Sox10: a pan-schwannian and melanocytic marker

Digital quantification of PRAME for distinguishing melanoma from nevi compared to manual assessment

AIMS

In this proof-of-concept study, we propose a new method for automated digital quantification of PRAME (PReferentially expressed Antigen of MElanoma) as a diagnostic aid to distinguish between benign and malignant melanocytic lesions. The proposed method utilizes immunohistochemical virtual double nuclear staining for PRAME and SOX10 to precisely identify the melanocytic cells of interest, which is combined with digital image analyse to quantify a PRAME-index.

METHODS

Our study included 10 compound nevi, 3 halo nevi, and 10 melanomas. Tissue slides were stained with PRAME, scanned, the cover glass removed, stained with SOX10, scanned again, and finally analysed digitally. The digitally quantified PRAME-index was compared with a manual qualitative assessment by a dermatopathologist using the standard PRAME-scoring system.

RESULTS

The digitally quantified PRAME-index showed a sensitivity of 70 % and a specificity of 100 % for separating melanomas from benign lesions. The manual qualitative PRAME-score showed a sensitivity of 60 % and a specificity of 100 %. Comparing the two methods using ROC-analyses, our digital quantitative method (AUC: 0.931, 95 % CI: 0.834;1.00, SD: 0.050) remains on par with the manual qualitative method (AUC: 0.877, 95 % CI: 0.725;1.00, SD: 0.078).

CONCLUSION

We found our novel digital quantitative method was at least as precise at classifying lesions as benign or malignant as the current manual qualitative assessment. Our method has the advantages of being operator-independent, objective, and replicable. Furthermore, our method can easily be implemented in an already digitalized pathology department. Given the small cohort size, more studies are to be done to validate our findings.

SOX-10 and TRP-1 expression in feline ocular and nonocular melanomas

In felines, ocular and nonocular melanomas are uncommon tumors that represent a diagnostic challenge for pathologists, especially when amelanotic. To date, the immunohistochemical diagnostic panel in cats is based on specific melanocytic markers (Melan-A and PNL2) and a nonspecific but sensitive marker (S100). In human medicine, SOX-10 is reported to be a sensitive antibody for the detection of melanoma micrometastasis in the lymph node. TRP-1, an enzyme involved in melanogenesis, has recently been used in humans and dogs as a specific melanocyte marker. The aim of this study was to evaluate the cross-reactivity and the expression of SOX-10 and TRP-1 antibodies in feline normal tissue and melanocytic tumors. Thirty-one cases of ocular, cutaneous, and oral melanomas were retrospectively evaluated and confirmed by histopathological examination and by immunolabeling with Melan-A and/or PNL2. SOX-10 nuclear expression in normal tissues was localized in epidermal, subepidermal, hair bulb, and iridal stromal melanocytes and dermal nerves. In melanomas, nuclear expression of SOX-10 was detected in ocular (11/12; 92%), oral (6/7; 86%), and cutaneous sites (12/12; 100%). TRP-1 cytoplasmic immunolabeling in normal tissue was observed in epidermal and bulbar melanocytes and in the lining pigmented epithelium of the iris and in its stroma. Its expression was positively correlated to the degree of pigmentation in the tumor and was observed in 75% of ocular (9/12), 43% of oral (3/7), and 33% of cutaneous melanomas (4/12). This study demonstrated the cross-reactivity of SOX-10 and TRP-1 antibodies in feline non-neoplastic melanocytes and their expression in ocular and nonocular melanomas.

Comprehensive analysis of diagnosis and treatment in 99 cases of abdominal Schwannoma

PURPOSE

Schwannoma is a rare mesenchymal tumor. In this study, we analyzed clinicopathologically 99 schwannomas.This retrospective study delves into the clinical, pathological, and immunohistochemical dimensions of abdominal schwannomas.

RESULTS

A cohort of 99 cases, comprising 4 malignant and 95 benign schwannomas, was meticulously examined. Clinical analysis revealed a notable gender distribution (1:1.7, male to female) and an average age of 58.5 years. The majority of cases were asymptomatic. A cohort of 99 cases, comprising 4 malignant and 95 benign schwannomas, was meticulously examined. Clinical analysis revealed a notable gender distribution (1:1.7, male to female) and an average age of 58.5 years. The majority of cases were asymptomatic. Tumor sizes ranged from 0.5 to 30 cm, with distinct locations in the stomach for most benign cases and the abdomen/small intestine for malignancies. Initial misdiagnoses were frequent. Pathological evaluations revealed distinct features, including Antoni A and B patterns, spindle cells, and lymphatic sheath structures in benign schwannomas. Malignant cases exhibited atypical cells, ulcers, and invasive growth. Immunohistochemical markers, such as S100, SOX10, and vimentin, consistently demonstrated positivity by contributing to accurate diagnoses. Treatment outcomes indicated a poor prognosis in malignant cases, with overall survival ranging from 10 to 41 months. Conversely, benign cases displayed no recurrence or metastasis during follow-up, despite atypical behaviors.

CONCLUSION

This study underscores the rarity of abdominal schwannomas and underscores the need for a comprehensive diagnostic morphology and immunohistochemistry. SOX10 emerges as a crucial and specific marker for accurate diagnosis. Further research is imperative to refine diagnostic protocols and enhance our understanding of the clinical behavior of abdominal schwannomas.

Quadruple Negative Metastatic Melanoma With Gain of SOX-11 Expression and TERT Mutation

Malignant melanoma is a common and aggressive skin cancer with a high incidence of metastases. Diagnosis is usually straightforward, based on a combination of histomorphology and immunohistochemistry. However, metastatic melanoma is notorious for its phenotypic diversity and loss of differentiation markers. Through recent developments in diagnostic immunohistochemistry and molecular pathology, several new markers are identified to be of use in confirming melanoma diagnosis, especially in undifferentiated and dedifferentiated cases. Here we report a challenging case of a 59-year-old male with splenic metastatic melanoma which revealed a loss of four diagnostic melanocytic markers including S100, SOX-10, HMB45, and MART-1, but a gain of SOX-11.

Merkel cell carcinoma: updates in tumor biology, emerging therapies, and preclinical models

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma thought to arise via either viral (Merkel cell polyomavirus) or ultraviolet-associated pathways. Surgery and radiotherapy have historically been mainstays of management, and immunotherapy has improved outcomes for advanced disease. However, there remains a lack of effective therapy for those patients who fail to respond to these established approaches, underscoring a critical need to better understand MCC biology for more effective prognosis and treatment. Here, we review the fundamental aspects of MCC biology and the recent advances which have had profound impact on management. The first genetically-engineered mouse models for MCC tumorigenesis provide opportunities to understand the potential MCC cell of origin and may prove useful for preclinical investigation of novel therapeutics. The MCC cell of origin debate has also been advanced by recent observations of MCC arising in association with a clonally related hair follicle tumor or squamous cell carcinoma in situ. These studies also suggested a role for epigenetics in the origin of MCC, highlighting a potential utility for this therapeutic avenue in MCC. These and other therapeutic targets form the basis for a wealth of ongoing clinical trials to improve MCC management. Here, we review these recent advances in the context of the existing literature and implications for future investigations.

