Spindle Cell Proliferation Research Articles

Primary cutaneous rhabdomyosarcoma with EWSR1/FUS::TFCP2 fusion: four new cases with distinctive morphology, immunophenotypic, and genetic profile.

EWSR1/FUS::TFCP2-rearranged rhabdomyosarcoma (RMS) is a rare tumor with an aggressive clinical course, a predilection for craniofacial bones, spindled and/or epithelioid histomorphology, and positive immunohistochemistry (IHC) for epithelial and myogenic markers, along with variable ALK expression. Herein, we present four additional cases of primary cutaneous TFCP2-rearranged RMS. Notably, one tumor (case 1) displayed a varied pathological spectrum, initially presenting as a low-grade spindle cell neoplasm, but progressed into a high-grade spindle/epithelioid tumor. Another case (case 2) exhibited a predominant high-grade epithelioid/rhabdoid morphology. The third case (case 3) demonstrated a biphasic appearance of spindle and epithelioid cell proliferation, presenting with a low-grade morphology, and the last case (case 4) showed a predominant epithelioid morphology. All cases showed myogenic differentiation associated with keratins and ALK immunoreactivity. Interestingly, the two cases with high-grade and epithelioid morphology demonstrated CD30 immunoexpression. RNAseq or FISH revealed EWSR1 or FUS::TFCP2 gene fusion, and two cases with aggressive evolution showed ALK cluster-amplification as well, a finding that has not been previously reported. Two cases displayed aggressive behavior, with case 1 experiencing local recurrences and undergoing transformation into a high-grade epithelioid tumor, whereas case 2 initially presented as an epithelioid high-grade neoplasm, subsequently developing lymph node metastases and shortly thereafter distant metastases. In contrast, patients 3 and 4 are alive with no evidence of disease. The distinctive morphology and immunoprofile of this neoplasm may pose challenges in the differential diagnosis with cutaneous neoplasms showing keratins, ALK, and CD30 immunoreactivity. Nonetheless, ALK and CD30 overexpression may offer avenues for targeted therapy.

Fibromatosis-Like Metaplastic Carcinoma of the Breast: A Challenging Diagnosis With Potential Pitfalls.

Fibromatosis-like metaplastic carcinoma (FLMC) is a rare subtype of metaplastic carcinoma of the breast. Diagnosing this entity poses significant challenges, particularly in core biopsies due to limited sampling and overlap with benign spindle cell lesions such as nodular fasciitis and fibromatosis. We present an example of FLMC in an asymptomatic middle-aged woman. As her breast imaging revealed an irregular lobulated mass, a core biopsy was performed which showed benign breast tissue with fibrosis. However, this was discordant with her imaging findings, hence a subsequent vacuum-assisted biopsy was done which revealed low-grade spindle cell proliferation, consistent with FLMC. This report emphasizes the necessity of a triple assessment and highlights the potential pitfalls in diagnosing FLMC, particularly the risk of misinterpretation due to its histological similarities with benign entities. Understanding these challenges will be crucial to avoid diagnostic delays of this rare breast cancer subtype.

Appendiceal neurofibroma after resection of multiple gastrointestinal stromal tumors of the small intestine in a patient with neurofibromatosis type 1: a case report

