Pancreatic PEComa: Case Report of an Extremely Rare Tumor.

THE DIAGNOSIS OF SO-CALLED ORAL EPITHELIOID LEIOMYOMA REVISITED AND REVISED. APPRAISAL OF IMMUNOHISTOCHEMICAL PROPERTIES REVEAL A “TRANSMOGRIFIED” MYOFIBROBLASTIC PROLIFERATION WITH SELECTIVE TERMINAL SMOOTH MUSCLE DIFFERENTIATION

Renal angiomyolipoma is a benign tumor histologically characterized by proliferation of spindle cells, epithelioid cells, and adipocytic cells in concert with many thick-walled blood vessels. To add further diagnostic confusion, an epithelioid cell-predominant variant of renal angiomyolipoma has recently been described. HMB-45 immunoreactivity correlates with ultrastructural striated organelles that closely resemble premelanosomes, although no evidence of melanogenesis has been documented in this tumor. To further characterize the immunophenotypic and ultrastructural profile of renal angiomyolipoma based on phenotypic cell type (epithelioid, spindle, and adipocytic cell). Formalin-fixed, paraffin-embedded tissues from 27 renal angiomyolipomas and 8 renal cell carcinomas were immunostained with monoclonal antibodies to the melanoma-associated antigens HMB-45, HMB-50, NKI/C3 (CD63), and tyrosinase; the smooth muscle-related antigens calponin and muscle-specific actin (HHF-35); S100; and cytokeratin (CK). All renal angiomyolipomas were also immunostained with a polyclonal antibody to renin. Ultrastructural examination was performed on 9 selected cases. All renal angiomyolipomas stained positive for HMB-45, HMB-50, NKI/C3, muscle-specific actin (HHF-35), and calponin. Overall, HMB-45, HMB-50, and NKI/C3 preferentially stained the epithelioid cells. Tyrosinase staining was present in 50% of the renal angiomyolipomas with adequate tissue for staining (12 of 24 cases); positive staining and intensity paralleled HMB-45, HMB-50, and NKI/C3. Muscle-specific actin (HHF-35) and calponin preferentially stained the spindle cells. The adipocytic cells stained positive for both melanoma-associated antigens and smooth muscle antigens. Epithelioid cells, spindle cells, and adipocytic cells were CK, S100, and renin negative. Ultrastructural findings paralleled immunohistochemical staining patterns. Premelanosome-like organelles and electron dense granules were more readily detected in the epithelioid cells within the tumor, whereas ultrastructural characteristics of smooth muscle cells were more easily found in the spindle cells. All renal cell carcinomas stained positive for CK, NKI/C3 staining was variable, and all were negative for HMB-45, HMB-50, smooth muscle actin (HHF-35), and calponin. In renal angiomyolipoma, the epithelioid and spindle cells have preferential staining patterns for melanoma-associated antigens versus smooth muscle antigens, respectively. Positivity in renal angiomyolipoma for HMB-50, NKI/C3, and tyrosinase, in addition to HMB-45, provides evidence for the presence of different melanoma-associated gene products. Immunophenotypic overlap of the 3 histologically distinct renal angiomyolipoma cell populations suggests a common cell line, supporting a unitarian concept for renal angiomyolipoma. Ultrastructural characteristics of the 3 renal angiomyolipoma cell phenotypes parallel the immunophenotype, giving further support to a common cell line. Our study lends further credence to the perivascular epithelioid cell concept as proposed by Bonetti and colleagues.

