FINE-NEEDLE ASPIRATION CYTOLOGY IN INFECTIOUS DISEASE

In the area of Medicine, infectious diseases constitute excellent examples where early and accurate diagnosis may be essential for obtaining a good therapeutical response. If on the one hand a great part of this group of diseases may be diagnosed through data obtained from clinical history, physical examination and laboratory tests (including microbiological, mycologic, parasitologic, and other tests), on the other hand, in other circumstances, the diagnosis has to be confirmed through anatomopathological tests.


FINE-NEEDLE ASPIRATION CYTOLOGY IN INFECTIOUS DISEASE
In the area of Medicine, infectious diseases constitute excellent examples where early and accurate diagnosis may be essential for obtaining a good therapeutical response.If on the one hand a great part of this group of diseases may be diagnosed through data obtained from clinical history, physical examination and laboratory tests (including microbiological, mycologic, parasitologic, and other tests), on the other hand, in other circumstances, the diagnosis has to be confirmed through anatomopathological tests.
Frequently infectious diseases may appear as tumoral masses.In such conditions, the aspirated cytology may play a fundamental role in the diagnosis.
In a strict sense, fine-needle aspiration (FNA) cytology means a morphologic diagnosis based on the examination of a material that has been punctured, aspirated, smeared and stained.However, its diagnostic limits increase significantly when the morphological interpretation is combined with clinical history, physical examination and complementary tests.Therefore, FNA cytology must constitute a part of a diagnosis system much more than a mere smear to be microscopically examined.
Although initially related to diagnosis of neoplasias, historically, one of the first uses of FNA cytology was for the study of an infectious disease.In 1904, Grieg and Gray utilized the aspiration of lymphatic ganglia for diagnosis of trypanosomiasis on the Africa highland 1 .With the propagation of the use of FNA cytology, almost all the organs susceptible of being envolved by infectious diseases can be studied through this technique, lungs and lymphatic ganglia being the more common ones 2 .Lymphadenopathies constitute the more frequent conditions in which FNA cytology is employed for the diagnosis of an infectious disease 3 .In our experience, the fungi such as Paracoccidioides brasiliensis, Cryptococcus neofor mans, Candida sp and Histoplasma capsulatum are easily shown in cytological material.In this way, in the cases of tuberculosis, over and above the presence of granulomas, the background of the smear is frequently necrotic.In pulmonary material, the BAAR positive index in Ziehl-Nielsen stain is of about 74% 4 , this positivity being a lesser one when the material studied is aspirated from lymphatic ganglia.
Pseudotumoral for ms of tuberculosis, schistosomiasis and several kinds of mycosis are conditions where often FNA cytology prevents from an unnecessary surgery.Leishmaniasis may also be diagnosed by cytology and sometimes in Giemsa stain it is possible to identify the microorganisms in the interior of macrophage.In several infectious diseases it is either impossible or very difficult to show the agent in the cytological material as in toxoplasmosis, infectious mononucleosis and cat scratch disease, but in these situations the cytomorphological feature combined with clinical examination and supplementary tests make possible a prompt and reliable diagnosis.
The increase of the number of acquired immune deficiency syndrome patients envolved a greater development of FNA cytology in the field of infectious diseases, since the risks of this method are lesser than those of a surgical biopsy.This made possible that almost every adenopathy in these patients could be studied rapidly through the cytology.The lymphoid hyperplasias and infectious processes were the more frequent diagnoses of material aspirated from the ganglia 5 .It was also possible to carry out, through FNA cytology, the study of oportunistic infectious such as pneumocystosis and atypical mycobacteriosis.
The risks and complications of FNA cytology are insignificant and rare such as small bloodletting, pain or pneumotorax in pulmonary punctures rarely requiring surgical drainage.The hydatid cyst represents one of the conditions where prudence is recommended by the authors.Some of them even counterindicate the puncture when a strong, either clinic or radiological, of this diagnosis is suspected 2 .
There would be many other examples of infectious diseases where FNA cytology could contribute to the diagnosis, but the important is to emphazise that this rapid, simple, cheap and effective procedure may and must be used in the field of infectious diseases, because it makes possible accurate diagnoses, often etiologic ones, thus allowing more rapid and effective procedures.