Cutaneous Non-Neural Granular Cell Tumors Harbor Recurrent ALK Gene Fusions

Oral granular cell tumors: an analysis of the clinical and histopathologic features of 126 tumors

OBJECTIVE

To characterize the clinical and histologic features of oral granular cell tumors (GCTs).

STUDY DESIGN

A retrospective search of the archives of our diagnostic oral pathology service was performed for GCTs diagnosed between 1989 and 2023. A total of 126 tumors in 122 patients were retrieved.

RESULTS

There was a female predilection with a female-to-male ratio of 2.3:1. The age range was 5-73 years (mean = 33.3). The most commonly involved site was the tongue (81.0%), followed by the lips (7.9%). Most GCTs were pink, but many lesions appeared yellow or white. Histologically, most GCTs were sessile masses comprised of sheets or nodules of tumor cells. Uncommonly, GCTs were pedunculated (3.2%), papillary (2.4%), ulcerated (3.2%), or desmoplastic (11.1%). Pseudoepitheliomatous hyperplasia, histologically mimicking squamous cell carcinoma, was present in 25.4% of tumors. While 65.9% of GCTs demonstrated positive surgical margins, only 3 tumors recurred.

CONCLUSIONS

To the best of our knowledge, this is the largest series of oral GCTs with a comprehensive analysis of the clinical and histologic features. It is important for clinicians and pathologists to be aware of the spectrum of features observed in GCTs in order to avoid erroneous classification as malignancy.

Multisystem ALK-Positive Histiocytosis With DCTN1::ALK Fusion in an Adult, Responsive to Alectinib: Case Report and Literature Review

Anaplastic lymphoma kinase (ALK)-positive histiocytosis has emerged as a clinically relevant diagnosis featuring a wide span of clinical presentations, which are unified by the presence of ALK-positive histiocytes on histopathology and molecular drivers involving the ALK kinase gene. This report presents an adult case of multisystem ALK-positive histiocytosis with xanthogranuloma-like features on histopathology that was responsive to ALK inhibition, and includes a review of ALK-positive histiocytoses with cutaneous involvement reported in the literature. A 56-year-old male developed a widespread eruption of red-brown papules on the face, trunk, and upper extremities. Histopathological evaluation revealed a well-circumscribed, nodular dermal infiltrate of epithelioid histiocytes with Touton giant cells, rare bizarre multinucleated cells, and focal emperipolesis. The lesional cells were positive for CD68 and ALK1 immunohistochemical stains, and negative for CD1a. Next-generation sequencing identified a DCTN1::ALK fusion. On imaging, he was found to have bone, lung, soft tissue, and salivary gland involvement. ALK inhibition was initiated with alectinib, resulting in rapid improvement of cutaneous lesions and eventual complete resolution of abnormal imaging findings, which was sustained at 24 months of follow-up. This case adds to the spectrum of ALK-positive histiocytoses and further demonstrates the positive response with targeted therapy.

Metastatic Granular Cell Tumor: A Rare Entity

Granular cell tumor, which is thought to recapitulate a Schwann cell phenotype, is a very rare neoplasm that belongs to soft tissue tumors. It can be classified as benign, atypical or malignant, based on specific histological criteria, with the majority of cases exhibiting an indolent behavior. Its biology and clinical course are poorly understood and its optimal management is yet to be defined, given the rarity of cases. Here we describe an atypical granular cell tumor in the upper middle back skin that evolved after a thirty-year indolent period. Despite complete surgical removal, the patient experienced a recurrence, both local and in the lungs, following an aggressive clinical course. Data on management of metastatic disease are extremely scarce, comprised exclusively of case reports. Therefore, we administered to the patient systemic therapy according to soft tissue sarcoma guidelines, which led to disease progression, with fatal outcome. In conclusion, recurrent and/or metastatic granular cell tumor is a rare disease that can be life-threatening, for which response to different therapies is unknown. The biologic behavior of atypical and malignant granular cell tumor is quite different from its benign counterpart, evoking soft tissue sarcomas, and its diagnosis should alert clinicians. The role of adjuvant chemotherapy and radiation therapy in this setting should be explored, to limit disease recurrence.

