Poroid adnexal skin tumors with YAP1 fusions exhibit similar histopathologic features: A series of six YAP1-rearranged adnexal skin tumors

Ancillary immunohistochemical and molecular testing in the classification of cutaneous sweat gland/duct neoplasms: A validation study with emphasis on histomorphologic correlation and pathological diagnosis

Sweat gland neoplasms represent a challenging area of dermatopathology, as they are relatively uncommon and often histopathologically complex. Recent studies have uncovered distinct immunohistochemical and molecular profiles in several sweat gland neoplasms, including digital papillary adenocarcinoma (DPA), papillary eccrine adenoma/tubular apocrine adenoma (PEA/TAA), poroid family tumors (PFT)/porocarcinoma, and clear cell hidradenoma (CCH)/clear cell hidradenocarcinoma (CCHCa). To further evaluate the diagnostic utility of ancillary studies in various sweat gland neoplasms, we performed an independent validation study in a cohort of patients with acral and non-acral tumors (9 DPA, 8 PEA/TAA, 13 PFT, 5 porocarcinoma, 23 CCH, 7 CCHCa, 6 sweat gland carcinoma not otherwise specified). p63 immunohistochemistry (IHC) demonstrated a myoepithelial pattern in 8/8 DPA and 4 of 4 tested PEA/TAA cases, and showed a ductal pattern in all tested PFT/porocarcinoma and CCH/CCHCa cases (42/42). All PEA/TAA (8/8) cases were positive for BRAF V600E IHC. 5 of 12 tested PFT and 5/5 porocarcinoma cases showed either positive staining with NUT IHC or harbored YAP1::NUTM1 fusion gene by RNA sequencing. MAML2 fluorescence in situ hybridization (FISH) was positive in all CCH and CCHCa cases (23/23 and 7/7, respectively). Our results further support the usefulness of appropriate ancillary studies in precise classification of sweat gland tumors, which may be routinely applied in diagnostic pathology practice when morphologic evaluation is in doubt.

Spindle cell porocarcinoma with a novel YAP1::MAML3 fusion

Porocarcinomas are rare sweat gland cancers representing the malignant counterpart to benign poromas. Their diagnosis can be challenging, especially in the absence of an associated poroma or when the tumor is poorly differentiated. Since recurrent YAP1::MAML2 and YAP1::NUTM1 fusions have been identified in poroid tumors, molecular studies provide an opportunity to support the diagnosis in challenging cases. We describe a case of a female patient in her early 90s, with a polypoid mass of the hip. Histopathologically, there was a poorly differentiated malignant spindle cell tumor adjacent to a poroma. Because of the close association with a poroma and immunoreactivity for p40, a diagnosis of spindle cell porocarcinoma was rendered, which was further supported by YAP1 immunohistochemical studies. Antibodies targeting both the N-terminus and C-terminus confirmed YAP1 rearrangement in both the poroma and the spindle cell neoplasm. Subsequent targeted RNA sequencing revealed a YAP1::MAML3 gene fusion. MAML3 has previously not yet been reported as a YAP1 fusion partner in porocarcinoma. With the illustration of a rare spindle cell variant of porocarcinoma and the identification of a novel gene fusion, this case report expands the spectrum of morphologic and genomic aberrations associated with porocarcinoma.

NUT Expression Is of Diagnostic Utility in the Distinction of Digital Papillary Carcinoma From Poroid Hidradenoma

ABSTRACT

The distinction between digital papillary adenocarcinoma (DPAC) and benign cutaneous adnexal tumors is clinically important and can be challenging. Poroid hidradenoma frequently occurs at acral sites and can show a number of histological features, which overlap with digital papillary adenocarcinoma. Recent work has shown that YAP1-NUTM1 fusions are frequent in poroid hidradenoma and are associated with nuclear protein in testis (NUT) expression by immunohistochemistry. We evaluated the expression of NUT-1 by immunohistochemistry in 4 cases of DPAC and 4 cases of poroid hidradenoma. Three of 4 cases of poroid hidradenoma showed strong NUT-1 expression, with no staining in any of the cases of DPAC. These results suggest that NUT-1 immunohistochemistry may be a useful additional tool in evaluating this differential diagnosis.