BackgroundNeurofibromatosis type 1 (NF1), also known as von Recklinghausen disease, is an autosomal dominant disorder that can affect multiple organs. Although gastrointestinal manifestations, such as neurofibromas and gastrointestinal stromal tumors (GISTs), can occur, appendiceal neurofibromas are extremely rare, with no documented cases of their occurrence following other gastrointestinal lesions. Herein, we report a case of an appendiceal neurofibroma following the resection of multiple small intestinal GISTs.Case presentationA 68-year-old man with NF1 presented with melena and was diagnosed with anemia due to bleeding from multiple small intestinal GISTs. Laparoscopic three partial resection of the small intestine was performed to control the bleeding. Histopathologic examination revealed the proliferation of spindle cells that are positive for c-kit and Discovered on GIST-1, confirming the diagnosis of GIST. Two years later, a follow-up computed tomography (CT) scan revealed a progressively enlarging mass in the appendix with suspected invasion into the small intestine. Positron emission tomography/CT showed fludeoxyglucose accumulation in the tumor. Therefore, considering the possibility of malignancy, laparoscopic ileocecal resection with lymph node dissection was performed. Postoperatively, melena was observed, but the anemia did not progress and improved with fasting and hemostatic therapy. The patient was eventually discharged on postoperative day 8. Histopathologic examination revealed spindle cell proliferation with positivity for S-100, confirming the diagnosis of neurofibroma.ConclusionsPatients with NF1 can develop a variety of gastrointestinal lesions. Appendiceal neurofibroma can be difficult to diagnose preoperatively and differentiate from malignancy. Hence, surgical resection should be considered.

Unicentric Castleman Disease: Updates and Novel Insights Into Spindle Cell Proliferations and Aggressive Forms of a Localized Disease.

Castleman Disease (CD) is a rare lymphoproliferative disorder that can be separated into two primary forms: Unicentric Castleman disease (UCD) and multicentric Castleman disease (MCD). UCD is localized, while MCD is systemic. Though UCD generally has a favorable prognosis following surgical resection, more aggressive forms of this disease have been identified, including cases associated with dendritic and spindle cell proliferation. Genetic analysis has deepened our understanding of UCD. Despite advancements in better understanding the pathophysiology of UCD, challenges persist in the diagnosis, management, and treatment due to its rarity and heterogeneity. Here, we review current knowledge on UCD, highlighting the epidemiology, clinical presentation, diagnostic criteria, and treatment options while emphasizing the need for further research and innovation in therapeutic strategies.

Rare Encounter: A Study of Oral Cavity Kaposi Sarcoma in Two Cases

Abstract Introduction/Objective Kaposi Sarcoma (KS) of the oral cavity, is an unusual vascular endothelial neoplasm and is the most common malignancy affecting the skin and internal organs in patients with AIDS. The tumor is caused by Human herpesvirus 8 (HHV-8). It rarely metastasizes and can be treated and totally cured by treating the AIDS disease. The oral cavity may be the only/ first site of KS, and therefore, is important in the diagnosis. The lesions present as multiple red-purple macules that develop into plaques or nodules. The hallmark microscopic features are spindle cell proliferation and irregular small, vascular slits, which often run parallel to the epithelium, as well as extravasated RBCs, with hemosiderin deposition and hyaline globules in 50% of lesions. HHV-8 nuclear staining is positive in all cases, which is crucial to differentiate it from other conditions with positivity for spindled cell markers: CD34, CD31, ERG, and FVIII R. The tumor can also be positive for lymphatic-specific markers (D2-40, LYVE-1, VEGFR3, and PROX1) Methods/Case Report We reviewed retrospectively archived cases from our TUH oral pathology database with available H&E slides diagnosed for Kaposi sarcoma between 2013 – 2023. We retrieved two confirmed cases, and we reviewed the slides and clinical information. Results (if a Case Study enter NA) Data were colleceted and analysed. Conclusion Incorporating Kaposi sarcoma into the differential diagnosis of pigmented red-purple vascular lesions in the oral cavity is of paramount importance. Detection of Kaposi sarcoma in this region bears significant prognostic implications, often serving as an initial sign of Kaposi sarcoma and indicating HIV infection. Lesions typically localize on the palate and gingiva. Heightened awareness of this clinical entity is crucial for facilitating early detection and treatment with antiretroviral drugs. Furthermore, the differential diagnosis for lesions with similar clinical presentations encompasses a broad spectrum, including benign conditions such as pyogenic granuloma, hemangioma, bacillary angiomatosis, and even granulation issue, as well as malignant tumors like angiosarcoma. It is noteworthy that considering Kaposi sarcoma in this context prompts pathologists to prioritize ordering stains for HHV-8. This diagnostic approach is supported by the exceptional sensitivity and specificity of HHV-8 stains, which exhibit 99% sensitivity and 100% specificity for diagnosing Kaposi sarcoma, while consistently yielding negative results in all other entities within the differential diagnosis.

