Taenia solium, a potentially dangerous parasite, causes human cysticercosis that can cause a gamut of manifestations affecting the various systems of the body. Sometimes, parasitic infestations present as only superficial palpable subcutaneous or intramuscular nodules that are usually mistaken for lymph nodes or benign tumors like lipoma, neurofibroma, or epidermal inclusion cysts. Fine-needle aspiration cytology (FNAC) has emerged as a useful tool in the diagnosis of these superficial parasitic lesions. It also helps in avoiding unnecessary open biopsy to obtain a diagnosis. We, herein, report a series of five cases of subcutaneous cysticercosis at different sites (axilla, chest wall, abdominal wall, lateral neck, and cheek) misdiagnosed as lipomas and lymph nodes and finally diagnosed on FNAC. Keywords: Cysticercosis, fine-needle aspiration cytology (FNAC), subcutaneous nodules, ultrasonography (USG)
Taenia solium, a potentially dangerous parasite, causes human cysticercosis. Humans acquire the infection through consumption of undercooked pork, raw vegetables, or by drinking water contaminated by this parasite. [1] Cysticercosis can cause a gamut of manifestations affecting the central nervous system (CNS), skeletal muscles, heart, eyes, and subcutaneous tissues. [1] The palpable nodules are usually mistaken for lymph nodes or benign tumors like lipoma, neurofibroma, or epidermal inclusion cysts. [2],[3] Fine-needle aspiration cytology (FNAC) has emerged as a useful tool in the diagnosis of these superficial parasitic lesions. We, herein, report a series of five cases of cysticercosis, misdiagnosed as lipomas or lymph nodes clinically and finally diagnosed on FNAC.
Case 1 A 23-year-old male presented with 1 cm × 0.5 cm swelling in the cheek near the angle of the mandible that was firm, fixed, and nontender [Figure 1]. USG showed a 1.1 cm × 0.8 cm well-defined hypoechoic lesion with mural nodule in the intramuscular plane, suggestive of cysticercosis. FNAC was done with a 24G needle and 10cc syringe. Aspiration yielded yellowish gelatinous material, which showed numerous fragments of fibrillar material (bladder wall) with small blue nuclei favoring the diagnosis of cysticercus cellulosae infestation [Figure 2]. Also seen were multinucleate giant cells, a few histiocytes, and multiple skeletal muscle bundles.
Case 2 An 18-year-old male presented with right-sided cervical swelling in the posterior triangle of the neck measuring 1 cm × 1 cm, which was firm in consistency, mobile, and nontender. USG showed a 14 mm × 9 mm heterogenous lesion intramuscularly with a hyperechoic rim and cystic areas with a hypoechoic scolex in the center [Figure 3]. Aspiration yielded brownish serous fluid. Cytology showed fragments of the bladder wall with small blue nuclei favoring cysticercal infection. There was no inflammatory infiltrate.
Case 3 A 30-year old female presented with left-sided axillary swelling measuring 0.6 cm × 0.6 cm, which was firm in consistency and tender. The clinical diagnosis was that of an axillary lymph node. Aspiration yielded scant clear fluid. Cytology showed a few tissue fragments composed of fibrillar material with interspersed small blue nuclei. There was no evidence of any inflammation. A diagnosis of subcutaneous parasite cysticercus cellulosae infestation was given on cytology. The tissue was excised and showed fibrocollagenous tissue with areas of necrosis, hyalinized epithelioid cell granulomas, and debris with dot-like nuclei reminiscent of bladder wall nuclei seen on cytology [Figure 4].
Case 4 A 45-year-old male presented with swelling on the left side of the chest; the swelling measured 3 cm × 3 cm, was diffuse, soft-to-firm in consistency, and nontender. Ultrasonography (USG) showed an intramuscular well-defined predominantly hypoechoic lesion measuring 1.7 cm × 1.7 cm with hyperechoic walls. An ectopic calcified mural nodule was also seen giving an impression of a parasitic cyst. Aspiration yielded 1 cc of mucoid colorless fluid. Cytology showed fragments of fibrillar material with small blue nuclei, supporting the diagnosis of cysticercus cellulosae. Background also showed histiocytic clusters, numerous neutrophils and a few multinucleate giant cells. Case 5 A 32-year-old female presented with right-sided abdominal wall swelling measuring 2 cm × 2 cm, which was firm in consistency, slightly tender, and nonmobile. Clinical diagnosis was lipoma. Aspiration yielded scant whitish aspirate. Cytology showed moderate cellularity with mixed inflammatory cells against a thick proteinaceous background. Also seen were fragments of fibrillar material with small blue nuclei, supporting the diagnosis of cysticercus cellulosae.
Human cysticercosis is caused by the parasite Taenia solium, which enters the human body through contaminated food or water. It can affect the CNS, causing lethal complications or more commonly present with superficial palpable lesions amenable to FNAC. Various diagnostic modalities can help to diagnose parasitic lesions like serology, USG, computerized tomography (CT) scan, and magnetic resonance imaging (MRI); the latter two are mainly limited to the diagnosis of CNS cysticercal lesions. [2] In three of our cases, USG was available that showed the presence of intramuscular cystic lesions favoring a parasitic lesion. The diagnostic role of FNAC was first described by Kung et al. in 1989. [4] FNAC has now become a very useful tool in the diagnosis of superficial palpable lesions since it is a sensitive, rapid, and cost-effective method. Aspiration of the lesion usually yields a clear fluid, which is a strong pointer to the diagnosis. [2],[5] The aspirates in our cases varied from clear to serous to mucoid. The parasitic fragments comprise bluish fibrillary structures, which are part of the bladder wall and contain tiny parasitic nuclei that appear dot-like. [5] Sometimes, detached hooklets and/or calcareous corpuscles can be found; however, these are rare. Background can show inflammatory cells and granulomatous inflammation with or without necrosis. In all our cases, we have studied only the bladder wall with the parasitic nuclei and have not seen the hooklets and scolices in any case. There are few parasites that can cytologically mimic Cysticercus. They include Echinococcus cyst and the larval form of Coenuri and Sparagna. [6],[7] However, they have certain points of differentiation on cytology. The bladder wall is membranous and thin in Cysticercus, whereas it is thicker and lamellated in Echinococcus. Suckers are present in Cysticercus and Coenuri, whereas they are absent in Sparagna. Also, Cysticercus has a single scolex, whereas Coenuri and Echinococcus have multiple scolices. Goyal et al., [5] in their study on superficial palpable parasitic lesions, found 21 cases of cysticercosis out of 41 parasitic lesions. In all their cases, they identified only the parenchymal layer with a loose fibrillary stroma. No hooklets/scolices were seen in any of their 21 cases. Histopathological correlation was available only in three of their cases. Another large study by Handa et al. [7] studied 122 subcutaneous parasitic lesions and diagnosed cysticercosis in 57 cases. Biopsy was available in only 10 cases in their study, out of which eight did not reveal the parasite. These studies prove that FNAC alone can prove useful and cost-effective in the diagnosis of superficial cysticercal lesions. Histopathological follow-up was available in only one of our cases. However, USG helped in the correlation in three of our cases. Aspiration of clear fluid and varying proportions of inflammatory cells consisting of eosinophils, neutrophils, plasma cells, and giant cells in a palpable subcutaneous or intramuscular nodule should be viewed with a high index of suspicion as that of parasitic origin even in the absence of identifiable parasitic fragments. We wish to emphasize the importance of FNAC alone in the diagnosis of superficial cysticercal lesions with some practical aspects, which could help practicing cytopathologists who do not have a lot of experience in this field.
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4] |
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