Gastrointestinal basidiobolomycosis: an unusual fungal infection mimicking colon cancer.
Abstract: * Context.--Basidiobolomycosis is a rare disease caused by the fungus Basidiobolus ranarum, an environmental saprophyte found worldwide. Patients with B ranarum infection may present with subcutaneous, gastrointestinal, or systemic lesions. Gastrointestinal basidiobolomycosis poses diagnostic difficulties, as its clinical presentation is nonspecific, with no identifiable risk factors.

Objective.--To discuss and compare the clinical features and histopathologic findings and other ancillary techniques that could be helpful in identifying gastrointestinal basidiobolomycosis.

Design.--We report 3 cases of gastrointestinal basidiobolomycosis and describe the clinical and morphologic findings while emphasizing the importance of identifying this unusual entity on endoscopic biopsies, thus avoiding unnecessary major surgeries. Fungal cultures were also performed, which are of diagnostic significance. Our first patient was lost to follow-up; however, patients 2 and 3 were followed up for 4 and 2 years, respectively.

Results.--In all 3 cases, patients presented with a clinical profile suggestive of malignancy. None of the patients gave any specific history. There was widespread abdominal disease with peritoneal involvement and colonic masses. Colonoscopic biopsy specimens showed nonspecific inflammation in 1 case; however, they showed only granulomatous inflammation in a second case and granulomas associated with fungal hyphae in a third. Typical morphology included hyphae, irregularly branched, thin-walled, occasionally septated and surrounded by a thick eosinophilic cuff (Splendore-Hoeppli phenomenon).

Conclusion.--Gastrointestinal basidiobolomycosis can be detected on small endoscopic biopsy. The unequivocal diagnosis requires microbiologic cultivation of the fungus obtained from tissues. The prognosis for this disease is usually favorable as seen in 3 of our cases; however, cases with fatal outcome are on record.

(Arch Pathol Lab Med. 2009;133:1938-1942)
Article Type: Case study
Subject: Mycoses (Diagnosis)
Mycoses (Case studies)
Mycoses (Prognosis)
Colon cancer (Diagnosis)
Colon cancer (Case studies)
Colon cancer (Prognosis)
Colonoscopy (Usage)
Biopsy (Usage)
Gastrointestinal diseases (Diagnosis)
Gastrointestinal diseases (Case studies)
Gastrointestinal diseases (Prognosis)
Authors: Nemenqani, Dalal
Yaqoob, Nausheen
Khoja, Hatem
Al Saif, Osama
Amra, Nasir K.
Amr, Samir S.
Pub Date: 12/01/2009
Publication: Name: Archives of Pathology & Laboratory Medicine Publisher: College of American Pathologists Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 College of American Pathologists ISSN: 1543-2165
Issue: Date: Dec, 2009 Source Volume: 133 Source Issue: 12
Accession Number: 230246906
Full Text: Basidiobolomycosis is a rare disease caused by the fungus Basidiobolus ranarum, an environmental saprophyte found worldwide. Basidiobolus ranarum is a fungus belonging to the Entomophthoraceae family of the class Zygomycetes and is mainly associated with subcutaneous fat tissue infection involving the limbs, trunk, or buttocks. It is presumed that infection is acquired after minor trauma to skin or insect bites. Most cases of basidiobolomycosis have been reported from tropical and subtropical regions of Africa, South America, and Asia. (1) The causative agent is common in soil, decaying vegetable matter, and the dung of amphibians, reptiles, fish, and insectivorous bats. A review of zygomycosis due to B ranarum1 suggests that this mold is known to produce several enzymes, for example, lipase and protease, that probably play a role in the pathogenesis of infections. Laboratory diagnosis is based on histopathology; however, definitive diagnosis requires microbiologic culture and serologic testing via immunodiffusion method. The mold's structural elements include both hyphae and zygospores. Visceral involvement is rare. Patients with B ranarum infection may present with subcutaneous, gastrointestinal, or systemic lesions. Recently, its etiologic role in gastrointestinal infections has been increasingly recognized. Ingestion of soil, animal feces, and food contaminated by either, as well as rectal inoculation are the most likely routes of infection. Symptoms include fever, abdominal pain, diarrhea, constipation, weight loss, and rarely, chills and rigors. Gastrointestinal basidiobolomycosis (GIB) poses diagnostic difficulties, as its clinical presentation is nonspecific, with no identifiable risk factors. All age groups are susceptible, and the condition is reported both in children (2) and adults.


