The opinion of the court was delivered by
Burling, J.This is a workmen’s compensation proceeding. The Workmen’s Compensation Division entered a judgment of temporary and permanent disability in favor of the petitioner. On appeal to the Passaic County Court, that court after a trial de novo on the record, entered a judgment affirming the Division. The respondent pursued a further appeal to the Appellate Division, which court affirmed the two lower tribunals. 47 N. J. Super. 90 (1957). We granted certification. 25 N. J. 405 (1957).
The issue concerns the scope of appellate review on factual findings in workmen’s compensation eases, and the applica*447tion of the appropriate review standard to the evidence in this ease.
On the scope of review the Appellate Division after an exhaustive analysis of the evidence held:
“It is settled that in review of workmen’s compensation cases great weight must be given to the judgment of the County Court. See Augustin v. Bank Building and Equipment Corp., 44 N. J. Super. 242, 243 (App. Div. 1957). We think this principle applies here, notwithstanding we find the ruling in the Division of no value because of absence of pertinent findings (other than the one unwarranted finding mentioned above). The County Court judgment will not be disturbed unless a study of the record indicates that the interests of justice plainly call for it. Ibidem; Mewes v. Union Bldg. & Construction Co., 45 N. J. Super. 88, 90 (App. Div. 1957). Ordinarily a fair criterion for that purpose is the existence of substantial evidence to support the findings underlying the judgment. Cf. Augustin v. Bank Building and Equipment Corp., supra (44 N. J. Super. at page 250) In the present case the medical factual issues are closely balanced, the predominance of the credible and logically persuasive proofs leaning, in our candid opinion, toward the position of the respondent. We think this is so particularly in respect to the issues as to whether the trauma affected the tumor itself, and, if it did or not, whether any increased rate of growth of the tumor resulted therefrom. But we cannot say that there was not substantial evidence in support of the conclusion of the County Court on these matters nor that the evidence contra overwhelmingly outweighed the supporting proofs.”
“Substantial evidence” is not the guiding criterion for appellate review of factual issues in workmen’s compensation proceedings in this State.
“It is the duty of the reviewing court to weigh the evidence and determine whether the claimant has sustained the burden of proof of an accident arising out of and in the course of his employment by a preponderance of the evidence. Full and respectful consideration of the views expressed, on both fact and law, by the Division and intervening appellate courts, shall be given.
R. R. 1:5—4(h) provides:
‘On a review of any cause, criminal or civil, involving issues of fact not determined by the verdict of a jury, new or amended findings of fact may be made, but due regard shall be given to the opportunity of the trial court to judge of Lhe credibility of the witnesses.’ Compare R. R. 4:88-13.
From a study of the entire record, it is the function and duty of the reviewing court to make a determination according to its considered judgment, and in doing so it is mandatory only to give *448due regard to the opportunity of the hearer of the evidence to judge of the credibility of the witnesses. A finding of fact in the Division or appellate courts does not lessen the duty of the appeal court to determine the facts and evaluate them by full investigation and analysis of the evidence so as to adjudge whether the general finding is consistent therewith, i. e., if upon such total consideration of the record and views expressed below, it is believed the judgment both in fact and the applicable law from which appeal is taken is correct, it should be affirmed; if the judgment is erroneous, it should be reversed or modified.” Russo v. United States Trucking Corp., 26 N. J. 430 (1958) decided this date.
Accordingly, we will weigh the evidence in order to determine whether the petitioner has sustained her burden of proof.
Petitioner, 46 years old at the time of the industrial accident, was a sheet wax packer. Her job entailed the piling and handling of ten-pound packages of sheet wax. On December 11, 1953, at approximately 11:15 A. m., one of the packages she was handling slid from atop of a pile and struck her on the left breast. The ensuing pain was immediate and severe, causing her to cease working for 10 or 15 minutes. During the lunch hour she examined the breast in the ladies’ room and observed a red bruise approximately two inches in diameter. Three days after the accident, on December 14, 1953, the petitioner first noticed a lump on her breast. The following day sire visited the plant physician, Dr. Bongiorno. Upon examination the doctor diagnosed the injury as a possible hematoma (tissue hemorrhage) and prescribed heat treatments.
Petitioner visited her family physician, Dr. Curtis, that same evening and he also recommended heat. Petitioner testified that the lump grew progressively larger and that she went to a Dr. Gallo who advised her that surgery would be necessary. She then returned to her family physician and upon his recommendation consulted Dr. Bender, a surgeon. Neither Dr. Curtis nor Dr. Gallo were called to testify at the hearing.
On March 11, 1954 the growth was diagnosed as cancerous and Dr. Bender performed a radical mastectomy (removal of left breast).