Feline Facial Spindle Cell Tumors in 29 Cats: Histomorphological and Immunohistochemical Characterization

Soft tissue tumors/sarcomas (STSs) in felines, encompassing a variety of mesenchymal tumors with similar histomorphological features, present diagnostic challenges due to their diverse cellular origins and the overlap with other tumor types such as feline sarcoid. This study aimed to delineate the clinical, histomorphological, and immunohistochemical characteristics of 34 feline facial spindle cell tumors affecting 29 cats, including testing for bovine papillomavirus type 14 (BPV14), the virus causing feline sarcoids. Only five out of 12 tumors previously diagnosed as feline sarcoids based on histomorphology were confirmed by PCR for BPV14, underscoring the importance of comprehensive diagnostic approaches to accurately distinguish between STSs and feline sarcoids. This study shows that most facial spindle cell tumors were compatible with peripheral nerve sheath tumors (PNSTs) based on positive immunohistochemical staining for Sox10 and other immunohistochemical markers such as GFAP, NSE, and S100. Some of these tumors displayed as multiple independent masses on the face or as erosive and ulcerative lesions without obvious mass formation, an atypical presentation and an important highlight for general practitioners, dermatologists, and oncologists. This study also describes periadnexal whorling of neoplastic cells as a novel histomorphologic finding in feline facial PNSTs and emphasizes Sox10 as a useful complementary immunohistochemical marker for the diagnosis of facial PNST in cats, providing valuable insights for veterinary pathologists.

Role of SOX10 Immunohistochemical Expression in Diagnosing Triple Negative Breast Cancer and Its Correlation With Clinicopathological Features

BACKGROUND

Triple-negative breast cancer (TNBC) poses a diagnostic challenge for histopathologists due to the reduced frequency of breast-specific markers. SOX10 has emerged as a useful diagnostic marker for TNBC. The aim of our study was to determine the frequency of SOX-10 immunohistochemical (IHC) expression in our cohort and assess its correlation with clinicopathological and histological features.

MATERIALS AND METHODS

We included 72 primary TNBC cases. Specimens included tru-cut biopsies and excision specimens. We stained whole slide sections of these specimens with SOX10 antibody and calculated its frequency (%) of expression and H-score. We applied the chi-square test to assess the correlation between SOX10 expression and clinicopathological and histological features such as the patient's age, specimen type, tumor size, histological type, histological grade, nuclear pleomorphism, mitotic count, tumor-infiltrating lymphocytes (TILs), necrosis, calcification, lymphovascular invasion (LVI), lymph node involvement, T stage, and N stage.

RESULTS

SOX10 expression was observed in 42 (58.3%) cases with a median H-score of 57.5. The expression was significantly higher in tru-cut biopsy specimens as compared to excision specimens (73.5 vs 41.7%) and TILs negative tumors as compared to TILs positive tumors (64.3% vs 27.3). Metaplastic carcinoma showed reduced expression when compared with non-metaplastic tumors (35.7% vs 63.8%), but statistical significance was not achieved. No correlation was observed with the patient's age, tumor size, histological type, histological grade, nuclear pleomorphism, mitotic count, necrosis, calcification, LVI, lymph node involvement, T stage, and N stage.

CONCLUSION

SOX10 was expressed in more than half of the TNBC cases of our study which not only highlights its diagnostic utility but advocated its application in combination with other breast-specific markers. The expression didn't correlate with the majority of clinicopathological and histological features, but correlation with tru-cut biopsy specimens and absence of TILs draws attention towards possible roles of proper fixation and host immunity, respectively.

Fabry disease Schwann cells release p11 to induce sensory neuron hyperactivity

Patients with Fabry disease suffer from chronic debilitating pain and peripheral sensory neuropathy with minimal treatment options, but the cellular drivers of this pain are unknown. Here, we propose a mechanism we believe to be novel in which altered signaling between Schwann cells and sensory neurons underlies the peripheral sensory nerve dysfunction we observed in a genetic rat model of Fabry disease. Using in vivo and in vitro electrophysiological recordings, we demonstrated that Fabry rat sensory neurons exhibited pronounced hyperexcitability. Schwann cells probably contributed to this finding because application of mediators released from cultured Fabry Schwann cells induced spontaneous activity and hyperexcitability in naive sensory neurons. We examined putative algogenic mediators using proteomic analysis and found that Fabry Schwann cells released elevated levels of the protein p11 (S100A10), which induced sensory neuron hyperexcitability. Removal of p11 from Fabry Schwann cell media caused hyperpolarization of neuronal resting membrane potentials, indicating that p11 may contribute to the excessive neuronal excitability caused by Fabry Schwann cells. These findings demonstrate that sensory neurons from rats with Fabry disease exhibit hyperactivity caused in part by Schwann cell release of the protein p11.

A case of a motor vehicle collision suspected as associated with development of angiosarcoma

Trauma has been suspected as a factor leading to development of angiosarcoma, a malignant soft-tissue tumor. We conducted a forensic autopsy to investigate a putative relation between a motor vehicle collision and the driver's later death from angiosarcoma. A vehicle operated by a man in his 60 s collided with an oncoming vehicle at a curve. The victim noticed no injury at the scene. However, 45 days later, he was transferred to an emergency room with dyspnea and bloody sputum. After diagnosis of angiosarcoma, he died of respiratory failure 132 days later. The bereaved family speculated about a relation between the collision and angiosarcoma onset. At autopsy, tumor cells of the scalp had metastasized to the lung, pleura, liver, and spleen. Histopathological examinations revealed characteristic features of angiosarcoma with positive immune-staining for CD31, CD34, and factor VIII. When a person dies some time after a collision, it is designated as a delayed death. In such cases, the relevance of trauma to the person's death is often an issue of concern. Because the interval between trauma and angiosarcoma development was short, only 45 days, the angiosarcoma might be coincidental. Therefore, we rejected the relation. Forensic experts sometimes need to investigate such inquiries.

Perineural differentiation in neurotized nevi

BACKGROUND

Perineuriomatous melanocytic nevi are rare and this may indicate the similar embryological source of melanocytes and peripheral nerves in the neural crest. Neurotized melanocytic nevi may resemble nerve sheath tumors histologically, and show schwannian differentiation. However, literature on whether neurotized nevi differentiate into perineural cells is controversial. We examined our cases of neurotized nevi for evidence of perineural differentiation.

MATERIALS AND METHODS

A total of 100 benign nevi with large neurotized component (microscopically involved a low power field 4.2 mm in diameter) were prospectively evaluated in excisional biopsy samples. Immunohistochemical stainings for EMA, Claudin1, Glut1 and neurofilament were performed.

RESULTS

Perineural differentiation was immunohistochemically detected in the neurotized component of the nevi in 61% of the cases with EMA and in all the cases with Glut1 and Claudin1. Axonal differentiation was not detected with neurofilament. The expression pattern, especially with Glut1, was usually in form of partial or complete staining surrounding the Meissner's corpuscle-like structure (MCLS). Also, a linear/curvilinear staining pattern was observed particularly with Claudin1. A diffuse staining pattern with EMA, Glut1 and Claudin1 was detected in a case with a microscopically distinct whorl structure, and in which spindle cells are separated from the superficial epithelioid melanocytes with an abrupt transition histologically. These findings of the case are compatible with previous reports of perineuromatous nevus.

