Clinicopathologic features of SMARCB1/INI1-deficient pancreatic undifferentiated rhabdoid carcinoma: A case report and review of literature

Abstract

BACKGROUND

SMARCB1/INI1-deficient pancreatic undifferentiated rhabdoid carcinoma is a highly aggressive tumor, and spontaneous splenic rupture (SSR) as its presenting manifestation is rarely reported among pancreatic malignancies.

CASE SUMMARY

We herein report a rare case of a 59-year-old female who presented with acute left upper quadrant abdominal pain without any history of trauma. Abdominal imaging demonstrated a heterogeneous splenic lesion with hemoperitoneum, raising clinical suspicion of SSR. Emergency laparotomy revealed a pancreatic tumor invading the spleen and left kidney, with associated splenic rupture and dense adhesions, necessitating en bloc resection of the distal pancreas, spleen, and left kidney. Histopathology revealed a biphasic malignancy composed of moderately differentiated pancreatic ductal adenocarcinoma and an undifferentiated carcinoma with rhabdoid morphology and loss of SMARCB1 expression. Immunohistochemical analysis confirmed complete loss of SMARCB1/INI1 in the undifferentiated component, along with a high Ki-67 index (approximately 80%) and CD10 positivity. The ductal adenocarcinoma component retained SMARCB1/INI1 expression and was positive for CK7 and CK-pan. Transitional zones between the two tumor components suggested progressive dedifferentiation and underlying genomic instability. The patient received adjuvant chemotherapy with gemcitabine and nab-paclitaxel and maintained a satisfactory quality of life at the 6-month follow-up.

CONCLUSION

This study reports a rare case of SMARCB1/INI1-deficient undifferentiated rhabdoid carcinoma of the pancreas combined with ductal adenocarcinoma, presenting as SSR - an exceptionally uncommon initial manifestation of pancreatic malignancy.

Key Words: Pancreatic undifferentiated carcinoma; SMARCB1/INI1; Spontaneous splenic rupture; Rhabdoid features; Switch/sucrose non-fermentable; Chemotherapy; Case report

Core Tip: SMARCB1-deficient undifferentiated rhabdoid carcinoma of the pancreas represents a highly aggressive and rare neoplasm. This study suggests that aggressive multimodal therapy, including surgical resection and chemotherapy, may prolong survival in selected patients; however, the overall prognosis remains poor. Given its distinct molecular characteristics and potential resistance to standard therapies, further research into targeted treatment approaches and prospective clinical studies is urgently warranted.

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy. It represents the fourth leading cause of cancer-related mortality worldwide in both men and women, accounting for approximately 90% of all primary pancreatic tumors[1,2]. Pancreatic undifferentiated carcinoma (UDC) is exceedingly rare, representing approximately 2%-7% of all pancreatic tumors[3], with some reports indicating an incidence as low as 0.25%[4]. According to World Health Organization 2019, pancreatic UDC is defined as a carcinoma lacking a definitive line of differentiation. Under this definition, four morphologic variants are recognized: Anaplastic, sarcomatoid, rhabdoid, and carcinosarcoma[5,6]. Pancreatic undifferentiated rhabdoid carcinoma (PURC), defined by the presence of a predominant rhabdoid cell component, is particularly uncommon and carries an extremely poor prognosis[7]. Based on KRAS status and SMARCB1 expression, PURC is stratified into two molecular subtypes: (1) The pleomorphic giant cell subtype, characterized by KRAS mutations and preserved SMARCB1 expression; and (2) The anaplastic monomorphic subtype, defined by wild-type KRAS and complete loss of SMARCB1 expression[8,9]. SMARCB1 is a member of the switch/sucrose non-fermentable (SWI/SNF) complex that exists in a combinatorial construction including a catalytic domain and a highly conserved functional core[10]. SWI/SNF-deficient malignancies were first described in 1998 in pediatric malignant rhabdoid tumors, which demonstrated pathogenic SMARCB1 mutations[11]. Since then, SWI/SNF complex mutations have been found in approximately 20% of human cancers[12], such as SMARCB1 and SMARCA4-deficient sinonasal carcinoma[13,14], SMARCA4 and SMARCA2-deficient small cell carcinoma of the ovary[15], and SMARCA4-deficient undifferentiated tumor of the lung[16]. In pancreatic tumors, alterations in the SWI/SNF complex have been detected in approximately 14%-34% of PDAC cases through whole-exome and whole-genome sequencing analyses[7,9]. To date, only 11 cases of SMARCB1-deficient PURC have been reported[17,18].