Solitary fibrous tumor of the stomach

Abstract Introduction/Objective Solitary fibrous tumor (SFT) is an uncommon fibroblastic tumor that originates from the mesenchymal tissue. It has been rarely reported within the stomach. None of these reported tumors have occurred in a background of autoimmune atrophic gastritis as was seen in our patient. Methods/Case Report Case report Results (if a Case Study enter NA) An 85-year-old female with history of anemia and autoimmune atrophic gastritis presented with two-month history of dysphagia and abdominal discomfort. Upper gastrointestinal endoscopy showed a 1 cm subepithelial lesion in the gastric body along the greater curvature. Upper endoscopic ultrasound showed mildly hypoechoic lesion in the submucosa of the stomach with the differential of leiomyoma, neuroendocrine tumor, gastrointestinal stromal tumor, and an atypical looking lipoma. The entire gastric lesion was lifted with submucosal saline injection and then resected using cap endoscopic mucosal resection (EMR) snare cautery. Gross examination showed a well-circumscribed lesion with firm, tan-white cut surface. On microscopy, a bland appearing spindle cell proliferation within a collagenous stroma was seen with alternating hypercellular and hypocellular areas and few dilated vessels. No significant mitosis, nuclear pleomorphism or necrosis was identified. Immunohistochemical stains were performed and the lesional cells were positive for STAT6. Markers for gastrointestinal stromal tumor (CD117, DOG1), smooth muscle tumor (desmin, smooth muscle actin) and schwannoma (S100, SOX10) were negative. Nuclear staining for STAT6 is a sensitive and specific marker for SFTs. This particular SFT was considered to be of low risk and non-malignant considering its small size, lack of mitotic activity and tumor necrosis. The etiology for SFT is not entirely clear but molecular studies have shown that the NAB2::STAT6 translocation in a spindle cell neoplasm is a diagnostic hallmark for SFTs. Conclusion Solitary fibrous tumors have been rarely reported within the stomach. Complete surgical resection with negative margins is the mainstay of treatment as they may recur after an incomplete resection.

Appendiceal Mucosal Schwann Cell Proliferation Associated with Incidentally Detected Goblet Cell Adenocarcinoma of Appendix in a Case of Invasive Adenocarcinoma of Sigmoid Colon- A Case Report

Abstract Introduction/Objective Appendiceal mucosal Schwann cell proliferation has been suggested to be a putative histologic marker of appendiceal diverticular disease. Appendiceal Goblet cell adenocarcinoma, (GCA) is amongst the most rare appendiceal tumors with a reported incidence of 0.05 cases per 100,000 population per year in United States. They have features of both neuroendocrine tumors and adenocarcinomas, but behave more similarly to adenocarcinomas. Methods/Case Report Herein, we report a case of appendiceal mucosal schwann cell proliferation associated with incidentally detected Goblet cell adenocarcinoma of appendix in a known case of invasive adenocarcinoma of sigmoid colon. A 75-year-old female presented with sigmoid colon obstruction. Intraoperatively, she was found to have gangrenous and perforated colon, as well as a large obstructing sigmoid mass, and underwent total abdominal colectomy with end-ileostomy. On gross examination, a tan bosselated tumor (up to 3.5 cm) was seen in proximal sigmoid colon. Microscopic examination showed Invasive adenocarcinoma, moderately-differentiated. Appendix was unremarkable on gross examination. Incidentally, the appendix microscopically demonstrated “Goblet cell adenocarcinoma”, histologic grade 1 out of 3 (pathologic stage pTis pN0), present in multiple foci within lamina propria of the distal third of appendix over an area measuring 1.5 cm. Additionally, there were foci of SOX10-positive bland- looking spindle cell proliferation in lamina propria of the appendix. This proliferation is rendered as “Schwann cell proliferation”. Results (if a Case Study enter NA) NA Conclusion One study found that “Schwann cell proliferation” is seen in 42% of appendiceal diverticula cases. It has never been reported in association with “Appendiceal GCA” before. Here we report an intriguing case of Schwann cell proliferation associated with this rare entity of GCA for the first time in literature. Therefore, awareness of such coexistence of these pathologic entities in the same appendix is essential to alert the pathologist to look for GCA, whenever Schwann cell proliferation is encountered in random section of an appendix. This case also emphasizes the importance of being vigilant of the possible presence of other tumors in a specimen with a known tumor.