Molecular Profiling of Syringocystadenocarcinoma Papilliferum Reveals RAS-Activating Mutations

CONTEXT.—

Syringocystadenocarcinoma papilliferum (SCACP) is a rare adnexal carcinoma and the malignant counterpart of syringocystadenoma papilliferum (SCAP), which is commonly located on the head and neck and may arise in association with a nevus sebaceus. RAS mutations have been identified in both SCAP and nevus sebaceus.

OBJECTIVE.—

To evaluate the clinicopathologic and molecular features of SCACPs, which have not been previously explored.

DESIGN.—

We obtained 11 SCACPs from 6 institutions and reviewed the clinicopathologic features. We also performed molecular profiling using next-generation sequencing.

RESULTS.—

The cohort comprised 6 women and 5 men with ages ranging from 29 to 96 years (mean, 73.6 years). The neoplasms occurred on the head and neck (n = 8; 73%) and extremities (n = 3; 27%). Three tumors possibly arose in a nevus sebaceus. A total of 4 cases showed at least carcinoma in situ (adenocarcinoma, n = 3; squamous cell carcinoma [SCC], n = 1), and 7 cases were invasive (SCC, n = 5; mixed adenocarcinoma + SCC, n = 2). A total of 8 of 11 cases (73%) had hot spot mutations consisting of HRAS (n = 4), KRAS (n = 1), BRAF (n = 1), TP53 (n = 4), ATM (n = 2), FLT3 (n = 1), CDKN2A (n = 1), and PTEN (n = 1). All 4 cases with HRAS mutations occurred on the head and neck, whereas the KRAS mutation occurred on the extremity.

CONCLUSIONS.—

RAS-activating mutations were detected in 50% of the cases, of which most (80%) involved HRAS and occurred on the head and neck, which shows overlapping features with SCAP, supporting that a subset may arise as a result of malignant transformation and likely an early oncogenic event.

Poroid Neoplasms: A Clinicopathological Study of 13 Cases

Introduction

Poroid neoplasms (PN) are a heterogeneous group of tumors deriving from sweat glands and folliculo-sebaceous units. Their histological classification and clinical features are challenging. Our aim was to report clinicopathological features of poroid neoplasms.

Methods

It is a retrospective study including all cases of poroid neoplasms registered at our Pathology laboratory of Niamey National Hospital (February 2020-February 2024).

Results

We registered 13 cases of benign poroid neoplasms: 10 classic poromas (CP) (76.9%), 2 poroid hidradenomas (PH) (15.4%) and 1 dermal duct tumor (DDT) (7.7%). Nine cases (69.2%) had preoperative clinical diagnosis of malignancy. The mean age was 41.1 years (range of 12-70 years) with a slight female predominance. Only 4/13 cases (30.8%) had classical palmoplantar locations. The tumors mean size was 3.7 cm (range of 0.4-8 cm). Clear cells were present in 7 cases (53.8%), apocrine ductal differentiation (mixed or pure) in 6 cases (46.2%), keratin horns in 2 cases (15.4%), squamous eddies in 6 cases (46.2%), melanin pigments in 1 case (7.7%) and sebaceous differentiation in 2 cases (15.4%).

Conclusions

Unlike what is classically reported, our study shows that apocrine ductal differentiation, younger age and non-palmoplantar locations are common in poroid neoplasms.

Gene fusions in poroma, porocarcinoma and related adnexal skin tumours: An update

Poroma is a benign sweat gland tumour showing morphological features recapitulating the superficial portion of the eccrine sweat coil. A subset of poromas may transform into porocarcinoma, its malignant counterpart. Poroma and porocarcinoma are characterised by recurrent gene fusions involving YAP1, a transcriptional co-activator, which is controlled by the Hippo signalling pathway. The fusion genes frequently involve MAML2 and NUTM1, which are also rearranged in other cutaneous and extracutaneous neoplasms. We aimed to review the clinical, morphological and molecular features of this category of adnexal neoplasms with a special focus upon emerging differential diagnoses, and discuss how their systematic molecular characterisation may contribute to a standardisation of diagnosis, more accurate classification and, ultimately, refinement of their prognosis and therapeutic modalities.