We report the case of a female patient diagnosed with SMARCB1-deficient PURC invading adjacent organs, including the spleen and left kidney. The patient underwent complete surgical resection followed by adjuvant chemotherapy consisting of gemcitabine and nab-paclitaxel and remained in good clinical condition throughout a six-month follow-up period during 6 months of follow-up.

CASE PRESENTATION

Chief complaints

A 59-year-old woman was admitted with a one-day history of persistent, dull pain and discomfort localized to the left upper abdomen.

History of present illness

The patient developed left abdominal pain and discomfort for one day without any apparent precipitating factors. She denied trauma, gastrointestinal bleeding, fever, or other systemic symptoms, and the pain persisted without significant relief. Initial abdominal computed tomography (CT) revealed findings suggestive of a splenic hematoma or mass with possible intraperitoneal hemorrhage, as well as multiple pelvic effusions (possible hemoperitoneum). She was admitted with a preliminary diagnosis of non-traumatic splenic rupture for further evaluation and management.

History of past illness

The patient reported a prior history of nephritis, which was not formally treated. She denied hypertension, diabetes mellitus, or other chronic medical conditions.

Personal and family history

The patient has no family history of hereditary or neoplastic diseases.

Physical examination

On admission, the patient was alert but fatigued. Pupils were round and equal, with a diameter of 3 mm and reactive to light. The tongue was midline, with no facial asymmetry. Lung auscultation revealed clear breath sounds and a regular cardiac rhythm. Abdominal examination demonstrated mild tenderness in the left upper quadrant without rebound tenderness or guarding. Bilateral Babinski signs were negative. Pelvic compression and thoracic cage compression tests were negative. Percussion tenderness over the thoracic spine was positive, while the lumbar spine showed no tenderness. Neurologic reflexes were normal, and no jaundice or lymphadenopathy was detected.

Laboratory examinations

Emergency biochemical tests revealed mild elevations in γ-glutamyl transferase, alanine aminotransferase (ALT), glucose, and lactate dehydrogenase. The tumor marker panel, including carcinoembryonic antigen, alpha-fetoprotein, carcinomic antigen 125, carcinomic antigen 15-3, carcinomic antigen 19-9, and squamous cell carcinoma antigen, was within normal reference ranges. Postoperatively, serum amyloid A was elevated, while cardiac troponin I remained negative. Interleukin-6 and procalcitonin levels were also elevated, suggesting postoperative inflammatory and metabolic responses. Parathyroid hormone, troponin I, and procalcitonin levels were elevated postoperatively. Urinalysis showed glucosuria (++). Repeat liver function tests demonstrated persistent elevations in ALT and aspartate aminotransferase.

Imaging examinations

The initial CT revealed a heterogeneous splenic lesion with intraperitoneal fluid, raising suspicion of spontaneous splenic rupture (SSR; Figure 1). Follow-up CT obtained one week postoperatively confirmed the absence of the spleen and left kidney, consistent with prior total splenectomy, distal pancreatectomy, and left nephrectomy. No abnormal enhancement was identified in the operative bed.

Figure 1 Emergency abdominal computed tomography scan revealed splenic rupture with perisplenic and intraperitoneal hemorrhage. A: Extensive perisplenic hemorrhage with obscuration of the normal anatomic interface between the pancreatic tail, spleen, and kidney; B and C: Disruption of the renal parenchyma observed on different computed tomography planes; D: A hypodense fluid-filled area within the spleen.

Pathological findings

Gross examination: The surgical specimen comprised the distal pancreas, spleen, and left kidney (Figure 2). The pancreas measured appropriately 3 cm × 2 cm × 1.5 cm. The spleen measured 13 cm × 9 cm × 3 cm, and a cystic area measuring 5 cm × 4 cm × 3 cm was identified on the cut surface, with a slightly thickened inner wall. A firm, nodular lesion measuring 4.5 cm × 2 cm × 2 cm was identified at the splenic hilum. The lesion exhibited dense adhesions to the spleen, kidney, and pancreas, with ill-defined borders and apparent communication with the splenic cyst. In the cut section, the mass was solid, gray-white to yellow, and firm. The tumor invaded the adjacent renal parenchyma but remained relatively well demarcated, with focal areas of atrophic renal tissue. The renal pelvis mucosa was smooth, and a 1 cm segment of ureter was identified. Two lymph nodes were palpated within the surrounding omental tissue.

