Citation Nr: 1319486 Decision Date: 06/17/13 Archive Date: 06/27/13 DOCKET NO. 06-36 593 ) DATE ) ) On appeal from the Department of Veterans Affairs (VA) Regional Office (RO) in New York, New York THE ISSUE Entitlement to service connection for squamous cell carcinoma of the left lower lip. REPRESENTATION Appellant represented by: The American Legion ATTORNEY FOR THE BOARD S. Higgs, Counsel INTRODUCTION The Veteran had active service from January 1966 to February 1968. This matter comes to the Board of Veterans' Appeals (Board) on appeal from a rating decision dated in May 2006 by the Department of Veterans Affairs (VA) Regional Office (RO) in Muskogee, Oklahoma. A review of the Virtual VA paperless claims processing system does not reveal any additional documents pertinent to the present appeal. The Board remanded the case to the RO in November 2010 for additional development of the record. In January 2013, the Board sought an expert opinion from a Veterans Health Administration (VHA) physician. The opinion obtained, dated February 2013, has been provided to the Veteran and his representative with an additional 60-day period to provide further evidence and/or argument. See 38 C.F.R. §§ 20.901-20.903. FINDINGS OF FACT 1. The Veteran is not shown to have been exposed to mustard gas during his period of active service. 2. The Veteran is not shown to have manifested squamous cell carcinoma of the left lower lip during active service or for many years thereafter. 3. The currently demonstrated residuals of squamous cell carcinoma of the left lower lip is not shown to be due to the episode of necrotizing ulcerative gingivitis treated in service or another event or incident of the Veteran's period of active duty. CONCLUSION OF LAW The Veteran's disability manifested by the residuals of squamous cell carcinoma of the left lower lip is not due to disease or injury that was incurred in or aggravated by active service, nor may it be presumed to have been incurred therein. 38 U.S.C.A. §§ 1110, 1112, 5107 (West 2002); 38 C.F.R. §§ 3.102, 3.303, 3.307, 3.309(a), 3.316 (2012). REASONS AND BASES FOR FINDINGS AND CONCLUSION Duty to Notify and Assist The Veterans Claims Assistance Act of 2000 (VCAA) describes VA's duty to notify and assist claimants in substantiating a claim for VA benefits. 38 U.S.C.A. §§ 5100, 5102, 5103, 5103A, 5107, 5126 (West 2002); 38 C.F.R. §§ 3.102, 3.156(a), 3.159 and 3.326(a) (2012). Upon receipt of a complete or substantially complete application for benefits, VA is required to notify the claimant and his or her representative, if any, of any information, and any medical or lay evidence, that is necessary to substantiate the claim. 38 U.S.C.A. § 5103(a) (West 2002); 38 C.F.R. § 3.159(b); Quartuccio v. Principi, 16 Vet. App. 183 (2002). Proper VCAA notice must inform the claimant of any information and evidence not of record (1) that is necessary to substantiate the claim; (2) that VA will seek to provide; and (3) that the claimant is expected to provide. 38 C.F.R. § 3.159(b)(1). A June 2005 VCAA notice letter explained the evidence necessary to substantiate the claim for service connection for squamous cell carcinoma. This letter also informed the Veteran of his and VA's respective duties for obtaining evidence. See 38 U.S.C.A. § 5103(a); 38 C.F.R. § 3.159(b). The June 2005 VCAA notice letter from VA was provided prior to initial adjudication of the Veteran's claim. See Pelegrini v. Principi, 18 Vet. App. 112 (2004). In addition, the June 2005 VCAA letter requested information specific to his claimed exposure to mustard gas or Lewisite, such as his claimed dates of exposure, where the exposure took place, what type of chemical he believed was used, and the unit to which unit he was assigned. Although the VCAA letter did not explain how a disability rating is determined for a service-connected disorder and the basis for determining an effective date upon the grant of any benefit sought, in compliance with Dingess/Hartman v. Nicholson, 19 Vet. App. 473 (2006), this omission is no more than non-prejudicial, harmless error, for the reason that the Board finds that the preponderance of the evidence is against the award of service connection. As a result, the claim is denied and any issue as to assignment of effective dates or disability ratings is rendered moot. With regard to the duty to assist, the claims file contains service treatment records, reports of VA post-service treatment, reports of private treatment, reports of VA examinations