ALK -rearranged Mesenchymal Neoplasms With Prominent Foamy/Pseudolipogenic Cell Morphology : Expanding the Phenotypic Spectrum of ALK Fusion Neoplasms and Report of Novel Fusion Partners

The category of ALK -rearranged mesenchymal neoplasms has been evolving rapidly, with reports of morphologically diverse lesions of cutaneous, soft tissue, and visceral origin. While some of these represent morphologically defined entities harboring recurrent ALK fusions (inflammatory myofibroblastic tumor and epithelioid fibrous histiocytoma), others are unclassified by morphology with variable overlap with the tyrosine kinase family of neoplasia and their underlying ALK fusions cannot be suspected based on morphology. We herein report 3 cases that expand the anatomic, morphologic, and genotypic spectrum of ALK -rearranged unclassified neoplasms. Patients were all adults aged 46 to 69 (median: 63) who presented with a mass located in the gingiva, subcutis of the back, and submucosal posterior pharyngeal wall. The tumor size ranged from 1 to 2.7 cm (median: 1.6). Conservative surgery was the treatment in all patients. Follow-up was available for one patient who remained disease-free at 14 months. Histologically, all tumors displayed large polygonal cells with foamy to granular and lipogenic-like microvacuolated copious cytoplasm and medium-sized round nuclei with 1 or 2 prominent nucleoli. Mitoses and necrosis were not seen. The initial diagnostic impression was PEComa, inflammatory rhabdomyoblastic tumor and unclassified pseudolipogenic neoplasm. Strong cytoplasmic ALK was detected by immunohistochemistry in all cases. Other positive markers include Cathepsin K (2/2), desmin (1/3), focal MyoD1 (1/1), focal SMA (1/3), and focal EMA (1/2). Targeted RNA sequencing revealed ALK fusions with exon 20 (2 cases) and exon 19 (one case) of ALK fused to RND3 (exon 3), SQSTM1 (exon 6), and desmin (intron 6). Methylation profiling in the desmin-fused case (initially diagnosed as inflammatory rhabdomyoblastic tumor) revealed an inflammatory myofibroblastic tumor match with a low confidence score of 0.5 and a flat copy number variation (CNV) profile. No NF1 mutation was detected in this case, altogether excluding an inflammatory rhabdomyoblastic tumor. Our study highlights and expands the morphologic and anatomic diversity of ALK- fused neoplasms and documents novel fusion partners ( RND3 and desmin).

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.

Deep learning-based pathological prediction of lymph node metastasis for patient with renal cell carcinoma from primary whole slide images

BACKGROUND

Metastasis renal cell carcinoma (RCC) patients have extremely high mortality rate. A predictive model for RCC micrometastasis based on pathomics could be beneficial for clinicians to make treatment decisions.

METHODS

A total of 895 formalin-fixed and paraffin-embedded whole slide images (WSIs) derived from three cohorts, including Shanghai General Hospital (SGH), Clinical Proteomic Tumor Analysis Consortium (CPTAC) and Cancer Genome Atlas (TCGA) cohorts, and another 588 frozen section WSIs from TCGA dataset were involved in the study. The deep learning-based strategy for predicting lymphatic metastasis was developed based on WSIs through clustering-constrained-attention multiple-instance learning method and verified among the three cohorts. The performance of the model was further verified in frozen-pathological sections. In addition, the model was also tested the prognosis prediction of patients with RCC in multi-source patient cohorts.

RESULTS

The AUC of the lymphatic metastasis prediction performance was 0.836, 0.865 and 0.812 in TCGA, SGH and CPTAC cohorts, respectively. The performance on frozen section WSIs was with the AUC of 0.801. Patients with high deep learning-based prediction of lymph node metastasis values showed worse prognosis.

CONCLUSIONS

In this study, we developed and verified a deep learning-based strategy for predicting lymphatic metastasis from primary RCC WSIs, which could be applied in frozen-pathological sections and act as a prognostic factor for RCC to distinguished patients with worse survival outcomes.

Superficial CD34-Positive Fibroblastic Tumor

Superficial CD34-positive fibroblastic tumor is a mesenchymal neoplasm of "intermediate malignancy" recently included in the fifth edition of the World Health Organization classification of soft tissue and bone tumors. In this review, we summarize the current knowledge on this rare entity with a special focus on its clinicopathological features, morphologic spectrum, and differential diagnosis. We also provide data regarding recent discoveries on its molecular profile and discuss its prognosis and management.