Eccrine Poroma: Pathogenesis, New Diagnostic Tools and Association with Porocarcinoma-A Review

Eccrine poroma (EP) is a relatively rare benign adnexal neoplasm that usually affects elderly patients. Its pathogenesis is still under investigation, but recent gene studies have revealed gene fusions as key incidences resulting in oncogenetic pathways. It often presents as a solitary, firm papule, mostly asymptomatic, located on the soles or palms. Due to its clinical and dermoscopic variability, it is characterized as the great imitator. We performed a literature review, aiming to summarize current data on the pathogenetic mechanisms, new dermoscopic features, and novel diagnostic tools that may aid in early diagnosis and proper management of this rare adnexal tumor. Furthermore, we reviewed the possible pathogenetic associations between EP and its malignant counterpart, namely eccrine porocarcinoma. This systematic approach may aid in understanding the pathogenetic mechanisms and how to use novel histopathologic markers and imaging methods to overcome the diagnostic dilemma of this rare tumor.

Cuticular Poroma: A Rare Poroma Variant Simulating a Malignant Neoplasm That Often Harbors YAP1::NUTM1 Fusions Similar to Their Conventional Counterparts

ABSTRACT

Cuticular poroma is a rare variant of poroma composed of exclusively or predominantly cuticular cells, namely of large cells with ample eosinophilic cytoplasm. We report 7 cases of this rare tumor identified among 426 neoplasms diagnosed as poroma or porocarcinoma. The patients were 4 males and 3 females, ranging in age from 18 to 88 years. All presented with a solitary asymptomatic nodule. The location included knee (2 cases), shoulder, thigh, shin, lower arm, and neck (each 1). All lesions were surgically removed. No evidence of disease was observed in 5 patients with available follow-up (range 12-124 months).Microscopically, all neoplasms were composed of variably sized, focally closed packed, or interconnecting nodules constituted mostly of cuticular cells. Small poroid cells were a focal feature in 5 tumors, whereas in the remaining 2 cases, poroid cells with conspicuous but still in minority. Five neoplasms were somewhat asymmetric, with irregular outlines. Ductal differentiation and intracytoplasmic vacuoles were seen in 6 tumors. Other features variably encountered were conspicuous intranuclear pseudoinclusions, cystic change, occasional multinucleated cells, increased mitoses, and stromal desmoplasia. Four of the 5 tumors analyzed with next-generation sequencing yielded YAP1::NUTM1 fusions. In addition, various mutations, mostly of unknown significance were identified in one neoplasm.

Eccrine Porocarcinoma: A Review of the Literature

Eccrine porocarcinoma (EPC) constitutes a rare malignant adnexal tumor, which accounts for about 0.005-0.01% of all cutaneous malignancies. It may develop de novo or arise from an eccrine poroma, after a latency period of years or even decades. Accumulating data suggest that specific oncogenic drivers and signaling pathways may be implicated in its tumorigenesis, while recent data have demonstrated a high overall mutation rate attributed to UV exposure. Diagnosis may be challenging and should rely on the combination of clinical, dermoscopical, histopathological and immunohistochemical findings. The literature is controversial regarding tumor behavior and prognosis and, therefore, there is no consensus on its surgical management, utility of lymph-node biopsy and further adjuvant or systemic treatment. However, recent advances in tumorigenesis of EPC may aid in the development of novel treatment strategies, which could improve survival of advanced or metastatic disease, such as immunotherapy. This review presents an update of the epidemiology, pathogenesis and clinical presentation of EPC and summarizes current data on diagnostic evaluation and management of this rare cutaneous malignancy.

