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Diagnosis & Discussion
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- Figure 1: FNA direct smear of mass, Diff-Quik stain, x100
- Figure 2: FNA direct smear of mass, Diff-Quik stain, x400
- Figure 3: FNA direct smear of mass, Papanicolaou stain, x400
- Figure 4: Surgical resection of mass, H&E stain, x100
- Figure 5: Surgical resection of mass, H&E stain, x200
- What is the diagnosis?
- Intraductal papillary mucinous neoplasm
- Acinar cell carcinoma
- Solid pseudopapillary tumor
- Pancreatic endocrine neoplasm
- Which of the following is not a characteristic cytologic feature of this tumor?
- Intranuclear inclusions
- Polarized nuclei with nuclei positioned away from the papillary or pseudopapillary core
- Inconspicuous nucleoli
- Hyaline globules
- Which of the following is false about this tumor?
- Typically large, friable, and hemorrhagic
- Poor prognosis
- Radiologically and grossly well-demarcated
- Usually presents in young women
- Which of the following immunostains is expected to always be negative in this tumor?
Solid pseudopapillary tumor of pancreas (SPT) is a rare low-grade malignant epithelial neoplasm accounting for 1%–2% of all pancreatic neoplasms. SPT occurs predominantly in young women and is often asymptomatic. It may arise anywhere within the pancreas. Presenting symptoms may include abdominal pain, palpable mass, dyspepsia, bloating, or obstructive jaundice. Most patients have long-term survival with surgical resection of the primary tumor and metastases. However, SPT with apparent malignant transformation and a highly aggressive course have been described.
Radiologically, SPT is usually a well-circumscribed multilocular cystic mass with solid portions partially replacing the pancreas, findings that are suggestive but not specific for this tumor.  Irregular calcifications may be seen. On CT scan and ultrasound, SPT shows solid areas as well as areas of cystic degeneration, hemorrhage, or necrosis.
Grossly, SPTs are well-demarcated, sometimes partially encapsulated tumors that are red-tan, soft, friable, and hemorrhagic, often with cystic changes. Most cases are large at presentation with a mean diameter of 9 to 10 cm, although the size may range from 1.5 cm to 30 cm.
Cytomorphologically, smears from fine-needle aspirations (FNA) are cellular and show single cells, clusters, and branching, papillary (pseudopapillae) fragments. The papillary structures typically demonstrate a central fibrovascular core and myxoid fibrillary stroma. The fibrovascular cores are covered by one or more layers of cells, which may be polarized with the nuclei positioned away from the core. The neoplastic cells are monomorphic and round to oval with fine, evenly distributed chromatin and inconspicuous nucleoli. Nuclear grooves may also be present. Hyaline globules are another characteristic feature of SPT and may be either extracellular or within gland-like/acinar structures.
Histologically, SPT shows a solid growth pattern of uniform cells with abundant small vessels. Degenerative changes occur in areas away from vessels resulting in the formation of pseudopapillae, cuffs of neoplastic cells clinging to the blood vessels. Other degenerative changes include macrophages, foreign-body giant cells, hemorrhage, cholesterol clefts, fibrosis, and calcifications. Similar to aspiration specimens, nuclei are sometimes oriented away from the vessels. Eosinophilic diastase resistant PAS-positive hyaline globules are a characteristic features. Mitotic figures are rare. A diffuse growth pattern with extensive tumor necrosis, high mitotic rate, and the presence of an undifferentiated component, such as sarcomatoid carcinoma, are associated with an aggressive clinical behavior.
Immunohistochemically, SPTs are typically positive for vimentin, CD10, neuron-specific enolase, CD56, PR, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. Beta-catenin is also commonly positive. SPTs are negative for chromogranin, trypsin, and chymotrypsin and variably express cytokeratins and synaptophysin.
The differential diagnosis includes pancreatic endocrine neoplasm (PEN), acinar cell carcinoma, intraductal papillary mucinous neoplasm (IPMN), and pseudocyst. PEN aspiration biopsies are cellular and often contain loosely cohesive cell groups and rosette-like structures, but lack papillary structures. The tumor cells are uniform, often plasmacytoid, and contain stippled, salt-and-pepper chromatin with inconspicuous nucleoli. Immunohistochemically, most PENs are positive for chromogranin, synaptophysin, and NSE. Acinar cell carcinoma has a predilection for older males, displays an ill-defined gross appearance, lacks pseudopapillary structures, and is composed of round to oval cells with distinct nucleoli. Acinar cell carcinomas are positive for trypsin, chymotrypsin, and cytokeratins and negative for neuroendocrine markers, though focal immunoreactivity with neuroendocrine markers can be observed. IPMNs are tumors involving the main pancreatic duct and/or branch ducts. Aspirations often contain viscous mucin and may contain cell clusters arranged in true papillae and cells with intracellular mucin. Cytologic atypia may range from mild to severe (in situ carcinoma). IPMNs are positive for keratins, including AE1/AE3, CAM5.2, CK7, and variably for CK20. Pseudocysts are distinguished by different clinical and microscopic findings. Pseudocysts usually occur in patients with a history of pancreatitis, i.e., middle-aged or older men. Microscopically, they are a collection of necrotic and hemorrhagic material surrounded by a fibrous capsule that lacks an epithelial lining.
Answers to the questions:
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John Crapanzano, MD
Columbia Presbyterian Hospital
Department of Pathology