and a VHA medical opinion. VA had sought the Veteran's SSA disability records but the Veteran has indicated that he had been denied SSA disability benefits for lack of an adequate work history and that SSA would not have records relevant to his VA disability claim. See 38 U.S.C.A. § 5103A(a)-(d). With respect to the VA examination, when VA undertakes to provide a VA examination or obtain a VA opinion, it should ensure that the examination or opinion is adequate. As noted, in January 2013, the Board sought an expert opinion from a Veterans Health Administration (VHA) physician. See 38 C.F.R. § 20.901. There is no requirement that a medical examiner comment on every favorable piece of evidence in a claims file. Monzingo v. Shinseki, 26 Vet. App. 97, 105 (2012); see Acevedo v. Shinseki, 25 Vet. App. 286, 293 (2012) (noting that the law imposes no reasons-or-bases requirement on examiners). Examination reports are adequate when they sufficiently inform the Board of a medical expert's judgment on a medical question and the essential rationale for that opinion. Monzingo, 26 Vet. App. at 105. As will be discussed, the VHA physician provided a thorough and well-researched opinion, based on an accurate factual review of the evidence of record, medical research, and his clinical experience. The opinion's focus was on whether the Veteran's post-service cancer of the left lower lip was related to his dental disease during active service. The explanations for the opinions provided included a complete rationale. Accordingly, the Board finds that the VHA medical opinion provided in this matter is adequate for purposes of adjudication of the Veteran's claim, and additionally finds the opinion to be of a very high probative value. This matter was remanded by the Board in November 2010 for VA to obtain additional records of treatment and SSA disability records. In a January 2011 letter, however, the Veteran wrote that he was not in receipt of SSA disability benefits and had been denied such benefits for lack of a sufficient work records (rather than on the basis of whether he was disabled). Thus, he indicated, he did not know of any SSA records that would be relevant to his claim. Additionally, the Veteran's VA records of treatment up to the year 2007, as would be potentially relevant to the diagnosis, treatment and etiology of his cancer of the left lower lip, have been obtained. (The excision of the cancer occurred in June 2005.) An October 2007 record states, for example, that the Veteran "refused to accept the idea presented to him by writer and others that cigarette smoking was also at least partially to blame" for the squamous cell carcinoma. Because this does not exclude the possibility that in-service dental disease, referenced in the service treatment records as trench mouth and necrotizing ulcerative gingivitis, to include in the area of the left lower lip, might also have been partially to blame, a VHA medical opinion was obtained in this matter, as discussed. For these reasons, the Board finds that the RO has achieved substantial compliance with the Board's remand instructions. Stegall v. West, 11 Vet. App. 268, 271 (1998). Although later VA treatment records may have been available, there is no indication or contention that such records, of VA medical treatment over two years after excision of the left lower lip cancer, would have been relevant to whether the cancer was a result of any incident of active service. Based on the foregoing, the Board finds that all relevant facts have been properly and sufficiently developed in this appeal and no further development is required to comply with the duty to assist the Veteran in developing the facts pertinent to his claim. Essentially, all available evidence that could substantiate the claim has been obtained. There is no indication in the claims file that there are additional available relevant records that have not yet been obtained. Merits of the Claim The Veteran seeks service connection for squamous cell carcinoma of the left lower lip, or current residuals after its excision, claimed on the basis that it is a result of in-service exposure to mustard gas or Lewisite, or alternatively, on the basis that it was the result of documented in-service dental disease in the area of the left lower lip. Service connection may be granted for a disability resulting from disease or injury incurred in or aggravated by active service. 