CD30 expression in an emerging group of mesenchymal spindle cell neoplasms with ALK fusion detected by flow cytometry and immunohistochemistry.

An emerging group of spindle cell neoplasms harboring fusions involving NTRK or non-NTRK kinase genes often share characteristic S100 and/or CD34 expression; however, the diagnostic utility of immunohistochemical stains is not well established in this family owing to their lack of specificity. Recently, CD30 expression in spindle cell neoplasms with kinase gene fusions, such as NTRK, BRAF, RAF1, and RET, has been increasingly identified. We herein report a 10-year-old girl with high-grade spindle cell sarcoma of the neck. Prior to histopathological evaluation, flow cytometry (FCM) analysis and touch smear cytology of the tumor tissue revealed CD34+ and dimCD30+ spindle cell populations. Histopathologically, the case was characterized by monomorphic spindle-shaped cytomorphology with CD30, S100, and CD34 positivity and harbored close similarities with spindle cell neoplasms with NTRK or non-NTRK gene fusions. Subsequently, a comprehensive next-generation sequencing sarcoma panel identified a rare PLEKHH2::ALK fusion, and a diagnosis of ALK-rearranged spindle cell neoplasm was made. The patient showed significant tumor response to single-agent treatment with alectinib, an ALK-tyrosine kinase inhibitor. This case supports that CD30 is expressed in an ALK-rearranged mesenchymal neoplasm. The benefit of the early detection of CD30 expression by FCM for a prompt diagnosis and treatment is highlighted in the context of an aggressive clinical course. This case represents a learning experience regarding the need to the check the status of CD30 expression in these tumors and suggests the potential clinical benefits of CD30-targeted therapy.

Novel low-grade renal spindle cell neoplasm with HEY1::NCOA2 fusion that is distinct from mesenchymal chondrosarcoma.

HEY1-NCOA2 fusion is most described in mesenchymal chondrosarcoma. This is the first case report of a primary renal spindle cell neoplasm of uncertain malignant potential with a HEY1::NCOA2 fusion identified by Fusionplex RNA-sequencing that is histologically distinct from mesenchymal chondrosarcoma. The neoplasm was identified in a 33-year-old woman without significant past medical history who underwent partial nephrectomy for an incidentally discovered renal mass. The histologic features of the mass included spindle cells with variable cellularity and monotonous bland cytology forming vague fascicles and storiform architecture within a myxoedematous and collagenous stroma with areas of calcification. The morphologic and immunophenotypic features were not specific for any entity but were most similar to low-grade fibromyxoid sarcoma. To date, the patient has not had recurrence, and the malignant potential of the neoplasm is uncertain.

Gene fusions in superficial mesenchymal neoplasms: Emerging entities and useful diagnostic adjuncts.

Cutaneous mesenchymal neoplasms are diagnostically challenging because of their overlapping morphology, and, often, the limited tissue in skin biopsy specimens. Molecular and cytogenetic techniques have identified characteristic gene fusions in many of these tumor types, findings that have expanded our understanding of disease pathogenesis and motivated development of useful ancillary diagnostic tools. Here, we provide an update of new findings in tumor types that can occur in the skin and superficial subcutis, including dermatofibrosarcoma protuberans, benign fibrous histiocytoma, epithelioid fibrous histiocytoma, angiomatoid fibrous histiocytoma, glomus tumor, myopericytoma/myofibroma, non-neural granular cell tumor, CIC-rearranged sarcoma, hybrid schwannoma/perineurioma, and clear cell sarcoma. We also discuss recently described and emerging tumor types that can occur in superficial locations and that harbor gene fusions, including nested glomoid neoplasm with GLI1 alterations, clear cell tumor with melanocytic differentiation and ACTIN::MITF translocation, melanocytic tumor with CRTC1::TRIM11 fusion, EWSR1::SMAD3-rearranged fibroblastic tumor, PLAG1-rearranged fibroblastic tumor, and superficial ALK-rearranged myxoid spindle cell neoplasm. When possible, we discuss how fusion events mediate the pathogenesis of these tumor types, and we also discuss the related diagnostic and therapeutic implications of these events.