Case 1

A 77-year-old farmer from the southern region of Saudi Arabia presented with right lower quadrant pain and constipation of 2 months' duration. He had been otherwise healthy. In September 2000, he presented to a regional hospital with pain and a tender mass in the right iliac fossa. Ultrasound was done that showed an irregular mass, 9.0 X 7.0 cm in size in the right iliac fossa. Barium enema showed a mass in the cecum and ascending colon. The patient refused any further management and left the hospital. Shortly after, he presented to Al-Hada Military Hospital in Taif, Western Saudi Arabia, with the same symptoms but we found out that his abdominal pain dated back 15 years. In addition, he gave history of weight loss and occasional rectal bleeding.

On physical examination the patient looked emaciated. His pulse, blood pressure, and temperature were normal. His abdomen was soft and lax, but the patient had a tender palpable mass in the right lower quadrant. Rectal examination was unremarkable.

Results of laboratory investigations showed normal white cell count, hemoglobin level of 15.1 g/dL, and normal liver function tests, electrolyte levels, blood urea nitrogen values, and creatinine levels. Computerized tomography showed diffuse thickening of the entire right colonic wall with nonhomogenous enhancement and considerable narrowing of lumen (Figure 1). Pericolonic infiltration was noted and a normal appendix identified retrocecally. No regional lymph node involvement was seen.

Colonoscopy showed a large infiltrating mass extending from the cecum into the ascending colon with multiple areas of mucosal hemorrhage and ulcerations. The biopsy specimen showed the lamina propria heavily infiltrated by lymphocytes, plasma cells, neutrophils, and eosinophils with areas of eosinophilic abscesses. The pathologic diagnosis was active colitis. Because of a clinical profile suggestive of malignancy with an impending colonic obstruction, an extended right hemicolectomy was done.

Grossly, the specimen was a segment of colon measuring 36.0 X 18.0 X 6.0 cm with pericolic fat. A hard nodular mass, involving and fixed to the pericolic fat, measured 10.0 X 9.0 X 7.0 cm. Upon opening the specimen, multiple areas of mucosal hemorrhage and ulceration were seen, with thickening of pericolic fat (maximum thickness of 5.0 cm). Abscess cavities were seen with numerous pericolic lymph nodes, with the largest measuring 1.5 cm.

Microscopic sections showed multiple areas of ulceration and infiltration by acute and chronic inflammatory infiltrate formed of neutrophils and numerous eosinophils, along with lymphocytes and plasma cells. They involved the entire colonic wall and extended to the pericolic fat. Microabscesses were also seen. There were areas of necrotizing inflammation with marked eosinophilic infiltrate, central necrotic debris surrounded by palisading histiocytes, and foreign body-type giant cell reaction (Figure 2). Among these areas were numerous broad, thick septate fungal hyphae surrounded by eosinophilic proteinaceous material (Splendore-Hoeppli phenomenon) (Figure 3). They stained positively with periodic acid-Schiff (Figure 4) and Grocott-Gomori methenamine-silver stain (Figure 5). Fungal hyphae were also seen in the multinucleated giant cell (Figure 6). Sections from the abscess cavities showed dense eosinophilic abscesses in the colonic wall. Sections from pericolic lymph nodes showed reactive lymphoid follicular hyperplasia. Features were suggestive of colonic basidiobolomycosis. No evidence of malignancy was seen. Postoperatively, the patient's recovery was uneventful. The abdominal wound healed satisfactorily. He was given oral itraconazole, 200 mg twice daily, and was discharged 2 weeks later. The patient was lost to follow-up, an occurrence well noted among Bedouins in Saudi Arabia.