Rare Presentation of Extraskeletal Osteosarcoma Mimicking Phyllodes Tumor

Abstract Introduction/Objective A 57-year-old female presented with a palpable mass in the left breast, measuring up to 9 cm by ultrasound. core needle biopsy identified an atypical spindle cell lesion. The differential diagnosis included a metaplastic carcinoma, borderline phyllodes tumor, malignant phyllodes tumor with potential sarcomatous transformation. Methods/Case Report Histological examination of the tumor was performed, and immunohistochemical stains were conducted to characterize the lesion. Further consultation with a specialized pathologist at the University of Michigan was sought to confirm the diagnosis. Molecular analysis was performed to assess for specific genetic alterations and expression patterns. The histological examination revealed a proliferation of atypical spindle cells forming a fascicular and storiform pattern, with numerous large, pleomorphic, multinucleated tumor cells and a high mitotic rate. Immunohistochemical stains showed strong positivity for CD10 and vimentin, with focal weak expression for desmin, and negativity for a broad panel of cytokeratins and other markers. Consultation with Dr. Abbott at the University of Michigan supported the diagnosis of extraskeletal osteosarcoma. Molecular analysis revealed PD-L1 expression and absence of NTRK gene fusions. FISH analysis showed suggestive alterations including loss of BRAF gene, loss of MYC, and suggestive gains or polysomy of PTEN gene. Results (if a Case Study enter NA) NA Conclusion The case represents a rare presentation of extraskeletal osteosarcoma in the breast, with distinctive histological and immunohistochemical features. The comprehensive workup including histology, immunohistochemistry, and molecular analysis aids in accurate diagnosis and potential therapeutic implications. Further research may elucidate the underlying mechanisms and treatment options for this uncommon malignancy.

A Case Report of Inflammatory Myofibroblastic Tumor Mimicking Leiomyosarcoma of the Uterus

Abstract Introduction/Objective Inflammatory myofibroblastic tumor (IMT) of the uterus is a rare entity that presents significant diagnostic challenges due to its infrequency and has the potential for being misdiagnosed as a leiomyoma, endometrial stromal tumor, or myxoid leiomyosarcoma, resulting in undertreatment or overtreatment. Methods/Case Report We present a case report of a 50-year-old woman with a history of anemia due to heavy menstruation caused by fibroids, who underwent hysterectomy. The concurrent pelvic wash cytology raised suspicious for myxoid leiomyosarcoma. Results (if a Case Study enter NA) Macroscopic examination revealed both well and poorly circumscribed nodules, ranging upto 4.7 cm in maximum dimension. Cut surfaces exhibited a spectrum of appearances, including tan-pink, whorled and rubbery, as well as soft, hemorrhagic, edematous, and mucinous areas with necrosis. Microscopically, the tumor exhibited myxoid spindle cell proliferation, in the background of lymphoplasmacytic inflammatory infiltrates. She was diagnosed with IMT metastasis to left fallopian tube, ovary, and omentum. Immunohistochemical (IHC) analysis further confirmed the diagnosis, showing strong and diffuse cytoplasmic positivity for ALK (anaplastic lymphoma kinase), caldesmon, and smooth muscle actin. This case underscores the critical importance of accurate diagnosis in guiding appropriate treatment strategies. Moreover, given the morphological overlap with other uterine tumors, the identification of ALK rearrangement emerges as a pivotal diagnostic marker, distinguishing IMT from its mimics such as leiomyoma, leiomyosarcoma and smooth muscle tumor of uncertain malignant potential (STUMP). Enhancing our understanding of the histomorphological features and ALK immunostaining of uterine IMT is essential for optimizing patient management and outcomes. Conclusion IMT in the female genital tract can mimic other more common benign and malignant tumors like leiomyoma, leiomyosarcoma, and endometrial stromal sarcoma. Familiarity with clinical and histologic features and the use of ALK immunostaining can be critical for correct diagnosis.

