepatocellular carcinoma (HCC, n=12) and cholangiocarcinoma (CC, n=13). The patients were from an area with low liver cancer incidence and with low hepatitis B and C prevalence. Patients with a benign liver disease (n=24) were included as controls. Paraffin-embedded liver samples were examined by a Helicobacter genus-specific PCR assay as well as group-specific PCR assays for Enterobacteriaceae, Bacteroides, Lactobacillus and Enterococcus. PCR products of positive samples were characterised by denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. RESULTS: PCR assay detected Helicobacter DNA in seven of 12 (58%) and eight of 13 (62%) normal liver tissue specimens from HCC and CC patients, respectively. Two cancer samples from HCC patients were Helicobacter-positive but none of the CC cancers. In the control group, three of 24 (12.5%) patients with a benign liver condition were positive for Helicobacter species (p<0.01 compared to results of tumour-free liver tissue from the cancer patients). DGGE and DNA sequence analysis showed that 90% of the detected PCR products were "H. pylori-like". DNA of some other enteric bacteria was detected in the liver of one cancer patient and one control (4% of all patients). CONCLUSION: The presence of DNA of Helicobacter species in liver specimens, but not of other common gut bacteria, was associated with human hepatic carcinogenesis.

Resistance to tumour challenge after tumour laser thermotherapy is associated with a cellular immune response.

Previous studies in our laboratory have shown that interstitial laser thermotherapy (ILT) of an experimental liver tumour is superior to surgical excision, at least partly due to a laser-induced immunological effect. The aim of the present study was to investigate the time-response relationship of the ILT-induced immunisation and the cellular response of macrophages and lymphocytes. A dimethylhydrazine-induced adenocarcinoma was transplanted into the liver of syngeneic rats. Rats with tumour were treated 6-8 days later (tumour size 0.25-0.40 cm(3)) with ILT of tumour or resection of the tumour-bearing lobe. Two groups of rats without tumour were treated with resection of a normal liver lobe or ILT of normal liver. A challenging tumour was implanted into the liver of each rat 2, 5 or 10 weeks after primary treatment. Rats were killed 6, 12 and 48 days (or earlier due to their condition) after challenge (n = 8 in all groups). Immunohistochemical techniques were used to determine lymphocytes (CD8, CD4) and macrophages (ED1, ED2) in rats having had treatment of a primary tumour. Interstitial laser thermotherapy of the first tumour was followed by eradication of challenging tumour and absence of tumour spread. This contrasted with rapid growth and spread of challenging tumour in the other groups. In the challenging vital tumour tissue and in the interface between the tumour and surroundings, the number of ED1 macrophages and CD8 lymphocytes was higher in rats having been treated with the ILT of tumour than in those having undergone resection of the tumour-bearing lobe. The number of ED2 macrophages and CD4 lymphocytes was low and did not vary between these two groups. Interstitial laser thermotherapy elicited an immune response that eradicated a challenging tumour and was associated with increased numbers of tumour-infiltrating macrophages and CD8 lymphocytes.

Percutaneous ablation of liver tumours.

The goal of local ablation treatment of hepatic disease is to prolong survival for patients with unresectable tumours. Presently, influence on survival is difficult to estimate because of the heterogeneity of indications and treatments and short follow-up. This chapter therefore focuses on potential benefits and limitations, complications and solutions for improvement. The main problems with in situ ablation are the lack of good imaging techniques to determine the extent of disease and the lack of a method for real-time monitoring of irreversible tissue effect. With one exception, there are no prospective, randomized studies comparing local destruction methods. It appears that percutaneous ethanol injection and cryotherapy should be replaced by radiofrequency ablation (RFA) or interstitial laser thermotherapy (ILT) and that there is little difference in outcome between RFA and ILT. Intraoperative RFA or ILT is valuable as an adjunct to hepatic resection in order to increase the rate of resectability. The percutaneous approach needs further development. It might be valuable in a few truly unresectable or inoperable patients or in selected patients with neuroendocrine liver metastases. In the large majority of unresectable patients it should, however, presently be used and evaluated only in prospective, randomized studies.