Recent advances in the role of Yes-associated protein in dermatosis

BACKGROUND

Dermatosis is a general term for diseases of the skin and skin appendages including scleroderma, psoriasis, bullous disease, atopic dermatitis, basal cell carcinoma, squamous cell carcinoma, and melanoma. These diseases affect millions of individuals globally and are a serious public health concern. However, the pathogenesis of skin diseases is not fully understood, and treatments are not optimal. Yes-associated protein (YAP) is a transcriptional coactivator that plays a role in the regulation of gene transcription and signal transduction.

AIMS

To study the role of Yes-associated protein in skin diseases.

MATERIALS AND METHODS

The present review summarizes recent advances in our understanding of the role of YAP in skin diseases, current treatments that target YAP, and potential avenues for novel therapies.

RESULTS

Abnormal YAP expression has been implicated in occurrence and development of dermatosis. YAP regulates the cell homeostasis, proliferation, differentiation, apoptosis, angiopoiesis, and epithelial-to-mesenchymal transition, among other processes. As well as, it serves as a potential target in many biological processes for treating dermatosis.

CONCLUSIONS

The effects of YAP on the skin are complex and require multidimensional investigational approaches. YAP functions as an oncoprotein that can promote the occurrence and development of cancer, but there is currently limited information on the therapeutic potential of YAP inhibition for cancer treatment. Additional studies are also needed to clarify the role of YAP in the development and maturation of dermal fibroblasts; skin barrier function, homeostasis, aging, and melanin production; and dermatosis.

YAP1::MAML2 fusions in poromatosis: A report of two patients

Poromatosis is a rare condition characterized by the development of multiple poromas, mainly reported in patients with a history of malignancy. Recently, frequent YAP1::MAML2 and YAP1::NUTM1 fusions have been described in poromas and porocarcinomas. To date, the molecular features of poromatosis have been investigated in one patient only, wherein the poromas harbored YAP1::MAML2 fusions. Herein, we present two additional cases of poromatosis with YAP1::MAML2 fusions. Case 1: An 81-year-old woman presented with nine papules on the scalp, trunk, and extremities persisting for a year. She had a history of breast cancer, with no information on the treatment. Seven papules were excised. Case 2: A 65-year-old woman presented with 21 lesions on her trunk and lower extremities persisting for 2 years. She had been diagnosed with breast cancer 11 years prior and had undergone partial mastectomy, radiotherapy, chemotherapy, and endocrine therapy. Four lesions were excised. All 11 lesions in both patients were histopathologically similar: anastomosing cords and strands extending from the epidermis, and poroid and cuticular cell proliferation with interspersed small ducts. The tumors showed diffuse nuclear expression of YAP1 N-terminus and loss of YAP1 C-terminus expression. No lesions showed NUT immunopositivity. Sanger sequencing identified YAP1::MAML2 fusions in the poromas of both patients.

An Unusual Case of a Scrotal Porocarcinoma and Review of the Literature

ABSTRACT

Porocarcinomas are rare tumors derived from the acrosyringium and eccrine ducts, which most commonly occur on the lower extremities or head and neck region in older adults. Microscopically, they invariably demonstrate continuity with the epithelium, showing downgrowth of broad anastomosing bands with more infiltrative intradermal cords and nests of pleomorphic tumor cells with ductal lumina; an associated poroma may also be seen. We report an unusual case of a porocarcinoma arising on the scrotum of a 55-year-old man. Because of the extraordinary location and the presence of keratinizing squamous differentiation, distinction from a squamous cell carcinoma was particularly challenging. Close examination revealed the presence of a co-existing poroma, and immunohistochemistry revealed loss of YAP1 with diffuse nuclear expression of NUT in both the porocarcinoma and poroma components. This finding is particularly suggestive of a YAP1::NUTM1 fusion which has been reported to be highly specific for poroid neoplasms. Distinction of porocarcinoma from its mimics is important due to the frequent aggressive behavior of this neoplasm.

