Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells

Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells is a rare epithelial neoplasm within the spectrum of undifferentiated pancreatic carcinomas and is now regarded in modern classifications as a distinct variant from “conventional” undifferentiated carcinoma because of its distinctive morphologic and microenvironmental features. Its defining feature is the presence of numerous osteoclast-like giant cells that are multinucleated and generally reactive rather than neoplastic, set within a background of highly atypical mononuclear tumor cells, often associated with components of pancreatic ductal carcinoma. The rarity of the entity, a clinical presentation overlapping with more common pancreatic carcinomas and histologic heterogeneity make diagnosis complex and dependent on adequate sampling and expert pathologic assessment.

Clinically, this neoplasm may present with epigastric pain radiating to the back, obstructive jaundice when the lesion is in the pancreatic head, weight loss and rapid deterioration in general condition. Anemia, elevated inflammatory markers and systemic findings related to tumor necrosis or intralesional hemorrhage are not uncommon. Diagnosis requires a pathway based on dedicated pancreatic imaging and histologic confirmation by core-needle biopsy or surgical sampling, with precise distinction from pancreatic mimics including neuroendocrine, acinar and sarcomatoid neoplasms.

Treatment follows a multimodal approach centered, when possible, on curative-intent surgical resection and the use of systemic therapies analogous to those employed for pancreatic ductal carcinoma, adapted to the patient’s clinical condition and the biology of the individual case. Prognosis is variable but often poor, although some patients have a relatively more prolonged course than those with pleomorphic undifferentiated carcinomas, possibly because of biologic differences and a lower propensity for fulminant dissemination in selected subgroups. Accurate staging and early multidisciplinary management remain essential.

The epidemiology of undifferentiated carcinoma with osteoclast-like giant cells is constrained by its extreme rarity. In pathologic series it accounts for a minute fraction of exocrine pancreatic carcinomas, and most available information derives from single-center series, systematic reviews and case reports, with inevitable limits to generalizability. It is diagnosed mainly in adults and older people, often in the sixth or seventh decade, without a universally consistent sex profile because of small numbers. It may arise in the head, body or tail, with clinical differences related mainly to obstructive effects of head lesions and a greater tendency for body-tail tumors to present as large masses.

The etiologic causes have not been defined, and no necessary and sufficient exposure has been shown to cause the disease. In the absence of a certain etiology, assessment considers that the neoplasm often lies on a biologic continuum with pancreatic ductal carcinoma and may share part of its natural history and carcinogenic context.

The risk factors are therefore discussed cautiously as conditions associated with an increased probability of exocrine pancreatic neoplasia and that may provide the background in which this variant rarely develops. Clinically relevant factors include tobacco smoking, chronic pancreatitis, diabetes mellitus of new onset or rapidly worsening in adulthood, obesity and genetic conditions predisposing to pancreatic tumors, although no evidence specifically links these factors to this histologic variant. For the individual patient, the practical priority remains prompt interpretation of pancreatic warning symptoms rather than definition of a dedicated risk profile.

For undifferentiated carcinoma of the pancreas with osteoclast-like giant cells, there are no screening programs for the general population because incidence is too low and no noninvasive tests have adequate performance for specific early diagnosis. The tumor is almost always identified after symptoms or incidental findings on examinations performed for other indications.

In clinical practice, “early diagnosis” means timely recognition of presentations that should prompt a dedicated pancreatic work-up, such as obstructive jaundice, persistent epigastric pain radiating to the back, unexplained weight loss, rapid worsening of diabetes or new-onset diabetes in adulthood with systemic symptoms. In these settings, the objective is not screening for this rare variant but initiation of appropriate assessment for suspected pancreatic neoplasia.

A separate issue concerns individuals at high hereditary-familial risk of pancreatic cancer, in whom surveillance follows specialist protocols using endoscopic ultrasonography and pancreatic MRI. Even in this setting, surveillance is not aimed specifically at detecting undifferentiated carcinoma with osteoclast-like giant cells but at identifying clinically relevant pancreatic lesions early. The rarity of the histologic subtype makes any dedicated strategy unsustainable, whereas appropriateness of the overall high-risk pathway remains central.

The biology of undifferentiated carcinoma with osteoclast-like giant cells is distinctive because it combines an aggressive neoplastic epithelial component with osteoclast-like giant cells that, in most studies, represent a reactive infiltrate of histiocytic/macrophage origin. This suggests that the tumor microenvironment, particularly recruitment of monocyte-macrophage lineage cells, plays an important role in architecture and possibly clinical behavior. An associated component or transition to pancreatic ductal carcinoma is identifiable in many cases, indicating a pathogenic relationship with ductal carcinogenesis pathways and progression toward undifferentiated phenotypes.

