Mesenchymal Hamartoma

Definition

Rare benign lesion, typically seen in infants, composed of vascularized mature connective tissue intermixed with elongated branching bile ducts.

Clinical Features

Rare
Predilection for infants
Most:
- asymptomatic
- present during the first 2 years of life with:
  - abdominal swelling
  - a palpable abdominal mass1
Sometimes grows to a huge size2
Also in adults,3,4 in whom it may be associated with distinct clinical features 5

Pathogenesis

May arise from the connective tissue of the portal tracts6
An ischemic pathogenesis has been suggested because the vascular pattern is similar to that of torsion of an accessory lobe of liver7
Neoplastic nature supported by detection of:
- specific translocations involving chromosome 198
- occasional aneuploid lesions9

Gross Pathology

In infants:
- a solitary, spherical, reddish nodule10 (Fig. 1
  Fig. 1: Gross appearance of mesenchymal hamartoma of liver. The tumor shown has a solid micronodular appearance.
  )
Some have a prominent cystic component11 (Fig. 2
Fig. 2: Gross appearance of mesenchymal hamartoma of liver. The tumor shown is of multicystic type.
)

Histopathology

A well-vascularized mature connective tissue intermixed with elongated branching bile ducts
Low-power appearance:
- reminiscent of fibroadenoma of the breast12 (Fig. 3
  Fig. 3: Mesenchymal hamartoma of liver. The appearance is reminiscent of a mammary fibroadenoma.
  )
Ultrastructurally:
- the cells have a mesenchymal, fibroblast-like appearance6,13

Differential Diagnosis

Select up to 2 differential diagnoses to compare with Mesenchymal Hamartoma

Genetics

Specific translocations involving chromosome 198
Occasional aneuploid lesions9

Prognosis

Benign
Exceptionally:
- malignant transformation into an undifferentiated embryonal sarcoma

References

1 Srouji MN, Chatten J, Schulman WM, Ziegler MM, Koop CE. Mesenchymal hamartoma of the liver in infants. Cancer. 1978;42:2483–2489.

2 Shuto T, Kinoshita H, Yamada C, Hirohashi K, Shiokawa C, Kubo S, et al. Bilateral lobectomy excluding the caudate lobe for giant mesenchymal hamartoma of the liver. Surgery. 1993;113:215–222.

3 Drachenberg CB, Papadimitriou JC, Rivero MA, Wood C. Adult mesenchymal hamartoma of the liver. Report of a case with light microscopic, FNA cytology, immunohistochemistry, and ultrastructural studies and review of the literature. Mod Pathol. 1991;4:392–395.

4 Wada M, Ohashi E, Jin H, Nishikawa M, Shintani S, Yamashita M, et al. Mesenchymal hamartoma of the liver. Report of an adult case and review of the literature. Intern Med. 1992;31:1370–1375.

5 Cook JR, Pfeifer JD, Dehner LP. Mesenchymal hamartoma of the liver in the adult: association with distinct clinical features and histological changes. Hum Pathol. 2002;33:893–898.

6 Dehner LP, Ewing SL, Sumner HW. Infantile mesenchymal hamartoma of the liver. Histologic and ultrastructural observations. Arch Pathol. 1975;99:379–382.

7 Lennington WJ, Gray GF, Page DL. Mesenchymal hamartoma of liver. A regional ischemic lesion of a sequestered lobe. Am J Dis Child. 1993;147:193–196.

8 Mascarello JT, Krous HF. Second report of a translocation involving 19q13.4 in a mesenchymal hamartoma of the liver. Cancer Genet Cytogenet. 1992;58:141–142.

9 Otal TM, Hendricks JB, Pharis P, Donnelly WH. Mesenchymal hamartoma of the liver. DNA flow cytometric analysis of eight cases. Cancer. 1994;74:1237–1242.

10 Lack EE. Mesenchymal hamartoma of the liver. A clinical and pathologic study of nine cases. Am J Pediatr Hematol/Oncol. 1986;8:91–98.

11 Raffensperger JG, Gonzalez-Crussi F, Skeehan T. Mesenchymal hamartoma of the liver. J Pediatr Surg. 1983;18:585–587.

12 Sutton CA, Eller JL. Mesenchymal hamartoma of the liver. Cancer. 1968;22:29–34.

13 Rhodes RH, Marchildon MB, Luebke DC, Edmondson HA, Mikitz VG. A mixed hamartoma of the liver. Light and electron microscopy. Hum Pathol. 1978;9:211–221.

Last updated: 24 Jan 2006