38 U.S.C.A. §§ 1110, 1131. Service connection connotes many factors but basically it means that the facts, shown by evidence, establish that a particular injury or disease resulting in disability was incurred coincident with service in the Armed Forces, or if preexisting such service, was aggravated therein. This may be accomplished by affirmatively showing inception or aggravation during service or through the application of statutory presumptions. Each disabling condition shown by a veteran's service records, or for which he seeks a service connection must be considered on the basis of the places, types and circumstances of his service as shown by service records, the official history of each organization in which he served, his medical records and all pertinent medical and lay evidence. Determinations as to service connection will be based on review of the entire evidence of record, with due consideration to the policy of the Department of Veterans Affairs to administer the law under a broad and liberal interpretation consistent with the facts in each individual case. 38 C.F.R. § 3.303(a). Certain chronic disabilities are presumed to have been incurred in or aggravated by service if manifest to a compensable degree within one year of discharge from service. 38 U.S.C.A. §§ 1101, 1112, 1113, 1137; 38 C.F.R. §§ 3.307, 3.309(a). The disability at issue in this case, squamous cell carcinoma of the lip, is a malignant tumor, and therefore is a "chronic disease" listed at 38 U.S.C.A. § 1101 and 38 C.F.R. § 3.309(a). 38 C.F.R. § 3.316, pertaining to claims based on chronic effects of exposure to mustard gas and Lewisite, provides as follows: (a) Except as provided in paragraph (b) of this section, exposure to the specified vesicant agents during active military service under the circumstances described below together with the subsequent development of any of the indicated conditions is sufficient to establish service connection for that condition: (1) Full-body exposure to nitrogen or sulfur mustard during active military service together with the subsequent development of chronic conjunctivitis, keratitis, corneal opacities, scar formation, or the following cancers: Nasopharyngeal; laryngeal; lung (except mesothelioma); or squamous cell carcinoma of the skin. (2) Full-body exposure to nitrogen or sulfur mustard or Lewisite during active military service together with the subsequent development of a chronic form of laryngitis, bronchitis, emphysema, asthma or chronic obstructive pulmonary disease. (3) Full-body exposure to nitrogen mustard during active military service together with the subsequent development of acute nonlymphocytic leukemia. (b) Service connection will not be established under this section if the claimed condition is due to the veteran's own willful misconduct (See § 3.301(c)) or there is affirmative evidence that establishes a nonservice-related supervening condition or event as the cause of the claimed condition (See § 3.303). Service connection may be granted for any disease diagnosed after discharge, when all the evidence, including that pertinent to service, establishes that the disease was incurred in service. 38 C.F.R. § 3.303(d). Generally, in order to prevail on the merits on the issue of service connection, there must be competent evidence of current disability; of in-service incurrence or aggravation of a disease or injury; and a nexus between the claimed in-service disease or injury and the present disability. Shedden v. Principi, 381 F.3d 1163 (Fed. Cir. 2004). The requirement that a current disability be present is satisfied when a claimant has a disability at the time a claim for VA disability compensation is filed or during the pendency of that claim, even in cases where the disability resolves prior to the Secretary's adjudication of the claim. McClain v. Nicholson, 21 Vet. App. 319, 321-323 (2007). Lay statements may serve to support a claim for service connection by supporting the occurrence of lay-observable events or the presence of disability, or symptoms of disability, susceptible of lay observation. Davidson v. Shinseki, 581 F.3d 1313 (Fed. Cir. 2009); Jandreau v. Nicholson, 492 F.3d 1372 (Fed. Cir. 2007). Although lay persons are competent to provide opinions on some medical issues, see Kahana v. Shinseki, 24 Vet. App. 428, 435 (2011), as to the specific issue in this case, whether squamous cell carcinoma of the lip manifested and diagnosed many years later is related to a disease or injury during active service, falls outside the realm of common knowledge of a lay person. See