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Infectious pseudotumors: red herrings in head and neck pathology
Samir K El-Mofty1, Shreeram Akilesh
1Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA. elmofty@wustl.edu
Abstract:
Infectious pseudotumors are tumor-like growths caused by specific microbial organisms. Proliferating histiocytes in these lesions may show atypical cytology with nuclear pleomorphism and increased mitotic activity, erroneously suggestive of malignancies including carcinoma, sarcoma, and lymphoma. Specific and nonspecific immunohistochemical staining profiles may lead to the consideration of a wide range of benign and malignant neoplastic processes. Two such cases are reported. The first is an obstructive endotracheal mass in an AIDS patient caused by Rhodococcus equi infection. The proliferating histiocyes were cytologically atypical with deeply eosinophlic granular cytoplasm leading to the consideration of oncocytic carcinoma, Hurthle cell carcinoma, and pleomorphic rhabdomyosarcoma. The second case is a nasal mass with a microscopic and immunohistochemical profile suggestive of chordoma and paraganglioma. Special microbial stains revealed intracellular bacilli consistent with Klebsiella rhinoscleromatis. In both cases, microbial virulence factors affecting phagocytosis prolonged their intracellular survival and resulted in active histiocytic proliferation. It is of importance that the surgical pathologist be conscious that some infectious processes can clinically and microscopically mimic malignant neoplasms. Accurately identifying these lesions and the specific causative agent is of particular significance since they can be successfully treated with antibiotics.
Insights
Infectious pseudotumors can mimic cancer due to atypical cell growth. Recognizing these infections is crucial for effective antibiotic treatment, preventing misdiagnosis of malignant neoplasms.
Area of Science:
- Pathology
- Infectious Diseases
- Oncology
Background:
- Infectious pseudotumors are tumor-like lesions caused by microbial agents.
- Proliferating histiocytes in these lesions can exhibit atypical cytology, mimicking malignancy.
- Immunohistochemical profiles may further complicate diagnosis, suggesting various neoplastic processes.
Observation:
- Two cases are presented: an endotracheal mass in an AIDS patient caused by Rhodococcus equi and a nasal mass with Klebsiella rhinoscleromatis.
- Cytological atypia and immunohistochemical findings in both cases initially suggested malignancies like carcinoma, sarcoma, chordoma, and paraganglioma.
- Microbial virulence factors contributed to intracellular survival and histiocytic proliferation.
Findings:
- Rhodococcus equi infection presented as an obstructive endotracheal mass with atypical histiocytes resembling oncocytic carcinoma or rhabdomyosarcoma.
- Klebsiella rhinoscleromatis infection manifested as a nasal mass with features mimicking chordoma and paraganglioma.
- Both infections demonstrated prolonged intracellular survival due to microbial virulence factors affecting phagocytosis, leading to histiocytic proliferation.
Implications:
- Surgical pathologists must be aware that certain infectious processes can clinically and microscopically resemble malignant neoplasms.
- Accurate identification of infectious pseudotumors and their causative agents is critical for appropriate management.
- Prompt diagnosis and treatment with antibiotics can lead to successful resolution of these lesions, avoiding unnecessary oncological interventions.
