Prognostic factors in metastatic nonseminomatous germ cell tumours

OBJECTIVE

To determine predictors of prognostic significance for patients with nonseminomatous testicular cancer (NSTC) who have advanced disease at the time of presentation.

DESIGN

A chart review with a mean patient follow-up of 5.5 years (range from 0.75 to 13 years).

SETTING

University hospitals in Halifax.

PATIENTS

All patients with NSTC, stages II-B, II-C and III. Patients were excluded if the follow-up status at the time the study closed could not be determined. Thirty-three patients were included in the study. Current patient status was determined from the clinical charts and personal communication with the patients or their physicians.

INTERVENTIONS

All patients received cisplatinum-based chemotherapy. The extent of the disease was assessed by chest radiography or lung tomography, bone scanning, abdominal computed tomography or lymphangiography.

MAIN OUTCOME MEASURES

Correlation between levels of beta-human chorionic gonadotropin (BHCG) and alpha-fetoprotein (AFP), comparison of duration of symptoms before initial treatment, response to treatment and survival, and relationship between stage, tumour volume and survival.

RESULTS

The 3-year overall survival rate was 76%. Seven of 18 patients with symptoms for more than 16 weeks died of disease (p < 0.01). Overall complete response was seen in 27 of 33 patients. All initial nonresponders died. A survival rate of 93% was seen among initial complete responders (p < 0.01). All seven patients with persistent elevation of BHCG levels (p < 0.001) and the two patients with persistent elevation of AFP levels (p < 0.01) after the second course of chemotherapy died.

CONCLUSIONS

A symptomatic interval of more than 16 weeks, poor response to initial treatment, bulky retroperitoneal disease, larger volume lung disease and persistently elevated levels of BHCG and AFP were all indicators of poor prognosis.

False elevations of alpha-fetoprotein associated with liver dysfunction in germ cell tumors

BACKGROUND

Determination of serum concentration human chorionic gonadotropin (HCG) and alpha-fetoprotein (AFP) is crucial in diagnosis, prognosis, treatment, and follow-up of patients with germ cell tumors. Elevation of these markers almost indicates progression or recurrence of the germ cell tumor. However, an increase in these tumor markers can be produced by several benign causes.

METHODS

The authors report nine cases of gonadal germ cell tumors that had increased serum levels of AFP without tumoral progression, recurrence, or residual tumor.

RESULTS

The AFP elevations were attributed to liver damage secondary to drugs (chemotherapy, anesthetics, or antiepileptics), virus, or alcoholism. No clinical evidence (or in some cases surgical evidence) of malignant tumor activity was found in any of the patients.

CONCLUSIONS

The elevation of serum levels of AFP in patients with germ cell tumors can be produced by liver dysfunction. These elevations must be interpreted with caution to avoid unnecessary treatments.

Metachronous germ cell and Leydig cell tumors of the testis. Do testicular germ cell tumors and Leydig cell tumors share common etiologic factors?

BACKGROUND

Testicular germ cell neoplasms occur bilaterally in approximately 2-5% of patients. Bilateral testicular tumors of different histogenesis are extremely rare, and the study of such cases may offer clues to the pathogenesis of both tumor entities.

METHODS

A report of a case and review of the literature are presented.

RESULTS

A 33-year-old man had a right-sided testicular neoplasm consisting of teratoma, embryonal carcinoma, and yolk sac tumor. Retroperitoneal lymph node metastases were excised, and, subsequently, adjuvant abdominal radiation therapy was administered. The patient later received six cycles of cisplatin-based chemotherapy for pulmonary relapse. When he was 40 years of age, a contralateral Leydig cell tumor (LCT) was treated by testis-sparing excision. This is the first observation of testicular germ cell tumor (GCT) and contralateral LCT. Three cases of germ cell neoplasm and concurrent ipsilateral LCT have been reported previously.

CONCLUSIONS

The association of GCT and LCT in one patient is quite unusual because both entities are rare. Sharing of common etiologic factors by both entities is a possible explanation.