Percutaneous fine-needle aspiration cytology in the diagnosis and management of liver tumours.

BACKGROUND: The aim of the study was to investigate the value of percutaneous fine-needle aspiration cytology (FNAC) in the diagnosis and management of liver tumours. METHODS: FNAC followed by histopathological examination was carried out in 216 patients with suspected liver tumours. The final diagnosis was primary liver cancer in 106, colorectal metastases in 51, non-colorectal metastases in 46, benign tumour in nine and no tumour in four patients. RESULTS: Cytology resulted in correct classification of the lesion as benign or malignant in 87 per cent of patients, correct discrimination between primary and secondary malignancy in half of the patients, and a correct diagnosis of tumour type in one-third of patients. The tumour was erroneously classified as benign or malignant in 22 patients (11 per cent) and four patients (2 per cent) respectively. When FNAC showed malignancy, the predictive value was 98 per cent, whereas the predictive value was 27 per cent when it did not. FNAC guided investigations and treatment in one-quarter of patients. Implantation metastases were recorded in seven patients (3 per cent), including five (10 per cent) of 51 patients with colorectal liver metastases, and caused major local problems and death in four patients. CONCLUSION: FNAC was valuable in about a quarter of patients with liver tumour. The risks of implantation metastases and a false-negative finding do not justify its use in candidates for curative therapy of liver tumours.

Interstitial laser thermotherapy of a rat liver adenocarcinoma.

The aim of this study was to compare interstitial laser thermotherapy with excision of a liver tumour. A dimethylhydrazine-induced adenocarcinoma was implanted into the left lateral lobe of the rat liver, and treatment was performed 8 days later. Rats were treated with resection of the tumour-bearing lobe or underwent interstitial laser thermotherapy, which was performed at a steady-state temperature of 46°C for 30 min, 3 mm from the tumour margin. The incidence and extent of intraperitoneal spread was smaller after laser thermotherapy than after resection, with no difference in local control. Using inoculation of tumour cell suspensions into the lateral and the median lobes of the liver simultaneously and treating the lateral lobe tumour only, we found that laser thermotherapy reduced take and growth of the untreated tumour in the median lobe indicating that laser thermotherapy may induce immunologic effects. It is concluded that interstitial laser thermotherapy reduces spread of liver tumour as compared to resection. It is suggested that this can be at least partly explained by a laser-induced immunologic effect.

Congenital absence of the intrahepatic portion of the portal vein in an adult male resected for hepatocellular carcinoma.

We report a case of congenital absence of the portal vein (CAPV) in an adult male who underwent resection for hepatocellular carcinoma. CAPV is a rare anomaly; only 29 cases, mostly in children, have been presented to date. An association between CAPV and cardiac abnormalities, polysplenia syndrome, skeletal abnormalities and liver tumors has been seen in children. To the best of our knowledge this is the first case of CAPV in an adult male resected for hepatocellular carcinoma. However, since CAPV can be without symptoms, the number of undiagnosed cases is not known.

Electrically mediated drug delivery for treatment of an adenocarcinoma transplanted into rat liver.

BACKGROUND: In this study, electrochemotherapy (ECT), i.e. tumour treatment based on local augmentation of intracellular drug delivery from short, intense electric pulses, was evaluated in rats with an adenocarcinoma implanted into the liver. Tumour response and concentrations of macrophages and T-lymphocytes (CD4 and CD8) in and around the tumour were measured. MATERIALS AND METHODS: Rats were treated with permeabilizing electric pulses, bleomycin, or both, eight days after implantation of the tumour, while one group received sham treatment. RESULTS: Treatment with electric pulses and bleomycin resulted in a significantly reduced lesion volume and 92% cure rate (12 out of 13, p<0.0002 compared to the other treatment groups). The highest concentration of CD8 lymphocytes was found in tumours treated with electric pulses and bleomycin. Macrophages were found mainly in tumours treated with electric pulses, with or without bleomycin. CONCLUSION: Electrochemotherapy using millisecond exponential pulses and bleomycin is efficient in a rat liver tumour model and appears to stimulate the host's immune system.

