Lung
Mesenchymal tumors
Pulmonary hamartoma
Author: Roseann Wu, M.D., M.P.H.
Topic Completed: 1 August 2016
Minor changes: 18 March 2021
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Hamartoma [title] soft tissue
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Etiology | Clinical features | Diagnosis | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosisCite this page: Wu R. Pulmonary hamartoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungtumorhamartoma.html. Accessed May 16th, 2021.
Definition / general
- Benign, generally solitary lesion composed of mature but disordered hyaline cartilage, fat and smooth muscle, with entrapped clefts of respiratory epithelium
- Also called pulmonary chondroma, although chondromas in Carney triad are often multiple, occur more in women, have thin fibrous pseudocapsule, frequent ossification or calcification, and lack entrapped epithelium and fat (Am J Surg Pathol 2007;31:1844)
- Nonfamilial Carney triad: pulmonary chondroma, gastric stromal tumors, functional extra-adrenal paraganglioma
Essential features
- Most common benign tumor of lung, most often with chondromatous element
- Typically solitary, < 4 cm, composed of disordered but mature hyaline cartilage, fibrous tissue, smooth muscle, fat, sometimes with calcification / ossification
- Shows some overlapping features with pulmonary chondroma of Carney triad, but hamartomas tend to be single rather than multiple, favor men rather than women, and show entrapped respiratory epithelium and fat, without a fibrous pseudocapsule
Terminology
- Pulmonary chondroma sometimes used interchangeably with pulmonary chondromatous hamartoma, but true pulmonary chondromas of Carney triad may be a distinct entity
- Descriptive term sometimes added to describe components, i.e. lipomatous, chondroid, chondromatous, fibrochondromatous, fibroleiomyomatous
- If lacks cartilage, could be diagnosed as lipoma, myxoma, leiomyoma or fibroadenoma
Epidemiology
- Most common benign neoplasm of lung
- Generally adults 40s to 60s, peripheral lesions more common in men
Sites
- Mostly arise in peripheral lung; endobronchial in < 10% of cases
Etiology
- Thought to arise from primitive mesenchymal tissue
Clinical features
- Asymptomatic, slow growth
- Occasionally with hemoptysis or may present with obstructive symptoms if endobronchial
Diagnosis
- Usually incidental; radiologic diagnosis may be confirmed with FNA biopsy or excision
Radiology description
- Incidental coin lesion; well circumscribed, small, smooth to lobulated nodule, with irregular nodular “popcorn” calcifications
- Xray: non-specific soft tissue mass, sometimes with calcification
- CT: May contain intralesional fat, calcifications
Radiology images
Contributed by Hanni Gulwani, M.B.B.S.
Chest Xray
CT scan
Prognostic factors
- Slowly enlarges if not excised
- Rare exceptional cases of malignant evolution reported
Case reports
- 30 year old man with multiple pulmonary chondroid hamartomas (J Thorac Oncol 2014;9:1053)
- 35 year old man with giant pulmonary chondroid hamartoma (Clin Nucl Med 2015;40:79)
- 50 year old man with incidental pulmonary hamartoma diagnosed by FNA (BMJ Case Rep 2013 Mar 25;2013)
- 55 year old and 68 year old men with fibroleiomyomatous hamartoma (Pathol Int 2014;64:618, Surg Case Rep 2016;2:53)
- 77 year old man with pulmonary chondromatous hamartoma with pleural dissemination (Surg Today 2015;45:1197)
- 2 cases of salivary gland-type tumors showing myoepithelial differentiation arising in pulmonary hamartoma (Am J Surg Pathol 2006;30:375)
Treatment
- Surveillance for biopsy proven asymptomatic pulmonary hamartomas, with resection for symptomatic patients or when diagnosis in doubt (Interact Cardiovasc Thorac Surg 2015;21:773)
- Excision is curative
Clinical images
Images hosted on other servers:
Large endobronchial hamartoma
Gross description
- Usually 4 cm or less, rarely > 10 cm
- Sharply delineated and lobulated, unencapsulated
- Glistening, translucent, homogenous, firm to hard cut surface (cartilaginous) with ill defined clefts and connective tissue septa
- Tan-white to gray without cystic change or hemorrhage
Gross images
Contributed by Hanni Gulwani, M.B.B.S.
Lobulated tumor
Images hosted on other servers:
Various images
Microscopic (histologic) description
- Variable mixture of mature hyaline cartilage, fat or smooth muscle
- Entrapped clefts lined by respiratory epithelium (ciliated or not)
- Cartilage may be calcified or ossified
- Periphery of cartilage may contain immature myxomatous tissue
- Resembles breast fibroadenoma if no cartilage present
- Entrapped small airways or alveolar epithelium with cuboidal metaplasia, hyperplasia, papillae
- 15% have papillary projections resembling immature placental villi (placental transmogrification), with stromal macrophages and lymphocytes and abundant mast cells (Arch Pathol Lab Med 2002;126:562)
- Consider other diagnosis if see multinucleated cells, pleomorphism, mitoses, necrosis, which occur only rarely
Microscopic (histologic) images
Contributed by Hanni Gulwani, M.B.B.S.
Lung hamartoma
Images hosted on other servers:
Various images
Cytology description
- Spindle and stellate cells scattered in chondroid or myxoid background
Cytology images
Contributed by Roseann Wu, M.D., M.P.H.
DQ
Pap
Positive stains
- Fibromyxoid cells are vimentin+
Negative stains
Electron microscopy description
- Primitive stellate fibroblasts with transition to cartilage
Molecular / cytogenetics description
- Abnormal karyotypes in mesenchymal component, including aberrations in 12q14-15, 6p21.3, 14q24 (Cancer Genet Cytogenet 2003;142:153)
Differential diagnosis
- Benign metastasizing leiomyoma
- Chronic interstitial pneumonitis - reactive smooth muscle proliferation
- Leiomyosarcoma
- Lymphangioleiomyomatosis
- Mesenchymal cystic hamartoma
- Native pulmonary muscle proliferation
- Primary or metastatic mesenchymal malignancy or sarcomatoid carcinomas
