Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas with poor prognosis due to their high recurrence rates. The prevalence of MPNST in the general population is 0.001%, with tumors arising from the retroperitoneum accounting for only 1% of all MPNSTs. In this report, we present a case of a 59-year-old male with pancreatic MPNST. To the authors’ knowledge, this is the first documented case of pancreatic MPNST in the Philippines.

The patient initially presented with a 3-month history of abdominal pain, weight loss, and anorexia. On abdominal computed tomography (CT) scan, a large cystic mass involving the pancreatic head and body, with an enhancing peripheral solid component in the superior region was seen. The patient underwent distal pancreatectomy, en bloc splenectomy and excision of duodenal cyst. Post-operative histopathology and immunohistochemistry staining were consistent with pancreatic MPNST with tumor very near the margin of resection adjacent to the portal vein. Adjuvant systemic chemotherapy and radiotherapy were not performed due to lack of evidence of benefit over risk for this population. Disease recurrence (nodal-peritoneal metastases) was noted six months post-operatively and he was given palliative chemotherapy with single-agent doxorubicin. However, disease progression was noted after five cycles of chemotherapy. Second-line regimen was planned but the patient died of a pulmonary embolism prior to the initiation of chemotherapy.

Due to the rarity and highly aggressive nature of MPNSTs, furthering knowledge on these tumors is important, particularly in their inclusion among the differential diagnoses for pancreatic tumors. Prompt diagnosis and histopathologic confirmation by a pathologist specializing in sarcomas are crucial in the treatment planning and prognostication of these tumors. Lastly, further studies are needed to establish more effective treatments in unresectable or metastatic disease.

Abstract Embryonal rhabdomyosarcoma (ERMS) is a primitive and aggressive soft tissue tumor that arises from premature mesenchymal cells and accounts for less than 1% of prostate malignancies. We present the case of a 26-year-old Filipino male who initially sought consultation and work-up for acute urinary retention. Although his prostate-specific antigen (PSA) level was normal, a kidney-ureter-bladder (KUB) ultrasound revealed an incidental finding of an enlarged prostate gland. Subsequent imaging tests (MRI and CT) identified a large, partially exophytic mass on the prostate with intravesical extension. The patient underwent a biopsy via transurethral resection at another institution, which yielded findings of a poorly differentiated carcinoma, primarily suggesting prostatic adenocarcinoma with a Gleason score of 10 (5+5). A request for slide review was submitted to our institution, and subsequent immunohistochemistry (IHC) studies—highlighting the tumor's immunoreactivity to myogenin and desmin—confirmed the diagnosis of ERMS. In this report, we discuss the clinical features, pathogenesis, treatment, diagnosis, and prognosis of this rare prostate tumor.
Embryonal rhabdomyosarcoma ; Immunohistochemistry ; Prostate ; Young adult

Objective: This study aimed to determine the prevalence, clinicopathologic features, and immunohistochemical profile of PTs diagnosed at the Philippine General Hospital – Department of Laboratories from January 1, 2018 to December 31, 2022. Methodology: This cross-sectional study reviewed surgical pathology cases of PTs within the study period. Immunoscores for β-catenin, E-cadherin, and CD10 were evaluated, with outcomes including histopathologic grade, stromal cellularity, atypia, overgrowth, tumor margin, and mitotic count. Results: A total of 191 PTs were diagnosed, with the fewest in 2020 (27 cases) and the most in 2018 (51 cases). Benign PTs comprised the majority (52.88%), followed by borderline (34.03%) and malignant (13.09%) types. Most patients (59.16%) were 50 years or older. Tumors commonly measured 5.0–19.99 cm, with the largest proportion ranging from 15.0–19.99 cm. No significant associations were observed between immunoscores and tumor grade or morphologic features, possibly due to limited sample size and uneven group distribution. A weak positive correlation was found between β-catenin and E-cadherin, while other markers showed negligible correlation. Conclusion Larger studies are needed to clarify potential relationships between IHC expression and PT grading. This study contributes to the limited local data on PTs and highlights their possible diagnostic utility, especially in cases with overlapping features.
Phyllodes Tumor ; beta Catenin ; Cadherins