Atypical Spitz tumor with SQSTM1::NTRK2 fusion: Report of a case with unique spindled cell features

A host of signature genetic alterations have been demonstrated in Spitz neoplasms, most notably fusions of kinase genes (including BRAF, ALK, ROS1, NTRK1, NTRK3, RET, MET, MAP3K8) or variants in HRAS. While there are multiple reports of rearrangements involving NTRK1 and NTRK3 in Spitz tumors, there are very few reports of NTRK2-rearranged Spitz nevi in the literature. This report presents an NTRK2-rearranged atypical Spitz tumor with spindled cell features. The patient was a 6-year-old female with a growing pigmented papule on the back. Histopathological evaluation revealed an asymmetric, biphasic, compound proliferation of melanocytes featuring an epithelioid cell population arranged as variably sized nests and single cells along the basal layer with extension down adnexa, as well as a population of spindled melanocytes with desmoplastic features and loss of Melan-A expression in the dermis. There was partial loss of p16 expression in the epidermal component and diffuse loss in the dermal component. Immunohistochemistry for PRAME, ALK, NTRK1, HRAS Q61R, p53, and BRAF V600E were negative. A SQSTM1::NTRK2 fusion was identified by RNA sequencing. No TERT promoter hotspot variants were detected. This case report expands the known histopathologic spectrum of genetic alterations in Spitz neoplasms.

A cutaneous epithelioid vascular tumor harboring a TPM3::ALK fusion

Substantial progress has been made in understanding the molecular pathways associated with vascular tumors over the last two decades. In addition to mutations and copy number aberrations, fusions have emerged as significant contributors to the pathogenesis of a notable subset of vascular tumors. In this report, we present a case of an unusual intradermal vascular tumor with epithelioid cytomorphology. Immunohistochemistry revealed diffuse positivity for CD31, ERG and Factor VIII, supporting its endothelial lineage. RNA sequencing (ArcherFusion Plex) revealed the presence of an in-frame fusion between the genes TPM3 Exon 8 and ALK Exon 20. Immunohistochemistry confirmed ALK expression by the endothelial cells. To our knowledge, this is the first documented case of a vascular tumor harboring an ALK fusion. It may fall within the spectrum of epithelioid hemangiomas; nevertheless, we cannot definitively exclude the possibility of it being a distinct and potentially unique benign entity on its own.

Lip Granular Cell Tumor (GCT) in a Pediatric Patient: Critical Literature Review on Pediatric Intraoral GCT and Acquired and Congenital Intraoral Non-Neural GCT

Granular cell tumor (GCT) is an uncommon benign neoplasm derived from Schwann cells, frequently affecting the oral cavity, skin, and gastrointestinal tract. On microscopy, pseudocarcinomatous squamous hyperplasia (PSH) and perineural involvement are potential diagnostic pitfalls. GCT should be differentiated from non-neural GCT (NN-GCT). A 13-year-old male patient was referred presenting a nodular lesion on the upper lip several months ago. After excisional biopsy, microscopy revealed GCT without PSH but presenting multifocal perineural involvement. By immunohistochemistry, ALK was negative, whereas Rb and INI1 expression was intact. Moreover, with few intraoral NN-GCTs being assessed, recent studies suggest that acquired dermal NN-GCT subgroup seems to correspond to ALK-rearranged variants of epithelioid fibrous histiocytoma. Accordingly, further research on this topic is strongly encouraged.

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.

Dermatofibroma-like dermal non-neural granular cell tumor

Non-neural granular cell tumor (NNGCT) is a rare tumor with uncertain lineage. It presents as an asymptomatic polypoid or plaque-like lesion, especially on trunk. Because the granular cells are usually strongly reactive with S-100 stain, conventional granular cell tumors (GCTs) are regarded as those of neural or Schwann cell origin. Unlike GCTs, NNGCT is not reactive for S-100 protein and is thought to derive elsewhere, presumably from mesenchymal stem cells. A 20-year-old woman presented with a solitary, dermatofibroma-like, brownish nodule on her right arm. The lesion developed 3 months before presentation without subjective symptoms. Histopathologic examination revealed a grenz zone overlying a poorly circumscribed tumor extending through the reticular dermis. The tumor cells were large and polygonal, and they had numerous eosinophilic small granules in the cytoplasm. Immunohistochemical stains were positive for CD68, vimentin, factor XIIIa, CD10, and cyclin D1. Stains for S-100 protein, neuron-specific enolase, and CD34 were negative. Based on these findings, the lesion was diagnosed as dermal NNGCT.

