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OJHAS Vol. 9, Issue 3:
(Jul - Sep, 2010) |
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| Amoeboma-
An Interesting Case Report With an Unusual Presentation |
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Vijayshankar S, Assistant Professor, Department of Pathology,
Usha Ramachandra, Professor and Head, Department of Pathology,
Vastala
Rao, Professor, Department
of Pathology,
Sujatha
Siddappa, Assistant Professor, Department
of Pathology,
Adichunchanagiri Institute of Medical Sciences, BG Nagara, Bellur cross, Mandya district, Karnataka, India. |
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Address For Correspondence |
No 45, Ananda
shylam, 3rd cross,
1st
main K N extension, Yeswanthpur,
Bangalore - 560022,
Karnataka
E-mail:
vijayshankarpatho@gmail.com |
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Vijayshankar S, Usha R, Rao V, Siddappa S. Amoeboma-
An Interesting Case Report With an Unusual Presentation. Online J Health Allied Scs.
2010;9(3):22 |
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Submitted: Aug 8, 2010;
Accepted:
Sep 20, 2010; Published: Oct 15, 2010 |
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| Abstract: |
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Amebiasis is an infectious disease caused by Entamoeba Histolytica
is more common in devolping countries, with various clinical manifestations
and sequalae. Amoeboma , is an unusual sequelae which manifests as a
tumor like mass within the colon. We present an unusual case of 5 year
old child with signs of acute abdomen. A mass was found on expoloratory
laparotomy attached to the small intestine. Histopathological examination
of the mass revealed numerous amoebic trophozoites and the diagnosis
of amoeboma was made. Our case is unusual because amoebomas presenting
as an extraluminal mass attached to small intestine is extremely uncommon.
Key Words: Amoeboma;
Small intestine; Extraluminal mass
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Amoeboma
is a tumour like mass involving the whole thickness of the bowel wall
and may extend into the surrounding part and other structures. It is
one of the manifestation of amoebiasis, but it is rare. The common sites
are cecum, rectosigmoid junction and rectum. Small intestinal involvement
is rare. Lesion presenting as an extraluminal inflammatory mass is very
uncommon. The final diagnosis depends on demonstration of Amoebic trophozoites
in sections by H & E and special stains.
Five year-old
male child presented with acute abdominal pain. On examination the patient
had developed signs of peritonitis. Emergency exploratory laparotomy
revealed a nodular mass in the right iliac fossa about 15 cm proximal
to ileocecal junction. Resection of the mass along with the portion
of small intestine was done.
Pathologic
findings: The specimen
was a segment of small bowel with 30 cm in length, with
a mass measuring 10X8 cm seen adherent to the intestinal wall on
mesenteric side.(Figure 1) The whole of the intestine was covered with
exudates with areas of patchy necrosis. Cut section of small intestine
showed patchy areas of necrosis of the mucosa and ulceration. Cut section
of the mass showed extensive area of necrosis along with gray white
areas.(Figure 1)
Microscopy:
Multiple
sections from the small intestine showed the ulceration of mucosa, necrotic
area with extensive infiltration by acute and chronic inflammatory cells. Many trophozoites
were seen in the margins of necrotic areas.
Multiple
sections from the mass showed extensive areas of necrosis, sheets of mixed
inflammatory cells and many multinucleated giant cells. Amidst these
are seen numerous trophozoites.(Figure2) These trophozoites resembled
large histiocytes with granular cytoplasm and inconspicuous nuclei.
These were confirmed by PAS stain and iron hemotoxylin and eosin
stains.(Figure3)
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Figure 1:Photograph showing
segment of small intestine with an adjacent greywhite mass |
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Figure
2: Photomicrograph showing many trophozoites in the background of
inflammatory cells and necrotic debris( hematoxylin & eosin x 400) |
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Figure 3: Photomicrograph
showing trophozoite (Iron hematoxylin & Eosin x 1000) |
Amebomas or amoebic granulomas are unusual sequelae of amebiasis. It
is rare with an incidence of 1.5% of patients with intestinal amebiasis.1
Amoebomas can occur in any age groups but are usually common in the
age 20 to 60 years. There are a greater proportion of men than women
who are affected by all forms of invasive amebiasis.