Introduction: Gastrointestinal neuroectodermal tumors (GNETs) are rare but distinctive sarcomas that often arise from the small intestines. Case Description: We report a 24-year-old Filipino male who initially presented with abdominal pain; imaging showed an enhancing circumferential mass involving the jejunum along with a peripherally enhancing focus in the liver and several enlarged superior mesenteric lymph nodes. Discussion: Histopathologic evaluation of the tumor revealed a monomorphic population of epithelioid cells with pale eosinophilic to clear cytoplasm and round nuclei with open chromatin and occasional conspicuous nucleoli. The tumor cells assume various architectural patterns with admixed osteoclast-like giant cells. Immunohistochemistry studies showed diffuse positivity with SOX10 and S100 and negativity for HMB45. Fluorescence in situ hybridization demonstrated EWSR1 gene rearrangement confirming the diagnosis of GNET. Despite their relatively bland morphology, these tumors demonstrate aggressive behavior. Conclusion In light of more recent reports of similar neoplasms occurring in extraenteric sites, heightened clinical suspicion and familiarity with this peculiar malignancy is recommended.
Jejunal Neoplasms ; Neuroectodermal Tumors ; Sarcoma

Introduction: Extraskeletal Ewing sarcoma (EES) is a rare subtype of Ewing Sarcoma. It is more common in older age group compared with Classic Ewing Sarcoma that is seen in pediatric patients. It usually presents in the upper extremities, hips, and pelvis. The breast is an unusual primary location for this tumor, and there are very few reported cases in the literature. In the Philippines, there have been no reported cases yet of EES primary to the breast in the pediatric age group. Case Description: This is a case of a right upper chest mass from a 13-year-old male noted with progression of size for the past 8 months associated with pain. A biopsy was done in the initial consult and yielded unremarkable results, hence management with unrecalled antibiotics and pain medications. Continuous worsening of symptoms led to consultation at our institution, wherein a non-tender, non-erythematous, non-movable, firm, 15 x 13 cm mass was noted at the right chest during his ER consult and subsequent admission. CT scan with contrast revealed a right chest wall mass (16.8 x 18.1 x 9.5 cm) with focal areas of intrathoracic extension and associated pleural thickening. The patient subsequently underwent an incision biopsy for further workup. Microscopically, sheets and cords of small round blue cells are seen with scant to ample amphophilic cytoplasm, increased nuclear to cytoplasmic ratio, coarse chromatin pattern, and inconspicuous nucleoli set in a background of fibrocollagenous stroma. About 5-10 mitoses are also seen per 10 high-power fields, some of which are atypical. Based on the patient’s medical history, radiographic findings and histomorphologic characteristics of the case, the primary working diagnosis for this case is a malignant small round blue cell neoplasm. Immunohistochemistry studies showed strong, diffuse, membranous, and cytoplasmic immunoreactivity to CD99, while the rest of the immunohistochemical stains (Desmin, Myogenin, Chromogranin, CD45, and SALL4) yielded negative results. Additionally, NKX2.2 was also performed which showed strong, diffuse, nuclear immunoreactivity to the neoplastic cells. The case is compatible with the diagnosis of Ewing Sarcoma. Subsequent molecular test on ESWR1 via Fluorescence in-situ hybridization (FISH) revealed an ESWR gene break apart, which further supports the diagnosis of Ewing Sarcoma. Six months after the biopsy, and having completed 3 cycles of chemotherapy, the patient subsequently underwent excision of the mass. The excised tumor was submitted for histopathologic evaluation, which showed good response (89% treatment effect, mainly composed of extensive necrosis). There is no involvement of the adjacent rib bone, and all surgical margins are negative for tumor; thus, this has been signed out as a case of Extraskeletal Ewing Sarcoma of the Breast. Discussion: Extraskeletal Ewing Sarcoma (EES) is a highly aggressive tumor seen among 12% of patients with Ewing Sarcoma (ES). It has a wide anatomic distribution.Typically, it is most common on the upper extremities, hips and pelvic area. It is also seen more among older age group, usually in the 4th decade of life in some of the reported cases, in comparison with classic ES. The breast is an unusual location for the tumor for both adult and pediatric patients. Most tumors of the breast commonly seen in the pediatric age group are metastatic processes, which include rhabdomyosarcoma and lymphoma. CD99 is an important and essential immunohistochemical stain (IHC) in the diagnosis of Ewing sarcoma; 95% of cases of ES has a diffuse, strong membranous expression. NKX2.2 is also useful in the diagnosis, as it is more specific with ES. S100, ERG and FL1 can also be used to support the diagnosis of ES. Molecular testing is also a requirement and helpful in the diagnosis of EES. The tumor is associated with FET-ETS fusion genes. EWSR1-FLI1 fusion is the most common genetic alteration with EES which resulted from translocation in the t(11;22)(q24;q12). Other mutation of the tumor include ESWR-ERG1. EES primary to the breast has a poorer prognosis despite multimodal treatments in comparison to EES located in different sites with a good prognosis. There have been nineteen (19) reported cases of EES primary to the breast. This accounts for less than 1% of overall cases for EES. Currently, there have been no reported cases of EES primary to the breast in the local setting. Conclusion Ewing sarcoma should still be considered as one of the main differential diagnoses for pediatric patients presenting with soft tissue mass in the breast as well as in other locations. Due to its aggressive clinical course, prompt diagnosis can help increase survivability, surveillance of recurrence, and metastasis.
Child ; Sarcoma, Ewing ; Mutation