Case 2

A 19-year-old Saudi woman had a history of right iliac fossa pain of 7 months' duration that was associated with intermittent fever with chills and weight loss of 5 kg. She had constipation but no history of melena or rectal bleeding. Colonoscopy was performed and revealed colonic mucosa with cobblestone appearance, suggestive of Crohn disease and a large colonic mass at the ileocecal junction. A colonic biopsy specimen revealed granulomatous inflammation only. Special stains for fungus and acid-fast bacilli were negative.

The mass in the right iliac fossa increased in size and a laparotomy was performed in October 2001. A large inflammatory mass was identified that extended from the distal 5 cm of the terminal ileum up to the hepatic flexure. This mass was adherent to the anterior abdominal wall and extended to the pelvic cavity. The abdominal wall on the right lower quadrant was thickened, edematous, and hyperemic with the mass densely adherent to it, with some infiltrations to the abdominal muscle. The mass was adherent to the right ovary, fallopian tube, and ureter. The hepatic flexure of the colon also showed a mass that was adherent to the duodenum. Perioperatively, widespread malignancy was suspected. We felt that resection of the mass would be a risky and difficult procedure and we decided to biopsy the omentum and the abdominal wall.

Histologic examination of biopsies taken from the abdominal wall adherent to the mass showed the presence of fungal hyphae that had large width, were pauciseptate, and were surrounded by eosinophils with multinucleated giant cells, lymphocytes, and histiocytes. A biopsy specimen from the omentum revealed fat necrosis.

The patient was referred to a specialist hospital for further evaluation and management. She underwent ultrasound-guided needle aspiration and Tru-Cut core biopsy of the colonic mass. The biopsy revealed granulomatous inflammation with fungal hyphae associated with prominent eosinophilic material (spendore hoeppli phenomenon) infiltrate and multinucleated giant cells (Figure 7), features suggestive of basidiobolomycosis. Fungal cultures were consistent with B ranarum. The patient was administered AmBisome (amphotericin B, liposome for injection) (Fujisawa USA, Deerfield, Illinois) and itraconazole. The patient responded well to treatment and remained afebrile with regression of the size of the abdominal mass. However, liver function started to deteriorate and AmBisome was discontinued and replaced with amphotericin B. The patient had been followed up for 4 years and her condition had improved markedly. She is currently receiving ketoconazole, 600 mg once a day.

Case 3

A 20-year-old man presented with a history of weight loss. On examination, he was cachetic and pale, had a hemoglobin level of 8 g/dL, and a positive test result for stool occult blood. Imaging revealed a large mass involving the colonic wall and porta hepatis, probably representing enlarged matted lymph nodes. The mass was obscuring the gall bladder and hepatic bed. Clinical diagnosis of suspected disseminated malignant disease was made. Colonoscopy showed ulceration and polypoid masses involving the right colon. Colonoscopic biopsy specimens showed acute and chronic inflammation with numerous eosinophils and poorly formed granulomas with giant cells surrounding organisms that were morphologically consistent with fungal elements that stain positively with periodic acid-Schiff and Grocott-Gomori methenamine-silver stains. A diagnosis of basidiobolomycosis was suggested. Because the patient was unable to eat, jejunostomy was planned with feeding tube insertion and biopsies from porta hepatis mass, gall bladder wall, and liver were performed. Histopathologic examination showed extensive inflammation, granulomas with eosinophils and numerous fungal hyphae, and zygospores surrounded by eosinophilic material called the Splendore-Hoeppli phenomenon. Hyphae were broad, thin walled, and septate and some contained zygospores (Figure 8). They were found in the tissue as well as inside giant cells. No angiovascular invasion was noted. The material was sent for fungal culture testing and the results were consistent with B ranarum. The patient received voriconazole, and significant reduction in mass size was observed on computed tomography scan, with improvement of general condition and weight gain. He is still receiving antifungal therapy, with a plan to continue therapy for 2 years with regular monthly follow-ups.


