This is a medical malpractice action arising out of surgery performed by the defendant physician upon the plaintiff, Golonka, at Archbishop Bergan Mercy Hospital at Omaha, Nebraska, on August 24,1970. A jury returned a verdict for the defendant. Plaintiff appeals. We reverse.
Plaintiff first saw Dr. Gatewood professionally on June 5, 1970. Plaintiff showed him a lump on the back of his left knee which had been present for 8 years. Plaintiff told him he had pain in the left knee and ankle when pressure was applied to the mass and numbness on the lateral surface of the left leg and top of the foot. The plaintiff also was concerned about a growth on his face which the defendant diagnosed as a sebaceous cyst. Plaintiff testified he selected defendant as a surgeon because he knew defendant did a lot of work in the area of plastic surgery and he was concerned about having a scar on his face after the removal of the facial growth.
In diagnosing the growth in the back of plaintiff’s left knee, defendant took the history of the growth, examined plaintiff’s blood pressure, listened to his heart, and felt the swelling behind the knee and attempted to move it up and down. Based upon this examination, defendant diagnosed the lump as a Baker’s cyst. Plaintiff’s family physician at some time prior to June 1970, had also diagnosed it as a Baker’s cyst. Defendant recommended that the lump be surgicially removed. He indicated it was rather minor surgery and told plaintiff he would be back to work within 2 days.
When plaintiff entered the hospital he was asked *218to sign and did sign a printed form which in its material portion and with certain blanks filled in, stated: “1. I hereby authorize Doctor Gatewood and/or such assistants as may be selected by him to perform the following operation(s) excision of L neck cyst and Baker’s cyst - L knee upon the above named and/or any other therapeutic procedure that his judgment may dictate to be advisable for the patient’s well-being.
“2. The nature and purpose of the operation, the risks involved, and the possibility of complications have been explained to me. I acknowledge that no guarantee or assurance has been made as to the results that may be obtained.”
Golonka testified that no one gave any statement to him as to hazards or possible complications that might arise from the contemplated surgery other than defendant’s statement that it was minor surgery. Actually, the situation was such that plaintiff had every reason to believe he was subjecting his person to only minor surgery consisting of the removal of two cysts, one from his face and one from behind his left knee.
Plaintiff was given a general anesthetic and rendered unconscious at approximately 7:45 a.m. on August 24, 1970. The defendant was assisted in surgery by Dr. Monson. During the course of the operation defendant cut the skin and divided the fascia, the covering over the muscles, and exposed the mass behind the plaintiff’s left knee. As soon as defendant saw the growth he knew he was not dealing with a Baker’s cyst, but rather a tumor of the peroneal nerve, a major nerve affecting the lower extremities. It controls the flexion of the foot and sensation to the top and lateral surface of the foot.
Defendant had never before removed a tumor of the peroneal nerve. He and Dr. Monson discussed the problem for approximately 15 minutes. They agreed the tumor could not be shelled out or enucle*219ated. Defendant testified the nerve fibers appeared to be permeated throughout the tumor. He further testified: “I didn’t think that it should be enucleated. I thought this had a good possibility of being a malignant tumor, and therefore I didn’t want to seed the area.” He testified why he thought the tumor was probably malignant: ‘ ‘It was a very hard tumor. There was some redness on either end and over the top of it. And it was my judgment, after having seen many tumors over the years, that this had a good possibility of being malignant.”
Defendant and Dr. Monson agreed that the proper course of action was to excise the tumor mass. Prior to making this decision the doctors palpated the tumor and lifted it by lifting the nerve at both ends and rotating it. Defendant then proceeded to resect the tumor. The nerve was cut on each side of the tumor and the tumor removed. About 1 inch of the peroneal nerve was removed in the process.
Defendant then sent the tumor and nerve which he had removed to Dr. Moran who was waiting in pathology. Completion of the surgery was suspended until Dr. Moran could examine it. He called a few minutes later advising the tumor was benign with no evidence of malignancy present. Defendant testified the tumor was sent to pathology for examination after it was removed because if the tumor was indeed malignant he wanted to remove some more of the nerve to make sure he got all of it. After receiving Dr. Moran’s report, defendant then anastomosed the nerve in an end-to-end fashion.
When Golonka regained consciousness after surgery he found his leg fully encased in a plaster cast and flexed at an angle of about 70 degrees. It was at this time that he was first advised by Dr. Gatewood as to the nature of the surgery that had been performed upon him, namely surgical removal of a benign solitary neurilemoma, together with approximately 1 inch of the peroneal nerve. He was also *220told that as a result of this surgery he would be totally incapacitated for some weeks or months, and that he would have some permanent impairment of the function of his left leg in an as yet unknown degree.
At the time of the surgery, plaintiff was 27 years old, in good health, and physically active. During his high school and college years he had been an athlete. Following surgery, plaintiff experienced considerable pain in his lower left leg. After a long and painful convalescence, plaintiff reached a point where he could walk with his left leg in a brace. At the time of trial he still had pain in his leg. He also had atrophy and altered sensation on the left side of the calf which he described as feeling like “if you take the hair on your arm and just pull it. Then when it really hurts, it’s — sometimes it’s like pouring boiling water on it.” Prior to the operation, plaintiff was employed full time. He was forced to give up his job in March 1971. At the time of trial plaintiff was unemployed and was receiving a Social Security disability pension.