*449At the time of the hearing in May 1956 petitioner was in generally good physical condition and was working at a lighter job, having returned to work in August of 1954.
There was a general agreement of medical opinion at the hearing that the cancer pre-existed the accident of December 11, 1953. There was further agreement that it would have been necessary to remove the breast even if there had been no traumatic insult to the malignant area.
The only factual issues projected in this appeal is whether the trauma had aggravated, in the sense of accelerating the pre-existent condition. Inherent in this question is the further dispute concerning whether the trauma occurred to the cancerous area or to the healthy surrounding tissues. We might at this point add one caveat. On the question of the legal right to recover on the tendered hypothesis of aggravation, the Appellate Division held:
“* * * it may appear questionable, in terms of the theory of compensation recovery as based upon disability or death arising from accident, N. J. S. A. 34:15-12, 13, that a faster rate of tumor growth should be relevant to the right of recovery, where, as here, there is no dispute but that removal forthwith of the entire breast, with such impairment or disability as would have attended such surgery, would have been required even if the supposed trauma had never taken place. We are satisfied, however, that the controlling decisions pertinent to this question, though not directly in point, require the conclusion that if, in fact, the accident caused this tumor to grow faster than it would have otherwise, there must be recovery for all of the disability incidents of the disease notwithstanding that such increased rate of growth did not have anything to do with the medical decision to operate beyond making the necessity to do so manifest earlier than otherwise.”
Because of the view we take, as hereinafter developed, that the petitioner has failed to sustain her burden as to whether there was aggravation of the cancer in fact, we deem it inappropriate to pass on that question within the factual context of this case. We will assume, arguendo, that the statute contemplates a right to recover.
We turn now to an examination of the evidence in order to determine whether the petitioner has sustained the burden of proof on her proffered hypothesis that the acci*450dent of December 11, 1953 resulted in a more rapid enlargement of the tumor than if there had been no accident.
One of petitioner’s theories concerning aggravation resolved around the rapid growth of the tumor from the date of the accident until the date of surgery some three months later. When first discovered, she testified that the lump was the size of about “the tip of my pinky” and that by March 11, 1954, the date of surgery, it was the size of the end of her little finger (distal phalange). Petitioner estimated that it doubled in size during the three months prior to surgery. Her testimony was corroborated by that of several of her co-workers who testified that the growth grew in size. One co-worker compared its original size on December 14, 1953 with a “small hazel nut,” and prior to hospitalization as “a little larger than a nickel.”
The medical evidence indicates little increase in size. Dr. Bongiorno, the plant physician testifying for the respondent, estimated on palpation on December 15, the date of his examination, that the growth was 1 cm. ('2/5") to y2" in size. Dr. Bender, the operating physician estimated that on the date of surgery it was 1 cm. in diameter. Examination at biopsy indicated its size to be iy2 cms. by 1 cm., while pathological examination in the laboratory showed the actual size to be 1 cm.
Dr. Bender was the first medical witness called by the petitioner. He first saw the petitioner on March 2, 1954, but at that time she never gave him any history of the accident. It was only after her temporary sickness benefits had been stopped that petitioner, sometime in August or September, informed Dr. Bender of the accident. Dr. Bender testified in answer to an extended hypothetical question setting forth the lay testimony as follows:
“Well, it seems within reason that if this petitioner had a mass that gradually increased in size from the time of the injury until it was removed, a factor of trauma or injury might cause an acceleration of an unkind process.”
When queried on cross-examination as to whether a tumor of the type diagnosed in this case, i. e., an infiltrating *451carcinoma, might be expected to grow from the “tip of your pinky to 1 x 1% centimeters,” he responded “Yes.” And when asked: “Now, in this particular case is there any evidence either in the pathologic report or in your observations during surgery, that this woman’s cancer was, in fact, aggravated by trauma?” he answered “that would be a very, very difficult thing to say. If you want a positive answer, I would say no.” It is evident that much of Dr. Bender’s conclusions were based upon the lay estimates concerning the growth of the tumor. But the lay evidence on this point is at best tenuous, and at worst directly contradicted by the medical opinion concerning size. Dr. Eriedman, who testified for petitioner, indicated that if a trained observer measured on two separate occasions the same tumor he would be approximately 30% in error, while if two separate doctors measured the same tumor the error could be 60% and “if a lay person measured it two times the error would be more than 60%.”
While the medical estimates of the size in this case seem fairly constant, the lay testimony is highly disparate and does not form a firm base for opining. Dr. Eriedman’s testimony on the point is sufficiently indicative of the untrustworthiness of hasty lay estimates concerning size when experts may have a large area of error.