Inflammatory myofibroblastic tumor of the mesentery with a SQSTM1::ALK fusion responding to alectinib

BACKGROUND

Inflammatory myofibroblastic tumor (IMT) is an ultra-rare soft tissue neoplasm associated with fusion proteins encompassing the anaplastic lymphoma kinase (ALK) protein fused to a variety of partner proteins. Data regarding response to ALK-targeting agents based on fusion partner is limited.

CASE

A 30-year-old female sought emergency care after onset of abdominal and lower back pain in 2019. Computed tomography (CT) demonstrated a cystic, mesenteric mass within the pelvis measuring up to 8.9 cm. Complete laparoscopic excision of the mass from the mesentery of the right colon and terminal ileum was performed. Pathologic assessment revealed IMT with a fusion between sequestosome 1 and ALK (SQSTM1::ALK), described in only two other cases of IMT. Four months after surgery, CT revealed multi-focal, unresectable disease recurrence. She was referred to the University of Washington/Fred Hutchinson Cancer Center and placed on therapy with alectinib, after which she experienced a partial response. Three years after IMT recurrence, disease remains under control.

CONCLUSION

This is the third reported case of IMT associated with the novel SQSTM1::ALK fusion protein, and the second treated with alectinib. Treatment with the ALK inhibitor alectinib appears to be active in this setting.

Dermal nonneural granular cell tumor: a case report

Dermal nonneural granular cell tumor is a rare neoplasm of uncertain histogenesis that Le Boit and colleagues originally described in 1991. It arises commonly from the back, extremities and head and neck. To the best of our knowledge, only 50 cases have been reported in adults in the English literature. A 42-year-old man presented with a polypoid skin nodule of the front side of the chest wall, measuring 1,8 × 1,5 cm. The lesion was removed completely with tumor-free margins. Microscopically, the tumor was composed of a diffuse infiltrate of polygonal cells, S 100 negatives, with abundant granular cytoplasm and vesicular nuclei. The diagnosis of dermal nonneural granular cell tumor was retained. No recurrence was noted during follow up of 6 months. The prognosis is good.

Cutaneous Inflammatory Myofibroblastic Tumor with CARS-ALK Fusion: Case Report and Literature Review

Cutaneous inflammatory myofibroblastic tumors (IMT) constitute a rare entity, generating a diagnostic pitfall when diagnosing spindle cell proliferation within the dermis. Raising awareness of this tumor among dermatopathologists remains vital in differentiating it from common cutaneous tumors such as fibrous histiocytoma, atypical fibroxanthoma, melanoma, poorly differentiated carcinoma, and other more aggressive tumors. Accurate diagnosis of IMT aid in ensuring appropriate management and follow-up for patients while preventing unnecessary harm and overtreatment. Here we report a case of a 38-year-old female with a painless, slow-growing nodule of the left posterior scalp initially diagnosed as a dermatofibroma. The histological examination revealed an ill-defined dermal nodule of spindled cells without connection or infiltration of the epidermis. At high power, the cells were arranged in fascicles with a prominent background of lymphocytic infiltrate. Immunohistochemical analysis showed strong diffuse immunoreactivity for anaplastic lymphoma kinase (ALK), targeted RNA sequencing identified a CARS-ALK fusion ultimately confirming the accurate diagnosis of a cutaneous IMT. This article is protected by copyright. All rights reserved.

Spitz nevus with EHBP1-ALK fusion and distinctive membranous localization of ALK

ALK rearrangements define a histopathologically distinctive but diverse subset of Spitz tumors characterized by fusiform to epithelioid melanocytes with frequent fascicular growth and ALK overexpression. Molecularly, these tumors are characterized by fusions between ALK and a variety of other genes, most commonly TPM3 and DCTN1. We describe an unusual case of a Spitz nevus occurring in a 13-year-old female that manifested ALK immunopositivity with cell membrane localization. The proliferation was polypoid and composed of elongated nests of epithelioid melanocytes with enlarged nuclei, prominent nucleoli, and abundant cytoplasm without significant atypia and lacking mitotic figures. The nevus exhibited strong and diffuse expression of p16. Targeted next-generation RNA sequencing revealed an in-frame EHBP1-ALK fusion, which has been reported only once in the literature. EHBP1 encodes an adaptor protein with plasma membrane targeting potential. Together, these findings suggest that the 5' ALK fusion partner in Spitz tumors may dictate the subcellular localization of the ALK chimeric oncoprotein. In summary, this case highlights a rare ALK fusion associated with a distinct immunohistochemical staining pattern and further expands the spectrum of ALK-rearranged melanocytic tumors. This article is protected by copyright. All rights reserved.

