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Clinical Infection & Immunity

Case Report

Volume 2, Number 1, March 2017, pages 13-15

A Case of Parotid Duct Rhinosporidiosis: Atypical Site of Involvement

Rhinosporidiosis is a benign chronic granulomatous fungal disease caused by Rhinosporidium seeberi (R. seeberi) [1]. It occurs sporadically and is known to be non-contagious. Although human rhinosporidiosis occurs universally with higher occurrence in parts of South Asia, it is endemic, especially in Southern India and Sri Lanka [2]. The most common site of infection in humans is the nose. Other sites include the nasopharynx, larynx, oropharynx, conjunctiva, lacrimal sac, and genital mucosa. Intraorally, rhinosporidiosis is known to involve the lip, palate, and uvula, secondarily, by direct extension from nasal and nasopharyngeal lesions [1]. Primary involvement of the parotid duct is extremely rare. The diagnosis is usually delayed and difficult when extranasal sites are involved. Occupational and personal history is helpful in achieving diagnosis and histopathological examination is also necessary. We present a case of a 40-year-old female from a village of Kishoregonj, Bangladesh with a proliferative mass in the right parotid region. Surgical excision was done and the presence of R. seeberi on histopathologic analysis of the specimen was identified.

A 40-year-old female presented to the department of otolaryngology with complaints of swelling on right side of the face since 5 months associated with a history of rapid increase in its size and also pain around the swelling. There was no history of trauma in the recent past. Patient had history of consumption of unprocessed well water. On clinical examination, patient was moderately built with no signs of parlor, jaundice, or lymphadenopathy. Systemic examination also did not reveal any abnormalities. The nose, nasopharynx, oropharynx, and eyes appeared normal. On local examination, there was a single, soft to firm consistency, discrete swelling on the right side of the cheek measuring about 4 × 3 cm. Overlying skin was normal in color and texture with no local rise of temperature. There was tenderness felt on palpation with no fixity to underlying skin or structure. Routine laboratory investigation revealed eosinophilia (eosinophils, 15%). The fine-needle aspiration cytology (FNAC) showed presence of neutrophils and lymphocytes admixed with clusters and acini of ductal and myoepithelial cells. Ultrasonography (USG) showed a solid and cystic lesion in the subcutaneous plane of cheek of size (3 × 1.6) cm, with echogenic debris and internal septations. Surgical excision of the lesion was done under general anesthesia. The lesion was identified as dilated segment of the parotid. The proximal and distal parts of the ducts were dissected further and were found to be in continuity with the mass itself. The excised specimen was submitted for histopathologic examination. The hematoxylin-eosin stained sections showed thin fibrocollagenous parotid duct wall lined by columnar to cuboidal cells with the presence of numerous, non-vital sporangia of R. seeberi (Figs. 1 and 2). Histopathological examination confirmed the diagnosis of rhinosporidiosis of the parotid gland duct.

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Figure 1. Section shows multiple variable sized sporangia with large number of microspores inside (H&E stain, low power view).

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Figure 2. Sporangia with large number of microspores inside (H&E stain, high power view).

The pathogen R. seeberi was first discovered by Malbran in 1892 and later cases in cattle were reported in India in 1894 [3]. It was first described by Seeber in 1900 in the nasal region in his doctoral thesis of medicine [4]. Surface water is considered to be the natural habitant of R. seeberi. Human infection probably occurs owing to its contact to traumatized epithelium present in contaminated water. For this reason, the highest incidence of infection is reported among river-sand workers [5]. Review of the literature shows frequency of the disease to be greater in South Asia, with the largest number of cases having been reported in Southern India and Sri Lanka [2]. Men are affected more than women (male to female ratio, 4:1). Patients of all ages are affected, but the disease most frequently occurs in those aged between 20 and 35 years. Common sites of involvement include the nose and upper respiratory tract [1]. In our case, the parotid was considered to be the primary site of inoculation of the organism because there were no other nasal or nasopharyngeal lesions. The diagnosis of rhinosporidiosis is primarily made by observing the distinctive morphologic features of R. seeberi in affected tissue. Its life cycle begins in the tissue as a spore, and it passes through several stages of development from trophocyte to juvenile sporangium to mature forms with changes in thickness and lamination of walls. Nuclear condensation takes place to form endospores embedded in a mucoid matrix. Characteristically, special electron dense bodies of about 1 - 3 mm are seen in mature endospores. These endospores become extruded into the surrounding thick sporangial wall and eventually develop into trophocytes to perpetuate their life cycle [5].

The most common mode of spread to host is by transepithelial infection or by autoinoculation. R. seeberi is most likely waterborne with a high incidence observed in patients who dive and swim in stagnant water [6]. Individuals probably acquire the disease from water contaminated by diseased cattle. Because the organism has not been isolated in culture, the histopathologic examination remains the gold standard for diagnosis [7]. The larger and thick walled sporangia of R. seeberi differentiate this lesion distinctly from the organism causing coccidioidomycosis [8]. The only drug which has been shown to have some rhinosporicidal effect is Dapsone, which arrests the maturation of sporangia and promotes fibrosis in the stroma, when used as an adjunct to surgery [6]. Treatment of choice is surgical resection as most recurrences occur due to spillage of endospores on adjacent mucosa [1].

Rhinosporidiosis is a benign chronic granulomatous fungal disease caused by R. seeberi. The most common site of infection in humans is the nose and the disease commonly presents as polypoidal lesions in nose and in extra-nasal sites. Histopathology is the standard method for confirmation of diagnosis. Cytology can be used as an adjunct for pre-operative diagnosis of extra-nasal rhinosporidiosis. The purpose of this report is to encourage clinicians to be flexible in the differential diagnosis of proliferative growth in the parotid duct, even in those from non-endemic areas.

Conflicts of Interest

None.

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