D-CECaT: a breakthrough for patients with neuroblastoma

In view of the high relapse rate following chemotherapy for patients with advanced neuroblastoma (NB) and primitive neuroectodermal tumors (PNET), we designed a novel chemotherapy program which incorporated the iron chelator deferoxamine. The purpose of the deferoxamine was to sensitize the cells to standard chemotherapy. The D-CECaT regimen contained (in mg/m2): deferoxamine 4500 during days 1-5; cyclophosphamide 600 mg over days 6 and 7; etoposide 300 mg over days 7 and 8; carboplatin 100 mg over days 7 and 8; and thiotepa 30 mg over days 6-8. Between October 1989 and May 1992 we entered 23 advanced NB and two PNET patients. Sepsis occurred in four courses, nausea and vomiting in 30 courses, and 50 courses required blood and platelets. Responses observed in previously untreated patients with stage III NB: six out of six CR (17+ to 41+ months), with stage IV NB, nine out of 11 CR (14+ to 28+ months), two out of 11 VGPR (22+ months), with stage IV PNET two out of two CR (1+ to 35+ months). With previously treated and failed stage IV NG, two out of six VGPR for 19+ and 20 months, and four out of six PR 1, 8, 9 and 11 months. Median survival for 19 new patients was 22+ months (6 to 41+ months; two patients in CR died at 7 months during adjuvant autologous marrow transplant). In conclusion, D-CECaT is an effective initial cytoreductive regimen for advanced stage NB/PNET patients. Additional patients and studies are required to determine its use as an alternative to autologous bone marrow transplantation.

Luteinizing hormone regulation by sex steroids in men with germinal and Leydig cell tumours

OBJECTIVE

We examined the gonadotrophin secretion in patients with increased plasma concentrations of testosterone and oestradiol due to hCG-producing tumours.

DESIGN

Comparison of plasma gonadotrophin concentrations before and after stimulation by GnRH, in eight men with hCG-producing tumours resulting in increased testosterone and oestradiol plasma levels, and in 29 men with Leydig cell tumours resulting in increased oestradiol and normal to low testosterone plasma levels.

PATIENTS

Eight men with hCG-producing tumours (six with testicular tumours, two with extratesticular tumours), 29 men with Leydig cell tumours and 15 normal men. The six men with germinal cell tumours of the testis were studied before and after unilateral orchidectomy.

MEASUREMENTS

Plasma concentrations of hCG, testosterone and oestradiol were measured before and after intramuscular injection of hCG. LH and FSH were measured before and after intravenous injection of 100 micrograms GnRH.

RESULTS

Plasma LH and FSH concentrations were low in patients with germ cell tumours, who exhibited increased plasma testosterone and oestradiol concentrations, and were normal in patients with Leydig cell tumours, in whom oestradiol only was increased. Plasma LH and FSH were normalized in the five patients with successful (e.g. normal hCG, testosterone and oestradiol) unilateral orchidectomy. Basal plasma testosterone concentrations correlated positively (P < 0.01) with plasma oestradiol concentrations in patients with germ cell tumours and negatively (P < 0.01) in patients with Leydig cell tumours.

CONCLUSIONS

In patients with hCG-secreting germ cell tumours complete suppression of plasma LH and FSH with increased plasma concentrations of both testosterone and oestradiol are often discovered. No such gonadotrophin suppression is found in patients with Leydig cell tumours, but the negative correlation observed between plasma testosterone and oestradiol in these patients suggests a weak negative feedback effect of oestradiol on LH secretion, which cannot be demonstrated by basal LH measurements in plasma.

Serum concentrations of G-CSF during high-dose chemotherapy with autologous stem cell rescue

In 20 patients treated for refractory germ cell tumors, endogenous G-CSF levels were monitored before and after high-dose chemotherapy with autologous stem cell rescue (ASCR). An inverse relationship was found between endogenous G-CSF levels and peripheral blood leucocyte counts. G-CSF levels were not detectable prior to ASCR, but increased to a maximum of 3400 pg/ml (range 120-15000 pg/ml) thereafter. There was no relationship between peak G-CSF levels and time to engraftment. A decrease in G-CSF levels preceded engraftment and was paralleled by a rise of nadir leucocyte counts.

Alternating combination chemotherapy in patients with extragonadal germ cell tumors. A Southwest Oncology Group study

BACKGROUND

Extragonadal germ cell tumors (EGGCT) are uncommon, occur primarily in the mediastinum and retroperitoneum, and have been noted to have variable response rates to cisplatin-based chemotherapy regimens.

METHODS

The Southwest Oncology Group (SWOG) has completed a prospective trial of combination chemotherapy followed by surgical removal of residual disease in patients with this type of germ cell neoplasm. Chemotherapy consisted of alternating cycles of vinblastine, bleomycin, and cisplatin with etoposide, bleomycin, doxorubicin, and cisplatin. Four cycles of therapy were given followed by surgical removal of residual disease where appropriate.