Immunohistochemical ALK Expression in Granular Cell Atypical Fibroxanthoma: A Diagnostic Pitfall for ALK-Rearranged Non-neural Granular Cell Tumor

ABSTRACT

Atypical fibroxanthoma (AFX) is a neoplasm that most commonly occurs on sun-damaged skin of the head and neck in elderly patients and that usually exhibits indolent clinical behavior with complete excision. The granular cell variant of AFX demonstrates overlapping histopathologic features with dermal non-neural granular cell tumor (NNGCT), which typically arises on the extremities of young to middle aged adults with rare reports of regional metastasis. A subset of NNGCT harbors ALK rearrangements and expresses ALK by immunohistochemistry. Here, we present 2 cases of granular cell AFX occurring on the scalp of males aged 73 and 87 with ALK expression by immunohistochemistry and no evidence of an ALK rearrangement on fluorescence in situ hybridization, representing a diagnostic pitfall for NNGCT.

Review and update in the diagnosis of peripheral nerve sheath tumors

PURPOSE OF REVIEW

Although tumors with nerve sheath differentiation are vast, the main clinically significant problems faced by the pathologist are the separation of malignant peripheral nerve sheath tumors (MPNSTs) from histologic mimics, the diagnosis of neurofibromatous neoplasms with atypical features, and the separation of cutaneous neurofibromatous neoplasms from melanoma. This review briefly discusses a variety of common nerve sheath tumors and summarizes recent advances on these diagnostic fronts.

RECENT FINDINGS

Much of recent work has focused on abnormalities in polycomb repressive complex 2, and the ways in which these abnormalities may be exploited in the diagnosis of MPNSTs. Progress has been made in the diagnostic and clinical understanding of atypical neurofibromatous neoplasms and low-grade MPNSTs. A number of reports have explored the diagnostic distinction between cutaneous neurofibroma and melanoma.

SUMMARY

New discoveries show promise in the diagnosis of peripheral nerve sheath tumors, but challenges - old and new - remain.

Diagnostic Immunohistochemistry of Soft Tissue and Bone Tumors: An Update on Biomarkers That Correlate with Molecular Alterations

The diagnosis of benign and malignant soft tissue and bone neoplasms is a challenging area of surgical pathology, due to the large number, rarity, and histologic diversity of tumor types. In recent years, diagnosis and classification has been aided substantially by our growing understanding of recurrent molecular alterations in these neoplasms. Concurrently, the role of diagnostic immunohistochemistry has also expanded, with the development of numerous biomarkers based on underlying molecular events. Such biomarkers allow us to infer the presence of these events and can therefore substitute for other ancillary molecular genetic techniques (e.g., fluorescence in situ hybridization, polymerase chain reaction, and next-generation sequencing). In this review, we discuss a range of biomarkers currently available for these neoplasms, highlighting the accuracy, staining characteristics, and interpretation pitfalls of each antibody. These include immunohistochemical antibodies that represent reliable surrogates for the detection of gene fusions (e.g., STAT6, CAMTA1, FOSB, DDIT3) and more recently described breakpoint-specific antibodies (e.g., SS18-SSX, PAX3/7-FOXO1). Additionally, discussed are markers that correlate with the presence of gene amplifications (e.g., MDM2, CDK4), deletions (e.g., SMARCB1, SMARCA4), single nucleotide variants (e.g., G34W, K36M), aberrant methylation (H3K27me3), and increased expression as discovered through gene expression profiling (e.g., MUC4, DOG1, ETV4, NKX2.2, NKX3.1).

Three additional cases of non-neural granular cell tumor with novel immunohistochemical findings

BACKGROUND

Non-neural granular cell tumor (NNGCT) is an uncommon neoplasm of controversial histogenesis and its histopathologic differential diagnosis includes, in addition to conventional GCT, other dermal tumors that may exhibit granular cell change.

METHODS

Three patients with a diagnosis of NNGCT were identified in the authors' files. Hematoxylin and eosin-stained sections and immunohistochemical studies were performed.

RESULTS

Histopathological study of the three lesions showed dermal proliferation of granular cells arranged in thick fascicles between collagen bundles. The lesions showed positivity for Factor XIIIa, CD163, CD68, NKIC3, vimentin, ALK, fascin, and cyclin D1.