Simplified treatment planning for interstitial laser thermotherapy by disregarding light transport: a numerical study.

BACKGROUND AND OBJECTIVE: The objective was to investigate the effect of light transport on the temperature distribution and the coagulated volume under conditions relevant to interstitial laser thermotherapy (ILT) of tumors in the human liver. STUDY DESIGN/MATERIALS AND METHODS: Temperature distributions and coagulated volumes produced with a diffusing laser fiber or a conductive heat source, at equal output power, were numerically calculated for tissue with different optical penetration depths. Four irradiation times (5, 10, 20, and 30 min) were studied. A three-dimensional finite-element model was used to calculate the temperature distribution during heating with four conductive heat sources (no light emission). Results were compared with measured temperature distributions during laser irradiation in a gel phantom with known optical properties. RESULTS: Numerical calculations showed that the influence of light transport on the coagulated volume was negligible in tissue with optical penetration depths below 3-4 mm at all studied irradiation times. The phantom experiment indicated good agreement with the calculated temperature distribution, both with a single diffusing laser fiber and with four fibers. CONCLUSION: Light transport influences coagulated volumes only slightly under conditions presented in this work, which is relevant to ILT of tumors in the human liver.

Clonal chromosomal abnormalities in congenital bile duct dilatation (Caroli's disease).

BACKGROUND: Caroli's disease is a rare congenital disorder characterised by cystic dilatation of the intrahepatic bile ducts and an increased risk of cholangiocellular carcinoma. The cause is unknown, but occasional familial clustering suggests that some cases are inherited, in particular when occurring in association with polycystic kidney disease and germline PKD1 gene mutations. To date, no gene responsible for familial isolated Caroli's disease has been identified, and no genetic investigations of liver tissue from patients with Caroli's disease have been reported. PATIENT/METHOD: A liver biopsy specimen from a patient with isolated Caroli's disease, without any signs of cholangiocellular carcinoma, was short term cultured and cytogenetically investigated after G banding with Wright's stain. RESULT: Cytogenetic analysis disclosed the karyotype 45-47,XX,der(3)t(3;8)(p23;q13), +2mar[cp6]/46,XX[18]. CONCLUSIONS: The finding of an unbalanced translocation between chromosomes 3 and 8 suggests that loss of distal 3p and/or gain of 8q is of pathogenetic importance in Caroli's disease. Alternatively, structural rearrangements of genes located in 3p23 and 8q13 may be of the essence. These chromosomal breakpoints may also pinpoint the location of genes involved in inherited forms of Caroli's disease not associated with polycystic kidney disease.

Dearterialization of colorectal liver cancer: institutional experience.

BACKGROUND/AIMS: Preliminary clinical trials have suggested that dearterialization (interruption of arterial blood supply) is beneficial to patients with liver tumours. The aim of this report was to review the outcome of all patients undergoing dearterialization for colorectal liver metastases and to analyze whether refinement of the technique was followed by improvement in outcome. METHODS: Retrospective review of 57 patients undergoing temporary (16 h) dearterialization during 1972-1984 (n = 24) or repeated transient dearterialization (1-2 h once or twice daily) during 1985-1995 (n = 33). RESULTS: The median survival after start of treatment was 1.1 years, and the 5-year survival rate was 0%. There was no significant difference in survival between temporary and repeated transient dearterialization. Liver tumour volume and extrahepatic metastases varied negatively with survival. The temporary dearterialization procedure was followed by hepatic or intra-abdominal abscess formation in 6 patients (24%), leading to postoperative death in 2 patients (operative mortality 8%). Complications after repeated transient dearterialization were related mainly to technical problems with the occluder device. CONCLUSION: Although this was not a randomized study, it appears that dearterialization is of no benefit in colorectal liver cancer.