RESULTS

Fifty patients were entered into the trial, and 41 were eligible, with 4 patients excluded by pathology review. Of the 41 eligible patients, 24 had mediastinal tumors, 15 had retroperitoneal tumors, and 2 had unknown primary sites. Complete response rates (chemotherapy +/- surgery) for the various sites were as follows: mediastinum, 18 of 24 (75%); retroperitoneum, 10 of 15 (67%); and unknown primary, 2 of 2 (100%). At 2 years, the disease-free survival rate for all patients was 87%. At a median follow-up of 6.8 years, 26 of 41 patients (63%) are alive. The toxicity of the chemotherapy regimen was substantial, with neutropenic fever developing in 17 of 41 patients (41%) during treatment. Additional side effects included nausea and vomiting (76%), mucositis (27%), and pulmonary toxicity (5%).

CONCLUSIONS

This prospective trial of chemotherapy in patients with EGGCT demonstrates a significant response in patients with either mediastinal or retroperitoneal tumors and a 4-year survival rate of more than 60% and 70%, respectively.

Alpha-fetoprotein half-life as a predictor of residual testicular tumor. Effect of the analytic strategy on test sensitivity and specificity

BACKGROUND

Alpha-fetoprotein (AFP) serum values after orchiectomy for testicular cancer can be used to predict the residual disease status. However, the optimal strategy for postorchiectomy marker analysis has not been studied. This article evaluated different analytic methods in an effort to identify the approach that provided the greatest sensitivity and specificity for occult residual disease.

METHODS

Statistical information on the AFP half-life (t1/2) derived from a clinical data set of 24 patients with AFP-secreting clinical Stage A testicular cancer and pathologically defined nodal status was incorporated into a mathematic model of postorchiectomy marker values as a function of residual tumor volume and time. The model was used to test the effect of various analytic strategies on detecting the residual tumor. The clinical data set then was analyzed to measure the effect of different analytic methods on the predictive value of the AFP t1/2.

RESULTS

In the model, the AFP t1/2 calculated from a single set of serum measurements obtained from the initial serum t1/2 was a poor predictor of disease status in patients with up to 40% residual tumor volume. Determined by the sequential addition of serum values obtained at normal t1/2 intervals, the AFP t1/2 improved in sensitivity but required up to seven serial values (35 days) to detect an abnormal t1/2 in patients with 10% residual tumor. By contrast, changes in the most recent interval t1/2 relative to the initial calculated t1/2 predicted the disease status in patients with 10% residual tumor after four t1/2 (20 days) and in patients with 1% residual volume after 35 days.

CONCLUSIONS

The use of this last strategy in the clinical data set improved both the sensitivity and specificity of the AFP t1/2 in predicting residual tumor relative to the other methods.

Update on malignant ovarian germ cell tumors

The evolution of therapy for malignant ovarian germ cell tumors has been one of the true success stories in oncology. This article reviews the major advances in this field, with emphasis on more recent developments. During the past two decades, the nomenclature and histologic criteria for the major histologic subtypes have been standardized. Although the role of secondary debulking is uncertain, it probably has merit in selected patients. The use of second-look laparotomy should be limited as much as possible. Chemotherapeutic regimens have evolved to the current "gold standard"--the combination of bleomycin, etoposide, and cisplatin, with overall disease-free survival rates of greater than 95%. For patients with metastatic dysgerminoma, chemotherapy has replaced radiation therapy as the treatment of choice. For those few patients who do not respond to first-line therapy, the combination of vinblastine, ifosfamide, and cisplatin is the most popular regimen for the subset of platinum-sensitive tumors. For those with platinum-resistant tumors, dose intensification with autologous bone marrow rescue or Phase II drugs are being investigated. Studies on the late effects of treatment reveal that reproductive potential can be preserved in most young patients. In summary, although the progress in this field has been phenomenal, small incremental advances will continue to occur during the 1990s.