CONCLUSION

To our knowledge, positivity for cyclin D1 has not been reported to date in NNGCT. In borderline cases, where the diagnosis is unclear despite histopathologic and immunohistochemical findings, positivity for cyclin D1 may favor the diagnosis of NNGCT. Further investigations to assess the differentiation of this rare neoplasm are needed.

Epithelioid Cutaneous Mesenchymal Neoplasms: A Practical Diagnostic Approach

Epithelioid cells are rounded or polygonal cells with abundant eosinophilic or clear cytoplasm and ovoid to round nuclei, superficially resembling epithelial cells. Cutaneous mesenchymal neoplasms composed predominantly or exclusively of epithelioid cells are relatively uncommon and can cause considerable diagnostic difficulties due to overlapping histologic features among heterogeneous groups of tumors. Familiarity with practical diagnostic approaches and recognition of key histopathologic features are important for correct diagnosis and management. This review summarizes the histologic features of epithelioid cutaneous mesenchymal neoplasms and discusses their differential diagnoses from malignant melanomas and carcinomas.

Desmoplastic stromal changes in cutaneous neural granular cell tumors: An under-recognized histopathologic feature of diagnostic and prognostic importance

BACKGROUND

Granular cell tumors (GCTs) are uncommon mucocutaneous and soft tissue neoplasms with distinctive histopathologic appearance but controversial histogenesis. Herein, we report a variant of cutaneous GCT featuring extensive desmoplastic stroma which may result in diagnostic difficulties with mesenchymal proliferations, particularly a dermatofibroma.

METHODS

Following a recent case of GCT with prominent stromal desmoplasia, we reviewed all cases diagnosed as GCT during the past 10 years accessioned at the dermatopathology unit in a tertiary university hospital.

RESULTS

Three additional cases with a similar excessive connective tissue were identified out of a total of 49 GCTs. Cytoplasmic granularity was often subtle and focal, S100 expression was weak, and nuclei had a tendency to show spindling in tumor cells entrapped within the desmoplastic areas. Of note, nuclear spindling is one of the criteria used to diagnose an atypical/malignant GCT.

CONCLUSION

We propose the term "desmoplastic GCT" for these tumors, which not only appropriately addresses the stromal changes but also raises an awareness of GCT being one of the cutaneous tumors which may show stromal desmoplasia. Differential diagnostic difficulties apart, awareness of this phenomenon is important so that desmoplasia and resultant spindling are not linked with potential aggressive behavior.

What's new in nerve sheath tumors

Peripheral nerve sheath tumors are commonly encountered and frequently pose challenges to the pathologist and the clinician. This review discusses the wide range of entities with an emphasis on new discoveries in the past decade. Clinical, histologic, immunohistochemical, and pathogenetic findings are discussed with an emphasis on clinical implications and differential diagnosis.

Oral neural tumors: Clinicopathologic analysis of 157 cases and review of the literature

Background

Oral neural tumors (ONTs) are rare lesions and represent reactive or neoplastic proliferations of nerve sheath cells. The purpose of the present study is to report the clinical, demographic and histopathologic features of 157 ONTs diagnosed in a single Oral Pathology Department and review the pertinent literature.

Material and Methods

157 cases of ONTs diagnosed during a 44-year period were retrospectively collected and the diagnosis was reconfirmed by studying representative haematoxylin and eosin stained tissue sections. The patients’ gender and age, as well as the main clinical features of the lesions, were retrieved from the biopsy submission forms.

Results

The 157 ONTs represented approximately 0.4% of 35,590 biopsies accessioned during the study period. They affected 71 male and 86 female patients with a mean age of 38.4±18.8 years. They mainly appeared as asymptomatic nodules of normal or white colour on the tongue, lip mucosa and hard palate. The most common ONT was granular cell tumour (38.9%) followed by neurofibroma (19.7%), schwannoma (15.9%), traumatic neuroma (15.9%), palisaded encapsulated neuroma (8.3%) and nerve sheath myxoma (1.3%).

Conclusions

This study confirmed the rarity of ONTs. Their clinical characteristics mimic other oral lesions; thus, microscopic examination is the only mean to arrive at a definitive diagnosis.

Key words:Oral neural tumors; oral neural neoplasms; neurofibroma; oral neurofibroma; schwannoma; oral schwannoma; neurilemmoma; oral neurilemmoma; granular cell tumor; oral granular cell tumor; traumatic neuroma; oral traumatic neuroma; palisaded encapsulated neuroma; oral palisaded encapsulated neuroma.