A cytological study of smear characteristics and its correlation with bacillary load in tubercular lymphadenopathy

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Author Details : Shilpa G*, CSBR Prasad

Volume : 4, Issue : 1, Year : 2019

Article Page : 63-66

https://doi.org/10.18231/2581-3706.2019.0012

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Abstract

Abstract

Introduction: Extrapulmonary tuberculosis in form of lymphonodes is the common presentation of tuberculosis in developing countries. Fine needle aspiration cytology helps in early diagnosis & treatment for tubercular lymphadenitis, which remains the cornerstone for the effective management of the disease.

Aim: To study the cytological characteristics and compare with the bacteriological load with the help of Zeihl Neelsen stain.

Materials and Methods: 445 smears were studied for a period of one year. Smears were categorized into 4 patterns Pattern A - epithelioid cell granulomas without caseous necrosis, Pattern B -epithelioid cell granulomas with caseous necrosis, Pattern C- caseous necrosis without granuloma, Pattern D – neutrophils with abundant caseous necrosis. Bacillary load was graded as 1+, 2+ and 3+ were compared with the cytological categories. A p value of <0>

Results: Pattern A was observed in 16.7% cases, Pattern B in 18.3%, Pattern C in 37.8% & Pattern D in 27.2% of cases. Statistical significance was seen between cytomorphological pattern & AFB grade (p=0.026 & X²=20.0639). It was found that pattern C& D showed the highest AFB grade of 3+ by a 2x2 analysis to test the degree of one hypothesis.

Conclusion: FNAC is an useful tool in the early diagnosis of tubercular lymphadenitis avoiding the un necessary burden of surgical intervention. Maximum bacillary load was correlated with the patterns C & D.

Keywords: Fine needle aspiration cytology, Tuberculosis, Lymph nodes, Caseous necrosis, Acid fast bacilli.

Introduction

Table 4: Correlation between cytomorphological patterns & AFB grading

 

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Fig. 1: a. Pattern A showing epithelioid cell granuloma (Giemsa, x400). b. Pattern B showing granuloma with caseous necrosis (Papanicolaou stain x100). c. Pattern D – neutrophils with caseous necrosis (H&E x200),. d. Grade 3+ AFB (ZN Stain x1000)

Discussion

Accurate and timely diagnosis together with effective treatment is the mainstay of tuberculosis care and control.^[9] A confirmed diagnosis of tuberculosis can only be given on isolating the M. tuberculosis or finding specific DNA sequence of the bacteria in aspirates. In the resource-poor countries, however, these tests are not within the reach of every individual. In these countries, cost-effective techniques, such as, sputum smear microscopy and morphological features are the corner stone of tuberculosis diagnosis.^[10] Extra pulmonary tuberculosis commonly presents as superficial lymphadenopathy. Fine needle aspiration cytology (FNAC) is a very useful and reliable test in these cases, which provides an early morphological diagnosis.^[11]

Prasoon D^[12] has opined that the immunological response of tubercle bacilli in extra pulmonary cases is similar to that seen in pulmonary cases. Type IV delayed hypersensitivity reaction, seen after 2-4 weeks of infection leads to secretion of ? interferon and TNF ?. These immunologic mediators activate the macrophages to form granulomas in order to phagocytose & kill the organism. When the immunity of the host is decreased, there is ensuing tissue destruction in the center is represented by caseous necrosis containing large number of bacilli. High degree of hypersensitivity reaction leads to infiltration by neutrophils in the necrotic foci. Hence few bacilli are seen in the setting of only granulomatous reaction, while abundant bacilli are seen in predominantly necrotic reaction with little or no granulomas.^[12]The results in our study can be explained by this phathophysiology of the organism.