Jandreau v. Nicholson, 492 F.3d 1372, 1377 n.4 (Fed. Cir. 2007) (lay persons not competent to diagnose cancer). The standard of proof to be applied in decisions on claims for veterans' benefits is set forth at 38 U.S.C.A. § 5107. A claimant is entitled to the benefit of the doubt when there is an approximate balance of positive and negative evidence. See 38 C.F.R. § 3.102. When a claimant seeks benefits and the evidence is in relative equipoise, the claimant prevails. See Gilbert v. Derwinski, 1 Vet. App. 49 (1990). The preponderance of the evidence must be against the claim for benefits to be denied. See Alemany v. Brown, 9 Vet. App. 518 (1996). As noted, the Veteran served on active duty from January 1966 to February 1968. The service treatment records show that, in March 1967, the Veteran was seen for "[n]ecrotic areas --vesicles, multiple areas soft tissue, inner side of lower lip opposite [teeth] numbers 22, 23, 24." The provisional diagnosis was that of apthous stomatitis. A clinician to whom the Veteran was referred in March 1967 noted a history of traumatic injury in the areas of multiple ulcerations (about two weeks) which "appear[ed] to be 'canker sores.'" The clinician to whom the Veteran was referred in March 1967 also noted that there were no lesions elsewhere. The March 1967 treatment records show that the described lesions as being on the inside of the left lower lip. (See service treatment records, and February 2013 VHA medical opinion, below.) A January 26, 1968, in-service dental treatment record described the Veteran as having scaling and indicated that the Veteran was treated with gentian violet for localized "NUG"-an abbreviation for necrotizing ulcerative gingivitis (see February 2013 VHA medical opinion, below). He was additionally placed on a saline rinse. A February 1968 service discharge examination report indicated that clinical evaluation of the Veteran's lungs, chest, head, face, neck, scalp, mouth and throat were normal. A record of dental treatment on February 15, 1968, the day before the Veteran was discharged from active service, included a diagnosis of Vincent's stomatitis, which was the eponym for necrotizing ulcerative gingivitis and the medical term for trench mouth. (See February 2013 VHA medical opinion.) The post-service treatment records reflected a long history of smoking and numerous dental and periodontal difficulties. In connection with private treatment in May 2005, cancer of the Veteran's left lower lip was suspected. A May 18, 2005, diagram showing the area of a biopsy site was associated with the claims file. A May 2005 biopsy report was also included in the claims file. In June 2005, the Veteran was determined to have squamous cell carcinoma of the left lower lip, which was surgically removed. The operative report and post-surgical pathology report are in the claims file. The post-surgical diagnosis was that of squamous cell carcinoma of the left aspect of the lower lip. The June 2005 private operative report indicated that the Veteran underwent an excision of squamous cell carcinoma, left lower lip, by wedge excision. A National Personnel Records Center NA Form 3101 dated in July 2005 indicated that a search of the Mustard Gas Data Base revealed that there were no records to show that the Veteran had been exposed to mustard gas. In February 2006, the Veteran submitted a completed VA Questionnaire for Exposure to Mustard Gas or Lewisite. He indicated that he was claiming to have squamous cell carcinoma of the lower lip as a result of the claimed exposure. He described his unit as 3rd Battalion, 6 Marines, Fleet Marine Force, L Company. With respect to number of exposures, he wrote that "[he thought] twice." With respect to the date of exposure, he wrote that "[he could not] remember exact dates, but had to be between Jan-June 1966." He described the exposure as having occurred at Camp Lejeune, North Carolina. As to the type of activity during which the exposure occurred, he wrote, "experiment, [he thought]." A February 2006 e-mail from the VA manager of the Mustard Gas section of the Compensation and Pension Service stated that the Veteran was not in the Department of Defense database of mustard gas participants. The Veteran's service personnel records and service treatment records have been obtained and associated with the claims file and contain no reference to mustard gas or Lewisite exposure. In November 2006 the Veteran wrote: 1967 -- a test was give to all men in 3/6, the test was a Q-tip