Pancreas chapter

Mucinous Ovarian Neoplasms

• Mucous ovarian neoplasms can occasionally present with mural nodules resembling:

  • Giant cell tumor

  • Pleomorphic sarcoma

  • Anaplastic carcinoma

• Classification and nature of these proliferations are debated but considered neoplastic with epithelial origin based on molecular evidence of monoclonal origin.

• Mucinous cystic neoplasms (MCN) without invasive adenocarcinoma typically show benign progression; therefore, not all should be regarded as low-grade malignant.

• Recommendations suggest a two-tiered classification for MCNs:

  • Low grade/borderline

  • High grade/carcinoma in situ

Features of Invasive Adenocarcinoma

• Various patterns observed in invasive adenocarcinoma include:

  • Ductal adenocarcinoma

  • Adenosquamous carcinoma

  • Mucinous adenocarcinoma

  • Undifferentiated carcinoma

• Invasive features may be small; complete submission of excised neoplasms is recommended to ensure no invasive components are missed.

Intraductal Papillary Mucinous Neoplasm (IPMN)

• Most common in the head of the pancreas and can involve any part of the ductal system.

• Tumor relationships with ducts must be well-documented; some may present multicentric cases.

• Microscopic findings range from:

  • Flat or papillary tall columnar mucinous epithelium

  • Complex architecture with high-grade nuclear features

• IPMNs classified as:

  • Low grade/borderline

  • High grade/carcinoma in situ

• Various types may include:

  • Intestinal type (often large, main ducts, high-grade dysplasia)

  • Pancreatobiliary type (frequently high-grade dysplasia)

  • Gastric type (may confuse with PanIN)

• Incidence of invasion:

  • Approximately 15% for branch duct type

  • 30-35% for main duct type IPMN

• Prognosis depends on invasive component:

  • Noninvasive IPMN shows excellent prognosis after complete resection with negative margins.

Molecular Characteristics of IPMNs

• Common mutations associated:

  • KRAS (increases with grade of dysplasia)

  • GNAS and RNF43

  • Rare mutations in TP53, STK11, and P16/CDKN2A

• Unlike ductal adenocarcinomas, DPC4 protein remains present in IPMNs.

Acinar Cell Carcinoma

• Typically occurs in adults; presents nonspecific signs like nausea, vomiting, and abdominal pain.

• Characterized by solid, fleshy intraductal masses and shape resembles tubular glands.

• Tumor cells often express:

  • MUC1, MUC6 (negative for MUC5AC, MUC2)

• Prognosis is better than ductal adenocarcinoma despite the possibility of invasive features.

Pancreatoblastoma

• Most common pancreatic neoplasm in childhood; can also occur in adults.

• Tumors are very cellular; histologically lobular with acinar cells demonstrating optically clear nuclei due to biotin accumulation.

• Associated with syndromes like Beckwith-Wiedemann; poor overall survival (approx. 50%).

Solid-Pseudopapillary Tumor (SPPT)

• Preferred term for neoplasms often found in young women with abdominal pain.

• These tumors are usually capsulated, with excessively rare infilsration.

• Histologically, characterized by pseudopapillae with discohesive cells and abundant cystic degeneration.

• Classified as having low malignant potential; aggressive features associated with larger size and extensive necrosis.

Endocrine Tumors (PanNET)

• Historically referred to as islet cell tumors; classified into well-differentiated NETs, poorly differentiated NECs.

• Associated syndromes include MEN, VHL disease, neurofibromatosis type 1.

• Tumor is well-vascularized with varying growth patterns (solid nests, trabecular, rosettes).

• Various morphologic variants exist but prognosis remains generally favorable.