Introduction: While uterine leiomyosarcoma, an aggressive smooth muscle malignancy, has a strong propensity for hematogenous spread—most commonly to the lungs and liver—gastric metastasis remains exceedingly rare. When it occurs, it presents as a masquerading lesion that mimics primary gastric tumors, creating a significant diagnostic pitfall for both clinicians and pathologists. Case Description: A 75-year-old female presented with recurrent melena. Esophagogastroduodenoscopy revealed a friable, bell-shaped mass measuring 7 × 6 cm in the gastric fundus, suspicious for GIST. Histopathology showed spindle to epithelioid tumor cells arranged in intersecting fascicles and solid sheets with vesicular nuclei, conspicuous nucleoli, numerous mitosis, and tumor necrosis. IHCs demonstrated strong SMA positivity but negative CD117, raising consideration of undifferentiated GIST. However, subsequent DOG1 staining was negative, arguing strongly against GIST. Additional markers including S100, PanCK, CD3, CD20, CD15, and CD30 were negative. Further IHCs revealed diffuse, desmin and H-caldesmon positivity, supporting smooth muscle differentiation. Review of prior records revealed TAHBSO in 2023 for uterine leiomyosarcoma. Discussion: Metastatic involvement of the stomach is rare and most commonly arises from breast or lung primaries. Gastric metastases are rare and most commonly originate from breast or lung primaries. Metastatic uterine leiomyosarcoma presenting as a solitary gastric mass is exceedingly uncommon and may closely mimic primary gastric tumors such as GIST both endoscopically and histologically, representing an important diagnostic pitfall. Conclusion This case highlights a rare metastatic pattern of uterine leiomyosarcoma presenting as an overt gastric mass with GI bleeding. Awareness of this deceptive presentation and careful clinicopathologic correlation are essential for accurate diagnosis. To our knowledge, this represents one of the few reported cases worldwide and possibly the first documented in the Philippines.
Gastrointestinal Stromal Tumors ; Immunohistochemistry ; Leiomyosarcoma ; Gastrointestinal Hemorrhage

Synovial sarcoma is an extremely rare soft tissue cancer that predominantly affects young adults, typically occurring at the para-articular region of the extremities. Primary synovial sarcoma of the prostate is exceptionally uncommon in clinical practice.

Presented here is a case of a 29-year-old male with prostatic synovial sarcoma. He experienced lower urinary tract symptoms and eventually had urine retention. The imaging findings, treatment plan, and differential diagnosis, were also discussed.

The patient experienced urinary frequency, dysuria, and acute urinary retention, which led to the insertion of a Foley catheter. Subsequent ultrasound scans revealed a large lobulated solid prostate gland. A prostate biopsy confirmed the presence of a malignant spindle cell neoplasm, indicating a prostatic stromal sarcoma. Immunohistomorphologic findings (TLE-1+, STAT6-, S100-, CD34-, ER-, PR-) were consistent with a diagnosis of Monophasic Synovial Sarcoma. The patient underwent six cycles of neoadjuvant chemotherapy before a Radical Prostatectomy was performed. The postoperative course was uneventful, and the patient was discharged in a significantly improved condition.

Given the rarity of this condition, the authors report a case of prostatic synovial sarcoma and how they managed it. They performed a radical prostatectomy with neoadjuvant chemotherapy, which had a positive effect. Subsequent postoperative monitoring and imaging showed no further symptoms.