Figure 2  Gross specimen showing a ruptured splenic mass with dense adhesions to the pancreatic tail and left kidney, necessitating en bloc resection of the spleen, distal pancreas, and left kidney.

Microscopic findings: Cytologically, the tumor demonstrated two distinct components - glandular and spindle cell elements. The adenocarcinoma component showed tubular, cribriform, and focal micropapillary architecture. Tumor cells were columnar to cuboidal, possessing eosinophilic cytoplasm and round-to-oval nuclei with mild nuclear pleomorphism. The surrounding desmoplastic stroma harbored foci of well-to moderately differentiated adenocarcinoma. Tumor cells were observed infiltrating the spleen, accompanied by hemorrhage and necrosis. At the transition between well-differentiated ductal adenocarcinoma and UDC, poorly cohesive rhabdoid tumor cells were identified. The spindle cell component exhibited a diffuse growth pattern with spindle-shaped morphology, large vesicular nuclei, prominent nucleoli, and abundant cytoplasm. A lymph node was included, within which UDC cells were identified (Figure 3A). In areas of renal invasion, the background showed loose stromal tissue with an admixture of preserved renal architecture and infiltrating tumor. Preserved renal tubules and collecting ducts were evident peripherally, whereas the central and left regions showed dense, poorly circumscribed clusters of tumor cells - consistent with an infiltrative growth pattern. Focal areas of necrosis were also present. This area was predominantly composed of large, pleomorphic cells with variable morphologies, including polygonal, oval, and spindle shapes. The tumor cells contained abundant eosinophilic cytoplasm, and focal areas demonstrated rhabdoid differentiation. Fine cytoplasmic striations were occasionally noted, suggestive of myofibrillar reorganization (Figure 3B). The tumor cell area shown in Figure 3C is composed of a mixture of tumor components, including 25% well-differentiated ductal adenocarcinoma, a small portion (15%) of micropapillary carcinoma, and 60% UDC. The UDC component contained both spindle and rhabdoid cells, associated with extensive hemorrhage and necrosis. Importantly, osteoclast-like giant cells were not identified.

Figure 3 Representative hematoxylin and eosin staining. A: Low-power view showing a nodular lesion with adjacent spleen and pancreas. The spleen is located in the upper part of the image, while a small portion of pancreatic tissue is visible in the lower left corner. Foci of micropapillary carcinoma and undifferentiated carcinoma (UDC) demonstrate transitional areas between ductal adenocarcinoma and UDC, with metastatic deposits identified in a regional lymph node; B: A purplish-red appearance with a background of loose stroma, demonstrating a mixture of residual renal architecture and tumor infiltration. Preserved renal tubules and collecting ducts are visible on the right. At the same time, dense clusters of tumor cells with indistinct borders occupy the central and left regions, consistent with an invasive growth pattern. Focal necrosis is also observed; C: Section showing multiple rounds to oval glandular structures, representing moderately to well-differentiated ductal adenocarcinoma with micropapillary components. Tumor cells are unevenly distributed, and cellular density and heterogeneity vary across regions.

Molecular features: A comprehensive panel of molecular markers was evaluated in both the well-differentiated PDAC and the undifferentiated rhabdoid carcinoma components. The ductal adenocarcinoma exhibited strong immunoreactivity for CK7 and CK-pan, both of which are widely utilized biomarkers to confirm epithelial origin and are particularly valuable in differentiating PDAC from colorectal adenocarcinoma (Figure 4A). In contrast, the PURC component demonstrated complete loss of CK7 expression, while CK-pan staining remained diffusely positive (Figure 4A). Similarly, strong nuclear immunoreactivity for SMARCB1 and SMARCA4 was observed, consistent with intact expression of SWI/SNF chromatin remodeling complex subunits (Figure 4A). Loss of SMARCB1 or SMARCA4 expression is typically observed in atypical teratoid/rhabdoid tumors, with SMARCB1 loss most frequently associated with the anaplastic monomorphic subtype of rhabdoid pancreatic carcinoma[8]. In this case, the PURC component demonstrated complete loss of SMARCB1 expression, while SMARCA4 expression was retained, indicating a selective deficiency within the complex (Figure 4A). The proliferation marker Ki-67 demonstrated low expression in the PDAC component but was markedly elevated in the PURC component, mirroring the expression profiles of CD10 and vimentin (Figure 4A). These findings indicate that a high proliferative index characterizes the PURC component and features consistent with aggressive malignant progression. Consistent with the immunohistochemical findings, fluorescence in situ hybridization confirmed complete loss of SMARCB1 mRNA expression in the rhabdoid carcinoma component (Figure 4B).