The Vital Role of Special Stains in Immunocompromised Cases: A Focus on Histoplasmosis Screenings for Enhanced Kaposi`s Sarcoma Diagnosis Beyond H&E Morphology

Abstract Introduction/Objective This case report emphasizes the critical importance of thorough pathology-based investigation before making a definitive diagnosis of Kaposi’s Sarcoma (KS). In particular, we demonstrate the importance of using special stains in addition to H&E staining to determine if the lesion is KS or a fungal infection, specifically cutaneous Histoplasmosis. This highlights the necessity of comprehensive diagnostics to ensure accurate and timely identification of underlying conditions, guiding appropriate treatment strategies. Methods/Case Report In Kampala Uganda, a 56-year-old male with a history of HIV/AIDS presented with skin lesions on the lower extremities. The lesions were initially suspected to be Kaposi’s Sarcoma due to their appearance and the patient’s immunocompromised status. Skin biopsy results supported the initial suspicion, showing spindle cell proliferation in the dermis, a common feature of KS. Given his compromised immune system, it was imperative to conduct a thorough investigation to rule out potential etiologies, including opportunistic infections. Additional tests, including a Grocott Methenamine-Silver Nitrate stain, revealed the presence of Histoplasmosis. The patient did not exhibit typical symptoms of Disseminated Histoplasmosis, such as respiratory distress or fever. Resource constraints hindered comprehensive follow-up, impacting long-term outcome assessment. Results (if a Case Study enter NA) NA Conclusion Histoplasmosis is widespread in Africa, accounting for 61% of global cases, with 87% concentrated in Western and Central Africa. The coexistence of KS and Histoplasmosis poses diagnostic challenges due to overlapping clinical manifestations. KS primarily affects the skin, while Histoplasmosis causes invasive vascular and pulmonary infections. However, in Africa, notably in immunocompromised individuals, histoplasmosis can cause cutaneous infections. Failure to recognize and address fungal infections may result in delayed or inappropriate treatment, exacerbating the patient’s condition. This case report underscores the importance of maintaining a high index of suspicion for opportunistic infections in this population for timely intervention.

Mediastinal Teratoma with Angiosarcomatous Overgrowth in a Background of Vasculogenic Mesenchymal Tumor

Abstract Introduction/Objective Vasculogenic mesenchymal tumor refers to neoplastic reiteration of embryonic vasculogenesis. It is most commonly associated with nonseminomatous germ cell tumors of the mediastinum, in particular yolk sac tumor. In rare instances these lesions progress to angiosarcoma. Herein, we describe a case of angiosarcoma in a background of vasculogenic mesenchymal tumor in the setting of a mediastinal teratoma. Methods/Case Report A 33-year-old male, with a past medical history of anxiety, and right orchiectomy for testicular torsion, presented with shortness of breath, chest pain, and left arm swelling. Imaging studies demonstrated a mediastinal mass. Biopsy of the mass showed a germ cell tumor most compatible with a teratoma in the limited specimen. The patient received two rounds of chemotherapy and additional treatments were discontinued due to poor tolerance. Subsequent imaging showed continued increase in the size along with mass effect causing moderate to severe compression of the superior vena cava. Subsequently, the patient underwent resection of the mass. Grossly the mass was predominantly encapsulated with areas of capsular disruption. Sectioning revealed heterogeneous cut surfaces with fleshy, cystic, and necrotic areas. Morphologically the tumor was composed predominantly of teratomatous elements with areas of anastomosing atypical vascular channels within a hypocellular stroma suggestive of vascular genic mesenchymal as well as areas reminiscent of Masson lesion. Focally within these areas were malignant spindle cell proliferations compatible with angiosarcoma. The patient had an elevated AFP; however, no yolk sac tumor component was identified after thorough sampling. Final diagnosis of teratoma with angiosarcoma in a background of vasculogenic mesenchymal tumor was rendered after expert consultation. Results (if a Case Study enter NA) NA Conclusion Somatic-type malignancy and sarcomatous overgrowth are known to occur in mediastinal germ cell tumors; however, classification of the sarcomatous overgrowth can be challenging. Vasculogenic mesenchymal tumor is an exceedingly rare sarcomatous overgrowth that can rarely progress to angiosarcoma.

