Cytodiagnosis of filariasis from a swelling of arm.

Cytological demonstration of microfilaria and adult worms often helps in diagnosis of asymptomatic filarial cases. But demonstration of microfilaria in cytological smears from upper extremity lesions is seldom reported. We are presenting a 32-year-old female patient with elongated, small subcutaneous swelling in the medial aspect of right lower arm. Aspirates from the lesion demonstrate microfilaria though there is no eosinophilia or microfilaremia on subsequent examination of blood sample. In endemic areas, filariasis should always be considered as a possible diagnosis during cytological assessment of any swelling.

INTRODUCTION

Filariasis, caused by slender thread-like nematodes of Filarioidea superfamily, can predominately involve skin and subcutaneous tissue (Onchocerca volvulus and Loa loa) or the lymphatic system (Wuchereria bancrofti and Brugia malayi).[1] Lymphatic filariasis or elephantiasis affects more than 125 million people worldwide and is regarded by World Health Organization as the second leading cause of permanent and long-term disability after leprosy.[2] In India, the prevalence of lymphatic filariasis is quite high (5-10%) with highest case burden from coastal areas and banks of big rivers.[3] Sustruta, the famous ancient Indian physician and surgeon, described the clinical picture of elephantiasis as early as 600 BC.[4] 98% of the diagnosed cases of lymphatic filariasis in India is caused by W. bancrofti.[3] The disease usually follows a chronic course with predominant involvement of the lymphatic system of lower limbs, retroperitoneal tissues, spermatic cord, and epididymis.[5] Aspiration cytology often helps in demonstration of microfilaria and adult worms from these common sites as well as from uncommon diverse areas like breast, thyroid, effusion fluid, soft tissue swellings, etc.[6] We are describing a case of bancroftian filariasis presenting with small subcutaneous swelling in the medial aspect of the upper arm.

CASE REPORT

A 32-year-old female, a resident of a village of Bankura district, West Bengal, India, attended fine needle aspiration cytology (FNAC) clinic of Bankura Sammilani Medical College (BSMC), Bankura with a small swelling near medial aspect of right lower arm. On examination, it was a small subcutaneous slightly elongated swelling 2×1 cm, non-tender, firm, and without any fixity to deeper tissue. FNAC was done with clinical diagnosis of benign soft tissue neoplasm and a drop of fluid was aspirated. Smears show the presence of numerous microfilaria of W. bancrofti without significant inflammatory cell infiltration [Figures 1–3]. There was no evidence of inguinal or femoral filariasis and no history of fever. Routine blood examination revealed normal eosinophil population (4%) and nocturnal blood sample as well as blood sample drawn 1 hour after an oral dose of diethyl carbamazine (provocative test)[1] failed to demonstrate microfilaraemia.

Figure 1

Photomicrograph of the microfilaria of Wuchereria bancrofti in a background containing thin serous fluid (MGG ×4)

Figure 3

Photomicrograph of the microfilaria of Wuchereria bancrofti with a clear space free of nuclei at the caudal end (MGG ×40)

Photomicrograph showing a sheathed microfilaria of Wuchereria bancrofti with a rounded anterior and tapered posterior end (MGG ×10)

DISCUSSION

Diagnosis of lymphatic filariasis in symptomatic cases with typical clinical presentation is often easy and straight forward. Unfortunately, a majority of the affected remain asymptomatic particularly in the endemic areas with continued disease transmission.[7] In endemic areas, microfilaremia is often absent or transient, further complicating detection of disease.[8] But microfilariae, even in asymptomatic cases can reach tissue spaces due to vascular or lymphatic obstruction, leading to extravasations of larva.[9] Cytology can demonstrate these extravasated larva in tissue spaces or fluids.

In our case, the patient came from an endemic area explaining lack of clinical symptoms and amicrofilaremic state. FNAC is proved to be an effective measure in diagnosis of this type of asymptomatic cases.

Microfilaria of W. bancrofti are identified on cytological smears as long, thin, colorless, transparent, sheathed, thread-like structures (280-300 × 67 μ) with blunt head, pointed tail, and absence of nuclei in the tip. Brugian larva in comparison is smaller with secondary kinks instead of a smooth curve and the presence of nuclei in the tip.[10] Adult worms of both the species appear as white, thin, thread-like structures with tapering ends and distinction is often impossible.[9]

CONCLUSION

FNAC can be helpful in diagnosis of symptomatic as well as asymptomatic cases of lymphatic filariasis.[6] During cytological evaluation of tissue fluids and aspirate from lesions of any part of the body, possibility of filariasis must be kept in mind as a possible differential diagnosis, particularly in endemic areas.