with mustard gas liquid form. The forearm about 4" up from the wrist, left arm about a 3" square area, was shaved and wiped down with alcohol or ether for preparation, th[e]n this swab of liquid mustard gas was rubbed on the pre-shaven area, sleeves of shirts were short at the time. We were told that this was a test; therefore we signed waiver slips [he thought]. We were then told that this would blister up and [not to] break it, they gave us the rest of the day off. We then went to an E.M.C. club for a few beers, some joker came through about 3 hours later and slammed all the bubbles down, which forced them to break and spread. We told the medic the next day what had happened and he wrote down what we said. Meanwhile, we did have extra bubbles appear for the next 2 or 3 days. End of contaminations, we were supposed to avoid sunlight and salt water so they said. A January 2007 VA examiner recounted, as part of the history provided by the Veteran, the incident in which he and others were exposed to what he thought was mustard agent as part of a training or testing program. The Veteran stated that the agent was placed in a liquid form on their forearms, and they then were allowed off duty for the rest of the day. He related that, while in the enlisted men's club someone came through and broke the blisters that that had formed on their arms. The Veteran told the January 2007 VA examiner that he felt that he was exposed to mustard agent during this testing. He also described having very little dental attention in service and indicated that, after service, he very seldomly received dental care. At the time of the VA examination in January 2007, the examiner reviewed the Veteran's service treatment records and the records of treatment thereafter. The examiner examined the Veteran, took a detailed history from him, and reviewed the relevant evidence in the claims file, as was evident from the VA examination report. He diagnosed the Veteran as having advanced periodontal disease likely the result of plaque accumulation, lack of professional dental treatment, and cigarette smoking. The examiner noted that the Veteran had a history of squamous cell carcinoma of the left lower lip, which was excised in 2005. The examiner further noted that the Veteran had some sensory loss and loss of function as the result of the surgery to remove the lesion. The examiner noted that the Veteran felt that his exposure to mustard gas agent during active service was the cause of his cancer that had been removed. The examiner added that the Veteran had an incident of apthous ulcerations while in the military. The examiner stated that there was no evidence that apthous ulcerations were a precursor to squamous cell carcinoma. Therefore, he reasoned, the squamous cell carcinoma was not caused by or the result of the previous apthous ulcerations that were diagnosed in the military. The examiner further recounted that he had no knowledge of mustard agents and their causing squamous cell carcinoma and any statement he made as to any such cause and effect would be speculation. In May 2007, the VA examiner provided an addendum opinion pertaining to post-service dental and periodontal problems, but not to the matter currently on appeal, the incurrence of squamous cell carcinoma of the lower lip. The opinion is not relevant to the current appeal. In a statement dated in September 2007, the Veteran's representative noted that the Veteran asserted that, while going through training with the United States Marine Corps, there was a time where his entire unit was required to go through some sort of chemical training. The Veteran recounted being required to enter an enclosed chamber where the trainer placed a drop of liquid chemical on his forearm (from which he still had a scar from a chemical burn). The representative noted that this chemical was what the Veteran claimed to have been mustard gas. The representative added that the Veteran's military records did not show this training or any other type of chemical training. The representative asserted that this lack of records did not mean that the event did not occur. In February 2013, the Board obtained a Veterans Health Administration (VHA) medical opinion in this matter. The VHA physician, a staff physician practicing in the area of hematology/medical oncology, reported as follows: 1. Oral Health while in the military a. In March 1967 he was referred for "Necrotic areas-vesicles, multiple areas of soft tissue, inner side of lower lip opposite [teeth] (brackets in original VHA opinion) numbers 22, 23, 24." Upon evaluation they were thought to be "can[k]er sores," also known as apthous ulcers. b. On January 26, 1968 records indicate that he was being treated for localized "NUG," or necrotizing ulcerative gingivitis. c. On February 15, 1968 records indicate that he was diagnosed with Vincent's stomatitis. This is the eponym for necrotizing ulcerative gingivitis. 