Lung
Papillomas and adenomas
Sclerosing pneumocytoma
Author: Roseann I. Wu, M.D., M.P.H.
Last author update: 1 October 2015
Last staff update: 18 April 2023 (update in progress)
Copyright: 2003-2023, PathologyOutlines.com, Inc.
PubMed Search: Sclerosing pneumocytoma [title] lung
Table of Contents
Definition / general | Terminology | Epidemiology | Sites | Etiology | Clinical features | Diagnosis | Radiology description | Prognostic factors | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Wu R. Sclerosing pneumocytoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungtumorsclerosingheman.html. Accessed June 1st, 2023.
Definition / general
- Described by Liebow and Hubbel in 1956 (Cancer 1956;9:53)
- Papillary pattern or islands filled with bland polygonal cells with abundant eosinophilic cytoplasm and indistinct cell borders, often with sclerotic stroma and blood lakes
- Called "sclerosing pneumocytoma" and moved from "miscellaneous tumors" to "Adenomas" in 2015 WHO Classification (J Thorac Oncol 2015;10:1243)
Terminology
- Historic misnomer "sclerosing hemangioma" originated from morphologic similarity to a dermatopathology lesion that was previously called "sclerosing hemangioma", now known as dermatofibroma / fibrous histiocytoma
- Also called pneumocytoma, papillary pneumocytoma (Arch Pathol Lab Med 2009;133:820)
Epidemiology
- Rare benign neoplasm
- 5:1 female to male ratio
- Wide age range with peak in middle age / 50s
Sites
- Peripheral lung parenchyma, any lobe
- Rarely arises centrally or in pleura
Etiology
- Apparently derived from and shows resemblance to pneumocytes (surface cells) and embryonic respiratory epithelium (round cells)
Clinical features
- Typically incidental solitary nodule on chest Xray
- Mostly asymptomatic but may present with nonspecific respiratory symptoms
- Case reports of recurrence and regional lymph node metastases
Diagnosis
- Challenging to distinguish from adenocarcinoma or carcinoid tumor on cytology, small biopsy, frozen sections (J Thorac Oncol 2015;10:1243)
Radiology description
- Solitary, peripheral, well defined, rounded to oval, homogenous mass on chest x ray
- Homogenous, round to oval, dense mass on CT, enhances with contrast, may show calcification and / or cystic changes
- Pleural-based, polypoid lesions may mimic solitary fibrous tumor
Prognostic factors
- Almost always benign, although 2 - 4% have nodal metastases that don’t appear to affect prognosis (Arch Pathol Lab Med 2003;127:321)
Case reports
- 23 year old woman with solitary pulmonary nodule (Arch Pathol Lab Med 2003;127:377)
- 40 year old woman with pulmonary sclerosing hemangioma with lymph node metastasis (Oncol Lett 2014;7:997)
- Pulmonary sclerosing haemangioma with metastatic spread to stomach (Histopathology 2012;60:1162)
Treatment
- Limited resection (enucleation or wedge) is considered adequate
Gross description
- Well circumscribed, nonencapsulated, easily shelled out, solid, firm
- Cut surface tan-yellow to gray, may be mottled or hemorrhagic, may show cystic areas
- Generally < 3 cm but can grow much larger
Microscopic (histologic) description
- Four patterns:
- Papillary
- Sclerotic
- Solid
- Hemorrhagic
- Morphologic heterogeneity; may show predominantly one pattern or all four; most show at least 3 patterns
- Comprised of "surface cells" lining papillae and "round cells" within papillary cores and solid sheets
- Surface cells are cuboidal, resembling type II pneumocytes, and may show foamy cytoplasm, nuclear pseudoinclusions, multinucleation
- Round cells are polygonal with abundant eosinophilic cytoplasm, indistinct cell borders, oval nuclei, even chromatin, indistinct nucleoli, and may show cytoplasmic vacuolization, hyperchromasia, pleomorphism
- May have sclerotic stroma, can be continuous with bronchial epithelium
- Commonly show hemorrhage, blood lakes, aggregates of histiocytes, chronic inflammation, lamellar structures (extracellular surfactant)
- Occasionally with calcification, cholesterolosis
- No / rare granulomatous reaction, no/rare mitotic figures
- No angiolymphatic invasion, limited or no necrosis
- Potential association with neuroendocrine hyperplasia / tumorlets in surrounding lung
Microscopic (histologic) images
Contributed by Dr. Pooja Navale
Whole mount view
H&E 2.5x
H&E 10x
TTF1 10x
EMA 10x
CAM 5.2 10x
Other
Young Asian woman with lung tumor
Images hosted on other servers:
Bundles and whirling patterns
CK-, TTF1+, EMA, SMA, Vimentin, Ki67
Cytology description
- Papillary and solid areas more likely represented than sclerotic and hemorrhagic areas
- Stroma may be present, with capillaries within papillary structures
- Papillary or microacinar arrangements with moderate cytoplasm, uniform round to oval nuclei with fine chromatin and smooth nuclear contours, inconspicuous nucleoli
- Dual cell population, with some large, single, binucleated and multinucleated tumor cells
- Bloody background with hemosiderin laden macrophages
- May not be able to distinguish from well differentiated adenocarcinomas due to morphologic overlap; requires clinical and radiologic correlation
- May show moderate pleomorphism and mild nuclear atypia, intranuclear pseudoinclusions, increased nuclear: cytoplasmic ratio, prominent nucleoli
- Absence of necrosis, frequent mitoses and marked pleomorphism
Positive stains
- EMA and TTF1 in both surface and round cell components
- Napsin, AE1/3, CK7, surfactant proteins positive in surface cells, while variable / weak in round cells; (Arch Pathol Lab Med 2012;136:1580)
- Vimentin, PR, ER (rarely, weak) in round cell component (Am J Surg Pathol 2000;24:906)
- p53 mutation higher in polygonal cells (J Clin Pathol 2008;61:192)
Negative stains
Electron microscopy description
- Surface cells with abundant microvilli, cytoplasm packed with rough ER and mitochondria, numerous lamellar bodies (similar to type II pneumocytes) (Am J Surg Pathol 2000;24:906)
- Round cells with sparse organelles and numerous intracytoplasmic, variably-sized, electron-dense bodies representing immature lamellar bodies (Am J Surg Pathol 2000;24:906)
Molecular / cytogenetics description
- Distinct expression of B-catenin, Axin, and C-myc in 2 cell types (Virchows Arch 2012;461:59)
- Shares similar genetic and epigenetic aberrations with adenocarcinoma, but also significant differences, especially in tumor suppressor genes (Exp Lung Res 2011;37:344)
Differential diagnosis
- Alveolar or papillary adenoma
- Carcinoid tumor
- Carcinoma (primary or metastatic)
- Clear cell ("sugar") tumor
- Epithelioid hemangioendothelioma
- Langerhans cell histiocytosis
- Meningioma
- Meningothelial-like nodules
- Mucoepidermoid carcinoma, low grade, papillary variant