Figure 4 Immunohistochemical staining intensity of several molecular markers. A: Immunohistochemical profiles of pancreatic ductal adenocarcinoma (PDAC) and pancreatic undifferentiated rhabdoid carcinoma (PURC). CK7 and SMARCB1 were positive in PDAC but negative in PURC, whereas CD10 and vimentin were positive in PURC but absent in PDAC. CK-pan and SMARCA4 were expressed in both PDAC and PURC. Ki-67 labeling was higher in PURC compared to PDAC; B: Fluorescence in situ hybridization analysis showing loss of SMARCB1 in a subset of tumor cells, consistent with rhabdoid carcinoma phenotype. Red probes denote SMARCB1, and green probes denote EWSR1. PDAC: Pancreatic ductal adenocarcinoma; PURC: Pancreatic undifferentiated rhabdoid carcinoma; H&E: Hematoxylin and eosin.

FINAL DIAGNOSIS

The final diagnosis was T3N1M0 PDAC with SMARCB1-deficient UDC.

TREATMENT

As mentioned above, following a multidisciplinary expert consultation, the patient underwent emergency open surgery, including total splenectomy, partial pancreatectomy, and left nephrectomy. Postoperatively, the patient received adjuvant chemotherapy consisting of gemcitabine, nab-paclitaxel, bevacizumab and sintilimab.

OUTCOME AND FOLLOW-UP

At two months postoperatively, a follow-up contrast-enhanced abdominal CT revealed a soft-tissue mass in the pancreatic tail measuring approximately 33 mm × 25 mm on axial sections, demonstrating mild heterogeneous enhancement (Figure 5A). Multiple enlarged lymph nodes were also observed along the abdominal aorta and in the retroperitoneum, the largest measuring approximately 26 mm in diameter and displaying ring-like enhancement following contrast administration (Figure 5A). The patient received adjuvant chemotherapy consisting of gemcitabine and nab-paclitaxel. Subsequent imaging evaluation demonstrated a reduction in the size the pancreatic lesion and lymph nodes compared to the previous scan, but enlargement and fusion of the perigastriс metastatic lesions (Figure 5B). Therefore, bevacizumab and sintilimab were added to the treatment regimen. The lesion at the pancreatic remnant demonstrated a reduction in size compared with the previous examination, and the retroperitoneal metastatic lesions also showed interval regression (Figure 5C).

Figure 5 Representative computed tomography scans after surgery and during neoadjuvant therapy. A: A recurrent mass at the pancreatic remnant and a retroperitoneal metastatic lesion after surgery; B and C: After neoadjuvant and targeted therapy, both the local recurrence and metastatic foci were reduced in size compared with pre-treatment imaging.

DISCUSSION

SMARCB1/INI1, a core component of the SWI/SNF chromatin-remodeling complex, regulates gene expression by altering chromatin structure and plays a critical role in diverse biological processes including cell cycle regulation, differentiation, proliferation, and DNA damage repair[10,12]. SMARCB1 functions as a canonical tumor suppressor gene, and its inactivation or loss of expression promotes dysregulated cell proliferation and oncogenesis[19]. Loss of nuclear SMARCB1 expression represents a diagnostic hallmark of malignant rhabdoid tumors and epithelioid sarcoma. Consequently, immunohistochemical evaluation of SMARCB1 has become a crucial diagnostic tool in these neoplasms[20]. Beyond these classic SMARCB1-deficient tumors, aberrant SMARCB1 expression or mutations have also been identified in various other tumor types, including certain UDC s of the gastrointestinal tract and pancreas[7,21].