Long term results of treatment in patients with extragonadal germ cell tumours

From 1979 to 1991 56 patients with extragonadal germ cell tumours (EGCT) received cisplatin based chemotherapy. From 16 patients with seminomatous EGCT 13 achieved complete remission (CR) with chemotherapy alone, 2 with additional radiotherapy with final CR rate of 94%. 5 (31%) patients developed relapses and at a median follow-up of 38 (5-103) months 11 (69%) are alive and 10 (62%) have no evidence of disease (NED). Only 7 patients with non-seminomatous EGCT reached CR with chemotherapy alone and 8 more with additional chemotherapy or surgery. Overall CR was 37% and 3 (20%) relapses have been observed. At a median follow-up of 26 (3-114) months 14 (35%) are alive and remain free of disease, 26 (65%) have died. By univariate analysis seminomatous EGCT patients had a significantly greater likelihood of achieving a CR, for non-seminomatous EGCT BEP induction chemotherapy was superior to VAB-6, and NSEGCT patients with serum levels > 2000 ng/ml had worse prognosis. Current staging systems are insufficient to predict the treatment outcome in EGCT.

Prognostic implications of tumour marker analysis in non-seminomatous germ cell tumours with poor prognosis metastatic disease

86 unselected patients with poor risk metastatic non-seminomatous germ cell tumours (NSGCT) treated from 1979 to 1990 at a single institution were reviewed with regard to the prognostic relevance of tumour marker analysis. The number of elevated tumour markers was not able to distinguish patients into prognostic subgroups. Pretreatment levels of human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP) and lactate dehydrogenase (LDH) did not have a significant influence on clinical outcome. HCG and AFP half-life analysis during the first chemotherapy cycles also failed to define prognostic subgroups. If early deaths within 90 days after the onset of chemotherapy were excluded, patients with a half-life of HCG decline greater than 3.5 days tended to have a poorer prognosis which did not reach significance.

Early intensified chemotherapy with autologous bone marrow transplantation in first line treatment of poor risk non-seminomatous germ cell tumours. Preliminary results of a French randomized trial

For 30 months we have treated 115 non-pretreated non-seminomatous germ cell tumour (NSGCT) patients with poor risk characteristics. Patients were allocated randomly to either arm A: NCI regimen with vinblastine, etoposide (E), bleomycin and double dose cisplatin (P2) (PVeBV) 3 or 4 cycles Q3W, or arm B: modified PVeBV protocol (bleomycin in continuous infusion) Q4W than a cycle of high-dose E + cyclophosphamide + P2 (PEC) and autologous bone marrow transplantation (ABMT). 114 patients are evaluable: 81 testicular, 18 mediastinal and 15 retroperitoneal primaries.

RESULTS

Arm A 57 patients: 7 patients did not complete the treatment. There were 15 failures, 9 PR, 33 CR. Seven patients relapsed. The 2-year survival is 82%. Arm B 57 patients: 16 patients did not complete the treatment. There were 26 failures, 7 PR and 24 CR. Nine patients relapsed. The 2-year survival is 60%. Both CR rates and survival are not statistically different. This trial fails to show any benefit of early intensified chemotherapy + ABMT to increase the CR and survival rates in poor risk NSGCT.

Prior chemotherapy does not prevent effective mobilisation by G-CSF of peripheral blood progenitor cells

In this study we demonstrate that the hemopoietic growth factor, G-CSF successfully mobilised progenitor cell populations into the peripheral blood in a population of patients despite intensive pretreatment with chemotherapy. Administration of G-CSF increased the numbers of peripheral blood progenitor cells (PBPC) by a median of 76-fold above basal levels. Maximal levels of PBPC were observed on days 5 and 6 after G-CSF treatment. In two patients a second cycle of G-CSF mobilised PBPC to levels comparable with those seen after the first cycle of G-CSF treatment. An earlier hemopoietic cell population (pre-CFC's) was also mobilised with levels increased up to 50-fold above basal levels. Using a standard mononuclear cell leukapheresis technique the PBPC were collected extremely efficiently (essentially 100%) and could be further successfully enriched by separation using a Ficoll gradient. For patients who underwent the optimal collection protocol (i.e. leukapheresis on days 5, 6 and 7) a total of 32 +/- 6 x 10(4) GM-CFC kg-1 were collected. The ability to mobilise PBPC using G-CSF alone and to successfully and efficiently harvest these cells has important implications for the future of transplantation and high dose chemotherapy procedures.

Surgical resection of solitary metastases after chemotherapy in patients with nonseminomatous germ cell tumors and elevated serum tumor markers

BACKGROUND

Chemorefractory metastatic germ cell tumors and elevated tumor markers generally indicate inoperable disease.