Expanding the Spectrum of the Soft Tissue Tumors with Kinase Gene Fusions: A Pediatric Spindle Cell Neoplasm Harboring MTAP-RAF1 Fusion.

Introduction: NTRK-rearranged spindled cell tumors have been increasingly recognized with the widespread use of molecular studies. We describe a pediatric spindle cell neoplasm with MTAP-RAF1 gene fusion that fits into this group. Case report: An 8-year-old girl presented with mandibular mass. Histopathologically, it was a moderate to increased cellular spindle cell tumor with mild-to-moderate nuclear pleomorphism, focal perivascular keloid-like collagen, that was positive for S-100 and CD34. MTAP-RAF1 fusion was detected by next generation sequencing, confirming a low-grade sarcoma with MTAP-RAF1 fusion that is presently included in the category of NTRK-rearranged spindled cell tumors. Discussion: MTAP-RAF1 fusion, in the spectrum of spindle cell neoplasms with kinase gene rearrangements, can occur in the pediatric age group.

ALK rearrangements in infantile fibrosarcoma-like spindle cell tumours of soft tissue and kidney.

AIMS: Recurrent alterations in receptor tyrosine kinase (RTK) and downstream effectors are described in infantile fibrosarcoma (IFS)/cellular congenital mesoblastic nephroma (cCMN) and a subset of spindle cell sarcomas, provisionally designated 'NTRK-rearranged' spindle cell neoplasms. These two groups of tumours demonstrate overlapping morphologies and harbour alterations in NTRK1/2/3, RET, MET, ABL1, ROS1, RAF1 and BRAF, although their relationship is not fully elucidated. We describe herein a cohort of paediatric tumours with clinicopathological features not typical for inflammatory myofibroblastic tumour, but rather with similarities to cCMN/IFS harbouring ALK fusions. METHODS AND RESULTS: Clinicopathological features were assessed and partner agnostic targeted RNA sequencing on clinically validated platforms were performed. Tumours occurred in patients aged from 2 to 10 years (median age 2 years) with a 2:2 male to female ratio and an average size of 8.4 cm. Two tumours arose in soft tissues and two in the kidney. Morphological features included spindle to ovoid cells arranged in long fascicles or haphazardly within a myxoid to collagenised stroma; a subset of cases had either dilated, ectatic vessels or focal perivascular hyalinosis. By immunohistochemistry, all cases tested showed cytoplasmic expression of anaplastic lymphoma kinase (ALK) and one case demonstrated co-expression of CD34 and S100. CONCLUSIONS: This series of ALK-rearranged IFS-like tumours expands the spectrum of targetable kinases altered in these tumours and reinforces the potential overlap between IFS/cCMN-like tumours and the provisional entity of 'NTRK-rearranged' spindle cell neoplasms.

Cutaneous solitary fibrous tumor: Report of three cases with review of histopathological mimics.

Solitary fibrous tumor (SFT) is a relatively uncommon spindle cell mesenchymal neoplasm that is most often based on the pleura but may rarely arise in extrapleural locations, including the skin. Herein, we describe three cases of cutaneous SFTs. SFT is characterized by epithelioid and spindle cells arranged in random patterns with focal prominent stromal collagen and pericytomatous vessels. Immunohistochemical evaluation is required for definitive distinction of SFT from other benign and malignant cutaneous spindle cell neoplasms. Although aggressive biologic behavior is uncommon, accurate diagnosis of it is required for prognostication and counseling. CD34, bcl-2, and CD99 stains are positive in SFT, but not specific. STAT6 is the most sensitive and specific immunohistochemical marker to confirm diagnosis of SFT.

NTRK-rearranged spindle cell neoplasm of the lower extremity: radiologic-pathologic correlation.

Neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasm is a recently characterized soft tissue tumor and has been classified as provisional by the World Health Organization. Detection of the genetic rearrangement is important because these tumors are amenable to targeted tyrosine kinase inhibitor therapy, which can play a key role in patients with unresectable or advanced disease. Although the spectrum of histopathology associated with this entity is broad, one notable feature is the infiltrative growth pattern, which is most reminiscent of lipofibromatosis-like neural tumor. Description of their diverse histologic attributes has aided recognition, but so far little attention has been paid to correlating the gross appearance and imaging features of these lesions. In this report, we describe the clinical, imaging, histopathological, and genetic features of a soft tissue NTRK-rearranged spindle cell neoplasm. Inclusion of this more recently identified entity into the imaging differential of tumors with intratumoral relatively hypovascular nodules and infiltrative margins is important because testing for NTRK rearrangement is not routinely performed.

Rare Variant of Adult Rhabdomyosarcoma Presenting as a Palatal Swelling.

A 26-year-old male was referred to the Department of Oral and Maxillofacial Surgery of a tertiary care hospital in Lahore with chief complaint of painless swelling on the right palate of 40 days duration. Clinical differential diagnosis included squamous cell carcinoma, Ewing sarcoma, fibrosarcoma, neuroblastoma and rhabdomyosarcoma. Computed tomography scan revealed hypodense mass with necrotic changes. Histological examination of the excised tumor revealed malignant neoplasm arranged in fascicles and bundles comprising of spindle cells with pleomorphic, hyperchromatic nuclei and increased atypical mitosis. Immunohistochemical analysis showed negative staining with Cytokeratin, S100, CD34, Stat6, h-Caldesmon and EMA while the tumour cells were positive for desmin, myogenin, smooth muscle actin, CD-99 and MyoD1 thus confirming the diagnosis of spindle cell rhabdomyosarcoma.

Synovial sarcoma of the stomach: case report and systematic review of the literature.

Synovial sarcoma is a rare mesenchymal malignant neoplasm that presents a specific t(X;18) translocation forming SS18(SYT)-SSX chimera gene. It is most commonly seen in soft tissues of the extremities. The digestive tract is an exceptional site of involvement. We report a case of primary gastric synovial sarcoma in a 48-year-old female. Differential diagnosis of synovial sarcoma from other spindle cell, mesenchymal and cytokeratin-positive tumors is critical for the treatment and prognosis. Immunohistochemistry studies and molecular analysis are required to settle a proper diagnosis.

Low-grade malignant peripheral nerve sheath tumour presenting as retroperitoneal spindle cell neoplasm.

Retroperitoneal spindle cell neoplasms are diagnostically challenging. Malignant peripheral nerve sheath tumours (MPNSTs) can sometimes present as sporadic primary retroperitoneal tumours. MPNSTs are usually high-grade and highly aggressive tumours and are associated with a poor prognosis. Low-grade MPNSTs are very rarely described. This current case report describes a case of sporadic primary low-grade MPNST presenting as retroperitoneal spindle cell neoplasm. The diagnosis, imaging and immunohistopathological findings, as well as its successful surgical management, are presented.

A rare case of cervical myofibroma in an infant: A case report.

INTRODUCTION: A solitary infantile myofibroma tumor arises as a hard, painless cutaneous or subcutaneous nodule and is defined as an uncommon soft tissue neoplasm that is usually seen in childhood. CASE PRESENTATION: A nine-month-old female infant presented with a solid mass that appeared one month ago. The mass gradually increased in size within the right posterior triangle of the neck, without any local or systemic accompanying symptoms. Laboratory tests were normal. Ultrasonography revealed a homogeneous tissue mass measuring 1.5 × 3 cm, with blood flow within it. Multislice CT scan accurately localized the isolated tumor. The mass was surgically excised and found within the sternocleidomastoid muscle, without any adhesions to adjacent tissues. Histological examination of the tumor and immunohistochemical tests confirmed infantile myofibroma. CLINICAL DISCUSSION: IM is one of the most common soft tissue tumors in children and mainly consists of myofibroblasts. 90 % of IM cases are diagnosed before the age of two years. Possible therapeutic measures for this tumor include conservative management, surgical resection, chemotherapy, radiation therapy, and steroid injections into the tumor. Surgical removal of the tumor is often performed, and if it is single and completely removed, the prognosis is good with a recurrence rate of less than 10 %. CONCLUSION: Infantile myofibroma is considered a benign tumor, but it may be fatal in some cases. Each case is treated individually according to the number (single or multicentric), size, location, symptoms, and visceral involvement. Surgical resection remains the therapeutic procedure of choice in most cases.