Ochsner and De Bakey coined the term”ameboma” to describe a cicartrical
inflammatory lesion that develops following acute amebic dysentery.2 Where as “amebic granuloma”
describes the microscopic pathologic finding seen in chronic amebiasis.
These lesions may vary in size from mucosal excrescences to large tumor
masses; the term “ameboma” is best reserved for those large amebic
granulomas.
Amebomas are found in descending order of frequency in the cecum, the
appendix,rectum, transverse colon, sigmoid colon and rarely hepatic
and splenic flexure.3 They can occur in single or at multiple
sites.4 Extension of the granuloma into the ileum may occasionally
be seen.
The appearance of ameboma is function of balance between inflammation
and fibrosis.2 If there is abundance of inflammatory cells,
an intraluminal polypoidal lesion may be mimicked. If there is marked
fibrosis with few inflammatory cells, intramural shortening and constriction
of the bowel wall may be seen.
Clinically
amebomas cause a variety of symptoms including alternating diarrhea
and constipation, weight loss and low-grade fever. Very rarely they
can present without any gastrointestinal symptoms.5 Most
often ameboma occurs in the course of proven amebic colitis, and a combination
of tumor and colitis justifies a presumptive diagnosis. Clinically if
there is a mass lesion it can mimic malignancy. Since amoebomas are
a rare entity, it is usually discovered at laparotomy. However in the
absence of clinical picture or proven amebic colitis, the diagnosis
may be a great challenge even at laparotomy, as was in our case. The
symptoms may be so insidious that the patient is unaware until a major
complication occurs.
The right diagnosis is by histopathological demonstration of trophozoites
in the inflammatory mass or the bowel wall. The trophozoites resemble
large histiocytes have granular and bluish gray cytoplasm and may contain
ingested RBC`s the nucleus is inconspicuous central or eccentric, with
a single central karyosome which is difficult to see in H & E stain. The
cytoplasm is PAS positive. Iron hematoxylin stain can also be used to
demonstrate trophozoites in the sections.
The primary
treatment is oral metranidazole therapy for 5 to 10 days. Longer intervals
of treatment is necessary in cases with ameboma formation. Surgical
intervention is indicated if there is bowel perforation, acute necrotizing
colitis or if the patient does not respond to anti amebic therapy.5
Our case is an unusual presentation of ameboma, as an extraluminal mass
adjacent to the small bowel. We haven’t come across such a presentation,
in spite of thorough search in the literature. Hence it is advisable
to keep “ameboma” as one of the differential diagnosis in the evaluation
of abdominal masses in children.A high index of suspicion is required
for appropriate diagnosis and management.
We thank Dr. Indira CS, Faculty, all other teaching and non teaching
staff, dept of pathology AIMS, Bellur and our institution, for providing
help during execution of this work.
- Misra SP, Misra
V, Dwivedi M. Ileocecal masses in patients with amebic liver abscess:
etiology and management. World J Gastroenterol. 2006 Mar 28;12(12):1933-1936.
- Levine SM, Stover
JF, Warren JG et al. Ameboma, the forgotten granuloma. JAMA. March 1971;215(9):1461–1464.
- Fernandes H, D'Souza
CR, Swethadri GK, Naik CN.Ameboma of the colon with amebic liver abscess
mimicking metastatic colon cancer. Indian J Pathol Microbiol. 2009 Apr-Jun;52(2):228-230.
- Haque R, Huston
CD, Hughes M, Houpt E, Petri WA Jr. Amebiasis. N Engl J Med. 2003 Apr
17;348(16):1565-1573.
- Hardin RE, Ferzli
GS, Zenilman ME, Gadangi PK, Bowne WB. Invasive amebiasis and ameboma
formation presenting as a rectal mass: An uncommon case of malignant
masquerade at a western medical center. World J Gastroenterol. 2007 Nov
14;13(42):5659-5661.
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