Solid pseudopapillary neoplasm of the pancreas (Hamoudi tumor)

CLINICAL HISTORY

A 27-year-old woman with a history of hypertension and insulin-dependent diabetes mellitus presented with mild abdominal pain. When questioned, the patient denied experiencing recent weight loss.

FINDINGS

Axial CT images were obtained in the arterial and venous phases after administration of oral and intravenous contrast media. A 6.4 × 5.9 × 8.6-cm mass was found to arise from the tail of the pancreas and protrude caudally into the left mid- and lower abdomen.

Figure 1 shows a soft-tissue mass containing focal calcifications centered within the tail of the pancreas. Figure 2 shows an additional view of the soft-tissue mass, centered within the tail of the pancreas and extending inferiorly. The tumor's more solid components demonstrate uniform enhancement. Figure 3, a coronal volume-rendered image, characterizes the same soft-tissue mass with focal calcifications and cystic components. The mass is centered within the tail of the pancreas.

DIFFERENTIAL DIAGNOSIS

Given the patient's age and the lesion's location, the differential diagnosis includes solid pseudopapillary tumor or islet cell tumor, particularly nonfunctioning islet cell tumor.

DIAGNOSIS

Solid pseudopapillary neoplasm of the pancreas (Hamoudi tumor).

DISCUSSION

Solid pseudopapillary tumors are rare tumors that are usually seen in younger women (age 20 to 40). These tumors are usually benign and have a good prognosis. Often these lesions are asymptomatic and patients typically present with vague abdominal symptoms or an enlarging abdominal mass. These lesions can often grow to a large size and can potentially cause compression of visceral structures.¹

Nearly all solid pseudopapillary tumors demonstrate some degree of internal hemorrhage or cystic degeneration. The typical location of the solid pseudopapillary tumor is the pancreatic tail, followed by its head, then body.²

The characteristic appearance of a solid pseudopapillary tumor on CT is generally a large encapsulated mass that contains both solid and cystic components. Calcifications and solid enhancing components are commonly seen. The solid enhancing component is usually seen at the periphery of the lesion with the cystic areas being more central.

The typical unenhanced MRI appearance is characterized by mixed areas of high and low T1 and T2 signal intensity. The heterogeneity of T1 and T2 signal is usually due to the varying degree and age of blood products found within the lesion. T2-weighted images often show a thick fibrous capsule. On postcontrast images, early enhancement of solid components is seen with progressive fill-in of the remaining lesion.³

Occasionally, solid pseudopapillary tumors can be mistaken for nonfunctioning islet cell tumors. Certain features, such as areas of cystic change, enhancing components, and a clear border, are commonly seen in both lesions. However, the level of enhancement of the solid components is usually greater in islet cell tumors. Islet cell tumors are also often seen in older patients and have no predilection for one sex or the other.³

The treatment for solid pseudopapillary tumors is surgery, which is usually curative. Venous invasion, high nuclear grade, and extracapsular extension are all associated with a poorer prognosis.¹

Case submitted by Jason Oaks, M.D., diagnostic radiology resident, and Elliot K. Fishman, M.D., director of diagnostic radiology and body CT at the Johns Hopkins University School of Medicine in Baltimore.