Correlation between cytological and histological grading of breast cancer and its role in prognosis.

CONTEXT: Assigning grade to breast cancer on FNAC provides prognostic information and guides optimal therapy. AIMS: The present study was undertaken to grade breast carcinoma on cytology by Robinson's grading system and correlate it with Elstons modified Bloom Richardson histological grading system. SETTINGS AND
DESIGN: It is a prospective study done on fifty cases of breast cancer reported on cytology.
MATERIALS AND METHODS: Fifty patients who underwent FNAC and mastectomy for breast carcinoma were cytologically and histologically graded. Correlation between cytological and histological grading system was determined. Sensitivity and specificity of Robinson's cytological grading system was calculated in each grade. All cases evaluated for presence of metastasis to axillary lymph nodes. STATISTICAL ANALYSIS USED: Correlation between cytological and histological grading was established using the non parametric Spearman’ s correlation coefficient.
RESULTS: Concordance rate between cytological and histological grade was 78%. The coefficient of correlation between cytological grade and histological grade was 0.804 and P value was <0.001 which indicated a strong correlation and significant association between the cytological and histological grade. Sensitivity was maximum in cytological grade I tumors (100%) and least in cytological grade III tumors (45.45%). Specificity was maximum in cytological grade III tumors (94.87%) and least in cytological grade II tumors (72.72%). The incidence of axillary lymph node metastasis was maximum in cytological grade III tumors and grade I tumors.
CONCLUSIONS: Cytological grade strongly predicts histological grade and is useful in selecting neoadjuvant chemotherapy.

Introduction

The evaluation of prognostic parameters in breast cancer is of growing interest. These include axillary lymph node status, estrogen receptor status, histological grade, and cell proliferation index.[1] As neoadjuvant chemotherapy is gaining popularity as primary modality of medical treatment of breast cancer, much attention is being focussed on grading of breast cancer on fine-needle aspiration cytology (FNAC) smears.[2] Such grading would allow assessment of the tumor in situ, thereby guiding the selection of most suitable treatment before primary surgery, and hence avoiding the morbidity associated with overtreatment of low-grade tumors.[3]

Materials and Methods

Fifty cases of infiltrating duct carcinoma (IDC) breast, diagnosed on cytology, and undergoing surgery were included in the study. May-Grunewald-Giemsa (MGG) stained smears were evaluated and the tumor was graded based on the grading system described by Robinson et al.[3] In the Robinson's grading system, six different cytological parameters, namely cell dissociation, cell size, cell uniformity, nucleolus, nuclear margin, and nuclear chromatin were used to grade the tumors. A score of 1-3 was given to each of these parameters, and the tumor was graded by adding up the scores. Cancers that were scored in the range of 6-11 were graded I, those that are scored in the range of 12-14 were graded II, and grade III was given for a score ranging from 15 to 18. The surgical specimens were evaluated and histologically graded according to the Elston's modification of Bloom-Richardson system.[4] Three parameters were taken into consideration: Degree of tubule formation, nuclear pleomorphism, and mitotic figures. Each parameter was given a score of either 1,2 or 3. The overall score for each case ranged from 3 to 9. Mitotic figures were scored using a Nikon Opitphot-2 microscope with a field diameter of 0.44 mm. Sections were stained by hematoxylin and eosin (H&E) stain. Statistical analysis was done employing Spearman rank correlation coefficient (r) to examine the degree of correlation between the cytological and histological grade. Sensitivity and specificity of Robinson's cytological grading method were calculated for each cytological grade. All 50 cases were evaluated for the presence or absence of metastasis to the axillary lymph nodes employing Chi-square test. Lymph nodes were obtained on histopathology specimens. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) statistical software package version 16 (SPSS-Inc., Chicago, IL) and EPI-INFO version 6 (Centre of Disease Control and Prevention, Atlanta, Georgia, USA). P value <0.05 was considered statistically significant.

Results

Fifty cases were cytologically graded on FNAC smears according to Robinson's grading system. The maximum number of cases i.e. 29 (58%) were cytological grade II, 14 (28%) cases were cytological grade I, and 7 (14%) cases were cytological grade III. All cases were subsequently graded on histology using Elston's modification of Bloom-Richardson grading system. On histological grading, 28 (56%) cases belonged to histological grade II, and 11 (22%) cases belonged to histological grade I and histological III each. Table 1 shows comparison of the case distribution between the cytological grade and histological grade. Out of 14 cases of cytological grade I [Figure 1a], 11 cases were correlated with histological grade I and the remaining 3 cases were upgraded grade II. Out of 29 cases of cytological grade II [Figure 1b], 23 cases correlated with histological grade II and the remaining 6 cases were histologically upgraded to grade III. Out of seven cases that were cytological grade III [Figure 1c], five cases correlated with histological grade III while two cases were downgraded to grade II on histology.

Table 1

Comparison of the case distribution between the cytological and histological grades

Figure 1

(a) Cytological grade I tumor showing cohesive clusters of cells with smooth nuclear membranes, vesicular chromatin, and inconspicuous nucleoli (MGG stain, ×1000). (b) Cytological grade II tumor showing cells having visible nucleoli, granular chromatin, and moderate pleomorphism (MGG stain, ×1000). (c) Cytological grade III tumor showing cells with highly pleomorphic nuclei, prominent nucleoli, and budding of nuclear membrane (MGG stain, ×1000)

The concordance rate between grade I tumors on cytology and histology was 78.57%, while for grade II tumors it was 79.31% and for grade III tumors it was 71.42%. Thirty-nine cases out of 50 cases showed an agreement between the respective cytological and histological grades. The absolute concordance rate was 78%. The Spearman rank correlation coefficient (r) was 0.804, which indicates that there is a strong correlation between the cytological and histological grade. The high value of coefficient of correlation showed a significant and marked association (P < 0.001) between the grades assigned to FNAC smears and surgical pathology specimens [Table 2].