CONCLUSION

Perineural differentiation is not uncommon and immunohistochemically observed in all nevi with a relatively large component of neurotization. To prevent misdiagnosing desmoplastic melanoma and overtreating patients, it is crucial to be aware of perineuromatous nevi.

Successful revascularization using a saphenous vein for a ruptured brachial artery aneurysm in a patient with neurofibromatosis type I

Vasculopathy in patients with type 1 neurofibromatosis is known. Brachial artery aneurysms in patients with type 1 neurofibromatosis are rare, but any rupture can be extremely serious. A 56-year-old woman presented to our hospital with sudden pain in her right upper arm. Computed tomography revealed a ruptured brachial artery aneurysm, and operative reconstruction using a saphenous vein graft was performed. This is one of the few case reports of such successful revascularization using saphenous vein. The pathologic findings suggest neurogenic tumor invasion, and end-to-side anastomosis was effective in avoiding hemorrhagic complications.

An Update and Review of Clinical Outcomes Using Immunohistochemical Stains in Mohs Micrographic Surgery for Melanoma

BACKGROUND

Mohs micrographic surgery (MMS) provides optimal margin control through complete peripheral and deep margin assessment. The treatment of melanoma using MMS has historically been limited by difficulty in interpreting melanocytes using frozen sections. Immunohistochemical (IHC) staining, a technique whereby chromogen-tagged antibodies are used to detect antigens of interest, has revolutionized the surgical treatment of melanoma.

OBJECTIVES

This article provides an update and literature review of current IHC stains used in MMS for melanoma, their sensitivities and specificities, and clinical outcomes.

MATERIALS AND METHODS

A PubMed search was performed using keywords including "immunohistochemistry," "staining," and "Mohs surgery." Articles related to the use of IHC staining for the treatment of melanoma with MMS were included.

RESULTS

Six IHC stains met the criteria for the review including melanoma antigen recognized by T cells (MART-1), SRY-related HMG-box (SOX10), microphthalmia-associated transcription factor, HMB-45, MEL-5, S-100, and preferentially expressed antigen in melanoma.

CONCLUSION

The adaptation of IHC methods to frozen sections has enabled MMS to become a preferred treatment option for melanoma in special-site areas. Future studies are needed to standardize IHC techniques and to define best practices when using frozen section in the treatment of melanoma.

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

Strategic Approach to Heterogeneity Analysis of Cutaneous Adnexal Carcinomas Using Computational Pathology and Genomics

Cutaneous adnexal tumors are neoplasms that arise from skin appendages. Their morphologic diversity and phenotypic variability with rare progression to malignancy make them difficult to diagnose and classify, and there is currently no established treatment strategy. To overcome these difficulties, this study investigated the transcription factor SOX9 expression, morphology, and genetics of skin adnexal tumors for understanding their biology, especially their histogenesis. We showed that cutaneous adnexal tumors and their nontumor counterparts of skin and appendages exhibit expression patterns similar to that of SOX9. Its expression intensity and pattern, as well as histopathologic evaluation of tumors, were analyzed using digital images of 69 normal skin adnexal 9-type organs and 185 skin adnexal 29-type tumors as references. It was possible to distinguish basal cell carcinoma from squamous cell carcinoma, sebaceous carcinoma, and pilomatrixoma with significant differences, along with porocarcinoma from squamous cell carcinoma. Furthermore, unsupervised machine learning "computational pathology" was used to derive a multiregion whole-exome sequencing fusion method termed "genocomputed pathology." The genocomputed pathology of three representable adnexal carcinomas (porocarcinoma, hidradenocarcinoma, and spiradenocarcinoma) was evaluated for total nine cases. We showed that there was more heterogeneity than expected within the tumors as well as the coexistence of components lacking driver fusion genes. The presence or absence of potential driver genes, such as PIK3CA, YAP1, and PTEN, in each region was identified, highlighting a therapeutic strategy for cutaneous adnexal carcinoma encompassing heterogeneous tumors.

SOX10

The SOX gene encodes for transcription factors that are involved in embryogenesis and cell differentiation. Specifically, SOX10 aids with neural crest shuttling and development. In diagnostic histopathology, Sox10 immunostain is a helpful ancillary test due to its high sensitivity for melanocytic and peripheral nerve sheath neoplasms, and its role in distinguishing triple-negative breast carcinomas from gynaecological carcinoma, cutaneous adnexal neoplasms and salivary glands neoplasms from histological mimics.

Mesenchymal Neoplasms of the Liver

Mesenchymal neoplasms of the liver can be diagnostically challenging, particularly on core needle biopsies. Here, I discuss recent updates in neoplasms that are specific to the liver (mesenchymal hamartoma, undifferentiated embryonal sarcoma, calcifying nested stromal-epithelial tumor), vascular tumors of the liver (anastomosing hemangioma, hepatic small vessel neoplasm, epithelioid hemangioendothelioma, angiosarcoma), and other tumor types that can occur primarily in the liver (PEComa/angiomyolipoma, inflammatory pseudotumor-like follicular dendritic cell sarcoma, EBV-associated smooth muscle tumor, inflammatory myofibroblastic tumor, malignant rhabdoid tumor). Lastly, I discuss metastatic sarcomas to the liver, as well as pitfalls presented by metastatic melanoma and sarcomatoid carcinoma.

Malignant Melanotic Nerve Sheath Tumors: A Review of Clinicopathologic and Molecular Characteristics

Malignant melanotic nerve sheath tumor (MMNST) which was formerly known as melanocytic schwannoma, is an uncommon aggressive type of nerve sheath tumor. It originates from nerve roots with clonal Schwann cell proliferation and melanin pigment production. MMNST which was once thought to be a benign tumor is now considered a malignant disease based on the latest 2020 World Health Organization classification of soft tissue tumors. Interestingly, despite the histologic features appearing benign with a low proliferation index, the clinical course of this tumor is malignant, which was demonstrated in case series with high rate of recurrences and metastasis. This tumor can occur sporadically or in patients with an underlying familial predisposition syndrome called, Carney's complex. Affected patients will often harbor a germline mutation in the PRKAR1A gene. MMNST can be histologically difficult to distinguish from malignant melanoma, other melanocytic tumors, and Schwannoma. Having a better understanding of its clinic pathologic characteristics and associated conditions is essential in properly diagnosing and managing affected individuals. This includes the possible need for genetic testing to detect germline mutations, genetic counseling, and surveillance according to published recommendations. In this article, we summarize the clinic pathologic and molecular features of MMNST and discuss what is known about its molecular biology and its associations with predisposing conditions. The review was conducted through an extensive PubMed search using keywords then relevant publications were selected.

A Spectrum of Histomorphological and Immunohistochemical Expression Profiles of S-100, CD56 and Calretinin in Benign Peripheral Nerve Sheath Tumours

INTRODUCTION

 Peripheral nerve sheath tumours comprise benign tumours; namely schwannomas and neurofibromas, and only rarely comprise hybrid benign tumours and their malignant counterpart, malignant peripheral nerve sheath tumours (MPNST). There may be diagnostic difficulties in histopathology analysis, especially in core needle biopsies where there is a limited amount of tissue. Immunohistochemistry (IHC) can play a beneficial role, especially in atypical and cellular histological variants and rarely hybrid tumours.