At the molecular level, substantial overlap with ductal carcinoma has been reported, including frequent alterations in driver genes characteristic of exocrine pancreatic neoplasia. The undifferentiated component may reflect cellular plasticity, epithelial–mesenchymal transition and dysregulation of cell-cycle control, with increased invasiveness and resistance. A rich macrophage infiltrate and proinflammatory cytokine signaling may promote angiogenesis, local immunosuppression and progression, although the net prognostic effect of these features varies among available series.

Essential histologic features for classification

• A component of atypical, often pleomorphic mononuclear tumor cells with variable mitoses and necrosis.
• Numerous multinucleated osteoclast-like giant cells, generally without marked atypia and interpreted as reactive.
• Possible association with a conventional ductal component or areas of recognizable epithelial differentiation.
• An often hemorrhagic or cystic-degenerative architecture that may influence radiologic appearance.

Immunohistochemistry is particularly useful for distinguishing the lesion from mimics. Osteoclast-like giant cells typically express histiocytic markers, whereas the neoplastic component may show variable, sometimes focal epithelial markers consistent with its carcinomatous nature. The differential diagnosis includes acinar neoplasms, neuroendocrine tumors, sarcomas and inflammatory pseudotumoral lesions; clinical-radiologic correlation and an appropriate immunophenotypic panel are therefore essential for correct classification.

Clinical manifestations largely overlap with those of exocrine pancreatic neoplasms and depend on location, size and involvement of biliary and vascular structures. Pain in the epigastrium radiating to the back is common and may be associated with nausea, early satiety and poorer food tolerance. Weight loss and fatigue reflect the combination of anorexia, systemic inflammation and exocrine pancreatic insufficiency, which may present with steatorrhea and malabsorption in more advanced stages.

When the lesion is located in the pancreatic head, obstructive jaundice may occur with dark urine, pale stools, pruritus and cholestatic biochemical abnormalities, often associated with biliary dilatation. Body-tail lesions may present more subtly and be dominated by mass effect and pain, with later diagnosis. Some patients develop fever, markedly elevated inflammatory markers or anemia, findings that may be caused by necrosis and intratumoral bleeding and may initially suggest infection or a pseudocyst.

Clinical presentations most likely to prompt dedicated pancreatic imaging

• Painless obstructive jaundice or jaundice associated with epigastric pain.
• Persistent epigastric pain radiating to the back and progressing over weeks.
• Weight loss and fatigue with laboratory evidence of inflammation or cholestasis.
• New-onset diabetes in adulthood or rapid worsening of known diabetes with systemic symptoms.
• Steatorrhea and signs of exocrine pancreatic insufficiency, especially in advanced disease.

Physical findings may be limited in early stages; jaundice, deep epigastric tenderness and signs of dehydration or malnutrition may emerge. Advanced disease may be associated with hepatomegaly, ascites or signs of venous thrombosis, particularly with vascular involvement or a cancer-related prothrombotic state. Clinical findings cannot identify the histologic subtype, so histologic confirmation remains indispensable.

The diagnostic pathway begins with suspicion of pancreatic neoplasia based on warning symptoms and laboratory abnormalities. First-line tests include a complete blood count, liver profile with bilirubin and cholestatic indices, renal function and electrolytes, coagulation testing and metabolic assessment. Serum markers such as CA 19-9 may be requested in the setting of a pancreatic mass, but are neither specific nor diagnostic and must be interpreted cautiously, especially in obstructive jaundice.

Imaging is the cornerstone of the initial phase. CT using a pancreatic protocol is often the reference examination for characterizing the lesion, assessing relationships with mesenteric vessels and the celiac axis, and identifying liver or peritoneal metastases. MRI with cholangiopancreatography is useful for more detailed ductal characterization, assessment of hemorrhagic or cystic-degenerative components and clarification of equivocal findings. In patients with jaundice, biliary assessment and planning of possible endoscopic drainage are integrated early in the pathway.

Diagnostic confirmation requires tissue sampling. Endoscopic ultrasonography with fine-needle aspiration or core biopsy provides material for cytology, histology and immunohistochemistry and is particularly useful for small lesions or lesions not clearly defined on CT. In resectable cases, the choice between preoperative biopsy and diagnosis on the surgical specimen depends on the clinical context, the need for neoadjuvant therapy and the probability of an alternative diagnosis that would change management.

Pathologic diagnosis must distinguish this entity from pleomorphic undifferentiated carcinoma, acinar neoplasms, neuroendocrine tumors and pseudocystic or inflammatory lesions. It is crucial to recognize that osteoclast-like giant cells alone do not define the nature of the tumor and that the mononuclear neoplastic component must be identified and characterized. When possible, assessment is supplemented by molecular analyses useful both for correct classification and for treatment guidance in advanced disease.