Table 2

Comparison of concordance rates between the cytological and histological grades

Table 3 shows that in cytological grade I tumors, the sensitivity of Robinson's cytological grading system was 100% and specificity was 92.30%. In cytological grade II tumors the sensitivity was 82.14% and specificity was 72.72% and in cytological grade III tumors the sensitivity is 45.45% and specificity was 94.87%.

Table 3

Calculation of sensitivity and specificity of Robinson cytological grading system[3] in each cytological grade considering histological grade as a base*

Out of the 50 cases, 31 (62%) were positive for axillary lymph node metastasis. Lymph node metastasis was present in 3 out of 11 (21.43%) cytological grade I tumors, 21 out of 29 (72.41%) cytological grade II tumors, and all the 7 (100%) cytological grade III tumors [Table 4]. This association between the increasing cytological grade and measure of axillary lymph node metastasis was found to be statistically significant with a Chi-square value of 15.41, degree of freedom (df) of 2, and P value < 0.001.

Table 4

Association of each cytological grade with incidence of axillary lymph node metastasis

Discussion

FNAC is a routinely used investigation for rapid diagnosis of breast cancer. The ability to predict the accurate grade on cytology smears would add to the diagnostic value of FNAC, without any additional morbidity or expense for the patients.

The purpose of prognostic grading on cytology is to identify high-grade tumors that are more likely to respond to chemotherapy than the low-grade tumors, which may be better suited to pretreatment with tamoxifen.[5] Assessment of biological aggressiveness by cytological grading without removing the tumor would therefore be valuable.[6]

Of the various cytological grading methods described for breast cancer, the method proposed by Robinson et al.[3] has been widely accepted. The concordance rate between the cytological grade (using Robinson's method) and histological grade, obtained in our study, was 78% that was found to be fairly comparable to that reported by previous studies [Table 5].[1267891011121314] The lack of correlation between cytological and histological grading in 22% of our cases may be the presence of varying degrees of atypia within the same tumor and interobserver subjectivity when assigning a cytological nuclear grade.[14] Another possible reason for the discordance may be the difficulty in identifying features such as nuclear margins (smooth/buds/folds), chromatin clumping, and granularity on cytology smears.[6] We found a statistically significant correlation between the cytological and histological grade with a “r” = 0.804 and P value of <0.001 [Table 4].

Table 5

Comparison of concordance rates in different studies with the present study employing Robinson's cytological grading system[3]

In the present study, we found sensitivities of 100%, 82.14%, and 45.45% for cytological grade I, II, and III tumors, respectively. The sensitivity was lowest (45.45%) in cytological grade III tumors. The reason for this low sensitivity of grade III tumors on cytology, could be that in our study, out of all the cases, number of cases falling in cytological grade III category was the lowest which thereby resulted in a low sensitivity. Sultana and Rehman[8] reported a similar finding of lowest sensitivity of cytological grade III tumors (37.50%) as compared to 96.96% for cytological grade I and 87.18% for cytological grade II tumors. We found that Robinson's cytological grading system was highly specific for cytological grade I tumors (92.30%) and cytological grade III tumors (94.60%), while being moderately specific (72.72%) for grade II tumors, owing to the highest number of false positive cases in cytological grade II category. This low specificity could also be due to the variation in cytological features in different areas of tumor on histology, which cannot be appreciated in cytology because of limited area of approach.

In the present study, we found an increasing incidence of axillary lymph node metastasis with increasing cytological grade. Frias et al.[15] and Khan et al.[1] also reported an increased rate of axillary lymph node metastasis with increasing cytological grade. These findings indicate that FNAC is a useful tool for predicting axillary lymph node metastasis that is one of the most important prognostic factors for breast carcinoma.

Although many studies have been conducted on cytological grading of breast cancer, only a few of them have calculated the sensitivity and specificity of cytological grading system in each grade. In this study, we have separately calculated the sensitivity and specificity of Robinson's cytological grading system in each grade that conveys how accurately this system has diagnosed the grade I, II, and III cases on cytology. Cytological grading on FNAC smears provides information about the aggressiveness of the tumor, which is a crucial parameter for selecting neoadjuvant chemotherapy/hormonal therapy. FNAC is especially useful in low-resource settings, where core biopsy is not routinely performed for diagnosis, and the treatment is often based on the cytology report itself. The National Cancer Institute (NCI), Bethesda, sponsored conference has recommended that tumor grading on FNAC material should be incorporated in cytology reports for prognosis.[16]

Conclusion

Our study shows that it is possible to grade breast cancer on fine-needle aspirates and that the cytological grade corresponds well with the histological grade. The cytological grade also provides relevant prognostic information regarding the aggressiveness of the tumor and lymph node metastasis. Thus, it is suggested that a conscious effort should be made to include the cytological grade in all the FNAC reports of breast cancer so as to guide the surgeon regarding the judicious use of neoadjuvant therapy and hence avoiding overtreatment of low-grade cancers.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.