The only assignment of error we need to consider is plaintiff’s principal contention on appeal. The District Court erred in failing to submit to the jury the question of whether defendant was negligent in failing to conduct proper and adequate diagnostic tests to determine the true nature of the growth behind plaintiff’s left knee before undertaking surgery thereon. A specific request was made for this instruction, but it was not given in any form.
At the instruction conference plaintiff’s attorney made the following comments concerning the tendered instruction which was refused by the court: “I will limit my remarks to the instructions of the Court as prepared for submission viewed by me. My first exception is to instruction No. 2, and the instruction (sic) is in failing to include as part of the allegations of negligence submitted to the jury. The *221first allegation set forth in Plaintiffs petition as amended, to-wit: ‘In failing to conduct proper and adequate diagnostic tests to determine the true nature of the growth behind Plaintiffs left knee before undergoing surgery thereon,’ in this respect I claim no absolute magic for particular wording of the allegation, but my request is, and my exception is, that the Court should, either in the words I have suggested, or in some adequate and proper words, tender to the jury the question as to whether Defendant departed from the standard accepted medical practice in failing to do the most fundamental thing required of all surgeons, and that is to make a proper and adequate diagnosis of the tumor which he contemplates surgically removing before undertaking surgically (sic) thereon, particularly where the proposed surgery or the contemplated surgery involves permanent physical harm to the patient.”
It is the duty of the trial court to instruct the jury upon the issues presented by the pleadings and supported by the evidence. Laux v. Robinson, 195 Neb. 601, 239 N. W. 2d 786 (1976). Plaintiff specifically requested the jury be instructed that plaintiff claims the defendant was negligent ‘‘in failing to conduct proper and adequate diagnostic tests to determine the true nature of the growth behind plaintiff’s left knee before undertaking surgery thereon.” This was the theory on which plaintiff predicated and tried his case.
It is argued plaintiff is actually contending it was the duty of defendant to make a correct diagnosis, or he had the obligation to correctly ascertain the true nature of the growth behind the plaintiff’s left knee during the course of the surgery on August 24, 1970, when he became aware that the growth was not a Baker’s cyst as originally thought but a tumor of the peroneal nerve. It is suggested this should have been done prior to making the decision to surgically remove the tumor and a portion of the nerve. Plain*222tiff’s evidence may be so construed. There is evidence in the record if accepted by the jury which would sustain a finding that the defendant should have sent a sliver or wedge of the tumor to pathology before its removal.
Plaintiff’s tumor was one of the peroneal nerve. Dr. Moran, the pathologist used by defendant, gave the following description of these tumors: “A nerve has many nerve fibers. It’s like a telephone wire cable. And each fiber is covered by a layer of Schwann cells, and each fiber plus the Schwann cells is covered by a thin coating of connective tissue, neurogenic connective tissue, and then several of these are gathered in a bundle, and then several bundles are gathered together, but they are separated by this neurogenic connective tissue.
“So the neurofibroma arises from the connective tissue covering of a nerve, whereas a neurolemmoma (sic) or Schwannoma is a tumor of the Schwann cells alone. But most of these tumors are mixed. They have both elements, and we call them by the predominant element.” The plaintiff’s tumor, according to Dr. Moran, was a mixture of a neurilemoma and a neurofibroma, but was primarily a neurilemoma.
Dr. Lawrence J. Minette testified for the plaintiff by videotape deposition. He testified he studied the pathology slides prepared by Dr. Moran from the cross section cut from the tumor material removed from behind the plaintiff’s left knee. He also obtained four paraffin blocks prepared by Dr. Moran containing additional tumor material and from these he cut and prepared additional cross sections of the tumor. On this basis he testified that the tumor, in his opinion, could have been carefully dissected away from the nerve; that a neurilemoma is a known entity; and that “generally it is accepted that a neurolemmoma (sic) should be dissected from the nerve with full preservation, as much as possible, of *223the nerve and its function.” He gave his opinion that the defendant should have dissected the neurilemoma from the capsule and nerve with preservation of the nerve and nerve function, and that in accordance with accepted medical standards practiced in the Omaha community, resection or excision of the neurilemoma and nerve tissue, such as was done by the defendant, should not have been done. Dr. Minette admitted that in attempting to enucleate a neurilemoma some portion of the nerve fibers may be cut.
Dr. Tapas K. Das Gupta also testified for the plaintiff by deposition. Dr. Das Gupta reviewed the slides prepared by Dr. Moran and Dr. Minette, and also had additional tissue slides prepared from the original paraffin blocks made by Dr. Moran. He gave his opinion that the plaintiff’s tumor was dissectible without excision of the nerve. Dr. Das Gupta testified he was the coauthor of an article entitled, ‘‘Tumors of Peripheral Nerve Origin: Benign and Malignant Solitary Schwannomas” which appeared in scholarly journals in 1970, in which he stated: ‘‘The benign form of peripheral nerve tumors can be easily separated from the nerve trunk and there is no reason to resect any specified peripheral nerve.”
