Solid and cystic tumor of the pancreas: clinicopathologic and genetic studies of four cases

Fine needle aspiration cytology with the aid of immunocytochemistry on cell-block confirms the diagnosis of solid pseudopapillary neoplasm of the pancreas

INTRODUCTION

To determine the diagnostic efficacy of fine needle aspiration cytology (FNAC) in cases of pancreatic solid pseudopapillary neoplasm (PSPN) with emphasis on the cytomorphological features and to evaluate the contribution of immunocytochemistry on FNAC cell-block (CB) in cases of PSPN.

METHODS

It is a retrospective study in which ultrasound-guided FNAC of pancreatic lesions diagnosed as PSPN between years 2009 and July 2019 were reviewed along with cytohistological correlation. Immunocytochemistry on CB was performed, wherever required.

RESULTS

A total of 16 patients with a cytological diagnosis of PSPN of the pancreas were identified. The most common cytological findings were characteristic branching pseudopapillary fragments with central thin, delicate capillaries associated with the amorphous myxoid substance, surrounded by tumour cells with mild pleomorphism. Immunocytochemistry was performed on CB of six cases. The tumour cells revealed nucleocytoplasmic positivity for β-catenin, cytoplasmic positivity for vimentin, membranocytoplasmic positivity for CD10 and nuclear positivity for progesterone receptor in all the cases, while they were negative for chromogranin, CD56, pan-cytokeratin and epithelial membrane antigen. The resected histopathological specimen was available in 10cases, and all were confirmed as PSPN.

CONCLUSION

Although PSPN has a characteristic cytomorphology, cell-block immunocytochemistry on FNA material confirms the diagnosis in problematic cases and excludes other pancreatic tumours, thus helping in appropriate management.

Nonductal neoplasms of the pancreas

Although the majority of pancreatic neoplasms are infiltrating ductal adenocarcinomas or other neoplasms with ductal differentiation, neoplasms with acinar, endocrine, mixed, or uncertain differentiation constitute a diverse and distinctive group. The most common and best-characterized nonductal neoplasms are pancreatic endocrine neoplasm, acinar cell carcinoma, pancreatoblastoma, and solid pseudopapillary neoplasm. This review details the clinical and pathologic features of these nonductal neoplasms, highlighting diagnostic criteria including the use of specific immunohistochemical stains to define the cellular differentiation of the neoplasms.

Non-cystic solid-pseudopapillary tumor of the pancreas showing nuclear accumulation and activating gene mutation of beta-catenin

Solid-pseudopapillary tumor (SPT) is an unusual pancreatic neoplasm that is characterized by a mixture of solid and cystic components and a fibrous capsule. Recently, the tumorigenesis of SPT has been reported to be associated with gene mutations of beta-catenin, which is a molecule participating in the Wnt signaling pathway. Reported herein is the case of a 53-year-old woman with SPT. The tumor, approximately 3 cm in diameter in the pancreas body, had a clear margin and central calcification but had neither a cystic component nor fibrous capsule. Several lines of pathological findings in the surgically resected specimen indicated SPT: (i) pseudopapillary proliferation of eosinophilic polygonal cells with oval nuclei; (ii) positive expression of several marker molecules indicating differentiation into acinar and endocrine cells; and (iii) zymogen granule-like structures in the cytoplasm on electron microscopy. Further, the tumor cells had intense nuclear accumulation of beta-catenin and an activating mutation, (34)Gly(GGA) to Arg(AGA), in exon 3 of the beta-catenin gene, as previously reported in most SPT. These findings suggest that association of the beta-catenin phenotype with development of the rare phenotype of SPT, a non-cystic and unencapsulated tumor, is unlikely.

The Clear Cell Variant of Solid Pseudopapillary Tumor of the Pancreas: A Previously Unrecognized Pancreatic Neoplasm

Solid pseudopapillary tumor is a rare but distinctive pancreatic neoplasm whose cell phenotype remains a mystery. We report 3 cases of a previously undescribed variant of solid pseudopapillary tumor of the pancreas composed almost entirely of multivacuolated clear cells (>90%). The cytoplasmic vacuoles did not contain glycogen, mucin, or lipid but seemed to be formed by dilatation of the endoplasmic reticulum and mitochondria. The tumors displayed prominent trabeculae and a solid growth pattern but lacked the characteristic pseudopapillary pattern of the classical solid pseudopapillary tumor. In contrast, the clinical features, gross characteristics, and immunoprofile were similar to those of classical solid pseudopapillary tumor. Two of the patients were young adult females with well-demarcated tumors involving the body and tail of the pancreas. Tumor cells showed immunoreactivity for vimentin, CD10, CD56, synaptophysin, and nuclear accumulation of beta catenin. In 2 patients, 1 male and 1 female, the tumors were discovered incidentally. Despite vascular invasion in one of the tumors all 3 patients are disease free after distal pancreatectomy. Clues to distinguish the clear cell variant of solid pseudopapillary tumor from endocrine pancreatic tumor composed of clear cells, clear and foamy cell variants of ductal carcinoma, metastatic renal cell carcinoma, serous cystadenoma and ectopic adrenocortical nodules are provided.

Contrast-enhanced ultrasonography of small solid pseudopapillary tumors of the pancreas: enhancement pattern and pathologic correlation of 2 cases

OBJECTIVE

The purpose of this series is to describe the value of contrast-enhanced ultrasonography (CEUS) in the characterization of small pseudopapillary tumors (SPTs) of the pancreas.