Entomophthoromycosis is a rare form of zygomycosis. The 2 principal species responsible for most of these infections are Basidiobolus ranarum and Conidiobolus coronatus. Basidiobolus ranarum was first isolated in 1955 from decaying plants in the United States and subsequently has been found in soil and vegetations throughout the world. (3)









Gastrointestinal basidiobolomycosis is extremely unusual; only 15 cases have been reported worldwide (2 cases from Nigeria, 4 from Brazil, 1 from Kuwait, and 8 from the United States). (4) From 1994 to 1997, a reported 7 cases of GIB occurred in Arizona, 4 of which were identified between December 1998 and April 1999. Lyon et al (5) studied the clinical and epidemiologic characteristics of these 7 patients to identify potential risk factors for GIB. Association of GIB with smoking and use of ranitidine was found to be of statistical significance. Most of the patients in the reported cases were adults. Al Jarie et al (6) have presented the largest reported series of 6 patients in the pediatric age group.

The Entomophthorales are true pathogens, infecting primarily immunocompetent hosts. Most patients are in apparent good health before acquiring infection. Basidiobolus ranarum organisms generally do not invade blood vessels and rarely disseminate. (7) However, van den Berk et al (8) have presented a case of obstructing colon tumor with associated liver mass and Bigliazzi et al (9) have presented a case of disseminated basidiobolomycosis in an immunocompetent woman, with lung involvement as the first clinical manifestation. The prognosis of GIB is usually favorable; however, both these cases had fatal outcomes.

The only organisms in the histologic differential are Conidiobolus coronatus, Conidiobolus incongruus, and Pythium insidiosum, organisms that are associated with head and neck disease in humans or pleuropericarditis in immunosuppressed patients; however, these microorganisms would be equally rare as a cause of disseminated disease in immunocompetent subjects. (9)

The unequivocal diagnosis requires microbiologic cultivation of the fungus obtained from tissues. It can be isolated from surgical specimens, and it should be inoculated soon after resection because it does not survive at 4[degrees]C. Sabouraud agar is an adequate medium, and visible growth is usually present 2 to 3 days after incubation at 25[degrees]C to 30[degrees]C. Colonies appear white or pale grey and have radial folds. The fungal elements appear as broad, pleomorphic, sparsely septated hyphae, which stain faintly with fungal stains (Grocott-Gomori methenamine-silver, periodic acid-Schiff). Khan et al (10) for the first time reported raised levels of Th2-type cytokines (interleukins 4 and 10) and macrophage cytokine tumor necrosis factor a and also elevated serum antibody levels of B ranarum mycelial antigen-specific IgG, IgG1, and IgG3. In our series, fungal cultures were done on 2 cases, which were positive, as the initial colonic biopsies showed granulomatous inflammation; however, no culture or serology was done in case 1 because of nonspecific findings on colonoscopic biopsies. Although culture or serology tests are required for definitive diagnosis, histologic analysis can provide a probable diagnosis of GIB.

Kaufman et al (11) have described immunodiffusion tests to detect and distinguish B ranarum antibodies from those of C coronatus and of other fungal pathogens. Serial serologic studies have shown that the immunodiffusion test results not only contribute to the diagnosis of disease caused by B ranarum but also correlate with its resolution. Serodiagnosis with immunodiffusion can be used as an adjunctive diagnostic method; the test appears to be very specific for B ranarum with no crossreactivity with other species of the order Entomophthorales, but its sensitivity has not been determined.