Dr. Eriedman, relying on petitioner’s testimony that there was no lump on the breast prior to trauma, her previous good health and the appearance of a black and blue mark two days after the accident, stated that “this traumatized tumor rapidly enlarged so that three days after the trauma a definite lump was felt for the first time.” When cross-examined as to how much more rapid the growth was than it would have been without trauma he answered “slightly” more rapid. Dr. Eriedman admitted that an “average” tumor without trauma would increase anywhere from 25% to 400% in size. While his belief as to the growth of petitioner’s tumor, based upon the lay observations, was that it increased five or six times in volume, we have previously alluded to the state of the proofs on the question of the increase in size *452of the tumor. Suffice it to say that the pillars of Dr. Friedman’s opinion have been considerably eroded by the weaknesses therein.
Respondent produced as a medical witness Dr. Yaguda, who had studied the pathological reports and made a microscopic examination of the tissue slides. Dr. Yaguda concluded that there was no evidence from which a deduction could be made that trauma had aggravated the cancerous condition. This opinion concerning the negative nature of pathological evidence was confirmed by Dr. Bender and Dr. Friedman. Dr. Yaguda testified that the specimen sections did not present “the picture of a rapidly growing tumor.” Dr. Hoffman, a cancer expert, testifying for respondent concluded that this was “a low grade, slowly growing type of cancer.” If one compares the estimate of Dr. Friedman that an untraumatized tumor could be expected to grow anywhere from 25% to 400%, with the estimate of Dr. Bongiorno as to the size of the growth on December 15, 1953 (1 cm. to %") and with the actual size established by the pathologist in the laboratory after surgery (1 cm.), the testimony of Dr. Yaguda and Dr. Hoffman are confirmed.
We next consider the crucial question of whether there was injury to the tumor itself by the accident rather than to the surrounding breast tissue.
Petitioner testified that the breast did not become black and blue until two days after the accident. On this factual premise it was Dr. Friedman’s opinion that the trauma was to the growth itself as distinguished from the healthy surrounding breast tissues. Dr. Friedman concluded that if the injury was to the surrounding tissue, ecehymosis (black and blue marks) would be apparent almost immediately. Since the ecehymosis did not appear for two days he deducted that this fact evidenced a rupture of the blood vessels in the cancer which was so deeply imbedded that it required several days for the hemorrhage to seep to the skin’s surface.
*453At the outset there is a direct conflict between the testimony of the petitioner and the plant physician, Dr. Bongiorno. Petitioner testified that the breast was discolored at the time of her examination by Dr. Bongiorno on December 15, 1953. The doctor, testifying for the respondent, claimed that the breast was not black and blue. In our opinion this controversy was conclusively resolved by the uncontradicted pathological findings of Dr. Yaguda concerning whether there had been any trauma to the tumor itself. Based upon his microscopic examination of the tissue slides Dr. Yaguda testified:
“also there is nothing in the tumor to indicate that there was any trauma to the tumor. If there had been any trauma to the tumor we should find evidence of hemorrhage there. There is no evidence of any blood pigment in the tumor to indicate that there had been any old hemorrhage, and there was no recent hemorrhage.”
and further that the revealing blood pigment might be evident for the life of the patient and that “it certainly would not disappear within less than 6 months or 7 months.” The microscopic examination was conducted some three months after the injury.
Removing from consideration all of the expert medical opinion revolving around whether trauma might or might not generally aggravate a cancerous condition, we feel that the medical testimony as it concerns the factual evidence in this case does not adequately support the petitioner’s thesis. Dr. Bender’s testimony is not particularly helpful to the petitioner. Aside from a presumptive attitude which he held that given a trauma a cancerous growth in the breast would probably be aggravated, he indicated that there was no evidence in the pathological report of the instant ease to support an aggravation by trauma and at one point admitted that a determination of the question of aggravation “would be based primarily upon your pathological record which you have there.” As previously indicated the pathologist, Dr. Yaguda, was of the opinion that the report did not show any evidence of aggravation. Dr. Eriedman’s *454testimony is largely dependent upon the lay estimates concerning the size of the tumor at various periods of time. Since he indicates that expert medical examiners may err from approximately 30% to. 60% in determining size, it perforce follows that lay estimates are totally inadequate.
Lastly, the state of the proofs on the question of trauma to the cancerous growth weigh heavily in support of the respondent’s hypothesis that the trauma, if it occurred, did not affect the tumor itself.
Eor these reasons, our independent examination of the record and evaluation of all the evidence leads to the general conclusion that the petitioner has failed to sustain the burden of proof imposed upon her.
The judgment below is reversed.