Background Renal angiomyolipoma is a benign tumor histologically characterized by proliferation of spindle cells, epithelioid cells, and adipocytic cells in concert with many thick-walled blood vessels. To add further diagnostic confusion, an epithelioid cell-predominant variant of renal angiomyolipoma has recently been described. HMB-45 immunoreactivity correlates with ultrastructural striated organelles that closely resemble premelanosomes, although no evidence of melanogenesis has been documented in this tumor. Objective To further characterize the immunophenotypic and ultrastructural profile of renal angiomyolipoma based on phenotypic cell type (epithelioid, spindle, and adipocytic cell). Design Formalin-fixed, paraffin-embedded tissues from 27 renal angiomyolipomas and 8 renal cell carcinomas were immunostained with monoclonal antibodies to the melanoma-associated antigens HMB-45, HMB-50, NKI/C3 (CD63), and tyrosinase; the smooth muscle-related antigens calponin and muscle-specific actin (HHF-35); S100; and cytokeratin (CK). All renal angiomyolipomas were also immunostained with a polyclonal antibody to renin. Ultrastructural examination was performed on 9 selected cases. Results All renal angiomyolipomas stained positive for HMB-45, HMB-50, NKI/C3, muscle-specific actin (HHF-35), and calponin. Overall, HMB-45, HMB-50, and NKI/C3 preferentially stained the epithelioid cells. Tyrosinase staining was present in 50% of the renal angiomyolipomas with adequate tissue for staining (12 of 24 cases); positive staining and intensity paralleled HMB-45, HMB-50, and NKI/C3. Muscle-specific actin (HHF-35) and calponin preferentially stained the spindle cells. The adipocytic cells stained positive for both melanoma-associated antigens and smooth muscle antigens. Epithelioid cells, spindle cells, and adipocytic cells were CK, S100, and renin negative. Ultrastructural findings paralleled immunohistochemical staining patterns. Premelanosome-like organelles and electron dense granules were more readily detected in the epithelioid cells within the tumor, whereas ultrastructural characteristics of smooth muscle cells were more easily found in the spindle cells. All renal cell carcinomas stained positive for CK, NKI/C3 staining was variable, and all were negative for HMB-45, HMB-50, smooth muscle actin (HHF-35), and calponin. Conclusion In renal angiomyolipoma, the epithelioid and spindle cells have preferential staining patterns for melanoma-associated antigens versus smooth muscle antigens, respectively. Positivity in renal angiomyolipoma for HMB-50, NKI/C3, and tyrosinase, in addition to HMB-45, provides evidence for the presence of different melanoma-associated gene products. Immunophenotypic overlap of the 3 histologically distinct renal angiomyolipoma cell populations suggests a common cell line, supporting a unitarian concept for renal angiomyolipoma. Ultrastructural characteristics of the 3 renal angiomyolipoma cell phenotypes parallel the immunophenotype, giving further support to a common cell line. Our study lends further credence to the perivascular epithelioid cell concept as proposed by Bonetti and colleagues.

Introduction: Accessory spleens are often incidental findings on imaging and usually present as a solid mass at splenic hilum or other organs such as pancreas. Most patients with accessory spleens are asymptomatic however abdominal pain has been associated with an accessory spleen. Intrapancreatic accessory spleen (IPAS) can mimic a pancreatic neuroendocrine tumor (NET) on imaging studies and therefore posing a diagnostic dilemma. We present a case of IPAS in which the concomitant use of nCLE and fine needle aspiration (FNA) helped make the diagnosis. A 24 year old female referred for EUS for a pancreatic mass on CT scan. She presented with abdominal pain and during the workup a 3cm x 2.9cm round hypervascular hypodense mass in the tail of the pancreas was found. Her past medical history is significant for second degree relative with pancreatic cancer. Patient has a past medical history of Thrombotic Thrombocytopenic Purpura (TTP) and she underwent splenectomy 5 years ago for profound thrombocytopenia. On EUS a 2.8cm x 2.9cm round homogenous hypoechoic mass in pancreatic tail was identified. Initially the mass was punctured using a 19-G needle that was pre-loaded with AQ-Flex 19 probe inside the needle before puncture in lieu of the stylet. Fluorescein (2.5mL of 10 % fluorescein sodium) was injected simultaneously with probe insertion. Numerous thick white bands with floating small black particles inside the bands suggestive of network of blood vessels and floating Erythrocytes. Interrogation of the mass did not identify any finger-like papillary projections, crypt-like structures or dark aggregates of cells which is seen in a villous structure or neoplastic cells. Then 4 passes using a 22 G FNA needle was performed with onsite pathology and endomicroscopy review supported the final diagnosis of IPAS. Discussion: Accessory spleen is a rare entity which can be seen in the splenic hilum or at the tail of the pancreas. In 3000 autopsies reported by Halpert et al, 364 accessory spleens were found in which 17% were IPAS. Accessory spleens can be acquired entities (splenosis) which is the auto transplantation of splenic tissue in abnormal locations as a result of trauma or post splenectomy. This is the first case that incorporates real-time endomicroscopy and onsite pathology to diagnose IPAS. Patients with IPAS may undergo distal pancreatectomy because they mimic a hypervascular NET on CT and MRI scans. Onsite pathology and endomicroscopy review increases the diagnostic accuracy for differentiating between IPAS and pancreatic NET. In patients with a hypervascular mass in the tail of pancreas addition of real time nCLE to traditional FNA can increase the diagnosis yield of EUS and potentially prevent unnecessary surgery.Figure 1Figure 2Figure 3

