Lung tumor
Benign tumors
Hamartoma

Author: Roseann Wu, M.D., M.P.H. (see Authors page)

Revised: 12 September 2016, last major update August 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Hamartoma [title] soft tissue

See also: Multiple pulmonary leiomyomatous hamartomas

Cite this page: Hamartoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/lungtumorhamartoma.html. Accessed December 7th, 2016.
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

Images hosted on PathOut servers:

Chest Xray, courtesy of Dr. Hanni Gulwani

CT scan, courtesy of Dr. Hanni Gulwani

Prognostic Factors
  • Slowly enlarges if not excised
  • Rare exceptional cases of malignant evolution reported
Case Reports
Treatment
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

Images hosted on PathOut servers:

Lobulated tumor, courtesy
of Dr. Hanni Gulwani



Images hosted on other servers:

Various images

Micro 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
Micro Images

Images hosted on PathOut servers:

Lung hamartoma, courtesy of Dr. Hanni Gulwani



Images hosted on other servers:

Placental transmogrification

Various images

Cytology Description
  • Spindle and stellate cells scattered in chondroid or myxoid background
Cytology Images

Images hosted on PathOut servers:

Pulm hamartoma DQ (left) and pap (right), courtesy of Roseann Wu, M.D., M.P.H.

Positive Stains
Negative Stains
Electron Microscopy Description
  • Primitive stellate fibroblasts with transition to cartilage
Molecular / Cytogenetics Description
Differential Diagnosis