In PDAC, mutations or loss of SWI/SNF complex subunits such as ARID1A, SMARCA4 (BRG1), and SMARCA2 (BRM) are relatively common, whereas loss of SMARCB1 (INI1) remains uncommon[22,23]. However, in pancreatic UDC, the frequency of SMARCB1 loss is significantly higher than in conventional PDAC, suggesting that SMARCB1 deficiency may be closely associated with the tumor dedifferentiation process[8,24]. A previous study demonstrated that SMARCB1 loss significantly correlates with reduced expression of other SWI/SNF subunits, including ARID1A, SMARCC1, and SMARCC2, in PURC[24]. Pancreatic SMARCB-deficient UDC is an exceedingly rare entity. Its clinicopathological characteristics have primarily been described in limited case reports and small series[18]. Clinical presentation is typically non-specific, and diagnosis often occurs at an advanced stage, characterized by local invasion and/or distant metastasis[25,26]. For example, reported symptoms include abdominal pain and weight loss or jaundice[18,27]. Imaging studies usually reveal a pancreatic mass, but its morphology is variable and may mimic other pancreatic neoplasms such as a solid pseudopapillary neoplasm (SPN). This may sometimes be misdiagnosed as other types of pancreatic tumors, such as SPN[18,28].

Common presenting symptoms of pancreatic cancer include persistent upper abdominal or back pain, progressive weight loss, decreased appetite, and jaundice, although some patients are diagnosed incidentally during routine examinations. In this case, the patient’s initial presentation with SSR is exceptionally rare and represents a novel diagnostic challenge in SMARCB1-deficient rhabdoid pancreatic UDC. SSR is most commonly associated with hematologic malignancies or inflammatory pancreatic processes, such as acute or chronic pancreatitis, via mechanisms including enzymatic erosion, splenic vein thrombosis, or pseudocyst expansion[29,30]. Solid pancreatic tumors presenting with SSR are exceedingly uncommon, with reported cases primarily involving acinar cell carcinoma, SPN, or conventional PDAC invading the spleen[31,32]. To our knowledge, there are no prior reports of SMARCB1-deficient rhabdoid pancreatic UDC manifesting first as SSR. The profound anatomical proximity of the pancreatic tail to the splenic hilum underscores a plausible pathophysiological link in which tumor invasion or necrosis precipitates capsular disruption and hemorrhage. Clinically, when SSR occurs in a patient without antecedent trauma but with a pancreatic mass, malignancy should be strongly suspected. Urgent imaging and prompt surgical management are therefore essential. Recognizing SSR as a rare but possible initial presentation of pancreatic malignancy - including SMARCB1-deficient variants - is critical for early diagnosis and timely intervention. Prompt splenectomy followed by definitive oncologic treatment may ultimately improve patient outcomes.

Studies investigating treatment outcomes in SMARCB1-deficient rhabdoid pancreatic UDC remain scarce, and those available lack sufficient statistical power to inform subtype-specific therapeutic strategies. This underscores an urgent need for robust evidence to inform optimal treatment strategies for this aggressive neoplasm. A systematic literature review of PubMed, EMBASE, MEDLINE, and Cochrane databases identified 55 reported cases of UDC with rhabdoid features (Table 1). Among the reported cases, treatment strategies and associated clinical outcomes were available for 51 patients. Most of the cases underwent surgery or biopsy alone[33-36], four received a combination of surgery and adjuvant chemotherapy, seven were treated with palliative chemotherapy only[34,37-44], and seven received supportive care without active oncologic treatment[45-47]. The prognosis of SMARCB1-deficient rhabdoid pancreatic UDC is generally poor, with most patients succumbing to the disease within a year of diagnosis. However, two cases of prolonged survival have been reported. One patient underwent distal pancreatectomy followed by adjuvant gemcitabine-paclitaxel, achieving 20 months of disease-free survival[44]. Another patient remained disease-free for at least 9 months after receiving a Whipple procedure and adjuvant gemcitabine-capecitabine therapy[48]. These cases suggest that complete surgical resection combined with gemcitabine-based adjuvant chemotherapy may extend survival in select patients with PRUC.

Table 1 Previously reported undifferentiated pancreatic carcinomas with rhabdoid features (n = 55).