METHODS

 A total of 45 cases of benign peripheral nerve sheath tumours were included in the study; there were 27 cases of neurofibroma including variants like plexiform and cellular neurofibromas and 18 cases of schwannomas including variants like ancient schwannoma and cellular schwannoma. Immunohistochemical staining (IHC) on these tumour tissues using S-100, CD56 and calretinin was done and scoring was done based on extent and intensity.

RESULTS AND DISCUSSION

 No significant differences were observed between neurofibromas and schwannomas on patient age and anatomical locations of these tumours. IHC results did not show statistically significant patterns of expression of S-100 protein between the schwannoma and neurofibromas groups (p=0.75). CD56 protein was expressed strongly (3+) in 90% of cases of schwannoma and negative in 86% of neurofibromas, the differential expression between the two groups was found to be statistically significant (p <0.0001). Calretinin was positive in 39% of schwannomas including one case of cellular schwannoma and negative in all (100%) cases of neurofibroma while the differential expression of calretinin between schwannoma and neurofibroma groups was found to be statistically significant (p < 0.005).

CONCLUSION

Our study shows that S-100 does not show differential expression between schwannomas and neurofibromas. CD56 could be a potentially useful IHC marker to aid in the diagnosis of peripheral nerve sheath tumours with significantly higher expression in schwannomas compared to neurofibromas. Calretinin was also found to be preferentially expressed in schwannomas, though the difference is statistically significantly lower compared to CD56. A panel of all these markers could be used for accurate diagnosis.

Local Recurrence Rates After Excision of Desmoplastic Melanoma: A Systematic Review and Meta-Analysis

BACKGROUND

Few prospective studies have evaluated local recurrence rates (LRR) after excision of desmoplastic melanoma (DM); however, several retrospective studies have reported high LRR.

OBJECTIVE

To determine LRR after excision of DM and evaluate factors affecting LRR.

MATERIALS AND METHODS

Systematic review of the PubMed, Embase, and Web of Science databases was performed to identify studies reporting local recurrence after excision of DM with conventional wide local excision (WLE), Mohs micrographic surgery (MMS), or staged excision (SE). Meta-analysis was performed to calculate summary LRR and pooled risk ratios (RR).

RESULTS

Literature search identified 4 studies evaluating MMS or SE (total n = 61 DM). 53 studies assessed WLE ( n = 3,080) and were analyzed quantitatively. The overall LRR after WLE of DM was 21% (95% CI, 0.16-0.28; n = 2,308). Local recurrence rate was higher with positive/unknown histologic excision margins (49%, 95% CI, 0.25-0.74; n = 91) versus negative histologic margins (11%, 95% CI, 0.07-0.17; n = 1,075; [ p < .01]). Neurotropism was also associated with increased LRR (RR, 1.79; 95% CI, 1.34-2.38, p < .01; n = 644).

CONCLUSION

DM has high LRR after WLE. Local recurrence risk was greatest with positive excision margins, indicating the importance of achieving negative microscopic margins. Greater study of MMS and SE for DM is required.

Primary Malignant Peripheral Nerve Sheath Tumor of the Stomach: A Rare Case Report and Review of Literature

Malignant peripheral nerve sheath tumor (MPNST) is a spindle cell sarcoma originating from peripheral nerves or showing differentiation of nerve sheath components. Primary MPNST of the stomach is an extremely rare neoplasm with only a few published reports in the literature. We present the case of a 58-year-old male patient with MPNST in the stomach. The patient was admitted due to upper abdomen discomfort. Gastroscopy revealed a huge ulcer lesion in the stomach, and biopsy revealed a spindle cell malignant neoplasm. No other specific findings were found in the whole-body imaging examination. Subtotal gastrectomy was performed. Histologically, an ulcer-type, push-infiltrating mass composed of dense, woven-like spindle cells with frequent mitosis could be seen. In immunohistochemistry, the tumor cells were negative for expression of H3K27 trimethylation (H3K27me3), keratin (AE1/AE3), epithelial membrane antigen (EMA), CD34, KIT, DOG1 (ANO1), S-100, SOX10, smooth muscle actin, desmin, myogenin, MDM2, CDK4, P16 (CDKN2A) and SS18-SSX (SS18::SSX). Primary MPNST of the stomach was diagnosed based on histological and immunohistochemical results. During the 2.5 years follow-up period after surgery, no recurrence was observed.

Diagnosis and Treatment of Peripheral and Cranial Nerve Tumors with Expert Recommendations: An EUropean Network for RAre CANcers (EURACAN) Initiative

The 2021 WHO classification of the CNS Tumors identifies as "Peripheral nerve sheath tumors" (PNST) some entities with specific clinical and anatomical characteristics, histological and molecular markers, imaging findings, and aggressiveness. The Task Force has reviewed the evidence of diagnostic and therapeutic interventions, which is particularly low due to the rarity, and drawn recommendations accordingly. Tumor diagnosis is primarily based on hematoxylin and eosin-stained sections and immunohistochemistry. Molecular analysis is not essential to establish the histological nature of these tumors, although genetic analyses on DNA extracted from PNST (neurofibromas/schwannomas) is required to diagnose mosaic forms of NF1 and SPS. MRI is the gold-standard to delineate the extension with respect to adjacent structures. Gross-total resection is the first choice, and can be curative in benign lesions; however, the extent of resection must be balanced with preservation of nerve functioning. Radiotherapy can be omitted in benign tumors after complete resection and in NF-related tumors, due to the theoretic risk of secondary malignancies in a tumor-suppressor syndrome. Systemic therapy should be considered in incomplete resected plexiform neurofibromas/MPNSTs. MEK inhibitor selumetinib can be used in NF1 children ≥2 years with inoperable/symptomatic plexiform neurofibromas, while anthracycline-based treatment is the first choice for unresectable/locally advanced/metastatic MPNST. Clinical trials on other MEK1-2 inhibitors alone or in combination with mTOR inhibitors are under investigation in plexiform neurofibromas and MPNST, respectively.

Recovering false negatives in CRISPR fitness screens with JLOE

It is widely accepted that pooled library CRISPR knockout screens offer greater sensitivity and specificity than prior technologies in detecting genes whose disruption leads to fitness defects, a critical step in identifying candidate cancer targets. However, the assumption that CRISPR screens are saturating has been largely untested. Through integrated analysis of screen data in cancer cell lines generated by the Cancer Dependency Map, we show that a typical CRISPR screen has a ∼20% false negative rate, in addition to library-specific false negatives. Replicability falls sharply as gene expression decreases, while cancer subtype-specific genes within a tissue show distinct profiles compared to false negatives. Cumulative analyses across tissues improves our understanding of core essential genes and suggest only a small number of lineage-specific essential genes, enriched for transcription factors that define pathways of tissue differentiation. To recover false negatives, we introduce a method, Joint Log Odds of Essentiality (JLOE), which builds on our prior work with BAGEL to selectively rescue the false negatives without an increased false discovery rate.

