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==Overview==
==Overview==


Hamartomas are tumours usually arise from connective tissue and are generally composed of [[cartilage]], [[fat]], and [[connective tissue]] cells. Hamartomas can be found in the [[lung]]s (most common), [[heart]], [[hypothalamus]], [[kidneys]], or [[spleen]]. The pathogenesis consists primarily of the disorganized replication of normal tissue cells. Many hereditary syndromes are associated with hamartomatous formation like: Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome, and Cowden's syndrome. Genes that are involved in the pathogenesis of hamartomatous syndromes include: [[BMPR1A]], [[SMAD4]], [[PTEN]], and [[STK11]].<ref name="so">Stojcev Z, Borun P, Hermann J, et al. Hamartomatous polyposis syndromes. Hered Cancer Clin Pract. 2013;11(1):4.</ref><ref name="radio1">Splenic hamartoma.Dr Henry Knipe et al Radiopedia.http://radiopaedia.org/articles/pulmonary-hamartoma-1 Accessed on December 09, 2015</ref>
Hamartomas are tumours usually arise from connective tissue and are generally composed of [[cartilage]], [[fat]], and [[connective tissue]] cells. Hamartomas can be found in the [[lung]]s (most common), [[heart]], [[hypothalamus]], [[kidneys]], or [[spleen]]. The pathogenesis consists primarily of the disorganized replication of normal tissue cells. Many hereditary syndromes are associated with hamartomatous formation like: Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome, and Cowden's syndrome. Genes that are involved in the pathogenesis of hamartomatous syndromes include: [[BMPR1A]], [[SMAD4]], [[PTEN]], and [[STK11]].


==Pathophysiology==
==Pathophysiology==

Revision as of 01:04, 14 September 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2] Vamsikrishna Gunnam M.B.B.S [3]

Overview

Hamartomas are tumours usually arise from connective tissue and are generally composed of cartilage, fat, and connective tissue cells. Hamartomas can be found in the lungs (most common), heart, hypothalamus, kidneys, or spleen. The pathogenesis consists primarily of the disorganized replication of normal tissue cells. Many hereditary syndromes are associated with hamartomatous formation like: Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome, and Cowden's syndrome. Genes that are involved in the pathogenesis of hamartomatous syndromes include: BMPR1A, SMAD4, PTEN, and STK11.

Pathophysiology

Pathogenesis

  • Hamartomas occur in the same location as the normal tissue (in the tissue of its origin) as opposed to choristomas, which grow in other tissues (different from its origin).
  • The pathogenesis consists primarily of the disorganized replication of normal tissue cells. The underlying mechanisms for the replication abnormality are not fully understood.[1]
  • Hamartomas arise from connective tissue and are generally formed of cartilage, fat, and connective tissue cells, although they may include many other types of cells.
  • Hamartomas grow at the same rate as the organ from whose tissue they are made.[2]
  • These can be located in the lungs, heart, hypothalamus, kidneys, or spleen.[1] In general, most hamartomas occur in the lungs.

Bone-forming tumors

  • Bone-forming tumors also called as bone islands most commonly located in intramedullary bones of[3][4][5]
    • Pelvis
    • Femur
    • Humerus and
    • Ribs
  • Bone-forming tumors are masses that are small, white-yellow and round
  • Bone-forming tumors that are larger than 2 cm are called as giant bone islands.

Cartilage-forming tumors

  • It is understood that cartilage-forming tumors like osteochondroma is produced from abnormal cartilaginous epiphyseal growth plate tissue and abnormal regulation of cartilage proliferation.[6][7][8]
  • Cartilage-forming tumors are termed as congenital error of epiphyseal development.

Fiber-forming tumors

  • It is understood that fiber-forming tumors is produced from continued growth of fibrous cortical defects that extrude into the medullary cavity.
  • The most commonly involved bone are tibia and the femur.

Lung

  • Lung hamartomas mostly arise from connective tissue and are generally formed of cartilage, fat, and connective tissue cells, although they may include many other types of cells.
  • About 5-8% of all solitary lung tumors and about 75% of all benign lung tumors are hamartomas.
  • The majority of pulmonary hamartomas form from connective tissue on the outside of the lungs, although about 10% form in the linings of the bronchi.
  • In the majority of patients, it can be difficult to distinguish hamartoma from malignancies.[2]
  • Pulmonary hamartomas can be divided into two subtypes: endobronchial and parenchymal.
  • An endobronchial location is described in 3%–20% of all pulmonary hamartomas. This subtype is mainly composed of cartilage and fibrous tissue.
  • Endobronchial hamartomas typically contain more fat tissue than parenchymal hamartomas.

