Clinicopathological study of rhinosporidiosis with special reference to cytodiagnosis.

BACKGROUND: Rhinosporidiosis is a chronic infective disorder caused by Rhinosporidium seeberi. It usually presents as a soft polypoidal pedunculated or sessile mass. Nose and nasopharynx are the commonest sites, followed by conjunctiva, maxillary sinuses, penis, urethra. AIMS: The aim of this study is to present the clinicopathological features of rhinosporidiosis in a large series of cases and to asses the role of cytology in diagnosis.
MATERIALS AND METHODS: 63 cases were included in the study group. Diagnosis of rhinosporidiosis was confirmed in all cases by histology with or without cytological evaluation. May-Grünwald-Giemsa and hematoxylin and eosin (H and E) staining was used in all cases, and special stains like periodic acid Schiff and mucicarmine were used in a few cases. Detailed clinical history of all the cases was noted. Routine hematological investigations including ABO blood grouping were done in all possible cases.
RESULTS: Evaluation of the clinical data in our series demonstrated male predominance (36 out of 63; 56%). Nose and nasopharynx were the commonest sites involved (74.6%). Routine hematology tests did not show any significant change in most of the cases. However, a significant proportion of the study population (18 out of 41; 44%) had blood group O. Cytodiagnosis attempted in 17 cases out of 63 cases achieved 100% correlation with histology.
CONCLUSION: Morphological appearance alone in a few cases failed to give diagnosis of rhinosporidiosis. Cytology can be very helpful in diagnosis in these cases, but histology is the mainstay of diagnosis.

Introduction

Rhinosporidiosis is a chronic granulomatous infective disorder caused by Rhinosporidium seeberi, whose taxonomy is still debated.[1] The first case was described as nasal polyp by Guillermo Seeber from Buenos Aires in 1900. The causative organism was considered as a fungus, and Asworth in 1923 described its life cycle establishing the nomenclature Rhinosporidium seeberi.[2]

Though sporadic cases of rhinosporidiosis are reported from all over the world, more than 90% cases are reported from India, Sri Lanka and Pakistan. Apart from human infections, the disease also affects several species of farm, domestic and wild animals-cattle, buffaloes, dogs, cats, horses, mules, several species of ducks and swans, etc.[3]

Clinically, rhinosporidiosis presents as polypoidal soft tissue mass, often pedunculated. Nose and nasopharynx are the commonest sites involved, accounting for more than 70% cases. Ocular lesions, particularly of the conjunctiva and lacrimal sac, account for 15% cases. Rare sites of involvement are lips, palate, uvula, maxillary antrum, epiglottis, larynx, trachea, bronchus, ear, scalp, vulva, penis, rectum and skin. Rarely, disseminated infections are also reported, involving limbs, trunks and viscera. Brain involvement may lead to fatality. Disseminated infection of limbs is often associated with destruction of underlying bones. Rarely, spontaneous regression of rhinosporidial nasal polyps has been documented.[4]

Here, we are presenting a large series of rhinosporidial lesions involving different parts of the body, with the following objectives:

Study of clinical features of the lesions along with routine hematological investigations

Assessment of the role of cytology in diagnosis

Materials and Methods

The present study was conducted in the pathology department of a rural medical college for a period of 2 years from March 2009 to February 2011. During the study period, all cases diagnosed as rhinosporidiosis either by histology or by combined cytology and histology were included in the study group.

Detailed clinical data regarding age, sex and clinical presentations were collected. Routine blood examination with ABO blood grouping was done in all possible cases of the study group.

Fine needle aspiration cytology (FNAC) of the lesions was available in only a few cases. Aspirations were done by using standard methods with 23-gauge needles to reduce the chance of bleeding. Samples were also collected by scraping in case of accessible lesions. Smears were stained with May-Grünwald-Giemsa (MGG) [Figure 1a and b] and periodic acid Schiff (PAS) stains. Diagnosis was confirmed by demonstration of endospores and sporangia, as reported by other workers.[5].

Figure 1

Smears showing (a) many scattered basophilic rhinosporidial endospores (MGG, ×400) and (b) rhinosporidial spores in a background of amorphous eosinophilic material (MGG, ×400)

Histopathological samples were processed according to the standard recommendation. Apart from the routine hematoxylin and eosin (H and E), PAS and mucicarmine stains were used. Final diagnosis was achieved by demonstration of thick-walled sporangia containing numerous endospores in a background of fibrovascular stroma [Figure 2a and b], in accordance with the findings of previous workers.[6].

Figure 2

Sections showing (a) multiple sporangia full of magenta.colored endospores in different stages of development (Mucicarmine, ×100) and (b) a large sporangium containing multiple pink.colored spores and capsule (PAS, ×1000)

Results

The total number of patients was 63. Among them, 36 were males and 27 females. The most common age group affected was 20-40 years [Table 1]. The distribution of cases according to the site of involvement and clinical features is presented in Table 2. Nose and nasopharynx were the most commonly affected sites (74.6%), followed by eye (19%). Other rare sites accounted for 4 (6.3%) cases. Most common presentation of the cases was presence of a superficial polypoid lesion, followed by nasal obstruction, epistaxis, rhinorrhea and watering of the eyes. No evidence of disseminated disease was identified in any of the lesions. Routine blood examination was done in all possible cases (n = 41) to note the total leucocyte count (TLC) and the relative proportion of eosinophils. Leucocytosis was seen in 4 cases, eosinophillia in 10 cases and others were in normal range. ABO blood grouping was also done. Among them, blood group “O” was the most common (44%), followed by blood group “AB” (22%).