2. Squamous cell carcinoma of the lip a. A History and Physical from September 15, 2004 list[ed] him as a 4-pack per day smoker b. A note from May 18, 2005 describes a left lower lip ulceration present for about 14 months. The drawing indicates that it was on the exterior surface of the lip rather than on the oral mucosa. c. A biopsy from May 18, 2005 diagnosed this lesion as a squamous cell carcinoma. d. The squamous cell carcinoma was resected June 17, 2005 with negative margins. [The medical specialist] was asked to address the following question: Was it at least as likely as not (is there a 50 % or greater probability) that the Veteran's post-service cancer of the left lower lip [was] causally related to the [lesions of the] oral mucosa or other disease process that was present during the period of active service? [The medial specialist's] conclusions [were] based upon the following findings: 1. The main risk factors for squamous cell carcinoma of the lip [were] tobacco usage, alcohol abuse, chronic sun exposure, and betel quid chewing (Oral Oncology 2009; 4: 309). This pattern ha[d] been observed in a wide variety of ethnic and geographic locations, including Europe (Anticancer Res. 2012; 32:1543-6), Brazil (Med Oral Patol Oral Cir Bucal. 2011;16;e757-62) and Mexico (Oral Oncol. 2004;40;992-9). In particular, smoking [was] strongly associated with the development of squamous cell carcinomas of the head and neck, including the lip. Patients with heavy smoking histories ha[d] a [six to thirteen]-fold increased risk of head and neck cancers compared to their non-smoking peers (Cancer 1998;82:1367; Eur J Cancer B Oncol. 1995;31B:301). For fair-skinned patients, chronic sun exposure [was] also a leading risk factor of lip cancer (Br J Dermatol. 2010;162;1103-9). 2. Necrotizing ulcerative gingivitis (NUG, aka "trench mouth") ha[d] not been associated with the development of squamous cell carcinomas of the lip. [He] performed a primary literature search combining a variety of terms including "necrotizing ulcerative gingivitis," "trench mouth," "Vincent's disease," "cancer," "neoplasm," "squamous cell carcinoma," and "carcinoma." No papers described NUG as a pre-malignant condition. Periodontal disease [was] considered a "speculative" risk factor of squamous cell carcinoma of the oral cavity (Oral Oncology 2009; 4: 309). There [were] limited data suggesting that periodontal disease [might] be a weak risk factor for the development of tongue cancer, but not squamous cell carcinomas of the lip (Arch Otolaryngol Head Neck Surg. 2007;133;450; Oral Oncol. 1998;34:284). 3. Apthous ulcers [were] not considered pre-malignant lesions (J Oral Pathol Med. 2011;41:577-83). Based upon his extensive tobacco usage and the lack of a clear correlation between necrotizing ulcerative gingivitis and squamous cell carcinoma of the lip, [the medical specialist] believed that there [was] less than a 50% chance that the oral disease documented during his service was the cause of his squamous cell carcinoma of the lip. The Board finds that, to the extent that the Veteran is not shown to have had full-body in-service exposure to mustard gas, the presumption of service connection for squamous cell carcinoma of the left lower lip, pursuant to 38 C.F.R. § 3.316(a)(1), is not established in this case. By the Veteran's own account, the claimed exposure with some form of liquid agent took place on a limited area of one forearm and only resulted in residual scar in that region. Full-body exposure generally contemplates exposure to actual mustard gas in testing of protective equipment or clothing in field or chamber tests, rather than under the condition described by the Veteran. In particular, the regulations drafted and codified at 38 C.F.R. § 3.316 were implemented with consideration of the fact that some service personnel were experimentally exposed to mustard gas during full-body field or chamber tests of protective equipment and clothing conducted at the Naval Research Laboratory, located at Edgewood Arsenal, between 1943 and 1945. Similar testing