Microfilaria in cytological smears at rare sites coexisting with unusual pathology: A series of seven cases.

Filariasis is a major public health problem in India and microfilaria is sometimes seen during routine fine needle aspiration cytology (FNAC) smears, but it is very rare to find microfilaria coexistent with neoplastic lesions. Here we report a series of seven cases in which microfilaria is associated with neoplastic lesions. Out of these seven cases one is benign and six are malignant. Also we first time report the microfilaria coexistent with parotid pleomorphic adenoma, undifferentiated carcinoma thyroid and gall bladder carcinoma.

INTRODUCTION

Microfilaria is a major public health problem in tropical and subtropical countries and is an endemic problem in India. Wuchereria bancrofti is the most common filarial infection.[1] Despite its high incidence it is unusual to find microfilaria in fine needle aspiration cytology (FNAC) smear and body fluids and it is rare to find microfilaria along with smears aspirated from neoplastic lesions. There are only few reported cases of coexistent microfilaria with neoplasm in the cytology literature.[2] Here we report a case series of seven cases in which microfilaria is found in the routine cytological smears without a clinical suspicion of filariasis. Out of these seven cases, six cases are benign and one is malignant.

CASE REPORTS

Case 1

A 35-year lady presented with firm to hard thyroid swelling of size 3×3 cm. Past history of high-grade fever with chills and rigor present two year back. Cytology revealed singly lying as well as loosely cohesive clusters of oval to spindle shaped cell along with microfilaria [Figure 1a]. A diagnosis of undifferentiated carcinoma was made. Peripheral blood smear (PBS) was positive for microfilaria.

Figure 1

Smears reveal microfilaria with neoplastic lesion (H and E, ×1000). (a) Undifferentiated carcinoma thyroid; (b) pleomorphic adenoma parotid; (c) adenocarcinoma breast; (d) metastatic adenocarcinoma vertebrae; (e) adenocarcinoma gall bladder; (f) lung adenocarcinoma

Case 2

A 25-year male presented with parotid swelling. There was no other significant complaint. Cytology revealed both mesenchymal as well as epithelial component along with microfilaria [Figure 1b]. A diagnosis of pleomorphic adenoma was made. PBS was negative for microfilaria.

Case 3

A 52-year female presented with right breast lump of 5×4 cm size. There was no other significant complaint. Cytology revealed highly atypical cell forming well-defined acini [Figure 1c]. A diagnosis of adenocarcinoma along with microfilaria was made. PBS was positive for microfilaria.

Case 4

A 55-year female presented with back pain. There was no other significant complaint. It was clinically suspected as Pott's spine. Cytology revealed highly atypical cell lying singly as well forming acini at places [Figure 1d]. A diagnosis of adenocarcinoma with microfilaria was made. Primary was unknown. PBS was negative for microfilaria.

Case 5

A 40-year male presented with gall bladder mass. There was no other significant complaint. Aspirate revealed adenocarcinoma along with microfilaria [Figure 1e]. PBS was negative for microfilaria.

Case 6

A 60-year female presented with lung mass in left upper quadrant. There was a past history of high grade fever with chills 10 year back. At that time PBS was positive for microfilaria and patient took treatment for one year. Cytology revealed atypical cells along with microfilaria [Figure 1f]. Diagnosis of “smears highly suspicious for adenocarcinoma” was made. PBS was positive for microfilaria.

Case 7

A 42-year male presented with neck secondaries with primary from larynx. There was no other significant complaint. Aspirate revealed atypical squamous cells along with microfilaria. A diagnosis of metastatic squamous cell carcinoma was made. PBS was positive for microfilaria.

DISCUSSION

Microfilaria is a public health problem in tropical region of south east Asia including Indian subcontinent. It is caused by the nematode W. bancrofti, Brugia malayi, Brugia tumori and others and transmitted through bite of Culex mosquitoes.[1] The adults of the lymphatic filariae inhabit lymph vessels, where blockage and host reaction can result in lymphatic inflammation and dysfunction, and eventually in lymphedema and fibrosis. Other filariae mature in the skin and subcutaneous tissues, where they induce nodule formation and dermatitis; migrating filariae of these species can cause ocular damage. They were observed occasionally during routine cytological and histological examination from various benign lesions and they have rarely been detected in association with neoplastic lesions in cytological smears. In most of the reported cases microfilaria have been detected in lymph node, breast lump, bone marrow, bronchial aspirate, nipple secretions, pleural and pericardial fluid, ovarian cyst fluid and cervicovaginal smears.[2] In thyroid aspirate most of the literature revealed colloid goiter or follicular neoplasm with filaria but to the best of our knowledge it is the first case of microfilaria found in undifferentiated carcinoma of thyroid.[34]

Microfilaria has been detected in breast, bone marrow, and lymph node aspirates, most being benign lesions with only few malignant cases.[25-7] Similarly in parotid gland, gall bladder carcinoma and lung malignancy no case is found in association with any neoplastic lesion. Here we report it for the first time coexisting with neoplasm.

Most of the authors have explained that as microfilaria circulate in the vasculature and lymphatic system and whenever the neoplastic lesion causes vasculature or lymphatic obstruction they appear in the tissue fluid or shed off into the surface material. In malignancy increased blood vasculature also causes the increase deposition of microfilaria to these sites.[8] Ahluwalia et al., stated that larva may be present in the vasculature and aspiration may lead to the rupture of vessel and release of microfilaria into the aspirate from neoplasm.[9] Gupta et al. reported six cases where microfilaria were found in body fluids cytology and FNAC smears in association with tubercular pleural effusion/lymphadenitis, pregnancy, non Hodgkin's lymphoma, malnutrition and young age. Although the finding of microfilaria in cytological smears was considered incidental, the association of microfilaria with debilitating condition suggest that it is an opportunistic infection.[10] In literature there has been no data suggesting role of microfilaria in causing malignancy.

In our view, in the present series the presence of microfilaria in aspirate from neoplastic lesion is an incidental finding and there is no change in the clinical presentation of the tumor and that the patient might harbor subclinical filariasis when the patient developed tumor or metastasis of tumor.

To summarize filariasis may be detected in clinically unsuspected cases, so a high index of suspicion should be kept in mind and careful screening is mandatory for the search of coexisting pathology.