Lung

• Chest radiograph, CT or MRI can aid in diagnosis (Children (Basel) 2019;6:86)
• Histological analysis via biopsy or resection is gold standard for diagnosis

Contributed by Aliya N. Husain, M.D.


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Contributed by Erdener Özer, M.D., Ph.D.


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• Type I: thin walled cysts lined by benign respiratory epithelium with small malignant mesenchymal cells in the walls of the cysts (Cancer 2023;129:600)
  • These primitive cells may have rhabdomyosarcomatous differentiation
• Type IR: thin walled cysts lined by benign respiratory epithelium without the malignant cell population mentioned above (Cancer 2023;129:600)
• Type II: areas of thin walled cysts lined by respiratory epithelium with areas of solid sheets of malignant mesenchymal cells that can appear as a spindled sarcoma, embryonal rhabdomyosarcoma or have no apparent differentiation (Children (Basel) 2019;6:86)
• Type III: heterogeneous solid tumor that can contain several different patterns (Children (Basel) 2019;6:86, Cancer 2015;121:276)
  • Blastema-like area with hyperchromatic nuclei, high N:C ratio and mitotic bodies
  • Larger malignant sarcoma cells in myxoid background
    • Can have rhabdomyosarcomatoid, chrondrosarcomatoid or liposarcomatoid features (Cancer 1988;62:1516)
  • Foci of anaplastic cells with pleomorphic nuclei, mitotic bodies and hyaline inclusions
  • Some microscopic areas of benign nonneoplastic respiratory epithelium

Contributed by Aliya N. Husain, M.D.

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• Small ovoid cells with granular chromatin, inconspicuous nucleoli and scant eosinophilic cytoplasm with poorly defined cellular borders (Diagn Cytopathol 1997;16:336, Lung India 2015;32:281)
• Sheets of oval to spindle shaped cells with poor differentiation (Lung India 2015;32:281)
• Tumor cells with granular chromatin and a high N:C ratio (Lung India 2015;32:281)
• Oval to spindle shaped cells that can have perivascular arrangement (Lung India 2015;32:281)

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Which of the following is true regarding pleuropulmonary blastoma type IR?

1. Can metastasize to the brain
2. Composed of both solid and cystic foci
3. Contains a population of malignant mesenchymal cells in addition to benign nonneoplastic epithelium
4. Does not contain any malignant mesenchymal cells
5. Often progresses to type III PPB

D. Does not contain any malignant mesenchymal cells. The lack of malignant mesenchymal cells is what differentiates PPB type IR from types I - III. Answer E is incorrect because type IR does not progress to type III due to its lack of malignant mesenchymal cells. Answer C is incorrect because type IR does not have malignant mesenchymal cells, although it does have a benign nonneoplastic epithelium. Answer B is incorrect because type IR does not contain any solid foci; it is purely cystic. Answer A is incorrect because type IR does not have a malignant component and therefore does not metastasize.

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Reference: Pleuropulmonary blastoma

A 2 year old patient with no past medical history presented to the clinic with a cough that persisted for 1 month. On CT scan, a solid tumor occupying the lung was seen. After resection, the tumor was sent to pathology where the diagnosis of PPB type III was made. It was noted that the tumor had rhabdomyosarcomatoid differentiation and no chondromatoid differentiation. A picture of the tumor with an immunostain is shown above. Which staining pattern would you expect to see in this tumor?

1. Positive desmin and S100, negative vimentin
2. Positive MSA and S100, negative SMA
3. Positive SMA and desmin, negative vimentin
4. Positive vimentin and desmin, negative S100
5. Positive vimentin and S100, negative desmin

D. Positive vimentin and desmin, negative S100. PPB is positive for vimentin and the rhabdomyosarcomatoid component will be positive for desmin. S100 will be negative in this tumor because there is no chondromatoid component. Answers A and E are incorrect because S100 would not be positive in a tumor without chondromatoid components; furthermore, we would expect desmin and vimentin to be positive in this tumor. Answer C is incorrect because we would expect vimentin to be positive in this tumor. Answer B is incorrect because S100 would not be positive in a tumor without chondromatoid components and we would expect SMA to be positive given the tumor's rhabdomyosarcomatoid component.

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Reference: Pleuropulmonary blastoma