Metastatic Multifocal Malignant Peripheral Nerve Sheath Tumour in the Cervicothoracic Spinal Cord of a Dog Initially Mimicking Meningomyelitis

A nine year old cross-breed dog was presented with a two week history of ambulatory tetraparesis and proprioceptive ataxia affecting all four limbs. Meningomyelitis of Unknown Origin (MUO) was presumptively diagnosed based on the magnetic resonance imaging (MRI) findings and cerebrospinal fluid (CSF) analysis. The dog received a tapering dose of glucocorticoids and cyclosporine, showing significant improvement and the stabilization of the clinical signs for seven months. After this period, the dog showed an acute clinical deterioration and a follow-up MRI revealed new multiple lesions affecting different spinal nerve roots along the cervicothoracic spinal cord. Following euthanasia, a final diagnose of multiple malignant peripheral nerve sheath tumors (MPNSTs) was made based on the histopathological examination. MPNSTs can affect the cranial nerves, spinal nerves or the associated nerve roots at any location and can lead to secondary spinal cord compression. The aim of the present case report is to describe the clinical presentation and atypical MRI findings of a dog with histologically confirmed multiple MPNSTs. According to the reviewed literature, this is the first reported case of simultaneous MPNSTs in the cervicothoracic spinal cord of a dog.

Case report: Brachial plexopathy caused by malignant peripheral nerve sheath tumor and review of the literature

Brachial plexopathy (BP) is easily misdiagnosed due to its complexity and varying clinical presentation. Malignant peripheral nerve sheath tumors (MPNST) can accumulate in the brachial plexus and share symptoms with BP, which may hinder the differential diagnosis between BP induced by radiation or metastases, and MPNST-derived BP, in patients with a history of breast cancer and radiation exposure. A 34-year-old Chinese female presented with MPNST. The tumor involved the brachial plexus. She had a history of breast cancer and radiotherapy. The first consideration was radiation- or breast cancer metastasis-derived BP. Clinical examination was performed. Finally, a diagnosis of MPNST of the brachial plexus was made, which guided an accurate treatment plan. This report highlights the importance of correctly diagnosing BP etiology for guiding precise treatment. BP caused by MPNST needs to be considered in clinical practice, and biopsy plays a central role in the differential diagnosis. Complete local surgical resection can prolong survival of patients with MPNST and improve treatment prognosis.

Marker assessments in ER-positive breast cancers: old markers, new applications?

Evaluation of oestrogen receptor (ER) expression by immunostaining is essential in the pathological assessment of breast cancer. Its expression is intercorrelated with clinicopathological features, molecular typing, and treatment selection. The development of novel therapeutic agents related to ER status, the recent ASCO introduction of an ER-low positive category of breast cancers, and the ever-increasing plethora of diagnostic and theragnostic markers call for a timely update. In this article we aim to review the clinicopathological features of ER-positive breast cancers, with an emphasis on ER-low positive breast cancers, and a focus on updating the (i) assessment, reporting and interpretation of ER immunohistochemical (IHC) staining, (ii) correlations of ER status with other diagnostic and theragnostic markers, and (iii) implications for treatment selection and response. In the face of the developments in IHC and molecular techniques and targeted therapy, ER immunostaining is still expected to remain as the core component of prognostic and theragnostic assessment of breast cancers.

Pitfalls in Cutaneous Melanoma Diagnosis and the Need for New Reliable Markers

Cutaneous melanoma is one of the most aggressive forms of skin cancer, with the development of advanced stage disease resulting in a high rate of patient mortality. Accurate diagnosis of melanoma at an early stage is essential to improve patient outcomes, as this enables treatment before the cancer has metastasised. Histopathologic analysis is the current gold standard for melanoma diagnosis, but this can be subjective due to discordance in interpreting the morphological heterogeneity in melanoma and other skin lesions. Immunohistochemistry (IHC) is sometimes employed as an adjunct to conventional histology, but it remains occasionally difficult to distinguish some benign melanocytic lesions and melanoma. Importantly, the complex morphology and lack of specific biomarkers that identify key elements of melanoma pathogenesis can make an accurate confirmation of diagnosis challenging. We review the diagnostic constraints of melanoma heterogeneity and discuss issues with interpreting routine histology and problems with current melanoma markers. Innovative approaches are required to find effective biomarkers to enhance patient management.

Dramatic response to entrectinib in a patient with malignant peripheral nerve sheath tumor harboring novel SNRNP70-NTRK3 fusion gene

Neurotropic tropomyosin receptor kinase (NTRK) gene rearrangements have been reported in limited cases of sarcomas; however, to date, there has been only one report of such rearrangements in malignant peripheral nerve sheath tumors (MPNSTs). Herein, we describe a 51-year-old male patient with a buttock tumor arising from the sciatic nerve, which was diagnosed as MPNST with positive S-100 staining, negative SOX10 staining, and loss of trimethylation at lysine 27 of histone H3 (H3K27me3) confirmed by immunohistochemistry. Soon after the resection of the primary tumor, the patient was found to have pulmonary and lymph node metastases. Chemotherapy with eribulin and trabectedin showed limited effects. However, the patient responded rapidly to pazopanib, but severe side effects caused discontinuation of the treatment. RNA panel testing revealed a novel fusion gene between Small Nuclear Ribonucleoprotein U1 Subunit 70 (SNRNP70) gene and NTRK3 gene. Furthermore, loss of NF1, SUZ12, and CDKN2A genes was confirmed by DNA panel testing, which is compatible with a histological diagnosis of MPNST. SNRNP70 possesses a coiled-coiled domain and seems to induce constitutive activation of NTRK3 through dimerization. In fact, immunohistochemistry revealed diffuse staining of pan-TRK within tumor cells. Treatment with entrectinib, which is an NTRK inhibitor, showed a quick and durable response for 10 months. Although NTRK rearrangements are very rare in MPNST, this case highlights the importance of genetic testing in MPNST, especially using an RNA panel for the detection of rare fusion genes.

Diagnostic utility of SOX10 immunostaining in benign lichenoid keratosis: A study of 21 cases

BACKGROUND

Benign lichenoid keratosis (BLK) is a cutaneous lesion that can clinically mimic malignancy and may represent regression of a pre-existing lesion. BLK may show epidermal pseudo-nests prompting evaluation for a melanocytic lesion. False positivity of MART-1/Melan-A immunostaining in pseudonests has been showed; however, the value of SRY-related HMG-box 10 (SOX10) staining in BLK with features suspicious for a melanocytic proliferation has not been previously reported.

METHODS

Twenty-one cases of BLK from 2015 to 2020 were identified. Slides were reviewed and SOX10 immunohistochemistry was performed on each case. Subsequently, Melan-A immunohistochemical staining was performed on all cases.

RESULTS

In 10 cases (47.6%), unexpected SOX10 staining was seen in rare to numerous small, single cells in the epidermis above the basal cell layer. No malignancy was identified. Of the 10 cases, 8 (80%) showed suprabasal SOX10 staining did not show similar suprabasal Melan-A staining; 2 (20%) cases showed scattered suprabasal cells positive for Melan-A.

CONCLUSION

SOX10 immunostaining in BLK can highlight scattered cells in the epidermis (not easily noticeable on routine stain). Performing SOX10 immunostain alone on BLK can prompt a misdiagnosis of a melanocytic lesion and should be done with caution.