Defendant testified the nerve fibers appeared to be permeated by the tumor material and, based upon the pathological report, it still appeared that way to him. The defendant interpreted the pathology report to the effect that the tumor permeated the nerve fibers and separated them; that it was interspersed between the nerve fibers and into them; and that it would not have been possible, in his opinion, to dissect them out. Dr. Monson testified the nerve went through the mass and was not identifiable. Dr. Moran testified the tumor conformed to the general description of a neurilemoma found in textbooks, where the nerve fibers are described as interspersed throughout the tumor.
*224Dr. Moran testified on cross-examination he would normally think that an 8-year-old fully encapsulated tumor was probably benign. The question asked him was: “Assume from the history of the patient
from whom this tumor was removed that he had this growth behind his knee for eight years, and assume further that that tumor was encapsulated and of the size that you saw it to be. A. Well, you would normally think it was benign.”
Dr. Browne, defendant’s principal expert witness, gave similar testimony on cross-examination. When he was pinned down to probabilities, he testified: “I would think in those circumstances if you were making a judgment one way or the other, I would say it was probably benign. I would say that.”
The proper procedure to follow, the plaintiff suggested, was to do a wedge biopsy on the tumor to determine conclusively whether it was benign or malignant prior to making a determination to excise it and a portion of the nerve. Dr. Walburn testified that, in his opinion, the standard of medical practice prevailing in Omaha in 1970 required that a frozen section of the tumor be taken before causing permanent damage to the nerve by surgery.
Dr. Browne testified that a biopsy is a standard recognized diagnostic technique available to a physician for arriving at an accurate diagnosis of the nature of a tumor prior to surgery. Defendant acknowledged that a biopsy can be made at the time of surgery to determine if a growth is benign or malignant.
Dr. Moran testified the tumor was of sufficient size to permit the taking of a wedge biopsy. If that had been done he would have used the same procedures he used in analyzing the whole tumor..
Defendant testified he was concerned about seeding the area with malignant cells. Dr. Walburn agreed that the seeding of malignant cells is a danger to be considered in all frozen sections. He also *225acknowledged that any time one surgically invades a malignant tumor, such as in conducting a wedge biopsy or attempting to enucleate, there is a substantial risk of seeding the area with malignant cells.
Plaintiff’s theory of the case as set forth in his tendered instruction and the evidence was not presented to the jury. The only issues submitted were the excision of 1 inch of nerve tissues when it was not necessary or proper to do so; failing to advise the plaintiff as to the risk inherent in the surgery; defendant’s lack of experience with the removal of neurilemomas; and in failing to make the disclosures a reasonably careful medical practitioner in the same circumstances would have made.
A litigant is entitled to have the jury instructed as to his theory of the case as shown by the pleadings and evidence, and a failure to do so is prejudicial error. Zavoral v. Pacific Intermountain Express, 178 Neb. 161, 132 N. W. 2d 329 (1965). While much evidence was adduced on the failure to properly diagnose as evidence of negligence, this issue was removed from the jury’s consideration by the failure to give the tendered instruction.
Malpractice may consist in the lack of skill or care in diagnosis as well as in treatment. We said in Cook v. Moats, 121 Neb. 769, 238 N. W. 529 (1931): “To make a skilful and careful diagnosis of the trouble from which the plaintiff is suffering is one of the fundamental duties of a physician, and if he fails in that regard as well as in the application of improper treatment, and damages result therefrom, he must answer therefor.”
In In re Estate of Johnson, 145 Neb. 333, 16 N. W. 2d 504 (1944), we said: “The rule is: ‘A patient is entitled to an ordinarily careful and thorough examination, such as the circumstances, the condition of the plaintiff, and the physician’s opportunities for examination will permit, and, while he does not in*226sure the correctness of his diagnosis, a physician or surgeon is required to use reasonable skill and care in determining through diagnosis the condition of the patient and the nature of his ailment, and is liable for a failure, due to a want of the requisite skill or care, to diagnose correctly the nature of the ailment, with resulting injury or detriment to the patient.’ ”
In the instant case, considering the fact defendant had had no previous contact with a tumor of the peroneal nerve, the instruction was essential for plaintiff’s theory of the case. There was testimony of experts that a proper diagnosis was not made. The jury, if properly instructed, could have found defendant was negligent in excising the tumor and a part of the peroneal nerve before a test was made. In In re Estate of Johnson, supra, we said: “It has repeatedly been held that ‘there is a fundamental difference in malpractice cases between mere errors of judgment and negligence in previously collecting data essential to a proper conclusion, * * * thus, if he omits to inform himself, * * * as to the facts and circumstances, and injury results, he is not relieved of liability for errors of judgment.’ ’’
The failure to give the tendered instruction was prejudicially erroneous. We reverse the judgment herein and remand the cause for a new trial.
Reversed and remanded.