Perivascular epithelioid cell tumor (PEComa) is a rare neoplasm considered to arise from myomelanocytic cell lineage. The uterus is reportedly the most common site to be involved. Orbital PEComa is extremely rare with only two cases reported till date. A 5-year-old male presented with a right medial orbital mass for the last 6 months. The patient was diagnosed with alveolar soft part sarcoma elsewhere. Magnetic resonance imaging features were suggestive of lymphangioma with bleeding. The excision biopsy revealed multiple tumor cells comprising epithelioid cells with clear cytoplasm, along with nuclear atypia and mitosis. Immunohistochemistry was positive for HMB-45, smooth muscle actin, vimentin, and CD-34. It was negative for cytokeratin, S-100, and synaptophysin, which clinched the diagnosis of malignant orbital PEComa. Neoadjuvant chemotherapy was administered. There was no recurrence at 24 months of follow-up. At present, there is no consensus on management protocol for malignant PEComa. Complete surgical excision with chemotherapy appears to offer the best prognosis.

GLI activated epithelioid cell tumour: report of a case and proposed new terminology

Gangliocytic paraganglioma (GP) is quite rare, and origin and entity remain to be elucidated. A 51-year-old man presented with GP as a sessile polyp with a smooth surface that measured about 1 cm in diameter in the descending portion of duodenum. Pathological examination displayed that a neoplasm was predominantly located in the submucosa and infiltrated mucosa focally. The tumor consisted of epithelioid, ganglion-like, and spindle cells admixing in a haphazard way. The epithelioid cells resembled paraganglioma in cytological and architectural features. The ganglion-like cells were scattered and merged with the bland spindle cells in fascicular clusters, which resembled ganglioneuroma. Synaptophysin (Syn), microtubule-associated protein-2 (MAP-2), and chromogranin A (CgA) were positive in the epithelioid and ganglion-like cells in variety, and neurofilament (NF) staining highlighted the ganglion-like cells. S-100 and SOX-10 were positive in the spindle cell proliferation and around the epithelioid cells. Progesterone receptor (PR) was positive in the epithelioid cells. The polyp was resected, and no adjuvant therapy was given. The patient remained with no recurrence in 2 years’ follow-up. Origin of GP is presumed to be related to pancreas islet. GP is distinguished from neuroendocrine tumor (NET) G1 and designated as paraganglioma-ganglioneuroma, a kind of composite paragangliomas.

2. Bilateral multiple nodules in lung: Epstein barr virus associated smooth muscle lesions

INTRAOSSEOUS BENIGN FIBROUS HISTIOCYTOMA RICH IN GRANULAR CELLS OF THE MAXILLA: IMMUNOHISTOCHEMICAL ANALYSIS

BackgroundGangliocytic paraganglioma (GP) is a rare neuroendocrine neoplasm, which occurs mostly in the periampullary portion of the duodenum; the majority of the reported cases of duodenal GP has been of benign nature with a low incidence of regional lymph node metastasis. GP arising from the pancreas is extremely rare. To date, only three cases have been reported and its clinical characteristics are largely unknown.Case presentationA nodule located in the pancreatic head was incidentally detected in an asymptomatic 68-year-old woman. Computed tomography revealed 18-, 8-, and 12-mm masses in the pancreatic head, the pancreatic tail, and the left adrenal gland, respectively. Subsequent genetic examination revealed an absence of mutations in the MEN1 and VHL genes. Macroscopically, the tumor located in the pancreatic head was 22 mm in size and displayed an ill-circumscribed margin along with yellowish-white color. Microscopically, it was composed of three cell components: epithelioid cells, ganglion-like cells, and spindle cells, which led to the diagnosis of GP. The tumor was accompanied by a peripancreatic lymph node metastasis. The tumor in the pancreatic tail was histologically classified as a neuroendocrine tumor (NET) G1 (grade 1, WHO 2010), whereas the tumor in the left adrenal gland was identified as an adrenocortical adenoma. The patient was disease-free at the 12-month follow-up examination.ConclusionsPancreatic GP is associated with a higher incidence of metastasis and larger tumor size than duodenal GPs, suggesting that the primary organ of GP is an important prognostic factor.