S100 and CD34 positive spindle cell tumors of the uterine cervix with EGFR mutation: a hitherto unrecognized neoplasm phenotypically and epigenetically overlapping with "NTRK-rearranged spindle cell neoplasms" of the uterus.

NTRK-rearranged spindle cell neoplasm represents an emerging entity included in the latest 5th edition of WHO classification of both soft tissue and female genital tumors. By immunohistochemistry, they are commonly positive for CD34, S100 protein, and CD30 and typically harbor fusions of kinase genes such as NTRK1/2/3, RET, and BRAF. In the gynecological tract, they typically affect the uterine cervix or uterine body. Most of the reported cases had fibrosarcoma-like morphology, occasionally showing perivascular and stromal hyalinization with only a few cases showing a less cellular spindle cell proliferation. Except for one case with RET fusion, all other gynecological cases harbored exclusively NTRK1/2/3 fusions. Besides kinase gene fusions, the analogous tumors in soft tissues may also harbor activating EGFR or BRAF point mutations, but no such case has been described in the uterus. Herein we are reporting two cases from the uterine cervix showing morphology and molecular features previously unreported at this anatomic site. The patients were 46 and 34years old and clinically presented with unremarkable cervical polyps each measuring 8mm in diameter. Histologically, both cases had a rounded polypoid outline and were composed of hypocellular proliferation of bland spindle cells lacking mitotic activity and growing in a fibrotic stroma which was punctuated by prominent small vessels with thick hyalinized walls. Immunohistochemically, both showed a diffuse expression of CD34, CD30, and S100 protein, whereas SOX10 was negative. Both cases harbored exon 20 EGFR mutation and did not reveal any fusions or significant copy number changes. The patient in case 1 was treated by hysterectomy with salpingectomy with no other residual tumor detected, and she was alive and well 27months after the diagnosis. The patient in case 2 had no other known tumors at the time of diagnosis, but no follow-up is available. We believe the reported cases represent a hitherto unrecognized variant of "NTRK-rearranged spindle cell neoplasms" of the uterine cervix with novel EGFR mutations.

Extra-Skeletal Osteosarcoma of the Prostate After Treated Prostatic Acinar Adenocarcinoma: A Case Report and Review of the Literature.

Extra-skeletal osteosarcoma is a rare form of malignant soft tissue sarcoma. Its occurrence in the prostate gland is particularly uncommon. In this case report, we present a patient diagnosed with osteosarcoma arising within the prostatic gland. A 58-year-old man was initially diagnosed with Gleason 8 prostate acinar adenocarcinoma following a transurethral resection (TUR) of the prostate. This diagnosis was accompanied by locoregional involvement and multiple bone metastases. The patient underwent a treatment regimen including complete androgen blockade, chemotherapy, greenlight laser prostate vaporization, and palliative radiotherapy. After treatment, he achieved a complete biochemical response, and his bone metastases remained stable. However, at 16 months post-diagnosis, clinical follow-up by means of radiological examinations revealed an increase in the size of the prostatic lesion, along with additional infiltration of the tumor into the rectum and bladder walls. Remarkably, a mesenchymal tumor proliferation with intratumor calcifications was observed. A subsequent TUR biopsy of the prostate showed a malignant tumor spindle and ovoid cell proliferation with high-grade nuclear atypia, necrosis, and islets of osteoid formation, leading to a final diagnosis of high-grade prostatic extra-skeletal osteosarcoma. Despite undergoing chemotherapy, the patient's condition progressed with the development of pulmonary and liver metastases, culminating in his demise.