Liposarcoma is a malignant mesenchymal neoplasm composed of adipose tissue with varying degrees of atypia. While generally indolent, some tumors have the potential to grow enormously particularly if located in the retroperitoneum. We report a 49-year-old female generally asymptomatic except for a 1-year history of gradual abdominal enlargement. Contrast-Enhanced Computed Tomography (CT) of the abdomen showed a large retroperitoneal mass with characteristic features consistent with liposarcoma. On laparotomy, the mass was encapsulated with good plane of dissection, great vessels were preserved, however the right kidney and suprarenal gland were undetachable from the primary tumor hence was removed en bloc with the liposarcoma. The post-operative course was uneventful with excellent outcome after 6 months of follow-up. Final histopathologic diagnosis revealed low-grade, dedifferentiated liposarcoma, which has favorable prognosis following radical surgery.

Epithelioid sarcoma is an uncommon mesenchymal malignancy which represents less than 1% of all sarcomas. Rarer still are reports of this tumor initially presenting in the vulva. We report a case of vulvar proximal-type epithelioid sarcoma.

A 52-year-old had a 5-month history of slowly growing papule on the right labia majora. Excision of the mass revealed a tumor composed of large polygonal cells with abundant eosinophilic cytoplasm. An immunohistochemistry panel revealed cytokeratin AE1/AE3 positivity only. She underwent radical vulvectomy with bilateral groin node dissection. The specimen revealed a cream tan, firm, fairly defined mass at the right vulva. Microscopic examination showed a sheet-like growth pattern of large pleomorphic epithelioid cells with large vesicular nuclei and prominent nucleoli. The tumor showed loss of INI1 nuclear expression and absence of CD34 staining. EMA was positive. The case was signed out as proximal-type epithelioid sarcoma of the right vulva. Two months post-operatively, the patient was given concurrent chemotherapy with 5 cycles of cisplatin 40 mg/m2 and 6600 centigray vulvar intensity-modulated radiotherapy. She had no evidence of disease for five months until repeat workup showed tumor recurrence in the perineum. She was subsequently given 6 cycles of gemcitabine 900 mg/m2 and gemcitabine 900 mg/m2 with docetaxel 100 mg/m2. Two months after, repeat workup showed persistent progressive disease in the vulva. She was subsequently given 4 cycles of doxorubicin 60 mg/m2 and is for repeat workup.

The immunohistomorphologic features of this tumor, in addition to its unusual location, present a diagnostic challenge. Clues to the diagnosis include an initial presentation as a soft tissue mass and microscopic features showing the presence of epithelioid to spindle cytomorphology with an infiltrative growth pattern. Immunohistochemistry studies revealing the loss of INI1 nuclear expression and expression of epithelial markers would ultimately establish the diagnosis of this rare clinical entity.

OBJECTIVES: This study aimed to evaluate the diagnostic accuracy of Cyclin D1 as an adjunct immunomarker in CD99 positive small round cell neoplasms with primary consideration of PNET/EWS. MATERIALS AND METHODS: Tissue from 2017 to 2023 with a histopathologic diagnosis of CD99 positive small round blue cell tumors with primary consideration of Primitive Neuroectodermal Tumor (PNET)/Ewing Sarcoma were retrieved and Cyclin D1 immunohistochemical staining done. Diagnostic accuracy of Cyclin D1 immunostaining was determined by calculating the sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: Cyclin D1 immunohistochemical staining was performed in 19 specimens available, of which 13 yielded a positive result. Of these, 8 had a final histopathologic diagnosis of CD99 positive small round blue cell tumor with primary consideration of PNET/Ewing Sarcoma, resulting in sensitivity of 61.54%, specificity of 100%, positive predictive value of 100% and negative predictive value of 50.0%. The overall accuracy is 72.2%. CONCLUSION Cyclin D1 can be used as an adjunct immunomarker to aid in the diagnosis of CD99 positive round cell tumor with primary consideration of PNET/Ewing Sarcoma specifically in resource limited settings where molecular testing is not readily available. Given the high specificity of Cyclin D1 in such cases, it can be used to rule out other small round blue cell tumors that can also stain positive for CD99 such as Rhabdomyosarcoma. However, interpretation must be done in conjunction with the results of other immunohistochemical stains in order to increase its diagnostic accuracy.
Human ; Male,Female ; Cells ; Sarcoma, Ewing ; Sarcoma ; Neuroectodermal tumors, Primitive ; Cyclin D1