A Retrospective Review and Comprehensive Tumour Profiling of Advanced Non-Melanomatous Cutaneous Spindle Cell Neoplasms Treated with Immune-Checkpoint Inhibitors.

Non-melanomatous cutaneous spindle cell neoplasms are a rare group of malignancies that present a diagnostic challenge, and for which there is a lack of consensus on how to best manage patients with advanced disease and only limited reports of immune-checkpoint inhibitor (ICI) responses. In this study, we performed a single-center retrospective review of treatment outcomes for all advanced non-melanomatous cutaneous spindle cell neoplasms treated with ICIs. Blinded histopathology reviews occurred to confirm each diagnosis. Comprehensive tumour profiling included whole exome sequencing for tumour mutational burden (TMB) and ultraviolet(UV) signatures, and immunohistochemistry for immune-cell infiltration (CD4/CD3/CD8/CD103/CD20) and immune-checkpoint expression (PD-L1/LAG3/TIGIT). Seven patients were identified. The objective response rate was 86% (6/7) with five complete responses (CR). Responses were durable with two patients in CR > 30 months after ICI commencement. All patients had high TMB and UV signatures. One patient had PD-L1 100% (combined positive score) with abundant immune-cell infiltration and LAG3 expression. In advanced non-melanomatous cutaneous spindle cell neoplasms, excellent responses to ICIs with durable disease control were observed. ICIs are worthy of further exploration in these patients. UV signatures and high TMB could be used to help select patients for treatment.

Co-relation of gastrointestinal stromal tumors in a patient with leiomyoma cutis- A rare association.

INTRODUCTION AND IMPORTANCE: Cutaneous leiomyomas, benign tumors from smooth muscle fibers, constitute about 5 % of all leiomyomas. They exhibit diverse inheritance patterns and can be linked to systemic malignancies. Gastrointestinal stromal tumors (GISTs), arising from the interstitial cells of Cajal, are the most common mesenchymal tumors in the gastrointestinal tract. Despite their prevalence, simultaneous occurrences of cutaneous leiomyomas and GISTs are rare, necessitating exploration of their potential relationship. CASE PRESENTATION: A 25-year-old male with no significant medical history presented with multiple painful erythematous nodules on his chest, upper back, and arms. Histopathological analysis diagnosed these as multiple cutaneous piloleiomyomatosis. Despite recommendations for surgical intervention, the patient chose medical management and experienced significant pain relief with nifedipine. Later, the development of abdominal symptoms led to the discovery of multiple gastric lesions, diagnosed as benign spindle cell neoplasms, necessitating partial gastrectomy. CLINICAL DISCUSSION: The differential diagnosis of cutaneous leiomyomas includes various soft tissue tumors, requiring histopathological confirmation. Genetic mutations affecting proteins critical to cellular energy production and tumor suppression underlie these conditions. Treatment options include pharmacological management and surgical excision. The discovery of GISTs in this patient aligns with rare literature reports, emphasizing the need for vigilant evaluation of systemic malignancies in patients with leiomyomatosis. CONCLUSION: This case highlights the potential of cutaneous leiomyomas to indicate deeper malignancies like GISTs, stressing the importance of interdisciplinary collaboration in diagnosis and treatment. It underscores the interconnectedness of benign dermatological conditions and internal malignancies, advocating for comprehensive evaluation in patients with leiomyomatosis. METHODS: This case report meticulously follows the SCARE 2023 guidelines: updating consensus Surgical Case Report guidelines (Sohrabi et al., 2023 [1]). These guidelines ensure high-quality reporting in surgical case reports. The report details the evaluation, diagnosis, and a comprehensive review of the literature pertaining to a patient with multiple leiomyoma cutis associated with gastrointestinal stromal tumors. By employing a multidisciplinary approach, this report achieves a thorough and standardized presentation of the case, serving as an additional tool for raising awareness regarding such rare conditions.

