Recurrent hepatic mesenchymal hamartoma with osseous metaplasia

Abstract

A 7-year-old Asian male presented with abdominal pain and enlarging abdomen status post-partial hepatectomy for mesenchymal hamartoma (MH) 2 years ago. The lesion was present at the resection margin during the initial procedure. Current imaging studies revealed a 4 cm hepatic lesion in segment 5 and 8, suggestive of recurrent MH. The patient underwent partial hepatectomy and macroscopic examination of the surgical specimen demonstrated a well-circumscribed, tan-white lesion with both solid and cystic components ( Figure 1A). Histologically, the lesion showed a myxomatous mesenchymal cell proliferation with cystic dilatation of bile ducts and entrapped hepatocytes, characteristic of hepatic MH ( Figure 1B). Focal white and firm area was identified at the edge of the lesion (Figure 2A) which histologically corresponded to lamellar bone with marrow formation, consistent with an osseous metaplasia.Hepatic MH is a benign tumour which is predominantly seen within the first 2 years of life. 1 Its pathogenesis is unclear, however, it shares recurrent chromosomal abnormalities involving chromosome 19q13.4 with its malignant counterpart, undifferentiated embryonal sarcoma of the liver. 1,2 Resection with a clear margin is the treatment of choice whenever possible. To our knowledge, this is the first case of recurrent hepatic MH with osseous metaplasia. The heterotropic bone formation is most likely a secondary reaction from previous procedure 3 as it was located at the periphery of the lesion and bone is not known to be a MH component.Recognizing this phenomenon is important to distinguish it from other entities, particularly mesenchymal component of hepatoblastoma.

Hepatic mesenchymal hamartoma and undifferentiated embryonal sarcoma of the liver: a pathologic review

“…The unusual presence of immature hepatocytes with extensive steatosis has also been reported [12]. Meanwhile, osseous metaplasia has been described in a case of recurrent HMH [17]. Atypical mitoses and infiltrative growth pattern are not identified in HMH [2].…”

“…Surgical resection is the mainstay treatment for HMH, although recurrence may occur in the setting of positive resection margins [1,2,17]. Liver transplantation may be considered in unresectable cases [37,38].…”

Mesenchymal Hamartoma of the Liver and Spleen-A Rare Pseudotumour in Adults

“…The differential diagnosis of the hepatic mesenchymal hamartoma implies other benign hepatic neoplasms such as focal nodular hyperplasia, bile duct adenoma and hemangioma, as well as malignant tumours [8,9]. Furthermore, differential diagnosis of mesenchymal hamartoma of the spleen implies both benign and malignant vascular lesions such as hemangioma, hemangioendothelioma and angiosarcoma [6].…”

“…This benign tumour is a very uncommon neoplasm of the adult with only 5% of the cases reported in patients older than 5 years of age [7]. A tendency of arising in the right hepatic lobe has also been described for this lesion [75% of cases] [7,8,9]. Although the first case of HMH was reported by Marsh in 1903, the term was established by Edmonds later in 1956 [5].…”