A practical approach consistent with assessment of pancreatic masses and modern classifications requires integration of clinical, radiologic and pathologic data, adequate sampling and a confirmatory histologic panel to establish a reliable diagnosis:

Essential elements for a reliable diagnosis

• Dedicated pancreatic imaging defining lesion location, size and vascular relationships.
• Histologic confirmation on biopsy or surgical specimen with identification of the mononuclear neoplastic component and osteoclast-like giant cells.
• Immunohistochemistry directed toward confirming carcinomatous differentiation and excluding the principal mimics (neuroendocrine, acinar, mesenchymal and lymphoproliferative).
• Staging with chest, abdominal and pelvic imaging and, in selected cases, PET or further investigations for metastases or secondary lesions.

After diagnosis, radiologic staging defines resectability and treatment strategy. Assessment of the mesenteric-portal venous axis, superior mesenteric artery and celiac trunk is decisive because it determines feasibility of resection and the potential role of neoadjuvant therapy. In patients with jaundice and cholangitis or malnutrition, clinical stabilization with biliary drainage and nutritional support may be an integral part of the pretreatment phase.

Staging is not specific to this rare histologic subtype and is performed using recognized systems for exocrine pancreatic carcinomas, particularly the current edition of the UICC/AJCC TNM classification applied to pancreatic carcinoma. This approach is necessary to standardize clinical communication, resectability assessment and prognostic stratification, while recognizing that the biology of the individual subtype may cause outcome variability relative to averages for ductal carcinoma.

TNM classification (AJCC/UICC 8th edition) for exocrine pancreatic carcinoma

• T1: tumor confined to the pancreas and measuring up to 2 cm, with size-dependent subcategories (T1a up to 0.5 cm, T1b >0.5 cm and up to 1 cm, T1c >1 cm and up to 2 cm).
• T2: tumor confined to the pancreas and measuring >2 cm and up to 4 cm.
• T3: tumor confined to the pancreas and measuring >4 cm.
• T4: tumor involving the superior mesenteric artery, celiac axis or common hepatic artery, generally associated with primary unresectability.
• N0: no regional lymph-node metastases.
• N1: metastases in 1–3 regional lymph nodes.
• N2: metastases in 4 or more regional lymph nodes.
• M0: no distant metastases.
• M1: distant metastases present.

Stage groups (AJCC/UICC 8th edition) for exocrine pancreatic carcinoma

• Stage IA: tumor up to 2 cm, with no lymph-node or distant metastases (T1) (N0) (M0).
• Stage IB: tumor >2 cm and up to 4 cm, with no lymph-node or distant metastases (T2) (N0) (M0).
• Stage IIA: tumor >4 cm, with no lymph-node or distant metastases (T3) (N0) (M0).
• Stage IIB: tumor up to and beyond 4 cm, with metastases in 1–3 regional lymph nodes and no distant metastases (T1 or T2 or T3) (N1) (M0).
• Stage III: tumor involving major arteries, with no distant metastases regardless of lymph-node status (T4) (N0 or N1 or N2) (M0), or tumor of any size with metastases in 4 or more regional lymph nodes and no distant metastases (T1 or T2 or T3 or T4) (N2) (M0).
• Stage IV: distant metastases present regardless of local extent and lymph-node status (T1 or T2 or T3 or T4) (N0 or N1 or N2) (M1).

Prognosis is heterogeneous. In many series, the feasibility of complete resection and absence of distant metastases remain the main determinants of survival, whereas lymph-node involvement and vascular invasion worsen outcome. For this subtype, some series suggest a course that is sometimes less fulminant than pleomorphic undifferentiated carcinomas, but variability is broad and depends on stage, resectability, an associated ductal component and response to systemic therapies. Tumor size, necrosis, proliferative index, perineural invasion and surgical margins retain practical prognostic value, and the pathologic report must be complete to support coherent treatment decisions.

Treatment is based on a multidisciplinary approach integrating surgery, systemic therapy and management of local complications, following principles that largely overlap with those for pancreatic ductal carcinoma. The initial objective is to define resectability and the presence of metastases accurately because these variables determine treatment sequence and the likelihood of curative intent.

In localized, resectable disease, surgical resection is the cornerstone. The procedure depends on location: pancreaticoduodenectomy for tumors in the head and distal pancreatectomy for body-tail lesions, with regional lymphadenectomy according to oncologic standards. In patients with obstructive jaundice, preoperative management may require endoscopic biliary drainage in selected settings, particularly when cholangitis, functional hepatic impairment or the need for neoadjuvant treatment is present. Surgery should be performed at high-volume centers because operative morbidity directly affects the ability to complete adjuvant therapy.

Systemic therapy is used in the adjuvant setting after resection and in the neoadjuvant setting for selected borderline-resectable or locally advanced cases, using regimens derived from exocrine pancreatic carcinoma. In metastatic disease, systemic therapy is the main treatment, and selection depends on performance status, hepatic and renal function, disease burden and goals of care. The rarity of the histologic subtype limits specific evidence, so decisions are often individualized and supported by molecular analysis when available, including to identify rare actionable alterations or eligibility for clinical trials.