METHODS

Solitary metastases were resected in 15 patients who had a nonseminomatous germ cell tumor and an elevated alpha-fetoprotein (AFP) and/or human chorionic gonadotropin (HCG) serum level after treatment with cisplatin-based chemotherapy. Patients underwent resection for a residual mass after chemotherapy or for a new solitary metastasis after achieving a complete response (CR) to salvage chemotherapy.

RESULTS

Seven patients were disease-free after surgical resection alone. All five patients with an elevated HCG level had a relapse after surgery compared with 3 of 10 patients with only an elevated AFP level. Only 4 of 10 patients with a retroperitoneal metastasis had a relapse after surgery compared with 4 of 5 patients with visceral disease. Eleven of 15 patients overall were disease-free after surgery and subsequent chemotherapy after a relapse.

CONCLUSIONS

Surgical resection of a solitary metastasis despite elevated serum tumor markers should be considered in patients who have not had a durable CR to cisplatin-based chemotherapy.

Fasting plasma lipid measurements following cisplatin chemotherapy in patients with germ cell tumors

PURPOSE

Elevated total serum cholesterol levels have been reported recently in a group of patients with metastatic testicular cancer after treatment with cisplatin combination chemotherapy. We have studied the lipid profile of a similar group of patients in an attempt to confirm this observation.

PATIENTS AND METHODS

Fasting plasma lipid concentrations were measured in 47 patients with advanced germ cell tumors who were previously treated with a cisplatin combination chemotherapy. The values obtained for mean total cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride, apolipoprotein A1, and apolipoprotein B concentrations were compared with those obtained from a control group of 59 patients with germ cell tumors who were not treated with chemotherapy and with data from the New Zealand male population. Median time from the completion of chemotherapy to lipid measurement in the treated group was 50 months (range, 2 to 138 months). The median total dose of cisplatin given was 720 mg (range, 300 to 1,625 mg).

RESULTS

Mean total plasma cholesterol concentrations in the cisplatin group (5.87 mol/L) and the control group (5.70 mmol/L) did not differ significantly (P > .4). There was no significant difference for any of the variables between the chemotherapy and control groups and those of the New Zealand male population. There was a trend toward higher mean triglyceride concentrations in the chemotherapy group, but this did not reach significance.

CONCLUSIONS

We have not demonstrated an elevation in total plasma cholesterol after cisplatin chemotherapy as has been reported by previous investigators. Our results suggest that in these patients, cisplatin-containing combination chemotherapy is not associated with a significant adverse effect on plasma lipid profile.

Primary intracranial germ cell tumor. Pathologic study of 51 patients

Fifty-one primary intracranial germ cell tumors (GCT), including germinoma, teratoma, endodermal sinus tumor, choriocarcinoma and mixed GCT, were studied. The incidence of GCT in the surgically removed intracranial neoplasms was 11.1% for pediatric patients and 0.6% for adult patients. The age/sex of the patients and the location of the tumors were analyzed. Morphologic findings of these tumors were identical to that of their gonadal counterparts. Immunohistochemical studies showed that alpha-fetoprotein (alpha-AFP), human chorionic gonadotropin (HCG), and placental alkaline phosphatase (PLAP) were helpful, whereas carcinoembryonic antigen (CEA) and cytokeratin (CKER) were of little help in determining the diagnosis. Serum tumor markers, alpha-AFP and HCG, were helpful in recognizing GCT producing them. However, they could not be used for specific diagnosis because different tumors could have similar serum levels. Histopathologic study was handicapped by the small size of most specimens (which usually could not include all of the components if the tumor was a mixed GCT), but it was the only means for specific diagnosis.

Hypercholesterolemia after chemotherapy for testis cancer

PURPOSE

The study was designed to determine prospectively the prevalence of fasting serum lipid abnormalities in patients who were treated with cisplatin-based chemotherapy for germ cell tumors. We unexpectedly had demonstrated hypercholesterolemia in 20 of 30 nonfasting patients in a prior study of long-term toxicity of chemotherapy for germ cell tumors. The present study was designed to explore this phenomenon further.

PATIENTS AND METHODS

Seventeen unselected patients with biopsy-proven germ cell tumors, who underwent cisplatin-based chemotherapy and who had no prior history of cardiac disease nor known hypercholesterolemia, were studied. In addition to the standard staging tests, blood was drawn for a pretreatment fasting lipid screen, which included cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, and apolipoproteins A1, B, and (a). Repeat samples were drawn 24 hours after the administration of cisplatin and at intervals of 6 to 24 months after the completion of treatment.