ALK-Rearranged Epithelioid and Spindle Cell Neoplasm of the Sinonasal Tract.

Anaplastic lymphoma kinase (ALK)-rearranged mesenchymal neoplasms (non-inflammatory myofibroblastic tumor and non-epithelioid fibrous histiocytoma) have been recently described which tend to occur in the superficial and deep soft tissues. Occurrence as a primary sinonasal neoplasm has not been reported thus far. Herein, we describe the first case of sinonasal ALK-rearranged mesenchymal tumor that harbored remarkable epithelioid and spindle cell morphology. The tumor affected a 40-year-old man who presented with flu-like symptoms and was thought to have influenza A. However, computed tomography demonstrated a nasal polypoid lesion causing curvature of the nasal septum. Histological examination revealed a heterogeneous tumor composed of round to epithelioid cells with foci of spindle cells. The tumor cells exhibited moderate pleomorphism and mitotic activity. By immunohistochemistry, they showed diffuse staining of CD34, S100, ALK (D5F3) and CD30. Fluorescence in situ hybridization analysis demonstrated ALK rearrangement. Subsequent next-generation sequencing (RNA-seq) identified a rare PLEKHH2exon6::ALKexon20 fusion. This study further demonstrates the importance of molecular profiling in identifying kinase fusion-positive soft tissue tumors, particularly for those that arise at unusual sites and display atypical cytomorphology.

NTRK-rearranged spindle cell neoplasms: a clinicopathological and molecular study of 13 cases with peculiar characteristics at one of the largest institutions in China.

NTRK-rearranged spindle cell neoplasms (NTRK-RSCNs) represent an emerging group of rare tumours defined using molecular means. To the best of our knowledge, there have been no large series of reports about this tumour in the Chinese population in English full-text articles. Herein, we present 13 NTRK-RSCNs with peculiar characteristics. Ten of the 13 (77%) patients were children without sex differences. The tumour locations included six trunks, four extremities, two recta, and one small bowel. The histological morphology included four lipofibromatosis-like neural tumour (LPF-NT)-like, eight malignant peripheral nerve sheath tumours (MPNST)/fibrosarcoma-like, and one extremely rare myxofibrosarcoma-like pattern. Immunohistochemically, all cases were CD34, pan-TRK and TRK-A positive, SOX-10 negative, and H3K27me3 intact. S-100 protein expression was identified in 11 of 13 (85%) cases. Genetically, NTRK1 rearrangements were considered positive (7/13, 54%) or suspicious for positivity (6/13, 46%) by fluorescence in situ hybridisation. Next-generation sequencing and Sanger sequencing confirmed NTRK1 fusions with a variety of partner genes, including five LMNA, three TPM3, one SQSTM1, three novel CPSF6, IGR (downstream PMVK), and GAS2L1 genes. Interestingly, the last tumour concurrently harboured a second EWSR1-PBX1 fusion, which has never been reported. Four patients developed local recurrence and two of them suffered metastasis. In our study, NTRK-RSCNs had peculiar fusions that displayed unusual or complicated clinicopathological features. Histological clues and IHC helped streamline a small subset of potential candidates. Although FISH is a powerful technology for identifying NTRK rearrangements, RNA-/DNA-based NGS is recommended for highly suspected cases in which FISH signal patterns are not discernible as classic positive patterns, particularly if targeted therapy is considered.

Unusual Presentation of Tonsillar Spindle Cell Neoplasm: A Case Report.

Spindle cell neoplasm of the tonsil are rare (Minami et al. in Am J Otolaryngol 29(2):123-125, 2008) and can be difficult to diagnose due to their non-specific clinical presentation and histological characteristics (Su et al. in J Chin Med Assoc 69(10):478-483, 2006). Differential diagnoses include lymphoma and squamous cell carcinoma (Hyams in Clin Otolaryngol Allied Sci 3(2):117-126, 1978). Oropharyngeal spindle cell neoplasms were more likely to occur in the tongue base and tonsil (58%) (Gerry et al. in Ann Otol Rhinol Laryngol 123(8):576-583, 2014). In this article, we report a case of tonsillar spindle cell neoplasm which is extremely rare.