Ref.	Histology	Age (years)/sex	Site	Size (cm)	Treatment	Metastasis	Prognosis
Guillan[34], 1968	Pleomorphic ADCA	65/M	Head	10	Palliative	Yes	DOD 3 months
	Pleomorphic ADCA	59/M	Body/tail	6	Palliative	Yes	DOD 3 months
	Pleomorphic ADCA	72/M	Body/tail	8	Palliative	Yes	DOD 4 months
	Pleomorphic ADCA	75/M	Body/tail	9	Palliative	Yes	DOD 5 months
	Pleomorphic ADCA	62/M	Body/tail	15	Palliative	Yes	DOD 3 months
Alguacil-Garcia and Weiland[33], 1977	Round cell anaplastic carcinoma	78/M	Body	30	Biopsy	Lung, liver	DOD in few days
	Round cell anaplastic carcinoma	74/M	Tail	15	Surgery + chemotherapy	None	DOD 4 months
	Round cell anaplastic carcinoma	51/F	Head	5	Surgery	Lymph node	DOD 1 months
	Round cell anaplastic carcinoma	73/M	Diffuse	11	Biopsy	Lymph node, adrenals	DOD in few days
	Round cell anaplastic carcinoma	30/M	Body	12	Autopsy	Lymph node, ileum, kidney, thyroid, lung	NS
Tschang et al[39], 1977	Pleomorphic carcinoma	67/M	Tail	3	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	49/M	Tail	NS	Biopsy	Lymph node, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	54/M	Body/tail	NS	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	65/M	Tail	NS	Autopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	72/M	Body	NS	Autopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	61/M	Body	NS	Biopsy	Lymph node, liver, peritoneum	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	72/M	Head/body	10	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	65/M	Body/tail	NS	Biopsy + chemotherapy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	69/M	Head	10	Biopsy + chemotherapy	Liver, peritoneum	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	65/M	Body/tail	NS	Biopsy + chemotherapy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	72/M	Head	10	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	53/M	Diffuse	10	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	81/F	Body/tail	15	Biopsy	Lymph node, liver, extra-abdominal	DOD median 3 months, mean 6 months
	Pleomorphic carcinoma	79/F	Head	10	Biopsy	Lymph node	DOD median 3 months, mean 6 months
Reyes et al[45], 1980	Pleomorphic giant cell carcinoma	59/M	Head	Mean 9	Supportive	Lymph node, widespread	DOD 1 month
	Pleomorphic giant cell carcinoma	37/M	Tail	Mean 9	Chemotherapy	Lymph node, widespread	DOD 13 months
	Pleomorphic giant cell carcinoma	59/M	Head	Mean 9	Supportive	Lymph node, widespread	DOD 1 month
	Pleomorphic giant cell carcinoma	71/M	Head	Mean 9	Palliative surgery	Lymph node, widespread	DOD 2 months
	Pleomorphic giant cell carcinoma	70/M	Head	Mean 9	Supportive	Lymph node, widespread	DOD 3 months
	Pleomorphic giant cell carcinoma	77/M	Head	Mean 9	Supportive	Lymph node, widespread	DOD 1 month
	Pleomorphic giant cell carcinoma	64/M	Head	Mean 9	Supportive	Lymph node, widespread	DOD 2 months
	Pleomorphic giant cell carcinoma	62/M	Head	Mean 9	Palliative surgery	Lymph node, widespread	DOD 1 month
	Pleomorphic giant cell carcinoma	54/M	Body	Mean 9	Supportive	Lymph node, widespread	DOD 4 months
Nishihara et al[35], 1997	Carcinoma with rhabdoid features	52/F	NS	10	Surgery	Lymph node, liver	DOD 19 months
Al-Nafussi and O'Donnell[46], 1999	Adeno carcinoma extensive rhabdoid	77/F	NS	NS	No	Soft tissue, liver, lung, kidney, heart, adrenals	DOD initially
Kuroda et al[38], 2007	Anaplastic carcinoma with rhabdoid features	68/F	NS	14	Palliative	Regional, bronchial	DOD 2 months
	Anaplastic carcinoma with rhabdoid features	59/M	NS	10	Surgery + chemotherapy	Liver	DOD 2 months
Chadha et al[47], 2004	Anaplastic pancreatic carcinoma	74/F	Tail	NS	Palliative	Lymph node, liver, adrenal, peritoneum	DOD 2 weeks
Cho et al[37], 2006	Carcinoma mucinous rhabdoid features	65/F	Tail	11	Surgery + RT	Omentum, mesentery, liver, lung	DOD 12 months
Jamali et al[36], 2007	ADSCA rhabdoid	75/M	NS	3	Surgery	Liver	DOD 6 months
Layfield and Bentz[40], 2008	Pleomorphic giant cell carcinoma	71/M	Head	NS	Surgery	Liver	Alive 2 months
	Pleomorphic giant cell carcinoma	81/F	Head	NS	Palliative	NS	DOD 3 months
	Pleomorphic giant cell carcinoma	59/M	Head	NS	Surgery	Lymph node, liver	Alive 3 months
	Pleomorphic giant cell carcinoma	81/M	Head	NS	Palliative	NS	NS
	Pleomorphic giant cell carcinoma	64/M	Body	NS	Palliative	Lymph node	Alive 4 months
	Anaplastic carcinoma	63/M	NS	10	Supportive	Synchronous, liver	DOD 11 days
Agaimy et al[8], 2015	Rhabdoid	76/M	Head	5	Surgery	NS	DOD 1 month
	Rhabdoid, angiosarcoma-like	44/F	Head	6	Surgery	NS	NS
	Rhabdoid, pseudopapillary acantholytic gland-like spaces	72/M	Head	4	Surgery	Liver, lymph node nodes	DOD postoperatively
	Rhabdoid, prominent neutrophils and focal glandular formation	61/M	Tail	5	Surgery	Intra-abdominal, stomach	NS
Sano et al[41], 2014	Rhabdoid	68/F	Body/tail	10	Palliative	Liver, kidneys, lungs, right adrenal gland, omentum, peritoneum	DOD in 2 weeks
Ohike et al[42], 2007	Rhabdoid, solid/diffuse	35/F	Head	6	Chemotherapy	Liver	DOD in 7 months
Tahara et al[43], 2018	Rhabdoid, solid/diffuse	67/F	Body	1.9	Chemotherapy	Liver, lung, bone, tongue, right thigh	DOD in 6 months
King et al[44], 2021	Rhabdoid; monomorphic epithelioid	59/F	Tail	1.6	Neoadjuvant FOLFIRINOX; distal pancreatectomy; adjuvant gemcitabine/paclitaxel	Liver	Disease-free 20 months
Our case	Rhabdoid	59/F	Tail	4.5	Gemcitabine/nab-paclitaxel; bevacizumab/toripalimab	Spleen, kidney, retroperitoneum	Alive 6 months