Table 1

Distribution of cases according to age and sex

Table 2

Distribution of cases according to the site of involvement, and clinical features

Out of 63 cases, only 17 cases were available for preoperative cytological examination. Among them, FNAC only was done in 11 cases. Both FNAC and scrape cytology were done in six cases. All these cases (n = 17) were correctly diagnosed by cytology, which was confirmed later by histopathological examination.

Discussion

R. seeberi is no longer considered as a classic fungus. Herr et al.[7] classified this organism as Mesomycetozoa which includes other fish and amphibian pathogens. Ground water is considered to be the natural habitant of R. seeberi. Human infection is presumed to occur due to contact of traumatized epithelium with contaminated water. Highest incidence of cases is reported among river-sand workers.[8] This particular mode of infection is probably responsible for increased number of case detection in our series (63 cases within 2 years). As our medical college is situated in a rural area, it caters to a large population of poor villagers who are accustomed to take bath in ground water and are prone to mucosal injuries by sand or dust.

Male cases outnumbered female cases in our series (57% vs. 43%). Majority of the cases also involved young adults. These features are in accordance with the observations of other workers and is a possible reflection of more outdoor activities.[49]

Nose and nasopharynx were involved in most (74.6%) of the cases, followed by eyes (19%). Rare sites of involvement in our series were lip, palate and urethra. Other workers reported similar experiences.[49]

Rhinosporidiosis of nasal passage usually appears as a polypoidal lesion, granular, red in color with multiple yellowish pin head-sized spots representing underlying mature sporangia. This gross appearance, though distinctive, is not diagnostic.[410] Rhinosporidial polyps are also reported from skin, subcutaneous tissue, conjunctiva and urethral meatus. Nasopharyngeal lesions are often multilobed and less vascular. Nasal obstruction is a prominent symptom in these cases. Epistaxis and rhinorrhea are the common manifestations of nasal and nasopharyngeal infections.[911] Watering of eyes, conjunctivitis, photophobia and itching are the prominent manifestations of ocular rhinosporidiosis.[12] Our experience was similar. Uncommon features noted in our cases were warty growth in the lips, palate and urethra, nasal infection with abscess formation, and anosmia.

Routine hematological investigations in our series did not reveal any significant abnormality. Majority of the cases presented with normal TLC. There was no significant rise of relative proportion of eosinophils. Similar experience has also been reported by other workers.[49-11] ABO blood group study showed that 44% of the cases were blood group O, followed by group AB (22%), as reported by previous researchers.[4]

Typical polypoid appearance of rhinosporidial lesions often helps in correct preoperative diagnosis. But atypical presentations may cause confusion with soft tissue tumors or papillomas. Aspiration cytology can be helpful in these cases.[4] Material can also be collected by scraping in case of superficially accessible lesions. Microscopically, demonstration of endospores of 5-10 μm and sporangium of 50-1000 μm in the cytological smears clinches the diagnosis. Background epithelioid granulomatous reaction can be evident, but eosinophils are rarely found.[512]

In our series, 17 cases were initially evaluated on cytology either by aspiration or with combined aspiration and scrape cytology. In every case, rhinosporidiosis was correctly diagnosed, which later on was confirmed by histopathology.

Identification of endospores is often difficult from epithelial cells of the respiratory site, particularly from nasopharynx. Residual mucoid sporangial material around the endospores, referred to as a “comet” form by Beattie,[13] can cause confusion with large nuclei and residual cytoplasm of the epithelial cells. PAS stain is particularly helpful in this setup as endospores are PAS positive in comparison to the negative staining of epithelial cells.[4]

Definitive diagnosis of rhinosporidiosis depends upon identification of the pathogen in its diverse stages on biopsied or resected tissues.[4] Histopathological sections show multiple sporangia in various stages of maturity, enclosed in a thin chitinous wall. The sporangia are 50-1000 μm in diameter, containing numerous endospores of diameter 5-10 μm. Overlying epithelium is usually hyperplastic and loose fibrovascular stroma infiltrated with lymphocytes, macrophages, plasma cells and even polymorphonuclear leucocytes. Rupture of sporangia can cause giant cell reaction.[46] Commonly invasive mycoses produce Splendore-Hoeppli reaction characterized by well-developed eosinophilic infiltration in the infected tissue. But rhinosporidiosis is characterized by absence of this reaction, and tissue infiltrate is almost devoid of eosinophils.[14] Thick-walled sporangia and endospores stain positively with various special stains like PAS, mucicarmine (as used in our study), Gomori's methenamine-silver, Grocott's stain, etc.[4615] Mucicarmine stain is particularly helpful in differentiating Coccidioides immitis as sporangia and spores of this organism do not stain positively. Coccidiomycotic lesions can cause confusion with rhinosporidiosis during cytological as well as histopathological evaluation, as the former has similar mature stages represented by large, thick-walled spherical structures containing endospores. But distinction can also be made by H and E stain as intra-sporangial endospores of R. seeberi are larger and more numerous in comparison to those of C. immitis.[4]

Histopathology in rare instances may fail to diagnose rhinosporidiosis. The causes of false-negative diagnosis are, inappropriate selection of portion of polyps containing scanty or no rhinosporidial tissue, though other portions contain rhinosporidial bodies, absence of well-developed bilamellar thick wall of sporangia, presence of only fragments of outer wall without endospores, and absence of typical rhinosporidial bodies as a result of possible immune reactions.[16]

Treatment of rhinosporidial lesions is mainly surgical. Total excision of the polyp, preferably electrocautery, is the recommended method of therapy. Recurrence may occur due to spillage of endospores in the surrounding mucosa during removal.[4] The only drug to have anti-rhinosporidal effect is dapsone, but it can only be used as an adjuvant to surgery.[17]

Conclusion

Morphological appearance alone in a few cases failed to give diagnosis of rhinosporidiosis. Cytology can be very helpful in diagnosis in these cases, but histology is the mainstay of diagnosis.