Adult Mesenchymal Hamartoma of the Liver: Case Report and Literature Review

Abstract

Mesenchymal hamartoma of the liver (MHL) is a rare benign lesion occurring primarily in the pediatric population. While the precise pathogenesis of the tumor is not certain, the most common theory relates to aberrant mesenchyme development in the portal tract likely related to the bile ducts. A 53-year-old female was evaluated for an incidental liver mass. Initial CT scan showed a cystic lesion in the right lobe of the liver and follow-up imaging revealed an increase in size and the percent solid component within the mass. In view of these changes, a nondiagnostic biopsy was obtained followed by extirpation of the lesion. Gross pathological review of the lesion identified a 9 × 9 × 7.5 cm, pink-yellow-tan, gelatinous mass, with a >1 cm clear surgical margin. Histologically, the mass consisted of benign dilated bile ducts, as well as myxoid stroma with spindle cells showing smooth muscle differentiation. The patient was discharged home on postoperative day five. A review of the literature for MHL in adults reports 30 previous cases, predominantly published as individual case reports describing the size, lobe(s) of the liver affected, and the cystic/solid nature of the tumor. MHL in adults may represent a potentially premalignant lesion, as the emerging literature supports a potential relationship between MHL and malignant undifferentiated embryonal sarcoma in regards to cytogenetic analysis. Aggressive surgical management of MHL in adults is mandated when feasible.

Fig. 1

Noncontrast CT scan from February 2007 demonstrating a 5.3 cm septate hypodense cystic lesion in the right lobe of the liver.

Fig. 2

Repeat abdominal CT scan in July 2008 revealing an enlarging heterogeneous, progressively enhancing solid and cystic mass in the anterior segment of the right hepatic lobe (Couinaud's segments V and VIII). The mass measures 8.9 × 8.7 × 7.5 cm and displaces hepatic and portal veins.

Fig. 3

Microscopic image. The liver mass consists of rare benign dilated bile ducts corresponding to the cystic areas. The cytologically benign stroma is extremely myxoid with spindle cells. The mass had a fibrous capsule with bile duct proliferation at the edge with a sharp transition into the normal liver tissue (arrow), diagnostic of mesenchymal hamartoma. 10×, HE stain.