Heart

  • Cardiac rhabdomyomas are hamartomas comprised of altered cardiac myocytes that contain large vacuoles and glycogen.
  • Cardiac hamartomas arises from the striated muscle cells (cardiac myocytes), which are normally involved in the coordinated contractions of cardiac muscle cells.
  • Development of cardiac hamartomas is the result of multiple genetic mutations.
  • Mutations in the TSC1 or TSC2 genes are related with tuberous sclerosis.
  • There is a strong association between cardiac rhabdomyomas and tuberous sclerosis (characterized by hamartomas of the central nervous system, kidneys and skin, as well as pancreatic cysts; 25-50% of patients with cardiac rhabdomyomas will have tuberous sclerosis.
  • Cardiac hamartoma symptoms will depend on the size of the tumor and location relative to the conduction system.
  • For more information on heart hamartoma, See here

Hypothalamus

  • Hypothalamic hamartoma is a benign tumor composed of disorganized collections of neurons and glia.
  • Hypothalamic hamartoma is a non-neoplasic heterotopia that typically occurs in the region of the hypothalamus. This tumor arises from the tuber cinereum, a part of the hypothalamus located between the mamillary bodies and the optic chiasm.
  • Unlike other hamartomas, hypothalamic hamartoma is symptomatic; it most often causes gelastic seizures, visual problems, and rage disorders associated with hypothalamic diseases.
  • For more information on hypothalamic hamartoma, See here

Kidneys, spleen, and other vascular organs

  • Spleen and kidney hamartomas may impinge on blood vessels, resulting in a risk of serious bleeding.
  • Because hamartoma typically lacks elastic tissue, it may lead to the formation of aneurysms and thus possible hemorrhage. When a hamartoma impinges into a major blood vessel, such as the renal artery, hemorrhage may be life-threatening.[1]
  • Hamartoma of the kidney is also called angiomyolipoma and can be associated with tuberous sclerosis.
  • Spleen hamartomas are often associated with hematologic abnormalities and spontaneous rupture.
  • For more information on angiomyolipoma, See here

Genetics

  • Genes involved in the pathogenesis of harmatomatous syndromes include:[9]

Associated Conditions

Gross Pathology

  • On gross pathology, a hallmark feature of hamartoma is a well-circumscribed mass that may show a variegated yellow and white appearance, which corresponds to fat and cartilage, respectively.[11]
  • Hamartomas are unencapsulated, lobulated tumors with connective tissue septa.
  • Tumor size ranges between 1 and 3 cm in diameter at the time of diagnosis.

Microscopic Pathology

  • On microscopic pathology, hamartomas have benign tumors features such as disorganized (non-neoplastic) growth, tissue of the region within it is found, and no invasion to surrounding tissue or structures.[11]
  • Common findings include:
  • Cartilage single cells in lacunae surrounded by abundant matrix and paucicellular vis-a-vis malignant lesions
  • Fat (adipocytes)
  • Respiratory epithelium (columnar epithelium with cilia), only present in lung hamartoma

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References

  1. 1.0 1.1 1.2 Splenic hamartoma.Dr Henry Knipe et al Radiopedia.http://radiopaedia.org/articles/pulmonary-hamartoma-1 Accessed on December 09, 2015
  2. 2.0 2.1 Zakharov V, Schinstine M (2008). "Hamartoma of the lung". Diagn. Cytopathol. 36 (5): 331–2. doi:10.1002/dc.20790. PMID 18418855.
  3. McCarthy EF, Dorfman HD (June 1980). "Vascular and cartilaginous hamartoma of the ribs in infancy with secondary aneurysmal bone cyst formation". Am. J. Surg. Pathol. 4 (3): 247–53. PMID 7396066.
  4. Balci P, Obuz F, Göre O, Yilmaz E, Demirpolat G, Aktug T, Kovanlikaya I (September 1997). "Aneurysmal bone cyst secondary to infantile cartilaginous hamartoma of rib". Pediatr Radiol. 27 (9): 767–9. doi:10.1007/s002470050224. PMID 9285745.
  5. Cohen MC, Drut R, Garcia C, Kaschula RO (1992). "Mesenchymal hamartoma of the chest wall: a cooperative study with review of the literature". Pediatr Pathol. 12 (4): 525–34. PMID 1409151.
  6. McCarthy EF, Dorfman HD (June 1980). "Vascular and cartilaginous hamartoma of the ribs in infancy with secondary aneurysmal bone cyst formation". Am. J. Surg. Pathol. 4 (3): 247–53. PMID 7396066.
  7. Balci P, Obuz F, Göre O, Yilmaz E, Demirpolat G, Aktug T, Kovanlikaya I (September 1997). "Aneurysmal bone cyst secondary to infantile cartilaginous hamartoma of rib". Pediatr Radiol. 27 (9): 767–9. doi:10.1007/s002470050224. PMID 9285745.
  8. Göre O, Kiliçalp A, Başdemir G, Ozer E, Aktuğ T (1999). "Cartilaginous hamartoma of the chest wall with secondary aneurysmal cyst-like areas in an infant: a case report". Turk. J. Pediatr. 41 (1): 139–42. PMID 10770690.
  9. Stojcev Z, Borun P, Hermann J, et al. Hamartomatous polyposis syndromes. Hered Cancer Clin Pract. 2013;11(1):4.
  10. Liaw D, Marsh DJ, Li J, Dahia PL, Wang SI, Zheng Z; et al. (1997). "Germline mutations of the PTEN gene in Cowden disease, an inherited breast and thyroid cancer syndrome". Nat Genet. 16 (1): 64–7. doi:10.1038/ng0597-64. PMID 9140396.
  11. 11.0 11.1 Kumar V, Abbas AK, Aster JC. Robbins Basic Pathology. Elsevier Health Sciences; 2012.
  12. 12.0 12.1 12.2 12.3 Hamartoma. Libre Pathology.http://librepathology.org/wiki/index.php/Pulmonary_hamartoma Accessed on December 8, 2015


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