The incidence of oral cancers as well as the mortality from oral cancers, most of which are histopathologically squamous cell carcinoma (SCC), has been increasing in the last six decades in Japan as well as in European and Asian countries [
The recent increase in the incidence of all types of cancer, including oral cancer, in Japan is partly due to longevity and improved detection of early stage lesions [
To this end we have also distinguished two categories of oral SCC:
The biggest issue in clinical interventions for superficial SCC has been postoperative local recurrences. To prevent local recurrences, we have recently introduced the frozen section technique (FS) to confirm surgical margins by the above-mentioned histopathological criteria which we developed over the last 10 years in our hospital. There have been extremely few reports which have carefully examined the effectiveness of FS in association with recurrence-based prognoses. Therefore, in this study, we analyze how effective FS has been against recurrences of oral SCC, especially for superficial types.
We selected 236 cases of oral cancer with at least 5-year follow-up data and sufficient clinical data from 343 samples of oral cancer which had been diagnosed clinically as oral SCC or leukoplakia and had been documented in the surgical pathology files of the Division of Oral Pathology, Niigata University Graduate School of Medical and Dental Sciences, during a 6-year period from 2002 to 2007. In addition to such patient clinical data as age, sex, tumor location, and tumor size (T factors), we were able to ascertain history of local recurrence from clinical records of the 236 patients and determine intervals between the last surgeries and recurrences. Since samples of recurrent cases were included, the total number of samples (tissue specimens) screened was larger than the number of cases. According to their local recurrence histories, the samples were classified into relapse and relapse-free groups, respectively. These cases separated into the two groups did not metastasize to regional lymph nodes or distant organs. There were 152 relapse and 191 relapse-free samples, for a total of 343. Cases of SCC, CIS, and epithelial dysplasia (mild and moderate) which recurred after primary surgery were categorized into the relapse group, while those without recurrence for at least five years after surgery were categorized into the relapse-free group. The study protocol for analyzing clinical records and surgical specimens was reviewed and approved by the Ethical Board of the Niigata University Graduate School of Medical and Dental Sciences (Oral Life Science).
During surgical operations, FS samples were obtained by pathologists from surgical margins (anterior, posterior, upper, and lower margins of mucosal surfaces and bottom margins towards muscle layers) of
The surgical materials were fixed routinely in 10% formalin and embedded in paraffin. Serial 3
We calculated the rate of performing FS during surgery in both relapse and nonrelapse groups, respectively, and their histopathological diagnoses by FS during surgery were reconfirmed by their paraffin sections from the same specimens used for FS. During surgery, excisional margins were evaluated and assigned to one of the following categories: normal, epithelial hyperplasia, epithelial dysplasia (mild and moderate), CIS, or SCC. We regard moderate dysplasia as true dysplasia, one of the borderline malignancy categories in addition to CIS [
Tissue samples obtained by additional incisions were also counted as samples, although they were diagnosed on paraffin sections only and not on frozen ones because we did not perform the second FS after additional excisions. Those histopathological diagnostic criteria were commonly shared by surgeons and pathologists, and reasons for additional surgery recommendations were mutually understood by them. Our diagnostic criteria for borderline malignancies including CIS and epithelial dysplasia were not always identical to those by WHO 2005 [
Surgical specimens were routinely fixed in formalin and embedded in paraffin, from which 5–7 mm-thick slices were frontally prepared from posterior to anterior directions. Sections were obtained from every tissue slice, stained with HE, and evaluated by three independent pathologists. In addition to histopathological diagnoses for the main foci of the surgical specimens, their surgical margins were carefully checked and evaluated into the same six categories—from normal epithelia, epithelial hyperplasia, epithelial dysplasia, mild and moderate, and CIS, to SCC—as mentioned above. In case additional surgeries were performed, additionally incised specimens were regarded as actual surgical margins. For histopathological diagnoses for both main foci and surgical margins, we performed immunohistochemistry to make objective judgments based on our diagnostic criteria for borderline malignancies as mentioned above.