Pitfalls in breast pathology

Accurate pathological diagnosis is the cornerstone of optimal clinical management for patients with breast disease. As non-operative diagnosis has now become the standard of care, histopathologists encounter the daily challenge of making definitive diagnoses on limited breast core needle biopsy (CNB) material. CNB samples are carefully evaluated using microscopic examination of haematoxylin and eosin (H&E)-stained slides and supportive immunohistochemistry (IHC), providing the necessary information to inform the next steps in the patient care pathway. Some entities may be difficult to distinguish on small tissue samples, and if there is uncertainty a diagnostic excision biopsy should be recommended. This review discusses (1) benign breast lesions that may mimic malignancy, (2) malignant conditions that may be misinterpreted as benign, (3) malignant conditions that may be incorrectly diagnosed as primary breast carcinoma, and (4) some IHC pitfalls. The aim of the review is to raise awareness of potential pitfalls in the interpretation of breast lesions that may lead to underdiagnosis, overdiagnosis, or incorrect classification of malignancy with potential adverse outcomes for individual patients.

Nerve Fiber Immunohistochemical Panel Discriminates between Nerve Sheath and Perivascular Wall Tumors

Benign and malignant nerve sheath tumors (NST) pose a major challenge in routine diagnostic anatomic pathology because of shared histomorphological features with other soft-tissue tumors (STT). As a result, NST are often diagnosed as STT, a broad category that encompasses various entities including perivascular wall tumors (PWT) and that represents approximately 15% of all skin tumors in dogs. Immunohistochemistry (IHC) can assist the identification of histologic subtypes of STT. This IHC pilot study applies various markers largely expressed by peripheral nerves to twelve benign and six malignant NST and determines the intratumoral protein expression of laminin, periaxin-1, Sox-10 and S-100 in the NST subtypes. Furthermore, this study assesses the usefulness of peripheral nerve markers applied to diagnostic work cases and demonstrates the relevance of laminin expression patterns, periaxin-1 and Sox-10 in assisting the differentiation of NST from other STT, in particular from PWT.

Single-cell chromatin landscapes of mouse skin development

The coat of mammals is produced by hair follicles, and hair follicle is an important and complex accessory organ of skin. As a complex physiological regulation process, hair follicle morphogenesis is regulated by a series of signal pathway factors, involves the interaction of multiple cell types and begins in the early embryonic stage. However, its transcriptional regulatory mechanism is unclear. We have therefore utilized single-cell ATAC sequencing to obtain the chromatin accessibility landscapes of 6,928, 6,961 and 7,374 high-quality cells from the dorsal skins of E13.5, E16.5 and P0 mice (Mus musculus), respectively. Based on marker gene activity clustering, we defined 6, 8 and 5 distinct cell types in E13.5, E16.5 and P0 stages, respectively. Furtherly, we integrated the fibroblasts and keratinocytes clusters, performed further analysis and re-clustered. The single cell map of the chromatin open area was drawn from each cell type and the mechanism of cell transcription regulation was explored. Collectively, our data provide a reference for deeply exploring the epigenetic regulation mechanism of mouse hair follicles development.

PRAME expression in spindle cell melanoma, malignant peripheral nerve sheath tumour, and other cutaneous sarcomatoid neoplasms: a comparative analysis

Diagnosis of spindle cell/sarcomatoid melanoma may be challenging due to frequent loss of expression of melanocytic marker(s) and histomorphologic resemblance to various mesenchymal tumours, particularly malignant peripheral nerve sheath tumour (MPNST). Overexpression of PReferentially expressed Antigen in MElanoma (PRAME) supports a diagnosis of melanoma when evaluating challenging melanocytic tumours. PRAME expression in MPNST and other cutaneous sarcomatoid neoplasms, however, has not been well characterised. We aimed to determine the utility of PRAME immunostain in distinguishing spindle cell melanoma from MPNST and other sarcomatoid mimics. PRAME expression was scored by extent (0 to 4+) and intensity (0 to 3) of staining. A strong positive correlation was observed between the extent and intensity scores (r = 0.84). An extent score of 4+, defined by staining in 76-100% of tumour cells, was seen in 56% (23/41) of spindle cell melanomas, 18% (7/38) of MPNSTs, 15% (4/27) of cutaneous sarcomatoid squamous cell carcinomas (SCCs), 33% (5/15) of poorly differentiated cutaneous angiosarcomas, 12% (4/33) of atypical fibroxanthomas (AFXs), 4% (1/25) of pleomorphic dermal sarcomas (PDSs), and none (0/16) of the high-grade cutaneous leiomyosarcomas. A significant difference was found between spindle cell melanoma and all other examined sarcomatoid neoplasms except angiosarcoma. While diffuse (and often strong) PRAME expression is more frequently observed in spindle cell melanoma than MPNST, sarcomatoid SCC, AFX, PDS, and high-grade leiomyosarcoma, its limited sensitivity and specificity caution against its use as a standalone diagnostic marker. PRAME may complement other epigenetic or lineage-specific markers and should only be used as part of an immunohistochemical panel when evaluating these sarcomatoid neoplasms.

Case report: Presumptive subcutaneous malignant peripheral nerve sheath tumor with intracranial invasion and osteolysis in the posterior fossa of a dog

A 13-year-old castrated male Toy Poodle presented with an acute vestibular disorder. Magnetic resonance imaging and computed tomography revealed a large oval space-occupying mass with skull destruction located from the subcutaneous tissue to the posterior fossa region. Histopathologically, the mass was a bundled growth of spindle-shaped mesenchymal tumor cells between the myofibrillar and collagen bundles. The cells were moderately irregular in size and had eosinophilic stained cytoplasm. The cells were highly atypical and had rare mitotic figures. Neoplastic cells were immunoreactive for S100, GFAP, Olig-2, SOX10 and immunonegative for NF, E-cadherin, and Claudin-1. Collective findings were presumptive with a diagnosis of malignant peripheral nerve sheath tumor.

Computer-Assisted Annotation of Digital H&E/SOX10 Dual Stains Generates High-Performing Convolutional Neural Network for Calculating Tumor Burden in H&E-Stained Cutaneous Melanoma

Deep learning for the analysis of H&E stains requires a large annotated training set. This may form a labor-intensive task involving highly skilled pathologists. We aimed to optimize and evaluate computer-assisted annotation based on digital dual stains of the same tissue section. H&E stains of primary and metastatic melanoma (N = 77) were digitized, re-stained with SOX10, and re-scanned. Because images were aligned, annotations of SOX10 image analysis were directly transferred to H&E stains of the training set. Based on 1,221,367 annotated nuclei, a convolutional neural network for calculating tumor burden (CNN_TB) was developed. For primary melanomas, precision of annotation was 100% (95%CI, 99% to 100%) for tumor cells and 99% (95%CI, 98% to 100%) for normal cells. Due to low or missing tumor-cell SOX10 positivity, precision for normal cells was markedly reduced in lymph-node and organ metastases compared with primary melanomas (p < 0.001). Compared with stereological counts within skin lesions, mean difference in tumor burden was 6% (95%CI, -1% to 13%, p = 0.10) for CNN_TB and 16% (95%CI, 4% to 28%, p = 0.02) for pathologists. Conclusively, the technique produced a large annotated H&E training set with high quality within a reasonable timeframe for primary melanomas and subcutaneous metastases. For these lesion types, the training set generated a high-performing CNN_TB, which was superior to the routine assessments of pathologists.