RESULTS

Seven of 17 patients (41%) had higher than desirable levels of total serum cholesterol and low-density lipoprotein cholesterol. Two of them had normal levels before treatment, four had preexisting hypercholesterolemia that increased further, and one patient had an elevated pretreatment level that did not alter. Absolute increases in serum cholesterol were noted in 14 of 17 patients. No consistent patterns of change beyond the reference ranges were found for other serum lipids.

CONCLUSIONS

We have confirmed our initial observation that serum cholesterol increases in patients who received cisplatin-containing chemotherapy regimens for germ cell tumors. Further studies will be necessary to define whether other lipid abnormalities occur and the biologic significance of these findings.

Comparison between clinical and pathological staging in low stage nonseminomatous germ cell testicular tumors

Between January 1985 and December 1990, 208 consecutive patients with low stage nonseminomatous germ cell testicular tumors underwent retroperitoneal lymphadenectomy. In all of the patients the disease was staged with post-orchiectomy serum alpha-fetoprotein and beta subunit of human chorionic gonadotropin determinations, as well as chest x-rays and computerized tomography or magnetic resonance imaging of the abdomen and pelvis. Bipedal lymphangiography was performed in 139 patients. Of the 208 patients 173 (83%) had clinical stage 1 and 35 (17%) had low clinical stage 2 disease: 21 had tumors on radiographic imaging that were smaller than 2 cm. (clinical stage 2A) and 14 had tumors between 2 and 3 cm. (clinical stage 2B less than 3 cm.). Retroperitoneal metastases were found in 31 of 156 clinical stage 1 cancer patients (19.8%) with negative or normally decreasing serum tumor markers after orchiectomy, 15 of 16 (93.8%) with persistent positive markers, 8 of 14 clinical stage 2A cancer patients (57.1%) with negative or normally decreasing markers, all 7 stage 2A cancer patients with positive markers and all 14 clinical stage 2B cancer patients. Lymphangiography added little to the reliability of clinical staging. We conclude that due to the relatively low accuracy of clinical staging, retroperitoneal lymphadenectomy remains the treatment of choice for clinical stages 1 and 2A nonseminomatous germ cell testicular tumors with normal serum markers after orchiectomy.

Correlations between presence of spontaneous lesions of the pituitary (adenohypophysis) and plasma prolactin concentration in aged Wistar rats

The predictive value of elevated plasma prolactin concentrations for the presence of spontaneous pituitary lesions was studied in 40 male and 38 female Wistar (Cpb:WU) rats, all 30 months old. The pituitaries were examined light microscopically and stained for prolactin using immunohistochemical methods. Plasma prolactin concentrations were measured by radioimmunoassay. Pituitary lesions were classified on the basis of their morphology in hematoxylin and eosin-stained sections as foci of hypertrophic or hyperplastic cells and hemorrhagic, pleomorphic, or spongiocytic adenomas; no carcinomas were found. There were significantly (P = 0.001) more female than male rats with pituitary adenomas (58% females, 33% males) or without any pituitary lesions (21% females, 5% males); however, there were less female (21%) than male rats (63%) with foci of hyperplastic and/or hypertrophic cells but no adenomas in the pituitary (P = 0.001). Elevation of plasma prolactin concentration above the upper 99th percentile value in age-matched rats without lesions was predictive, but not conclusively, of the presence of pituitary hemorrhagic adenomas in both sexes. It was, however, not predictive of the presence of foci of hypertrophic or hyperplastic cells. Elevation of plasma prolactin concentration above 10 ng/ml in male and 60 ng/ml in female rats was conclusive for the presence of hemorrhagic adenomas. Using multivariate analysis, significant positive correlations (P less than 0.01) were found between plasma prolactin concentration and presence and size of hemorrhagic adenomas and their prolactin staining intensity (correlation coefficients between 0.392 and 0.652). Foci of hyperplastic cells stained positively for prolactin, whereas hypertrophic cell foci and pleomorphic and spongiocytic adenomas did not stain for prolactin. There were no correlations (coefficients of less than +/- 0.189) between plasma prolactin concentration and the presence of hypertrophic or hyperplastic cell foci and pleomorphic or spongiocytic adenomas in the pituitary. The morphologic criteria developed to distinguish spontaneous hypertrophic, hyperplastic, and neoplastic lesions of the rat pituitary corresponded well with their prolactin immunoreactivity and/or ability to elevate plasma prolactin concentration. These criteria constitute a biologically meaningful classification system for these rat pituitary lesions.