Immunohistochemical expression of metallothionein in resected hepatic primary tumors and colorectal carcinoma metastases.

Metallothionein is a protein with affinity for metals and is present in several tumors. We examined its immunohistochemical expression in 37 resected primary liver tumors and 117 colorectal metastases. The reaction was intense in the two fibrolamellar hepatocellular carcinomas and in many of the hepatocytes of the pseudotumor case of focal nodular hyperplasia. The reaction was low or moderate in 5 of 17 ordinary hepatocellular carcinomas and in 4 of 14 cholangiocellular carcinomas. There was no reaction in one case each of spindle cell hepatocellular carcinoma, oncocytic adenoma and hemangioendothelial sarcoma. In the metastases, the reaction was low or moderate in 14 cases and negative in 103. Surrounding hepatocytes and stromal cells were more or less positive in all cases.

Cytogenetic analyses of secondary liver tumors reveal significant differences in genomic imbalances between primary and metastatic colon carcinomas.

To investigate if karyotypic features of secondary liver tumors may provide diagnostic information and if the cytogenetic patterns of primary and metastatic colorectal carcinomas (CRC) are different, 33 liver metastases were analyzed: 25 CRC, 4 small intestine carcinoids, 1 ovarian carcinoid, 1 lobular breast cancer, 1 head-and-neck squamous cell carcinoma, and 1 uveal malignant melanoma. Chromosomal aberrations were detected in 24 cases, whereas 5 had normal karyotypes and 4 were uninformative due to lack of mitoses. Trisomy 12 was detected in 2 small intestine carcinoids, suggesting that +12 may be of pathogenetic importance in this tumor type. The breast and head-and-neck carcinomas and the uveal melanoma displayed aberrations previously reported as characteristic in primary tumors, e.g., der(1;16) and deletion of 3p in the breast cancer, losses of 3p and 8p and partial gain of 8q in the head-and-neck carcinoma, and monosomy 3 and i(8)(q10) in the uveal melanoma, indicating that cytogenetic investigations provide important diagnostic information in secondary liver tumors. In the 18 CRC metastases with chromosomal abnormalities, the cytogenetic findings agreed well with previously reported primary CRC. Common numerical abnormalities included gains of chromosomes 7, 11, 13, and 20, and losses of Y, 4, 18, 21, and 22. Structural rearrangements most often affected chromosome bands 1p13, 1q10, 3p21, 5q10, 5q11, 7q10, 8q10, 8q11, 12q13, 16p13, 17p11, 20p13, 20p11, and 20q10, and frequently resulted in losses of 1p, 8p, and 17p, and gains of 5p, 6p, 7p, 8q, and 20q. Comparing the present cases with primary CRC previously analyzed in our department revealed that additional gains of 6p, 6q, 7p, and 20q, and losses of 1p, 4p, 4q, 8p, 18p, 18q, and 22 were more common (P < 0.05) in the metastases, suggesting that these genomic sites harbor genes of importance in the metastatic process of CRC.

Changes in local hepatic blood perfusion during interstitial laser-induced thermotherapy of normal rat liver measured by interstitial laser Doppler flowmetry.

Interstitial laser Doppler flowmetry was used to measure the effect of interstitial laser-induced thermotherapy on local blood perfusion in normal rat liver in the peripheral treatment region elevated to hyperthermic temperatures. The Nd:YAG laser emitting at 1064 nm was utilised as heat generation source. The plane-cut tip of an optical fibre was placed in the middle of the exteriorised left liver lobe. Blood perfusion and temperature were measured in the liver parenchyma 4 mm from the laser fibre. The temperature at the location of the liver temperature sensor was maintained at 41 or 44°C during 30 min by regulating the power of the heating laser. The laser Doppler signal was recorded during and after heat treatment, for a total time of 60 min. At 41°C, a significant increase in perfusion up to 1.3 times the initial value was observed 2-16 min after start of treatment. At 44°C, perfusion decreased continuously during and after treatment, and was significantly different from control 40 min after start of treatment. The results may be valuable in assessing the thermal response of tissues surrounding the target in interstitial laser-induced thermotherapy of liver tumours during conditions of normal blood flow.