Nestin is a marker of unipotent embryonic and adult progenitors differentiating into an epithelial cell lineage of the hair follicles

Nestin is an intermediate filament protein transiently expressed in neural stem/progenitor cells. We previously demonstrated that outer root sheath (ORS) keratinocytes of adult hair follicles (HFs) in mice descend from nestin-expressing cells, despite being an epithelial cell lineage. This study determined the exact stage when nestin-expressing ORS stem/precursor cells or their descendants appear during HF morphogenesis, and whether they are present in adult HFs. Using Nes-Cre/CAG-CAT-EGFP mice, in which enhanced green fluorescent protein (EGFP) is expressed following Cre-based recombination driven by the nestin promoter, we found that EGFP⁺ cells appeared in the epithelial layer of embryonic HFs as early as the peg stage. EGFP⁺ cells in hair pegs were positive for keratin 14 (K14) and K5, but not vimentin, SOX2, SOX10, or S100 alpha 6. Tracing of tamoxifen-induced EGFP⁺ cells in postnatal Nes-CreERT2/CAG-CAT-EGFP mice revealed labeling of some isthmus HF epithelial cells in the first anagen stage. EGFP⁺ cells in adult HFs were not immunolabeled for K15, an HF multipotent stem cell marker. However, when hairs were depilated in Nes-CreERT2/CAG-CAT-EGFP mice to induce the anagen stage after tamoxifen injection, the majority of ORS keratinocytes in depilation-induced anagen HFs were labeled for EGFP. Our findings indicate that nestin-expressing unipotent progenitor cells capable of differentiating into ORS keratinocytes are present in HF primordia and adult HFs.

Human cutaneous interfollicular melanocytes differentiate temporarily under genotoxic stress

DNA-damage response of cutaneous interfollicular melanocytes to fractionated radiotherapy was investigated by immunostaining of tissue sections from punch biopsies collected before, during, and after the treatment of patients for breast cancer. Our clinical assay with sterilized hair follicles, excluded the migration of immature melanocytes from the bulge, and highlighted interfollicular melanocytes as an autonomous self-renewing population. About thirty percent are immature. Surrounding keratinocytes induced and maintained melanocyte differentiation as long as treatment was ongoing. Concomitant with differentiation, melanocytes were protected from apoptosis by transient upregulation of Bcl-2 and CXCR2. CXCR2 upregulation also indicated the instigation of premature senescence, preventing proliferation. The stem cell factor BMI1 was constitutively expressed exclusively in interfollicular melanocytes and further upregulated upon irradiation. BMI1 prevents apoptosis, terminal differentiation, and premature senescence, allowing dedifferentiation post-treatment, by suppressing the p53/p21-and p16-mediated response and upregulating CXCR2 to genotoxic damage. The pre-treatment immature subset of interfollicular melanocytes was restored after the exposure ended.

The Role of Nerve Fibers in the Tumor Immune Microenvironment of Solid Tumors

The importance of neurons and nerve fibers in the tumor microenvironment (TME) of solid tumors is now acknowledged after being unexplored for a long time; this is possible due to the development of new technologies that allow in situ characterization of the TME. Recent studies have shown that the density and types of nerves that innervate tumors can predict a patient's clinical outcome and drive several processes of tumor biology. Nowadays, several efforts in cancer research and neuroscience are taking place to elucidate the mechanisms that drive tumor-associated innervation and nerve-tumor and nerve-immune interaction. Assessment of neurons and nerves within the context of the TME can be performed in situ, in tumor tissue, using several pathology-based strategies that utilize histochemical and immunohistochemistry principles, hi-plex technologies, and computational pathology approaches to identify measurable histopathological characteristics of nerves. These features include the number and type of tumor associated nerves, topographical location and microenvironment of neural invasion of malignant cells, and investigation of neuro-related biomarker expression in nerves, tumor cells, and cells of the TME. A deeper understanding of these complex interactions and the impact of nerves in tumor biology will guide the design of better strategies for targeted therapy in clinical trials.

The Utility of SOX10 Immunohistochemical Staining in Breast Pathology

OBJECTIVES

SOX10 expression helps identify melanocytic lesions. Over time, novel uses have been identified, such as expression in triple-negative breast cancer (TNBC). We evaluated the usefulness of SOX10 in breast pathology-specifically, identification and subtyping of TNBC and distinction from gynecologic carcinomas, use as a myoepithelial marker, and in the distinction of usual ductal hyperplasia (UDH) from atypical ductal hyperplasia (ADH).

METHODS

Several breast and gynecologic carcinoma tissue microarrays containing a total of 492 cases were stained with SOX10. Whole sections of 34 ADH, 50 UDH, and 29 ductal carcinoma in situ (DCIS) samples were also stained with SOX10.

RESULTS

SOX10 expression was identified in 67% of consecutive TNBC cases. Expression was mostly seen in nonapocrine, androgen receptor (AR)-negative TNBCs. All gynecologic carcinomas (n = 157) were negative. All UDH cases showed mosaic SOX10 expression, while all ADH cases lacked expression. All estrogen receptor (ER)-positive DCIS (n = 19) specimens were negative for SOX10, while 2 of 10 ER-negative DCIS specimens were positive for SOX10. The latter 2 cases showed SOX10-positive invasive carcinomas.

CONCLUSIONS

SOX10 identifies nonluminal AR-type TNBC and is useful in distinguishing TNBC from gynecologic carcinomas. SOX10 can distinguish UDH from ADH. SOX10 is not useful in distinguishing ADH from DCIS.

Expression and Role of TRIM2 in Human Diseases

Tripartite motif (TRIM) protein family proteins contain more than 80 members in humans, and most of these proteins exhibit E3 ubiquitin ligase activity mediated through a RING finger domain. Their biological functions are very complex, and they perform diverse functions in cell evolution processes, such as intracellular signaling, development, apoptosis, protein quality control, innate immunity, autophagy, and carcinogenesis. Tripartite motif-containing protein 2 (TRIM2), a member of the TRIM superfamily, is an 81 kDa multidomain protein, also known as CMT2R or RNF86, located at 4q31.3. TRIM2 functions as an E3 ubiquitin ligase. Current studies have shown that TRIM2 can play roles in neuroprotection, neuronal rapid ischemic tolerance, antiviral responses, neurological diseases, etc. Moreover, based on some studies in tumors, TRIM2 regulates tumor proliferation, migration, invasion, apoptosis, and drug resistance through different mechanisms and plays a critical role in tumor occurrence and development. This review is aimed at providing a systematic and comprehensive summary of research on TRIM2 and at exploring the potential role of TRIM2 as a biomarker and therapeutic target in many kinds of human diseases.

Pulmonary Sialadenoma Papilliferum and Its Mimics: What You Need to Know

Pulmonary salivary gland-type tumors (SGT) represent a small but distinct group of primary lung neoplasms. These types of tumors originate from the submucosal bronchial glands of the tracheobronchial tree. Pulmonary SGTs differ greatly in the incidence of individual tumors from salivary gland tumors of the head and neck. Additionally, the vast majority of pulmonary SGT are malignant. Recently, pathologic diagnosis has significantly improved with the application of molecular diagnostic technologies. However, the current knowledge of benign SGTs is limited; moreover, tumor diversity and overlapping morphological features of SGT represent diagnostic challenges such as correct tumor categorization and their accurate differentiation from malignant lesions. Compounding this inherent difficulty has been the recent introduction of new variants, including sialadenoma papilliferum (SP). Pulmonary SP is very rare, with limited reports available, and most of the initial diagnoses rendered so far were incorrect, resulting in inappropriate treatment. Several cases of SP have recently been reported. This review will serve to update practicing pathologists on the morphology, immunophenotype, and molecular characteristics of SP and its mimics.