On histopathologic examination, the infection seems to involve the nonmucosal layers of the gastrointestinal tract; imaging and endoscopic biopsy specimens may show nonspecific inflammation. Neutrophilic infiltrate is rare. Yousef et al (12) have described 2 cases of colonic perforation in a case series of 6 patients with GIB. Resected stomach and intestinal specimens were characterized by marked mural thickening with fibrosis, prominent tissue eosinophilic infiltration, and palisading granulomatous inflammation around pale fungal hyphae. Typical morphologic features include hyphae that are irregularly branched, thin walled, occasionally septated, and surrounded by a thick eosinophilic cuff (Splendore-Hoeppli phenomenon); the presence of a few associated sporelike spherules, although not entirely specific, are characteristic histologic features. Most reported cases of basidiobolomycosis show the presence of a prominent or intense Splendore-Hoeppli phenomenon surrounding fungal elements. This phenomenon refers to radiating or annular amorphous eosinophilic deposits of host-derived materials and possibly of parasite antigens. It usually forms around fungi, helminths or their ova, or bacterial colonies and, on rare occasions, suture material in tissues. It is usually surrounded by inflammatory cells including eosinophils, neutrophils, histiocytes, lymphocytes, and multinucleated giant cells. The infiltrate varies from one case to another. Immunohistochemical studies13 reveal the presence of immunoglobulin deposition or deposits of eosinophil major basic protein. This phenomenon was described for the first time in 1908 in Brazil by Splendore, who thought that it was a new species of Sporotrichum. In 1932, Hoeppli noticed similar raylike eosinophilic structures around schistosomal ova in rabbit tissue. In the following years, authors used the term Splendore-Hoeppli phenomenon to describe the radiating eosinophilic deposits. (14) This phenomenon had been reported most commonly in association with cases of botryomycosis, which are not fungal infections but are due to aggregates of bacteria. (15) Other infections had been associated with this phenomenon, including actinomycosis, (16) aspergillosis, (17) and zygomycosis particularly basidiosis.

Gastrointestinal basidiobolomycosis should be kept in the differential diagnosis of inflammatory diseases of the gastrointestinal tract. Zavasky et al (18) have reported a case of GIB that was initially treated as inflammatory bowel disease.

Optimal treatment of GIB combines surgical and medical methods. Patients should undergo resection of all affected bowel segments and debridement of involved tissue that is followed by antifungal therapy for a period of more than 3 months. The role of adjunctive systemic antifungal therapy is established. The efficacy of amphotericin B in visceral infections has been unsatisfactory, with resistance observed in greater than 50% of cases. (2) Prolonged treatment with itraconazole is the best option. Potassium iodide (KI) has been used successfully for treatment of subcutaneous basidiobolomycosis but not GIB.

In all 3 cases, patients presented with a clinical profile suggestive of malignancy. None of the patients gave any specific history that could point toward possible causes of fungal exposure. There was widespread abdominal disease with peritoneal involvement and colonic masses. Colonoscopic biopsy specimens showed nonspecific inflammation in 1 case; however, they showed only granulomatous inflammation in a second case and granulomas associated with fungal hyphae in a third; these findings were correlated with depth and number of biopsies taken. Gastrointestinal basidiobolomycosis can be detected on deeper mucosal biopsies, as the infection seems to involve the nonmucosal layers of the gastrointestinal tract.

Gastrointestinal basidiobolomycosis may be emerging as a result of various environmental and demographic factors. The worldwide distribution may be attributed to globalization and increased travel within different geographic areas. (19) Increased awareness of this entity will lead to earlier diagnosis, a reduction in unnecessary surgeries, and a likely reduction in mortality.


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Dalal Nemenqani, MD, FRCPath, FPath KSU, FIAC; Nausheen Yaqoob, MBBS, FCPS; Hatem Khoja, MD; Osama Al Saif, MD, FRCPC; Nasir K. Amra, MD; Samir S. Amr, MD

Accepted for publication February 23, 2009.

From the Department of Pathology and Laboratory Medicine, King Abdul Aziz Specialist Hospital, Taif, Kingdom of Saudi Arabia (Drs Nemenqani and Yaqoob); the Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia (Dr Khoja); the Department of Pathology and Laboratory Medicine, King Fahad Specialist Hospital, Dammam, Kingdom of Saudi Arabia (Dr Al Saif); and the Department of Pathology and Laboratory Medicine, ARAMCO Health Care Centre, Dammam, Kingdom of Saudi Arabia (Drs Amra and Amr).

The authors have no relevant financial interest in the products or companies described in this article.

Reprints: Dalal Nemenqani, MD, FRCPath, FPath KSU, FIAC, Department of Pathology and Laboratory Medicine, King Abdul Aziz Specialist Hospital, Al Shafa, Taif, Western 5262, Kingdom of Saudi Arabia (e-mail:
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