Liver resection of noncolorectal secondaries.

BACKGROUND AND OBJECTIVES: Hepatic resection of noncolorectal metastases appears to be performed with increasing frequency. Reported experience is limited and indications are controversial. METHODS: Retrospective review of curative hepatic resection in 32 patients (median age 58 years) during 1970-1995. The primary tumor was a carcinoid in seven patients, other endocrine tumor in five patients, malignant melanoma in three patients, stomach cancer in three patients, exocrine pancreatic cancer in two patients, gynecological cancer in two patients, sarcoma in two patients, and miscellaneous in eight patients. Seven patients (22%) had bilobar disease and 12 patients (38%) had extrahepatic growth. RESULTS: Median survival was 32 months, and 5-year actuarial survival rate was 36% (including operative mortality). Median survival in the endocrine (n = 12) and nonendocrine (n = 20) groups was 72 and 18 months, respectively (corresponding 5-year survival rates were 56 and 25%) (P = 0.16). Prognostic factors could not be established in either group. It is, however, noteworthy that no patient with nonendocrine secondaries and more than one liver tumor or extrahepatic disease survived for 5 years. Major complications were seen in eight patients (25%), including three postoperative deaths (operative mortality 9%) occurring during the first 5 years of the study period. CONCLUSIONS: Hepatic resection of metastases from endocrine primary tumors was followed by long-term survival in a substantial proportion of patients. Long-term survival for patients with nonendocrine tumors was observed only when there was a single liver tumor and no extrahepatic growth. Further experience is needed for definition of resection criteria.

MRI thermometry in phantoms by use of the proton resonance frequency shift method: application to interstitial laser thermotherapy.

In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 degrees C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 degrees C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approximately linear relationship (0.0085 ppm degrees C(-1)) between proton resonance frequency shift and temperature change was found for agarose gel, whereas deviations from a linear relationship were observed for porcine liver. The optically tissue-like agarose gel allowed reliable MRI temperature monitoring, and the MR relaxation times (T1 and T2) and the optical properties were found to be independently alterable. Temperature distributions around a diffusing laser fibre, during irradiation and subsequent cooling, were assessed with high spatial resolution (voxel size = 4.3 mm3) and with random uncertainties ranging from 0.3 degrees C to 1.4 degrees C (1 SD) with a 40 s scan time.

Frequent rearrangements of chromosomes 1, 7, and 8 in primary liver cancer.

Fifteen primary liver carcinomas (PLCs), including 12 hepatocellular carcinomas and three cholangiocellular carcinomas, were investigated cytogenetically after short-term culture. Ten tumors displayed clonal chromosomal abnormalities, whereas only normal karyotypes were detected in four cases, and one sample failed to grow in vitro. Structural rearrangements most often involved chromosomes 1, 7, and 8 and chromosome bands 1p36, 1q25, 3q10, 5q13, 6p10, 7p15, 7q22, 7q32, 8q10, 8q13, 14q10, and 17p11. Frequent genomic imbalances included gains of 1q, 3q, 6p, 7p, and 8q and losses of 1p, 8p, 10q, 14p, 17p, and 19p. A compilation of findings for all 19 cytogenetically abnormal PLCs reported to date, including the present cases, reveals that structural aberrations particularly affect 1p11, 1p22, 1p32, 1p34, 1p36, 1q25, 7p15, 7q22, 8q10, 8q13, 14q10, 16q24, and 17p11, and that the abnormalities frequently result in overrepresentation of 1q, 3q, 6p, 7p10-14, 8q, and 17q and underrepresentation of 1p34-36, 6q27, 7q32-qter, 8p, 13p, 14p, 16q24, and 17p. These genomic regions are likely to harbor genes of importance in hepatocarcinogenesis, and the present cytogenetic mapping may hence be of value for further molecular genetic investigations of PLC.