D107-12 Incidental Pulmonary Malakoplakia in an Immunocompromised Host: A Diagnostic Challenge During Chemotherapy Surveillance

Abstract Introduction Malakoplakia is a chronic infection-related non-granulomatous phagolysosomal histiocytic disorder that can occur in immunocompromised patients with hematologic malignancies. The most affected organ system includes the genitourinary tract, followed by the gastrointestinal tract, skin, and other soft tissues. Pulmonary or bronchial involvement accounts for less than 5% of all cases of reported malakoplakia. Case Report A 68-year-old man with a past medical history of gastroesophageal reflux disease, chronic tobacco use, skin cancer status post excision, and large B-cell lymphoma with plasmablastic differentiation (Stage 4b) involving the stomach was admitted for cycle number 3 of inpatient chemotherapy with rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin. A restaging positron emission tomography scan showed borderline enlarged mediastinal lymph nodes and a new hypermetabolic area in the left lower lobe of the lung. Chest computed tomography showed a 1 x 1.2 cm spiculated lesion encasing a subsegmental bronchus. A robotic-assisted bronchoscopy with bronchial wash and culture, in addition to fine needle aspiration of the nodule, was performed. No organisms or polymorphonuclear leukocytes were seen. Subsequent cytology of the biopsied specimen demonstrated malakoplakia. He received meropenem for infection prophylaxis, acyclovir, and trimethoprim-sulfamethoxazole for antimicrobial prophylaxis and was scheduled for outpatient pegfilgrastim administration post-discharge. Doxycycline was initiated at discharge for infection prophylaxis. Discussion Pulmonary malakoplakia represents a rare mass-forming, chronic infection-related, non-granulomatous response caused by the defect of phagolysosomal function of macrophages. In the present case, the patient presented for inpatient chemotherapy and was found to have an incidental nodule on surveillance radiographic studies, which was initially believed to be secondary to lymphoma. Bronchoscopy and subsequent cytology of biopsied specimens were instrumental in establishing the diagnosis. Clinically and radiographically, pulmonary malakoplakia can mimic microaspiration (secondary to GERD), or smoking-related histiocytosis or malignancy; the latter, especially secondary to hematologic malignancies. It is important to consider malakoplakia earlier on in the differential when evaluating incidental or enlarging lung nodules that are found on radiographic studies. Awareness of this rare clinical manifestation is essential to prevent misdiagnosis and unnecessary invasive procedures in immunocompromised patients presenting with new pulmonary nodules. Bronchoscopy and cytological evaluation of bronchoscopy-accessible nodules remain the gold standard diagnostic modalities. Cytological or histological examination of specimens demonstrates the presence of macrophages with characteristic Michaelis-Guttman inclusion bodies. This abstract is funded by: None