Cysticercosis of tongue: Cytohistologic approach to diagnosis.

Cysticercosis is continuing to be a major health problem in developing countries. Radiological and serological techniques are routinely used for pre-operative diagnosis of cysticercosis. But fine needle aspiration cytology (FNAC) is cost effective and simple procedure, so it is important to be aware of diagnostic pitfalls in the cytomorphologic diagnosis of cysticercosis. We present a case of cysticercosis of tongue, which accounts for only 34 cases in the world literature.

INTRODUCTION

The word Cysticercus is derived from Greek words Kystis = cyst and Kertos = tail because of their appearance.[1] Cysticercosis commonly involves intermuscular and subcutaneous tissues, whereas commonly affected organs are central nervous system and eye. Inspite of abundant intermuscular tissue in oral tissues, it is not a common site for cysticercus due to high muscular activity and metabolic rate of oral tissues in humans, which act against lodgement and development of cysticerci. When present, frequently involved oral locations for cysticercosis are tongue, labial or buccal mucosa and mouth floor.[2] Cytomorphology and histopathological findings are confirmatory and necessary before starting treatment.

CASE REPORT

A 23-year-male patient came with a painless, slowly progressive swelling over the lateral border of tongue for the past 2 years. On oral examination, a solitary nodule mass of 2 × 1 cm was noted on left lateral border of tongue. [Figure 1] a On fine needle aspiration, 1.6 ml of colorless clear watery fluid was aspirated. Amorphous acellular fragments were seen on cytology smear along with scattered squamous cells and hooklets. [Figure 1b and c] Since benign cystic lesions like mucocele, mucus retention cyst and lipoma are common in this location, excision biopsy was done. Gross examination revealed a single gray-brown nodule measuring 1.5 × 1 cm. Cystic cavity with thick wall and focal gray white solid area was seen on cut-section. [Figure 1d] Microscopy showed tongue musculature with central cystic space surrounded by dense fibrous capsule infiltrated by lymphocytes, plasma cells and foreign body type giant cells. [Figure 2a–d]. Cysticercus cellulosae was seen in cystic space, however, calcareous corpuscles could not be appreciated in the sections.

Figure 1

(a) Solitary nodule measuring 2 × 1 cms on left lateral border of tongue. (b) Clear fluid on aspiration. (c) Cytology smear showing hooklets and single hooklet in inset. (Papanicoloau stain, ×1000). (d) Gross appearance of nodule with central cystic space

Figure 2

(a) Section showing tongue muscles with central cystic space surrounded by fibrous wall. (H&E stain, ×40). (b) Section showing cysticercus larva in cystic space. (H&E stain, ×40). (c) Section shows thick tegument with absence of calcareous corpuscles in the mesenchyme (H&E stain, ×400). (d) Section shows mixed infiltrate of acute and chronic inflammatory cells admixed with foreign body giant cells and epitheliod macrophages (H&E stain, ×100) and inset (H&E stain, ×400)

DISCUSSION

Cysticercus diagnosis was not thought of clinically in the present case and various benign cystic swellings were considered as well. Cysticercosis of tongue is a rare entity, and till now only 34 cases have been reported in the world literature.[3] Since fine needle aspirate from swelling yielded clear fluid, amorphous acellular fragments and hooklets on smear, parts of parasite was suspected on cytologic examination but the possibility of artifacts could not be ruled out. Fine needle aspiration (FNA) of viable cyst of cysticercus yields clear fluid and fragments of bladder wall in a clear acellular background, whereas aspirates of necrotic lesions contain fragments of bladder wall including calcareous corpuscles and detached single hooklets. Diagnosis of cysticercosis is made on fine needle aspiration cytology (FNAC) only when fragments of larval cuticle and parenchyma are identified, which were absent in present case. Even to suspect about a parasitic infection characteristic inflammatory background comprising of eosinophils, neutrophils, palisading histiocytes and giant cells must be present in the aspirate from a subcutaneous nodule.[4] Again this finding was lacking in the present case. Although, gross and microscopy of cysticercoses are related to evolution of parasite and tissue reaction around it, both are almost similar irrespective of tissue or organ from where they are removed. They consist of well-preserved or dead disintegrating parasites. Usually growth of cysticercus is slow eliciting mild inflammatory reaction and only some tissues elicit formation of host capsule around it. After attaining full growth, parasite remains viable for several months to years depending on the location, type of host and other unknown factors. When cysticercus dies in tissues, parasitic antigens leak into surrounding tissues and elicit more inflammatory reaction. Dead or degenerating cyst is slowly invaded by inflammatory cells, macrophages and finally replaced by fibrous tissue with complete resorption of parasite and often dead parasite undergoes calcification. This is frequent when cysticerci are not surrounded by thick fibrous capsule like central nervous system and eye.

Histopathological diagnosis is based on the recognition of cysticercus in the excised lesion. Viable cysticercus is usually present in excised tissue from the oral mucosa, breast, conjunctiva, subcutaneous tissues and other sites where presence of cysticercus arouses some concern and is readily accessible. In all cases, typical histologic characteristics of cestode tissue must be recognized, even if morphologically a cysticercus with scolex is not evident. Viable cysticerci of T.solium have typical histological characteristic of bladder wall, scolex and the neck.[5] Calcareous corpuscles which are one of the most important histologic markers of cestode tissue (larve or adult) were not seen, which could be due to exposure of tissue to acid. Presence of neutrophils, lymphocytes and foreign body giant cells in the surrounding tissue were suggestive of ongoing degenerative process, because viable cysticerci do not elicit any inflammatory reaction.[6] However, cysticercus of T.solium is the most common but not the only cysticercus occurring in humans. Cysticercus of other species like T.crassicepss, cysticercus bovis of T.saginata have been reported in human. Although histologic differences have been described in these two cysticerci, they are not evident. Size of the rostellae, hooklets, asexual reproduction by exogenous and occasionally endogenous budding at opposite pole of scolex help in identifying cysticercus of T.crassiceps (Cysticercus longicollis). The diagnosis of C.bovis is more difficult. Absence of hooks in the rostellum of C.bovis is its characteristic feature, but entire specimen has to be cut serially to demonstrate the absence of hooklets in histologic sections. Even so, the possibility of an abnormal C.cellulosae (without rostellar hooks) should be considered. Another rare type of cysticercus, that is C.racemosus has also been described in humans.[6]

CONCLUSION

Whenever clear fluid is aspirated and smear shows hooklets, depending on the location, cysticercosis must be considered, especially in case of subcutaneous swellings and intramuscular swellings. However, possibility of hydatid cyst should also be ruled out in such cases.