Papillomas and adenomas

Sclerosing pneumocytoma

Last author update: 1 October 2015
Last staff update: 18 April 2023 (update in progress)

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PubMed Search: Sclerosing pneumocytoma [title] lung

Roseann I. Wu, M.D., M.P.H.
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Cite this page: Wu R. Sclerosing pneumocytoma. website. 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)
  • 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)
  • Rare benign neoplasm
  • 5:1 female to male ratio
  • Wide age range with peak in middle age / 50s
  • Peripheral lung parenchyma, any lobe
  • Rarely arises centrally or in pleura
  • 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
  • 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
Case reports
  • 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

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Young Asian woman with lung tumor

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Bundles and whirling patterns

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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
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
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