When multiple and different foci were included in one specimen and thus multiple diagnoses were obtained, those of the most severe grades were regarded as final diagnoses of the main lesions. Those cases were further investigated for follow-up studies by referring to their final diagnoses for the surgical specimens. When categorized into the relapse group, we compared frozen sections and biopsy or surgical specimens from recurrent lesions to determine whether or not they could be regarded as recurrence and calculated the intervals from FS to surgery for recurrent lesions.
Clinical data were statistically analyzed using GraphPad Instat (version 3.06 for Windows, GraphPad Software, San Diego, CA, USA). The average scores for patients’ ages were calculated using a
Among the 236 cases, 191 (80.9%) were classified into the relapse-free group and 45 (19.1%) into the relapse group. In the 191 cases of the relapse-free group, 120 (62.8%) were diagnosed as SCC, 44 (23.0%) as CIS, 11 (5.8%) as moderate epithelial dysplasia, and 16 (8.4%) as mild epithelial dysplasia. In the 45 cases of the relapse group, 35 (77.8%) were SCC, 6 (13.4%) CIS, 3 (6.7%) moderate epithelial dysplasia, and 1 (2.2%) mild epithelial dysplasia (Table
Clinicopathological summary and recurrence status of 236 cases of oral epithelial lesions.
Clinicopathological parameters | Clinical outcomes |
| |||
---|---|---|---|---|---|
Relapse-free ( |
Relapse ( | ||||
Number of cases | Ratio ( |
Number of cases | Ratio ( |
||
Sex | |||||
Male | 115 | 60.2 | 18 | 40.0 | 0.019 |
Female | 76 | 39.8 | 27 | 60.0 | |
|
|||||
Location | |||||
Tongue | 77 | 40.3 | 14 | 31.1 | 0.308 |
Gingiva | 77 | 40.3 | 22 | 48.9 | 0.317 |
Buccal mucosa | 22 | 11.5 | 7 | 15.6 | 0.454 |
Floor of the mouth | 15 | 7.9 | 2 | 4.4 | 0.537 |
|
|||||
Histopathological diagnosis of main focus | |||||
Squamous cell carcinoma (SCC) | 120 | 62.8 | 35 | 77.8 | 0.080 |
T1 |
|
|
|
|
0.655 |
T2 |
|
|
|
|
1.000 |
T3 |
|
|
|
|
0.171 |
T4 |
|
|
|
|
0.841 |
Carcinoma in situ (CIS) | 44 | 23 | 6 | 13.4 | 0.223 |
Epithelial dysplasia, moderate | 11 | 5.8 | 2 | 4.4 | 1.000 |
Epithelial dysplasia, mild | 16 | 8.4 | 2 | 4.4 | 0.538 |
|
|||||
Intraoperative assessment of surgical margins by frozen sections | |||||
Yes | 128 | 67.0 | 83 | 54.6 | 0.025 |
No | 63 | 33.0 | 69 | 45.4 |
In terms of SCC cases, we categorized 120 SCC cases of the relapse-free group and 35 of the relapse group according to their T factors (tumor size). In the relapse-free group, there were 30 T1 (15.7%), 41 T2 (21.5%), 8 T3 (4.1%), and 41 T4 (21.5%). The relapse group included 7 T1 (15.6%), 12 T2 (26.7%), 5 T3 (11.1%), and 11 T4 (24.4%). There were no statistically significant differences between T factors and relapse tendencies (
Out of the 236 patients, 133 (56.4%) were males, and 103 (43.6%) were females, with an overall male-to-female ratio of 1.3 : 1. Their ages ranged from 21 to 92 years, and the average was 67.2 years (male 64.2, female 69.8, resp.).
