Pulmonary sclerosing pneumocytoma: Cytomorphology and immunoprofile
Zahra Maleki1, Stephanie Muller2, Lester Layfield3
1Division of Cytopathology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
Insights
Sclerosing pneumocytoma (SP) is a rare lung tumor. This study details its cytomorphology and immunoprofile, highlighting features that distinguish it from lung adenocarcinoma to prevent misdiagnosis.
Area of Science:
- Pulmonary Pathology
- Cytopathology
- Surgical Pathology
Background:
- Sclerosing pneumocytoma (SP) is an uncommon, benign lung neoplasm.
- This study represents the first series to analyze the cytomorphology and immunoprofile of SP.
Purpose of the Study:
- To evaluate the cytomorphologic features of sclerosing pneumocytoma (SP) in fine-needle aspiration samples.
- To determine the immunoprofile of SP and differentiate it from malignant lung neoplasms.
- To establish diagnostic criteria for SP in cytopathology.
Main Methods:
- Retrospective analysis of 9 fine-needle aspiration (FNA) cases of SP.
- Inclusion of histopathology and immunohistochemistry data for all cases.
- Cases were obtained from 5 different institutions, with CT-guided and EBUS-guided FNA.
Main Results:
- SP cases presented as lung nodules (mean size 2.2 cm) in patients with a mean age of 54 years (female:male ratio 3.5:1).
- Cytology revealed epithelioid cells with clear features, columnar cells, and spindle cells in papillary, sheet-like, and acinar patterns.
- Tumor cells showed mild to moderate pleomorphism; immunohistochemistry was positive for TTF-1 and EMA in all cases.
Conclusions:
- Cytomorphological features of SP can mimic well-differentiated lung adenocarcinoma.
- Distinct immunoprofile and cytomorphologic findings of SP are crucial for accurate diagnosis.
- Awareness of these features can prevent misdiagnosis and unnecessary aggressive treatment.
Background:
Sclerosing pneumocytoma (SP) is a rare, benign pulmonary neoplasm. To the authors' knowledge, the current study is the first to evaluate the cytomorphology and immunoprofile of SP in a series.
Methods:
A total of 9 fine-needle aspiration cases of SP (7 of which were computed tomography guided and 2 of which were endobronchial ultrasound guided) including histopathology and immunohistochemistry were collected from 5 institutions.
Results:
The female-to-male ratio was 3.5:1, and the mean age of the patients was 54 years (range, 27-73 years). All cases presented as lung nodules, with a mean size of 2.2 cm (range, 1.1-5 cm), and were interpreted as atypical on rapid on-site evaluation. The final diagnoses were favor adenocarcinoma (1 case), well-differentiated lung adenocarcinoma (2 cases), low-grade epithelial neoplasm (2 cases), and sclerosing pneumocytoma (4 cases). Samples were moderately cellular, and consisted of round epithelioid cells with clear cell features, columnar cells, and spindle cells. A papillary arrangement with prominent hyalinized fibrovascular cores was the most common architectural pattern, followed by flat sheets and acinar formations. Tumor cells demonstrated mild, focally moderate nuclear pleomorphism with prominent nucleoli, hyperchromasia, nuclear elongation, nuclear overlap, and occasional nuclear inclusions and grooves. The background consisted of foamy macrophages (9 cases), hemosiderin pigment (6 cases), and lymphoid aggregates (3 cases) with no mitoses and/or necrosis. The surface cells and underlying round cells were positive for both thyroid transcription factor 1 and epithelial membrane antigen in all cases, which was the most notable immunohistochemical finding.
Conclusions:
Cytomorphological findings of SP overlap with those of well-differentiated lung adenocarcinoma. Awareness of these cytomorphologic findings and the distinct immunoprofile of the 2 cell types found in SP should prevent a misdiagnosis and aggressive treatment.
