Anatomic Pathology: Infectious Disease Pathology

1033) A renal transplant recipient developed an enlarging cavitating pulmonary lesion that did not respond to conventional antibiotic therapy. A tuberculin skin test was negative. A bronchoscopic biopsy was nondiagnostic. A lobectomy was performed. A section of the necrotic tissue surrounding the cavity was stained with Gomori methenamine silver (GMS) and disclosed fungal hyphae. All of the following statements about the infection are true EXCEPT:

Mucor is a broad, ribbonlike, pleomorphic hypha, branching at angles of between 45 and 90 degrees, with few or no septa (pauciseptate rather than aseptate).

• Most patients who develop this infection have an underlying disease; diabetes is the most common (36%).

• The most common clinical presentation in patients with diabetes is rhinocerebral mucormycosis (66%). In this population, pulmonary disease accounts for 16% of cases of mucormycosis.

• The inflammatory response may be neutrophilic (50%), predominantly granulomatous (5%), pyogranulomatous (25%), or absent (20%).

• Blood vessel invasion is said to be present in 100% of cases, and perineural invasion is present in 90%.

Frater JL, Hall GS, Procop GW: Histologic features of zygomycosis: emphasis on perineural invasion and fungal morphology. Arch Pathol Lab Med 2001;125(3):375-378.

Sun HY, Singh N: Mucormycosis: its contemporary face and management strategies. Lancet Infect Dis 2011;11(4):301-311.

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