Among the 191 relapse-free patients, there were 115 males (60.2%) and 76 females (39.8%) with a male-to-female ratio of 1.5 : 1. In contrast, among the 45 patients of the relapse group, females (27, 60.0%) were more predominant than males (18, 40.0%) (Table
The age of the relapse-free group ranged from 21 to 92 years, with a mean of 64.2 years (63.0, males; 65.9, females), while that of the relapse group ranged from 27 to 91 years, with a mean of 67.2 years (males, 64.2; females, 69.2) (Figure
Age and sex distribution of patients with squamous cell carcinoma: relapse-free type (a) and relapse type (b). Open square: male; gray square: female. A total of 236 patients were analyzed in this study. There were 133 male (56.4%) and 103 female (43.6%) patients with an overall male-to-female ratio of 1.3 : 1. Their ages ranged from 21 to 92 years, and the average was 67.2 years (male 64.2, female 69.8, resp.). There were 191 relapse-free and 45 relapse patients. Among the 191 patients who were relapse-free, there were 115 males (60.2%) and 76 females (39.8%), with a male-to-female ratio of 1.5 : 1. In contrast, in the 45 cases with relapse, sex differences were reversed with 18 males (40.0%) and 27 females (60.0%). The mean age of the relapse-free group was 64.2 years (range from 21 to 92 years; male 63.0, female 65.9), while that of the relapse group was 67.2 years (range from 27 to 91 years; male 64.2, female 69.2). In the relapse patients, their sex difference was reversed as compared with the relapse-free group, and the difference was statistically significant (
In the relapse-free group, the most frequent sites were the tongue (77, 40.3%) and the gingiva (77, 40.3%) followed by the buccal mucosa (22, 11.5%) and floor of the mouth (15, 7.9%). However, in the relapse group, the gingiva was the most frequent site of lesions (22, 48.9%), followed by the tongue (14, 31.1%), buccal mucosa (7, 15.6%), and floor of the mouth (2, 4.4%). Statistically, there was no significant difference in site distributions between two groups (Table
The intraoperative assessment by FSs was more frequently performed in the relapse-free group (128, 67.0%) than in the relapse group (83, 54.6%), with a statistically significant difference (
Histopathological diagnoses of surgical margins by FS are shown in Table
Clinical outcomes and histopathological diagnoses of surgical margins by frozen section techniques (FS).
Clinical outcomes | Histopathology of surgical margins by FS | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
SCC | (%) | CIS | (%) | Epithelial dysplasia | Others | (%) | Total | (%) | ||||
Moderate | (%) | Mild | (%) | |||||||||
Relapse-free | 0 | (0.0) | 8 | (6.2) | 47 | (36.7) | 61 | (47.7) | 12 | (9.4) | 128 | (100.0) |
Relapse |
|
|
|
|
|
|
20 | (24.1) | 6 | (7.2) | 83 | (100.0) |
|
||||||||||||
Total | 5 | (2.4) | 32 | (15.2) | 75 | (35.5) | 81 | (38.4) | 18 | (8.5) | 211 | (100.0) |
In the relapse-free group, among the 55 margins which contained borderline malignancies diagnosed by FS, 38 (69.1%) were additionally incised, while the remaining 17 margins were left behind because additional incisions were not surgically possible. In the relapse group, 39 (68.4%) among the 57 margins were additionally incised. There was no significant difference in the rates for additional surgery after FS (Table
Additional surgery according to FS and final histopathology at margins of surgical specimens.
