Pulmonary hamartoma

Pulmonary hamartoma, also lung hamartoma, is a benign lesion of the lung that may be confused with malignancy.

Pulmonary hamartoma
Diagnosis in short
Pulmonary hamartoma. H&E stain.
LM	benign cartilage, adipocytes and respiratory epithelium; lesion without significant nuclear atypia
Gross	well circumscribed, cartilageous or fatty appearing
Site	lung - see lung tumours
Prevalence	uncommon
Radiology	popcorn-type calcifications
Prognosis	benign
Clin. DDx	slow growing lung tumours

General

• Benign.
• Malignant transformation reported.
• Typically an incidental (radiologic) finding.
• Treatment: surgical resection.

Gross

• Well circumscribed lesion.
• Varied morphology.

Radiology

• Popcorn-type calcifications.
  • Irregular nodular/linear calcifications.

Microscopic

Features:

• Cartilage - key feature.
  • Single cells in lacunae surrounded by abundant matrix.
    • Paucicellular vis-a-vis malignant lesions.
• Fat (adipocytes) - key feature.
• Respiratory epithelium (columnar epithelium with cilia).

Notes:

• No nuclear atypia.

DDx:

• Other lung tumours - especially slow growing ones.
• Myxoid sarcomas, e.g. myxoid chondrosarcoma.

Images

www:

• Pulmonary hamartoma (studentdoctor.net).
• Lung hamartoma (path.utah.edu).

• 

  Pulmonary hamartoma - low mag. (WC)

• 

  Pulmonary hamartoma - intermed. mag. (WC)

• 

  Pulmonary hamartoma - high mag. (WC)

IHC

• S100 +ve - highlights the fat.

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Biopsy

Right Upper Lobe of Lung, Core Biopsy:
     - Chondromyxoid neoplasm, favour pulmonary hamartoma versus chondroma, 
       see comment.
     - Scant lung parenchyma, benign.

Comment:
The lesion stains with S-100.

Excision

LUNG LESION, LEFT UPPER LOBE, WEDGE RESECTION:
- PULMONARY HAMARTOMA WITH MILD FOCAL ACUTE INFLAMMATION AND SURROUNDING EDEMA.
- SURROUNDING LUNG WITH MILD EMPHYSEMATOUS CHANGES.

Micro

The sections show lung with a well circumscribed lesion with a fibrous capsule partially lined by respiratory-type epithelium. The lesion consists of abundant respiratory epithelium and glands with focal sheeting and small collections of neutrophils focally. Small foci of degenerative changes are seen. The epithelium of the lesion as a bland cytomorphology. Mitotic activity is not readily apparent. Fat is not identified as a component of the lesion. Around the periphery of the lesion pulmonary edema is present.

The piece surrounding lung more distant from the lesion has mild emphysematous changes. No interstitial fibrosis is identified. No significant inflammation is present. The arteries are approximately the size of accompanying airway. The arteries have no appreciable intimal thickening.

See also

• Pulmonary pathology.
• Multifocal micronodular pneumocyte hyperplasia associated with tuberous sclerosis.
• Hamartoma.