METHODS

Two cases of SPTs found on conventional ultrasonography, both located at the pancreatic body, were studied with spiral computed tomography, magnetic resonance imaging, and CEUS. A final diagnosis was obtained with histologic analysis after distal pancreatectomy. Immunohistochemical analysis of the tumors with the CD34 antigen was performed.

RESULTS

At CEUS, the 2 SPTs had a slight peripheral rim enhancement in the early dynamic phases. The presence of this enhancement pattern at CEUS, not clear at spiral computed tomography or at magnetic resonance imaging, suggested the diagnosis of SPTs with a peripheral pseudocapsule deriving from the compression of the pancreatic parenchyma. The presence of a perilesional pseudocapsule was proved at immunohistochemical analysis of the tumors with the CD34 antigen.

CONCLUSIONS

Contrast-enhanced ultrasonography can improve the characterization of SPTs by showing the typical rim enhancement of these pancreatic tumors.

Solid-pseudopapillary tumor of the pancreas: a neoplasm with distinct and highly characteristic cytological features

The solid-pseudopapillary tumor of the pancreas (SPTP) is an unusual low-grade malignant epithelial tumor affecting predominantly adolescent girls and young women. Although approximately 500 cases of SPTP have been described in the last 40 yr, its pathogenesis remains uncertain. However, the clinical features of this neoplasm are very characteristic and SPTP must be suspected in any young woman with a cystic or partially cystic pancreatic mass. In this report, we describe the cytologic features of seven cases of SPTP investigated by preoperative fine-needle aspirates. The analysis of the cytologic features in these cases and in 43 cases collected from the literature reveals that they are highly characteristic and quite distinct from those of other cystic or solid tumors of the pancreas. On this basis, a cytologic diagnosis of SPTP may be rendered with great confidence, not only in clinically typical examples, but also in unusual presentations, such as in older patients, in males, in ectopic locations, and in metastatic sites.

Solid-pseudopapillary tumors of the pancreas are genetically distinct from pancreatic ductal adenocarcinomas and almost always harbor beta-catenin mutations

Solid-pseudopapillary tumors (SPTs) are unusual pancreatic neoplasms of low malignant potential that most frequently affect young women. Genetic events contributing to the development of SPTs are unknown. Whereas the more common ductal adenocarcinomas of the pancreas essentially never harbor beta-catenin or APC gene mutations, we have recently identified alterations of the APC/beta-catenin pathway in other nonductal pancreatic neoplasms including pancreatoblastomas and acinar cell carcinomas. We analyzed a series of 20 SPTs for somatic alterations of the APC/beta-catenin pathway using immunohistochemistry for beta-catenin protein accumulation, direct DNA sequencing of beta-catenin exon 3, and direct DNA sequencing of the mutation cluster region in exon 15 of the APC gene in those SPTs that did not harbor beta-catenin mutations. Immunohistochemical labeling for cyclin D1 was performed to evaluate the overexpression of this cell-cycle protein as one of the putative downstream effectors of beta-catenin dysregulation. In addition, we analyzed the SPTs for genetic alterations commonly found in pancreatic ductal adenocarcinomas, including mutations in the K-ras oncogene and p53 and DPC4 tumor suppressor genes, using direct DNA sequencing of K-ras and immunostaining for p53 and Dpc4. Almost all SPTs harbored alterations in the APC/beta-catenin pathway. Nuclear accumulation of beta-catenin protein was present in 95% (19 of 20), and activating beta-catenin oncogene mutations were identified in 90% (18 of 20) of the SPTs. Seventy-four percent (14 of 19) showed overexpression of cyclin D1, ranging from 10 to 70% of tumor nuclei. In contrast, no K-ras mutations were present in any of the 20 SPTs, and Dpc4 expression was intact in all 16 SPTs for which immunohistochemical labeling was successful. Overexpression of p53 was limited to only 3 of 19 (15.8%) SPTs. These results emphasize the two distinct, divergent genetic pathways of neoplastic progression in pancreatic ductal and nonductal neoplasms.

Solid-pseudopapillary tumor of the pancreas (Frantz tumor) in children: report of four cases and review of the literature

BACKGROUND

Solid-pseudopapillary tumor of the pancreas (SPT) is an exceptionally rare neoplasm in children. Its origin remains enigmatic. It is of low malignant potential and occurs most frequently in young females.

PATIENTS AND METHODS

A cumulative review of the tumor's clinicopathological characteristics from the world's literature is presented. The clinical course, pathohistologic data and outcome of surgery of four Austrian children treated at the general hospital of Vienna are analyzed.

RESULTS

Between 1987 and 1999, four girls (age: 12--16 years) with SPT were diagnosed at our institution. All patients presented with an abdominal mass and uncharacteristic abdominal pain. Two tumors were located in the tail, one in the body and tail and one in the head of the pancreas (diameter: 7--15 cm). Surgical procedures included three distal pancreatectomies and one partial duodenopancreatectomy (Whipple procedure). One patient had two recurrences with metastases that could only be partially resected. Chemotherapy was initiated for this patient. In the follow-up period (range: 6 months to 12 years) all patients are alive with no evidence of recurrence.

CONCLUSIONS

SPT is a rare differential diagnosis of a pancreatic mass in children. It is mandatory to establish this diagnosis since complete surgical removal of the tumor even in case of metastases or local invasion offers an excellent prognosis.