Clinical outcomes | FS | (%) | Borderline malignancies recognized by FS | (%) | Additional Surgery according to FS | (%) | Final histopathological diagnoses at surgical margin | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
SCC | (%) | CIS | (%) | Epithelial dysplasia | Normal | (%) | |||||||||||||
Moderate | (%) | Mild | (%) | ||||||||||||||||
Relapse-free ( |
Yes | 128 | (67.0) | Yes | 55 | (43.0) | Yes | 38 | (69.1) | 2 | (5.3) | 6 | (15.8) | 12 | (31.6) | 18 | (47.3) | 0 | (0.0) |
No | 17 | (30.9) | 0 | (0.0) | 3 | (17.6) | 8 | (47.1) | 5 | (29.4) | 1 | (5.9) | |||||||
No | 73 | (57.0) | — | — | — | 1 | (1.4) | 1 | (1.4) | 11 | (15.0) | 57 | (78.1) | 3 | (4.1) | ||||
No | 63 | (33.0) | — | — | — | — | — | — | 0 | (0.0) | 8 | (12.7) | 33 | (52.4) | 22 | (34.9) | 0 | (0.0) | |
|
|||||||||||||||||||
Relapse ( |
yes | 83 | (54.6) | Yes | 57 | (68.7) | Yes | 39 | (68.4) | 6 | (15.4) | 17 | (43.6) | 13 | (33.3) | 3 | (7.7) | 0 | (0.0) |
No | 18 | (31.6) | 3 | (16.7) | 9 | (50.0) | 6 | (33.3) | 0 | (0.0) | 0 | (0.0) | |||||||
No | 26 | (31.3) | — | — | — | 4 | (15.4) | 6 | (23.1) | 8 | (30.8) | 7 | (26.9) | 1 | (3.8) | ||||
No | 69 | (45.4) | — | — | — | — | — | — | 10 | (14.5) | 32 | (46.4) | 13 | (18.8) | 13 | (18.8) | 1 | (1.5) |
To confirm whether the additional surgery according to FS was clinically useful, surgical margins were comparatively examined between paraffin sections of surgical specimens and frozen sections at surgery. Table
In the relapse-free group (
In the relapse group (the lower part of Table
To investigate the risk of recurrences of the borderline malignancies, and to determine how long patients should be followed up for recurrences, all of the primary surgical margins of 84 lesions which recurred within 10 years were retrospectively reviewed. The results are summarized in Table
Histopathology of surgical margins where malignant lesions recurred.
Histopathological diagnosis of margins by previous surgeries | Numbers (%) of recurrent lesions and intervals (month) until recurrences | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Epithelial dyspl asia | CIS | SCC | Total | ||||||||||||
Mild | Moderate | ||||||||||||||
Number | ( |
|
Number | ( |
|
Number | ( |
|
Number | ( |
|
Number | ( |
Period | |
Normal/hyperplastic epithelia | 0 | (0.0) | 0.0 | 0 | (0.0) | 0.0 | 1 | (50.0) | 12.0 | 1 | (50.0) | 43.0 | 2 | (100.0) | 27.5 |
Epithelial dysplasia | 1 | (3.2) | 11.0 | 5 | (16.1) | 28.4 | 8 | (25.8) | 41.8 | 17 | (54.9) | 26.1 | 31 | (100.0) | 30.0 |
Mild |
|
( |
|
|
( |
|
|
( |
|
|
( |
|
|
( |
|
Moderate |
|
( |
|
|
( |
|
|
( |
|
|
( |
|
|
( |
|
CIS | 0 | (0.0) | 0.0 | 0 | (0.0) | 0.0 | 15 | (42.9) | 14.1 | 20 | (57.1) | 25.1 | 35 | (100.0) | 20.4 |
SCC | 1 | (6.2) | 2.0 | 0 | (0.0) | 0.0 | 3 | (18.8) | 12.3 | 12 | (75.0) | 22.5 | 16 | (100.0) | 19.3 |
|
|||||||||||||||
Total | 2 | (2.4) | 6.5 | 5 | (6.0) | 28.4 | 27 | (32.1) | 22.0 | 50 | (59.5) | 25.1 | 84 | (100.0) | 23.9 |
Among the 84 surgical samples with recurrences, 35 were identified as CIS (41.7%), 22 as moderate dysplasia (26.2%), 16 as SCC (19.0%), 9 as mild dysplasia (10.7%), and 2 as normal or hyperplasia (2.4%). In terms of recurrent lesions, SCC was found in 50 samples (59.5%), CIS in 27 (32.1%), and moderate dysplasia in 5 (6.0%). Among the 50 recurrent SCC, 20 samples (40%) originated from CIS, and 12 each were from SCC and moderate dysplasia (24.0% each). Among the 16 surgical margins with SCC, 12 samples recurred as SCCs (75.0%) with an average interval of 22.5 months, and 3 as CIS (18.8%) in 12.3 months. Of the 35 surgical margins with CIS, 20 samples recurred as SCC (57.1%) in 25.1 months, and 15 as CIS (42.9%) in 14.1 months. Of the 22 surgical margins with moderate dysplasia, 12 recurred as SCC (54.5%) in 33.3 months and 6 as CIS (27.3%) in 42.7 months. The results indicated that the lesions which we had diagnosed as borderline malignancies (moderate dysplasia and CIS) possessed the potential to develop into SCC, and that it was necessary for any categories of oral epithelial lesions, including mild dysplasia, to be followed up for at least 4 years for possible recurrences.