ADCA: Adreno carcinoma; ADSCA: Adenosquamous carcinoma; NS: Not specific; M: Male; F: Female; RT: Tadiation therapy; DOD: Day of dead.

In this case, despite locally advanced disease at presentation, upfront resection combined with adjuvant gemcitabine and nab-paclitaxel has resulted in six months of disease-free survival to date, suggesting that aggressive multimodal management may confer benefit in selected patients. Given the absence of standardized treatment protocols, current management is largely extrapolated from PDAC guidelines. According to the National Comprehensive Cancer Network guidelines, R0 surgical resection remains the cornerstone for localized disease, while adjuvant chemotherapy - typically gemcitabine-based - is indicated to reduce the risk of recurrence[49]. For unresectable or metastatic disease, FOLFIRINOX or gemcitabine/nab-paclitaxel are preferred systemic therapies[49]. However, the distinct molecular biology of SMARCB1-deficient tumors, defined by loss of SWI/SNF complex function, may limit responsiveness to conventional cytotoxic therapy, emphasizing the need for novel targeted approaches. Ongoing research on EZH2 inhibitors[50], immune checkpoint blockade[51], and CDK4/6 inhibitors in SMARCB1-deficient malignancies may hold promise for future therapeutic strategies in this rare but highly aggressive entity[52]. An alternative hypothesis is that, although Combined Positive Score (CPS) is not routinely used as a predictive biomarker in pancreatic cancer, a high CPS was observed in cases that may reflect substantial tumor immunogenicity[24,51]. This elevated programmed death ligand-1 expression in the immune microenvironment may have primed an antitumor immune response, contributing to the observed benefit from second-line therapy. Nevertheless, further mechanistic studies are warranted to elucidate predictive biomarkers of treatment response in this rare pancreatic neoplasm.

CONCLUSION

SMARCB1-deficient rhabdoid pancreatic UDC represents a rare and highly aggressive tumor subtype with limited published evidence to guide optimal management. Our case, together with previously reported cases, suggests that aggressive, multimodal treatment - including complete surgical resection and adjuvant chemotherapy - may prolong survival in selected patients. However, the majority of patients experience rapid disease progression and poor prognostic outcomes. Given the distinct molecular biology of SMARCB1-deficient tumors and their potential resistance to conventional cytotoxic therapies, there is an urgent need to develop molecularly targeted agents and to conduct prospective, multicenter studies to establish evidence-based management strategies for this challenging and rare entity.