might have been conducted at other locations during World War II. These World War II tests were classified, participants were instructed not to discuss their involvement, and medical records associated with the tests are generally unavailable. No long-term follow-up examinations were conducted. See Pearlman v. West, 11 Vet. App. 443 (1998), quoting 57 Fed. Reg. 1699 (1992) (proposed rule) and 57 Fed. Reg. 33876 (1992) (final rule). In this case, the evidence shows that the Veteran's squamous cell carcinoma of the left lower lip was first diagnosed in 2005. There is no contention or evidence to the contrary. Accordingly, a presumption of service incurrence for squamous cell carcinoma pursuant to 38 C.F.R. §§ 3.307 and 3.309(a), as a chronic malignant tumor that was manifested to a degree of 10 percent disabling or greater within one year after discharge from service, is not established. The Board finds the Veteran's statements to be credible and reliable generally as to the nature and extent of his exposure. As noted, in February 2006, the Veteran wrote that the exposure had to have occurred between January 1966 and June 1966, and that he thought there had been two exposures. In November 2006, he wrote that the exposure occurred in 1967 and only described one exposure. In November 2006, he wrote that the liquid mustard was applied by a Q-tip rubbed on a pre-shaven area on his arm. In September 2007, the Veteran's representative related that the exposure was during chemical training, not testing; that it occurred in a closed chamber; and that the trainer placed a drop of liquid chemical on his forearm, not that it was applied by a Q-tip on a pre-shaven area. Even with the inconsistencies as to the time frame and the nature of the claimed exposure, the Board finds that the Veteran's account serves to show that he did not have full-body exposure to mustard gas as comtemplated by the applicable regulation. Moreover, and quite significantly, the official sources have confirmed that the Veteran had not been identified as a participant in mustard gas testing. As a result, the Board finds that the preponderance of the evidence is against the claim to the extent that the Veteran is not shown to have had the requisite full-body exposure during his period of service in the Vietnam era. The Board additionally finds that the preponderance of the evidence is against a finding that the Veteran's squamous cell carcinoma of the left lower lip is attributable to his documented in-service dental and periodontal disease of the left lower lip. As noted, in February 2013, the Board obtained a Veterans Health Administration (VHA) medical opinion in this matter. The VHA physician, practicing in the area of hematology/medical oncology, opined that there was less than a 50 percent chance that the Veteran's squamous cell carcinoma of the left lower lip was related to documented in-service "trench mouth," Vincent's stomatitis, or necrotizing ulcerative gingivitis, which, as the VHA physician recounted, are alternative terminologies for the same condition. The reviewing physician conducted medical literature research and cited several published medical treatises and articles supporting his conclusion. He demonstrated a high degree of expertise in providing his opinion, thoroughly and accurately recounted the relevant history, and explained his opinions in detail and in a well-reasoned manner. This medical opinion significantly outweighs any other lay or medical evidence provided on this point. Other opinions provided have not been based on as thorough a history and have not been as well explained or as well supported by citation to medical literature, and have not demonstrated as high a level of the required medical expertise on the part of the persons providing the opinions. In sum, the preponderance of the evidence shows that the Veteran was not exposed to mustard gas during service and therefore did not have squamous cell carcinoma that could be linked to presumed exposure to mustard gas or to his medically documented in-service "trench mouth," alternatively referenced as Vincent's stomatitis or necrotizing ulcerative gingivitis. Accordingly, on this record, service connection for squamous cell carcinoma of the left lower lip must be denied. ORDER Service connection for squamous cell carcinoma of the left lower lip is denied. ______________________________________________ STEPHEN L. WILKINS Veterans Law Judge, Board of Veterans' Appeals Department of Veterans Affairs