In this study, we demonstrated the importance of the intraoperative FS for surgical margins of oral SCC in the prevention of local recurrences. In our series of oral SCC cases which were surgically treated, additional surgery according to FS was shown to be effective at reducing recurrences from surgical margins, though FS was not applied to all of the cases. There have been several reports investigating the accuracy of FS [
It has been emphasized that the control of metastasis is the ultimate, most important issue in cancer treatment [
These surgical aids provide a reference only, whereas FS allows pathologists to evaluate surgical margins directly and histopathologically. There is no room for macroscopic determination of lesional extensions by individual surgeons, who must rely on past experience. As shown in the present study, oral SCC cases in which FS was performed showed significantly better prognoses.
We could not confirm the reasons why FS was not performed in the relapse group, but it was speculated that surgeons were unable to use FS when lesions were too small or when surgery was done under local anesthesia. We did not investigate the size factor of other lesions than SCC because our series were composed of various kinds of malignancies ranging from simple leukoplakia types to bulky and invasive SCC. However, independent of lesion size, it is obviously helpful for surgeons to receive detailed histopathological reports directly concerning their own surgeries, which may further give feedback to their macroscopic judgments to improve treatment outcomes.
As shown in the present study, there were two major problems for FS as a tool for prevention of local recurrence to be solved. The first one was a matter of where to sample frozen sections. FS is applicable to only the marginal areas from which frozen sections are prepared but not to other areas which are not sampled for FS. Thus, inappropriate sampling can result in what we call “false negatives.” It is actually impossible to examine the whole surgical margin around a lesion; therefore only several representative points, such as front, rear, upper, and lower, of margins were selected for FS in our series. In case marginal areas are not examined by FS, there may be recurrences from those areas. To solve this problem, surgeons have to be experienced at judging where to check by FS. The second issue is insufficient extension of incisional areas in additional surgery. Surgical margins by additional incisions were not examined by FS in the present series, and it was not confirmed whether those extended margins were free from malignancies. Therefore, additional surgeries should be performed with enough extensive distance from borderline malignancy margins; otherwise, extended margins should be reexamined by FS. In reality, it is difficult to perform multiple FSs for one surgery because surgery time should be kept as short as possible to reduce the physical burden on patients. Thus, there is a need for surgeons and pathologists to discuss how to manage FS more effectively.
The present study has demonstrated a clear difference in clinical features between the relapse and relapse-free groups. Local recurrences were significantly frequent among elderly females whether the samples belonged to the relapse or relapse-free groups. The most characteristic feature in the relapse group samples was the high frequency of borderline malignancies, especially CIS, in their margins. As shown in Table
According to the findings of the present survey for recurrences, patients should be followed up for at least 4 years even if their surgical margins are free from borderline malignancies. In cases where borderline malignancy lesions were left behind, their outcome for recurrence intervals could be predicted from 12 to 47 months dependent on malignant grades from moderate dysplasia, CIS, and SCC. One of the important lessons from the present study was that any of the oral borderline malignancy categories possesses a potential to progress into SCC.
It should be noted that most oral mucosal lesions have risks of recurrence from their surgical margins and that the intraoperative assessment of margins using FS was effective in preventing recurrences of oral mucosal malignancies. In order to improve surgical treatment outcomes, surgeons and pathologists should share a common viewpoint on surgical margins.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors would like to thank Dr. Satoshi Maruyama for his help in preparing the paper. This work was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science and by a grant for the Promotion of Niigata University Research Projects.