Treatment objectives according to the clinical setting

• Resectable: complete curative-intent resection and adjuvant treatment when appropriate.
• Borderline resectable: neoadjuvant therapy to increase the likelihood of negative margins and select favorable biology, followed by scheduled reassessment.
• Locally advanced: disease control with systemic therapy and assessment for conversion to surgery after a major response.
• Metastatic: systemic therapy and symptom control, with attention to pain, nutrition and biliary complications.

Supportive management is often decisive. Pain requires a stepwise approach that may include celiac plexus blocks. Exocrine pancreatic insufficiency benefits from pancreatic enzymes and nutritional support, whereas diabetes requires careful metabolic control because weight loss and inflammation may destabilize glycemia. In intratumoral hemorrhage or cholangitis, stabilization and endoscopic or interventional treatment may determine whether effective oncologic therapy can be initiated.

Follow-up after curative-intent treatment is organized according to schedules used for exocrine pancreatic carcinomas, with frequency and intensity adapted to pathologic stage, margins, lymph-node status and clinical condition. Surveillance integrates clinical examination, nutritional and metabolic assessment, targeted laboratory tests and periodic imaging to identify local or metastatic recurrence early.

During the first years after resection, recurrence risk is higher. Clinical follow-up should assess pain, weight loss, signs of malabsorption and diabetes control. Management of exocrine pancreatic insufficiency and nutritional deficiencies should be an integral component of follow-up because it affects performance status and quality of life, as well as tolerance of any subsequent therapies.

Chest and abdominal CT, or MRI when indicated, is used to monitor the pancreatic bed and liver. Serum markers may be followed as supportive information but must not replace clinical-radiologic assessment. In patients receiving systemic therapy for advanced disease, surveillance focuses on response and toxicity, with scheduled radiologic reassessment and early intervention for biliary, nutritional and thromboembolic complications.

Long-term quality-of-life considerations depend mainly on the impact of pancreatic surgery, effects of systemic therapy and metabolic sequelae of pancreatic functional loss. After major resections, many patients experience reduced meal tolerance, weight loss and the need for lasting dietary reorganization. Exocrine pancreatic insufficiency may cause steatorrhea, bloating and malabsorption, affecting energy, physical activity and work participation, and requires pancreatic enzymes, dietary modification and monitoring for vitamin deficiencies.

Metabolic consequences are often important. Pancreatogenic diabetes may develop or worsen after surgery and requires careful balancing of glucose-lowering therapy, nutritional status and hypoglycemia risk, especially in patients with poor intake. Chronic pain, when present, may limit sleep, daily activities and independence and benefits from integrated pathways including pain therapy and rehabilitation.

Systemic therapies may leave persistent effects such as neuropathy, prolonged fatigue and susceptibility to infection, affecting functional recovery. The psychological impact of a pancreatic cancer diagnosis, often perceived as highly threatening, may also sustain anxiety, insomnia and reduced quality of life; integration of psycho-oncologic support and structured communication about goals of care reduces uncertainty and improves adherence to follow-up. Overall, quality of life requires an active approach that combines oncologic control with systematic management of nutrition, metabolism, pain and psychological well-being.

Complications arise from local progression, systemic dissemination and treatment effects. Disease may be complicated by biliary obstruction and cholangitis in pancreatic head lesions, requiring endoscopic drainage and antibiotic therapy. Vascular invasion and the cancer-related prothrombotic state increase the risk of venous thrombosis, including portal or mesenteric vein thrombosis, with clinically important consequences. Liver and peritoneal metastases cause organ failure, ascites and rapid deterioration in general condition.

Surgical complications include pancreatic fistula, delayed gastric emptying, infection, hemorrhage and anastomotic stenosis, directly affecting length of stay and the ability to receive adjuvant therapy. Over the long term, exocrine pancreatic insufficiency and diabetes are common functional complications requiring ongoing management. In some cases, the mass may show necrosis or intralesional bleeding with anemia and pain, requiring stabilization and supportive treatment.

• Toxicity from systemic chemotherapy: neutropenia, infection, peripheral neuropathy, mucositis and diarrhea, requiring monitoring and dose adjustment.
• Biliary complications: stent displacement or obstruction, recurrent cholangitis and cholestatic pruritus.
• Nutritional and metabolic complications: sarcopenia, fat-soluble vitamin deficiencies and glycemic instability, especially after major resections.

Prevention and management of complications are based on early diagnosis, treatment at experienced centers, nutritional and metabolic optimization, pain control and close monitoring during systemic therapy. In advanced disease, early integration of palliative and supportive care provides better symptom control and greater continuity of care.