Pulmonary sclerosing pneumocytoma: Cytomorphology and immunoprofile

Abstract

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 fineneedle 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 femaleto-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. Cancer Cytopathol 2020;128:414-423.

Pulmonary Sclerosing Pneumocytomas Mimicking Lung Cancer

“…These characteristics suggest, according to a study published by Chan et al [ 7 ], that these tumors are derived from either primitive respiratory epithelium or incompletely differentiated type II pneumocytes. As revealed in a 2020 study by Maleki et al [ 8 ], foamy macrophages, nuclear inclusions, and hyalinized fragments are commonly observed cytomorphologic features of sclerosing pneumocytoma. Similarly, the nuclei may occasionally show pleomorphism, hyperchromasia, and prominent nucleoli.…”

Sclerosing Pneumocytoma With Pulmonary Sarcoidosis: A Case Report

“…Tumor cells demonstrate mild, focally moderate nuclear pleomorphism with prominent nucleoli, hyperchromasia, nuclear elongation, nuclear overlap, and occasional nuclear inclusions and grooves. In a study by Maleki et al, the background of samples consisted of foamy macrophages in nine cases, hemosiderin pigment in six cases, and lymphoid aggregates in three cases with no mitoses and/or necrosis [20]. The staining relies on the presence of a two-cell population; TTF-1 positive and cytokeratin negative round cells as well as TTF-1 positive and cytokeratin positive surface cells.…”

Analysis of the value of enhanced CT combined with texture analysis in the differential diagnosis of pulmonary sclerosing pneumocytoma and atypical peripheral lung cancer: a feasibility study

“…Pathological diagnosis of PSP before and during surgery is difficult, as some lesions need postoperative pathological examination and immunohistochemical analysis to make a definite diagnosis [ 9 , 14 ]. Maleki et al [ 8 ] believe that there is overlap between the morphological features of PSP and well-differentiated lung adenocarcinoma, so we should guard against the possibility of misdiagnosis. The complicated pathological structure of PSP determines the diversity of its imaging manifestations.…”