BackgroundPerivascular epithelioid cell tumor (PEComa) of the pancreas is a rare tumor of pancreatic mesenchymal origin with malignant potential. Critical to appropriate clinical management is determining whether the tumor is benign or malignant. Because of its rarity, morphologic and histologic characteristics and limited patient follow-up of pancreatic PEComa have precluded precise definition of malignancy. However, because malignant pancreatic PEComa appears to be distinctly uncommon, further improvements characterizing its preoperative imaging features could facilitate use of diagnostic endoscopic ultrasound biopsy and perhaps ablative treatment. This paper presents a case of pancreatic PEComa treated at the Affiliated Hospital of North Sichuan Medical College and includes a systematic literature review with special emphasis on the key imaging features of pancreatic PEComa.Case presentationIn February 2024, a woman in her 50s was admitted to the hospital with subxiphoid discomfort. Magnetic resonance imaging (MRI) of the upper abdomen revealed a round, solid mass in the pancreatic uncinate process. The patient underwent pancreatic mass resection and pancreaticojejunostomy, and the diagnosis of pancreatic PEComa was confirmed through pathological examination.ConclusionsImaging examinations appear valuable for a tentative diagnosis of pancreatic PEComa. Key imaging features include its frequent occurrence in the pancreatic head, typically small to moderate size, “pushing” as opposed to infiltrative growth pattern with well-defined margins, and the presence of a capsule. The lesions are usually solid and often exhibit mild to moderate heterogenous enhancement during the arterial phase, with reduced enhancement in the portal and delayed phases.

Clinical Challenges and Images in GI

Gastrointestinal stromal tumor (GIST) typically occurs in the gastrointestinal (GI) tract, and expresses KIT protein that is associated with KIT or platelet-derived growth factor receptor-α (PDGFRA) gene mutation. Extragastrointestinal stromal tumors (EGISTs) are a minor subset of GIST that occurs in the soft tissue outside the GI tract, and in very rare cases, these tumors can be KIT negative. We examined the clinicopathologic and molecular characteristics of 10 cases of KIT-negative EGIST by using immunohistochemical staining and gene mutation analysis. The tumors occurred in the omentum (n=5), mesentery (n=2), retroperitoneum (n=1), pelvic cavity (n=1), and not otherwise specified regions of the abdominal cavity (n=1). They ranged from 4 to 33 cm (median, 15 cm) in maximum diameter with relatively low mitotic counts (median, 3.5 per 50 high-power fields). Morphologically, most cases were of epithelioid cell (n=9) or mixed epithelioid and spindle cell (n=1) type, accompanied by variable amounts of myxoid stroma. By immunohistochemical staining, the tumors were positive for CD34 (80%), protein kinase C (PKC) θ (90%), and discovered on GIST-1 (DOG1) (90%), but were negative for KIT (0%). The majority of the examined cases (7 of 9 cases; 78%) had PDGFRA mutations in exon 12 (n=1) or exon 18 (n=6). One case (11%) had a mutation in KIT exon 11, and the remaining 1 had no mutation in either KIT or PDGFRA. Distant metastasis and local recurrence occurred in 1 (10%) and 2 (20%) patients, respectively, and adverse outcome was correlated with larger (>10 cm) tumor size and high mitotic counts (>5/50 high-power fields). Therefore, KIT-negative EGISTs can be characterized by preferential omental origin, epithelioid cell type, low mitotic activity, and mutation of the PDGFRA gene, and these features are similar to those of KIT-negative gastric GISTs. As KIT-negative EGISTs should be considered to be a potential abdominal soft tissue neoplasm, immunohistochemical staining panel and molecular analysis are necessary not only to confirm the diagnosis but also to determine the therapeutic strategy.

MYOEPITHELIOMA IN THE MINOR SALIVARY GLAND

Islet cell tumors of the pancreas are uncommon, and nonfunctioning tumors are even rarer than functioning ones. We report the case of a 67-year-old woman with a small nonfunctioning islet cell tumor, 6 x 5 mm in diameter, which was detected incidentally by ultrasonography, and subsequently confirmed by double-helical computed tomography. Diagnosis was established by histopathological examination after 80% distal pancreatectomy with splenectomy, and by various laboratory tests. Histologically, the islet cell tumor showed highly cellular spindle or epithelioid cells, which were positive for Grimelius stain. Immunohistochemical examination revealed that the tumor cells were positive for chromogranin A, but negative for somatostatin, insulin, glucagon, and gastrin. Its small size, location, and benignity make this a very rare type of nonfunctioning islet cell tumor.