AGE- Tuberculous lymphadenopathy in our study was seen in all age groups, although the majority of the cases were in the second and third decade. This was also observed
in studies done by Nidhi P et al, Chand P et al & Hemalatha A et al.^[5],^[6],^[13]

SEX- Female preponderance was noted in this study with male to female ratio of 1:1.36, which was also reported by Nidhi P et al & Purohit MR et al.^[5],^[14]

SITE – Cervical group of lymph nodes were the most affected group (73.1%) and inguinal group being the least involved, which was similar to the data published in the literature.^[15]Masilmani S et al have opined that this is due to the easy access of the organism through the tonsillar lymphoid region to the cervical lymphnodes.^[16]

PATTERN- Various patterns or categories are used to describe the cytomorphological features of tuberculosis.^[4],^[5],^[6],^[12],^[13],^[17]In the current study Pattern C (37.8%) was the predominant pattern followed by Pattern D(27.2%), which was concordant with studies done by Nidhi P et al.^[5]

AFB POSITIVITY- Varying AFB positivity has been described in literature from 35.6% to 55.2%.^[4],^[6],^[13],^[17]The overall AFB positivity in our study was 61.86%. Chand P et al have reported 44.54%, while in a study done at a tuberculosis referral center by Nidhi P et al, AFB positivity was reported as 71%.^[6],^[5]In highly suspicious cases of tuberculosis, additional slides can be re-stained with ZN stain to increase the AFB detection rate.^[5]Whenever feasible a repeat FNAC can also be attempted.

When AFB positivity was correlated with the various patterns, the highest detection rate of AFB was seen in Pattern C (83.8%) followed by Pattern D (81.6%), which is similar to the findings of Nidhi P et al.^[5]Chand P et al have reported 94.1% AFB positivity in cases displaying caseous necrosis & 52.8% in cases with caseous necrosis along with degenerated inflammatory cells.⁶ Ergete W et al & Das DK et al have reported 68.7% & 77.4% of AFB positivity in cases having caseous necrosis with/without neutrophils respectively.^[4],^[17]AFB positivity was the least in cases with only granulomas, in all these series, which was observed in our study also.^4,5,6,17

MATERIAL OF ASPIRATION & AFB POSITIVITY –Aspirate which yielded cheesy or purulent material had the highest AFB positivity (69%) in the current study, which was also reported by the other studies.^[5],^[6],^[18]Prasoon D has also opined that AFB finding chance will be the highest in cases yielding cheesy or purulent aspirate.^[12] A differential diagnosis of acute suppurative lymphadenitis or caseous lymphadenitis is entertained when purulent material is aspirated. However, clinically the enlarged lymph node does not show signs of acute inflammation in the form of local rise of temperature or redness in a case of tuberculous lymphadenitis. Nonetheless all cases of purulent aspirate warrants a ZN stain to detect AFB. It has to be also noted that in metastatic deposit in lymph nodes, especially in elderly patients, a purulent material can be the aspirated. Hence a thorough search for atypical viable cells has to be made or a repeat aspirate from the periphery of the lymph node has to be performed in these cases.

GRADING- Similar to studies done by Hemalatha A et al & Masilmani S et al, there was statistical significant correlation between cytomorphological pattern & AFB grade.^[13],^[16]It was also noted that in the combined group of pattern C & D,the possibility of finding AFB was the highest. However >10000 bacterial organisms/ml of the sample are required for AFB detection by ZN stain. Those cases with high suspicion of tuberculosis, but with no AFB on ZN stain, has to be subjected to other methods of detecting the bacilli like culture, or cartridge based nucleic acid amplification tests.^[3]

Conclusion

The present study confirms that FNAC of lymphnodes is an excellent first line method, for investigating the nature of the lesions and the immunological response. Also combination of fine needle aspiration cytology with acid fast staining is highly valuable for routine diagnosis of tuberculosis. It gives valuable insight into the disease burden in the patient. Other ancillary investigations can be reserved for cases, in which there is a strong clinical suspicion with equivocal result of FNAC and acid-fast staining. It is an economical and convenient alternative to open biopsy of lymph node. The diagnostic accuracy of FNAC can be further improved manifold when used in conjunction with other special techniques like cytochemistry, bacteriologic culture, immuno-cytochemistry, ultrastructural studies and molecular hybridization.

Conflict of Interest: None.

 

References

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How to cite : Shilpa G, Prasad C , A cytological study of smear characteristics and its correlation with bacillary load in tubercular lymphadenopathy. IP J Diagn Pathol Oncol 2019;4(1):63-66

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