Biphenotypic Sinonasal Sarcoma- A case Series with a Review of Literature.

Biphenotypic sinonasal sarcoma (BSNS) is a rare malignant tumor that affects the upper nasal cavity and ethmoid sinuses. It is more commonly found in middle-aged women and is characterized by the infiltration and hypercellular proliferation of spindle cells. These cells exhibit specific immunoreactivity. We add seven cases diagnosed as BSNS, to the handful of cases already available in the literature.BSNS is a malignant disease of the sinonasal tract that requires prompt and accurate diagnosis, followed by surgical resection and consideration of radiotherapy. Our analysis of seven cases supports previous research that confirms the aggressive nature of the disease but also shows that it is treatable with the right approach.

An unusual cause of liver neoplasm in an older female.

We presented a 66-year-old woman with T2DM who had a liver mass discovered incidentally during hospitalization. She was asymptomatic with a right upper abdominal mass that was smooth, mobile, and non-tender. Hepatitis virus markers and tumor markers were normal. The computed tomography (CT) images showed a 4.7×4.0 cm lesion in the left liver lobe with indistinct borders. Further magnetic resonance imaging (MRI) revealed low T1 and high T2 signal intensity with ring-shaped enhancement following contrast administration. Surgical resection was performed, and histology confirmed hepatic angioleiomyoma with thick-walled vessels and spindle cell proliferation. Immunohistochemistry was positive for SMA, desmin, caldesmon, CD31, and CD34. The patient had no recurrence during 5 years follow-up.

Polypoid Kaposi Sarcoma Involving the Lower Gastrointestinal Tract: Clinicopathologic Study of 15 Cases.

Gastrointestinal manifestations of Kaposi sarcoma are rare but may cause morbidity. Lower gastrointestinal involvement is particularly rare and lesions may resemble conventional bowel polyps. To study 15 patients who presented with lower gastrointestinal tract Kaposi sarcoma with polypoid architecture. The surgical pathology files of the departments of pathology at multiple institutions were searched for cases of Kaposi sarcoma forming polyps in the lower gastrointestinal tract (jejunum, colon, rectum); 15 cases with such features were identified. Clinicopathologic information was extracted from the medical record and documented by reviewing individual hematoxylin-eosin stained slides. The patients were 13 men and 2 women aged 26-80 years (median = 44 years). Gastrointestinal tract involvement was multifocal in 11 cases and unifocal in 4. The tumors involved the rectum, recto-sigmoid junction, cecum, ascending colon, transverse colon, and descending colon and presented as polypoid lesions measuring 0.2-2.1 cm. Six patients had upper gastrointestinal tract involvement in addition to lower gastrointestinal lesions. Histologically the tumors were characterized in 6 cases by a dense spindle cell proliferation in the lamina propria; however, the remaining cases showed only a subtle fascicular spindle cell proliferation in the lamina propria that did not form an expansile mass. Biopsies of gastrointestinal polyps showing absence of the common features of hyperplastic or adenomatous polyps, particularly in immunocompromised patients, should be carefully examined for the presence of a stromal spindle cell proliferation. Use of immunohistochemical stains, particularly human herpesvirus-8, can help in establishing the correct diagnosis.

