Pathologic Quiz Case: A Woman With Human Immunodeficiency Virus With Right Lower Quadrant Pain and Ascending Colon Mass

Archives of Pathology & Laboratory Medicine,  Feb 2005  by Jani, Jigna C,  Brown, Russell,  Kajdacsy-Balla, Andre,  Guzman, Grace

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A 44-year-old African American woman with a past medical history of acquired immunodeficiency syndrome and hepatitis C cirrhosis presented to our institution with complaints of right lower quadrant pain for 2 months. The pain occurred daily and was constant, with acute exacerbations from food consumption and mild relief from ibuprofen and lying down. She had history of anorexia but no history of nausea or vomiting. She also had a history of diarrhea for 2 months, with 2 episodes daily. There was no history of melena or hematochezia. She was taking a number of antiretroviral medications.

Her physical examination revealed mild abdominal distension and marked tenderness in the right lower quadrant, with guarding but without rebound. Hepatomegaly to 2 to 3 cm below the right costal margin was noted. A digital rectal examination revealed external hemorrhoids and a 2-cm palpable rectal mass that was soft, mobile, and somewhat tender. The stools were heme positive and brown in color.

Computed tomographic scan of the abdomen showed an irregular thickening of the cecum and ascending colon with mild fat stranding. The thickening was abrupt and had sharp margins, with adjacent colon appearing normal. There was no evidence of abscess. Para-aortic and mesenteric lymphadenopathy were seen measuring 2 cm in greatest dimension; retrocrural lymphadenopathy was seen as well.

Colonoscopy demonstrated a large, polypoid, ulcerated, and malignant-appearing tumor in the ascending colon. There was no active bleeding noted or stigmata of recent hemorrhage (Figure 1). The mass was biopsied and sent for histology and viral cultures. A similar but smaller lesion was seen in the rectum, and it was also biopsied. Multiple sessile polypoid lesions were also found in the transverse, descending, and sigmoid colon.

The specimen received in the surgical pathology laboratory consisted of biopsy of ascending colon and rectal masses. Biopsy of the ascending colon mass consisted of few irregular fragments of tan soft tissue measuring 0.7 × 0.3 × 0.3 cm, whereas the rectal lesion consisted of a cobblestone, polypoid, brown tan structure measuring 0.7 × 0.6 × 0.3 cm.

Microscopically, both biopsies showed colonic mucosa with florid histiocytic infiltrates within the lamina propria containing multiple organisms (Figures 2 and 3). Special stains were performed, including periodic acid-Schiff and Gomori methenamine silver (shown in Figure 4). Giemsa, acid-fast bacilli, and mucicarmine stains were negative.

What is your diagnosis?

Pathologic Diagnosis: Histoplasmosis of the Colon

Histoplasma capsulcaum is a ubiquitous dimorphic fungus. It grows as mold in nature and as budding yeast in host tissue and on enriched agar.1 The fungus usually grows in soil enriched with accumulations of bat or bird droppings. The disease is acquired via inhalation of spores (conidia) from soil contaminated with bat or bird droppings.

Primary gastrointestinal infection is an uncommon manifestation of histoplasmosis. It is almost always associated with disseminated disease and often occurs in an immunocompromised host.

Gastrointestinal histoplasmosis is an uncommon complication of acquired immunodeficiency syndrome, but it is occasionally seen, particularly in some endemic areas of North America. Histoplasmosis is more common in the southeastern and south-central United States, especially along major waterways (eg, the watershed areas of the Ohio and Missouri rivers). An association with a disseminated mycotic infection is common. The ileum and cecum are the most common sites involved.2 When the mycologic study is not performed or is negative, only morphologic and immunohistochemical methods can establish the diagnosis and eliminate other mycotic diseases occurring during acquired immunodeficiency syndrome.3 Depending on the layer of bowel wall involvement and the extent of the disease, the manifestations of histoplasmosis vary and can include gastrointestinal bleeding, perforation, peritonitis, and malabsorption syndrome. Perforation most commonly occurs in the small intestine, although colonic perforation is also reported.4 Human immunodeficiency virus disease is often associated with diarrhea, which may be accompanied by enteric infection or gastrointestinal tumor. Patients with CD4 counts of less than 50 cells/mm^sup 3^ and with low albumin levels are more likely to have a primary infectious diagnosis.5

Four different types of intestinal histoplasmosis have been described.6-9 First is the silent infection, with no gross abnormalities but presence of fungus in the lamina propria. Macrophages positive for periodic acid-Schiff in the small intestine biopsy are described in histoplasmosis, and so it is an important element in the differential diagnoses of Whipple disease, Mycobacterium avium intracellulare infection, and macroglobulinemia.9 Small pseudopolyps and plaques characterize the second form. The third type involves discrete ulcerations in the mucosa. Fourth, rarely, thickening of bowel leads to obstructive symptoms mimicking Crohn disease or malignancy.2,6 This fourth type is the extremely rare category of gastrointestinal histoplasmosis. Our patient had both the second type and this rare fourth type.