Rare serosal cystic gastric gastrointestinal stromal tumor with extensive intestinal metaplasia in an adherent gastric mucosa; a case report in a 65-year-old male.

Gastrointestinal (GI) intestinal stromal tumors account for 60% of mesenchymal GI tract tumors commonly located in the stomach and small intestine, predominantly solid tumors that rarely undergo cystic degeneration. A 65-year-old patient with increasing upper abdominal swelling and a computed tomography scan abdomen showed a large unilocular 17 × 16 × 15 cm lesion. A colossal cystic swelling in the lesser omentum, anterior to the stomach, was found upon exploration. Histopathological examination showed a spindle cell tumor turned out to be CD117 positive and S100 negative on immunostains. The tumor was moderate risk gastric gastrointestinal intestinal stromal tumor (GIST) based on the site; Stomach, Size >10 cm; Mitosis <5/5 mm2 according to risk assessment of GIST, 2006. GISTs are predominantly solid tumors and rarely undergo cystic transformation. The primary differential diagnoses of spindle cell neoplasm are GISTs, Leiomyoma, Leiomyosarcoma and Schwannoma. These spindle cell neoplasms are differentiated by applying a panel of Immunohistochemical stains, CD117, SMA and S100.

Multicystic Solitary Fibrous Tumor of the Kidney: A Case Report With Review of Literature.

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm known to occur at various soft tissue and visceral locations. Kidney is one of the rare locations for these tumors with around 64 cases being available in the literature. Most of the renal SFTs are tan-white, solid, firm, unencapsulated, and lobulated masses. A predominantly cystic renal SFT has never been reported in the literature. Herein we describe a case of multicystic renal SFT in a 44-year-old male with the characteristic CD34 + /STAT6 + immunophenotype. A careful gross and microscopic examination is warranted while dealing with cystic spindle cell neoplasms of the kidney and SFT should always be considered in the differential diagnosis. STAT6 immunohistochemistry is quite specific for the diagnosis. Moreso, a detailed immunopanel is necessary to exclude other spindle cell neoplasms of the kidney because of significant therapeutic and prognostic implications.

NTRK-Rearranged soft tissue neoplasms: A review of evolving diagnostic entities and algorithmic detection methods.

The spectrum of tumors with NTRK1/2/3 rearrangements has expanded with widespread use of next generation sequencing (NGS) technology. For many years it was known that a majority of infantile fibrosarcomas (IFS), and their counterpart in the kidney, cellular congenital mesoblastic nephroma, contain the recurrent ETV6-NTRK3 fusion. Sequencing RNA transcripts from IFS and their morphologically similar counterparts in older children and adults has shown rearrangements with other 5' partners combined with NTRK1, NTRK2, and NTRK3 can also occur. For those tumors occurring outside of the infant age group, this has resulted in a proposed new diagnostic entity of "NTRK-rearranged spindle cell neoplasm." The clinical behavior of NTRK rearranged soft tissue tumors varies, though most show localized disease with rare metastases. The pathology of NTRK rearranged tumors exists on a spectrum, with overlapping features of classic infantile fibrosarcoma, lipofibromatosis, and malignant peripheral nerve sheath tumor. In this tumor spectrum, clinical and pathologic predictive factors are largely still to be determined, with no clear association between histologic grade and severity of disease. Of critical importance is detection of the NTRK rearrangement in order to guide treatment in patients with unresectable and metastatic disease. While resection is the definitive treatment, these tumors do show response to targeted TRK kinase inhibitors. Multiple detection methods are available, including immunohistochemistry, FISH, and next generation sequencing, which each have their merits and potential pitfalls. We aim to review the clinical characteristics and histomorphology of mesenchymal tumors with NTRK rearrangements as well as discuss molecular detection methods and diagnostic algorithms specific for soft tissue tumors.