Head and Neck Cystic Lesions: A Cytology Review of Common and Uncommon Entities

BACKGROUND

Cystic lesions of the head and neck are a diagnostic challenge since they are seen in the clinical presentation of a wide variety of conditions. Herein, common and uncommon entities that present as cystic lesions in the head and neck are reviewed.

SUMMARY

In this study, peer-reviewed articles were selected using the database PubMed, Google, Google Scholar, and Scopus. Emphasis was placed on peer-reviewed articles that discuss the cytomorphology and differential diagnosis of entities that present as cystic lesions of the head and neck. In the anterior neck, both benign and malignant neoplasms can present, including papillary thyroid carcinoma (PTC), thyroid adenomatoid nodule, parathyroid cysts, and thyroglossal cysts. In the lateral neck, branchial cleft cyst, PTC, ectopic thyroid cyst, and squamous cell carcinomas (human papilloma virus and non- human papilloma virus-related) are common. Age over 40 years raises the possibility of malignancy. In the deep neck, mostly benign cystic entities occur such as a pleomorphic adenoma, paraganglioma, schwannoma, branchial cyst, epidermal inclusion cyst, and lymphoepithelial cyst. Lesions with squamous cell features can pose diagnostic dilemmas.

CONCLUSION

Cytologic examination of head and neck cysts can provide valuable information regarding the nature of the cystic lesions. Information about anatomic site and clinical history can assist with the differential diagnoses. Ancillary studies can improve the diagnosis in some cases. Each case should be evaluated very carefully since there are a wide variety of congenital conditions, infectious/inflammatory conditions, benign neoplasms, and primary and secondary malignancies presenting as a cystic mass in the head and neck.

Case Report: Neuroblastoma-Like Schwannoma in a Domestic Short-Haired Cat

An axillary mass was detected in a 6-year-old, neutered, male, domestic short-haired cat during a wellness exam. Gross examination following surgical removal revealed a discrete, deep subcutaneous, discoid mass that was between 0.5- and 0.7-cm-in-diameter and diffusely firm and white. Histologically, the mass was well-demarcated, partially encapsulated, and expanded the panniculus carnosus. It was composed of tightly packed, giant rosettes of radially arranged fusiform cells stacked in one to 10 layers with peripherally palisading nuclei and with centrally oriented, fibrillary, cytoplasmic processes, and collagenous fibers. Laminin immunoreactivity and ultrastructural examination highlighted a continuous basal lamina outside the plasma membrane of each neoplastic cell. Neoplastic cells were immunoreactive for GFAP, S100, periaxin, and Sox-10 and were immunonegative for synaptophysin, smooth muscle actin, and pancytokeratin. Collective findings were consistent with a diagnosis of neuroblastoma-like schwannoma. This is the first veterinary report of this rare variant of benign schwannoma.

Cutaneous Melanomas: A Single Center Experience on the Usage of Immunohistochemistry Applied for the Diagnosis

Cutaneous melanoma (cM) is the deadliest of all primary skin cancers. Its prognosis is strongly influenced by the stage at diagnosis, with early stages having a good prognosis and being potentially treatable with surgery alone; advanced stages display a much worse prognosis, with a high rate of recurrence and metastasis. For this reason, the accurate and early diagnosis of cM is crucial-misdiagnosis may have extremely dangerous consequences for the patient and drastically reduce their chances of survival. Although the histological exam remains the "gold standard" for the diagnosis of cM, a continuously increasing number of immunohistochemical markers that could help in diagnosis, prognostic characterization, and appropriate therapeutical choices are identified every day, with some of them becoming part of routine practice. This review aims to discuss and summarize all the data related to the immunohistochemical analyses that are potentially useful for the diagnosis of cM, thus rendering it easier to appropriately applicate to routine practice. We will discuss these topics, as well as the role of these molecules in the biology of cM and potential impact on diagnosis and treatment, integrating the literature data with the experience of our surgical pathology department.

CDX2 expression in malignant peripheral nerve sheath tumour: a potential diagnostic pitfall associated with PRC2 inactivation

AIMS

Malignant peripheral nerve sheath tumour (MPNST) is a soft tissue sarcoma that exhibits features of Schwann cell differentiation. Heterologous, often mesenchymal-type differentiation occurs in a subset of MPNST, while glandular morphology also is encountered in rare cases. We observed in MPNST unanticipated expression of CDX2, a transcription factor that regulates intestinal epithelial differentiation, and aimed to further characterize this phenomenon.

METHODS/RESULTS

Expression of CDX2 was assessed by immunohistochemistry in a total of 32 high-grade MPNSTs lacking morphological evidence of epithelial differentiation, including twelve tumours (38%) that developed in the setting of neurofibromatosis and four (13%) in the setting of prior radiation therapy. CDX2 was expressed by 14 of 32 MPNSTs (44%), wherein immunoreactivity, varying from weak to strong, was present in 2-95% of neoplastic spindle cells (median 10%, mean 23%). Notably, CDX2 expression was limited to tumours with PRC2 inactivation (22/32; 69%), as evidenced immunohistochemically by diffuse loss of trimethylated histone H3K27. Analysing publicly available RNA-sequencing data from twelve MPNST cell lines, two of which are clonally related, we observed CDX2 expression in all six PRC2-inactivated cell lines, while CDX2 expression was negligible in six cell lines with intact PRC2, amounting to a 58-fold increase in CDX2 expression on average with PRC2 inactivation.

CONCLUSIONS

CDX2 is expressed in a subset of MPNSTs, even in the absence of morphological evidence of epithelial differentiation. CDX2 expression in MPNST is strongly associated with underlying PRC2 inactivation.

Histopathological and Immunohistochemical Evaluation of Canine Nerve Sheath Tumors and Proposal for an Updated Classification

Nerve sheath tumors are a group of tumors originating from Schwann cells, fibroblasts, and perineurial cells. In veterinary pathology, the terminology for nerve sheath tumors remains inconsistent, and many pathologists follow the human classification of such tumors in practice. Immunohistochemistry plays an important role in the diagnosis of nerve sheath tumors, but specific immunohistochemical and molecular biomarkers are lacking. In our study, we histopathologically reevaluated 79 canine nerve sheath tumors and assessed their reactivity for the immunohistochemical markers Sox10, claudin-1, GFAP, CNPase, and Ki-67. Based on the results, we classified the tumors according to the most recent human classification. Twelve cases were diagnosed as benign nerve sheath tumors, including six neurofibromas, three nerve sheath myxomas, two hybrid nerve sheath tumors (perineurioma/neurofibroma and perineurioma/schwannoma), and one schwannoma. Sixty-seven tumors were malignant nerve sheath tumors, including fifty-six conventional, four perineural, one epithelioid malignant nerve sheath tumor, and six malignant nerve sheath tumors with divergent differentiation. We believe that with the application of the proposed panel, an updated classification of canine nerve sheath tumors could largely follow the recent human WHO classification of tumors of the cranial and paraspinal nerves, but prospective studies would be needed to assess its prognostic value.