Spindle cell squamous cell carcinoma of the maxillary sinus as a metachronous head and neck cancer

AbstractBackgroundSpindle cell squamous cell carcinoma (SpSCC) is a rare subtype of squamous cell carcinoma (SCC) showing an unfavorable prognosis. Histologically, SpSCC shows biphasic proliferation of spindle cells and nests of SCC.Case presentationAn 85‐year‐old Japanese man with a medical history of oral SCC three years ago had SpSCC of the right maxillary sinus. The tumor showed aggressive proliferation of spindle cells with nests of conventional SCC. Subsequent lymph node metastases revealed findings of conventional SCC.ConclusionThis case report contributes to the accumulation of a rare subtype of SCC and multiple cancers of the head and neck region.

Nodular Fasciitis of the Buccal Mucosa with a Novel USP6 Gene Rearrangement: A Case Report and Review of the Literature.

Nodular fasciitis is a rare but benign fibroblastic proliferation that typically presents as a solitary lesion with rapid growth and variable mitotic activity. The lesions usually occur on the extremities and occasionally in the head/neck region. Involvement of the buccal mucosa is extremely rare with only few reports in the literature; in this case report, we describe a 41 year old female who presented with a 6-month history of a stable intraoral lump at the junction of the upper and lower lip. Fine needle aspiration revealed an atypical spindle cell population with plump cells. The surgical excision demonstrated a well circumscribed tan-white firm nodule. Histologic examination revealed a spindle cell proliferation that grew in short, intersecting fascicles with focal storiform architecture. The lesion had a pushing border that was not overtly infiltrative and the stroma contained focal myxoid changes giving a "tissue culture" appearance to the cells. Immunohistochemical testing showed the tumor cells were vimentin (+), SMA (+), weakly Calponin (+), and desmin (-), cytokeratin (-), AE1/AE3 (-), S100 (-), ALK (-), STAT6 (-), and beta-catenin (-). Fluorescence in-situ hybridization (FISH) revealed a USP6 gene rearrangement with an atypical probe pattern. Next generation sequencing identified a novel SPTAN1::USP6 fusion gene confirming the diagnosis of buccal nodular fasciitis. Identification of the characteristic histologic features and USP6 gene rearrangements helped support the diagnosis. A review of the literature identified 25 cases of nodular fasciitis involving the buccal mucosa. The occurrence of this tumor in an unusual location may pose difficulties for diagnosis.

Primary extraskeletal osteosarcomas of the pleura: A clinicopathological, immunohistochemical, and molecular analysis of 4 cases

Four primary extraskeletal osteosarcomas of the pleura are presented. The patients were men between the ages of 63 and 78 years (average: 70.5 years) who presented with symptoms of chest pain, cough, and shortness of breath. Diagnostic imaging showed variably calcified, pleural-based masses and/or diffuse pleural thickening, clinically mimicking mesothelioma. Thoracoscopic surgical material was obtained for histopathological diagnosis. Histological findings showed the presence of a neoplastic spindle cell proliferation composed of fusiform cells with scant cytoplasm, elongated nuclei and inconspicuous nucleoli. Mitotic activity was easily identified. Additionally, all tumors showed extensive osseous differentiation in the form of osteoid matrix production; one tumor demonstrated additional chondrosarcomatous elements and another showed focal myxoid changes. Immunohistochemical analysis revealed that the tumor cells were uniformly negative for a wide variety of antibodies, including keratin AE1/AE3, keratin 5/6, D2-40, EMA, calretinin, WT-1, BerEP4, and HEG1; BAP1 was retained in all cases. In addition, fluorescence in situ hybridization for CDKN2A (p16) was negative for homozygous deletion in all tumors. Clinical follow-up showed that one patient had died 8 months after diagnosis and one had remained alive with short post-diagnostic follow-up. The tumors herein described highlight a challenging issue in the separation of mesothelioma with heterologous elements from true osteosarcomas of pleural origin. We propose that a diagnosis of extraskeletal osteosarcoma of the pleura is rendered for tumors with malignant osseous and/or cartilaginous differentiation in which comprehensive immunohistochemical studies and FISH analysis have failed to provide support for a diagnosis of mesothelioma with heterologous elements.

Atypical spindle cell proliferation of indeterminate biological potential

Atypical spindle cell proliferation of indeterminate biological potential