Clinicopathological and genomic copy number variation analysis in nodular hidradenoma and hidradenocarcinoma with focus on prognostically important features

Nodular hidradenoma is a cutaneous adnexal tumor of sweat gland origin, characterized by its diverse but overlapping histomorphologic features with other skin tumors. In addition, distinction of benign hidradenoma and its malignant counterpart hidradenocarcinoma can be challenging, especially in prognostic prediction. We retrospectively reviewed pathological features of 29 cases, including benign nodular hidradenoma (n = 17) and hidradenocarcinoma (n = 12), with clinical follow-up ranging from 18 to 216 months. Genomic copy number variation (CNV) was studied in selected cases (n = 18) by single nucleotide polymorphism microarray. None of the benign hidradenomas (0/17) or low-grade hidradenocarcinomas (0/6) had recurrence or metastasis after complete excision, whereas all 6 high-grade hidradenocarcinomas (6/6) showed locally destructive disease, recurrence, or local metastases. In benign hidradenomas, CNV abnormality was absent in all clear cell hidradenomas (0/5) but was detected in a considerable portion of poroid hidradenoma (3/5), with number of abnormalities ranging 2, 4, and 9. In malignant cases, regardless of morphological classification, both low-grade hidradenocarcinomas demonstrated limited CNV abnormalities in 2 areas (2/2), whereas all high-grade hidradenocarcinomas contained 8 or more CNV abnormalities (6/6). No disease-associated death was recorded in the cohort except one case was lost to follow-up after the development of metastatic disease. Overall, the findings support that genomic CNV abnormalities may serve as a sensitive but less specific tool in detecting malignancy in these tumors, and potentially have a role in predicting clinical behavior particularly in the tumors of nonporoid morphology.

YAP1-NUTM1 Gene Fusion in Eccrine Porocarcinoma with Late Metastatic Recurrence: A Case Report

Abstract is missing (Short communication)

Molecular analysis of NUT-positive poromas and porocarcinomas identifies novel break points of YAP1::NUTM1 fusions

BACKGROUND

Poromas, and their malignant counterparts, porocarcinomas, harbor recurrent translocations involving YAP1-MAML2, YAP1-NUTM1, and infrequently WWTR1-NUTM1; YAP1-NUTM1 being the most common in porocarcinomas. NUT immunohistochemistry (IHC) can be used to identify NUTM1-translocated tumors. This study sought to investigate potential novel NUTM1-fusion partners among NUT IHC-positive poromas and porocarcinomas.

METHODS

13 NUT IHC-positive poroid tumors (4 poromas, 9 porocarcinomas) were identified within a multi-institutional international cohort. Next Generation Sequencing (NGS) assessed for NUTM1 fusion partners.

RESULTS

NGS detected a NUTM1 fusion in 12/13 cases: YAP1-NUTM1 (11/12 cases) and WWTR1-NUTM1 (1/12 cases). Two of the cases (2/12) with NUTM1 fusion were not called by the NGS algorithm but had at least one read spanning YAP1-NUTM1 breakpoints upon manual review. A NUTM1 fusion was not identified in one case, however, the sample had low RNA quality. The following fusion events were identified: YAP1 exon 4 :: NUTM1 exon 3 in six cases, YAP1 exon 6 :: NUTM1 exon 2 in one case, YAP1 exon 3 :: NUTM1 exon 3 in three cases, WWTR1 exon 3 :: NUTM1 exon 3 in one case and YAP1 exon 8 :: NUTM1 exon 3 fusion in one case.

CONCLUSION

While no novel NUTM1 fusion partners were identified within our cohort, twelve of thirteen cases had discoverable NUTM1 fusions; YAP1-NUTM1 fusion was detected in 11 cases (92%) and WWTR1-NUTM1 in 1 case (8%). These data corroborate findings from other recent investigations and further substantiate the utility of NUT IHC in diagnosing a subset of poroid neoplasms. Additionally, two of our cases harbored fusions of YAP1 exon 6 to NUTM1 exon 3 and YAP1 exon 8 to NUTM1 exon 2, which have not been reported before in poroid neoplasms and indicate novel break points of YAP1.

Porocarcinoma - a review

From the first report in 1969 to the present day, diagnosis of eccrine porocarcinoma, also known simply as porocarcinoma (PC), remains a challenge. This review presents a concise update of the history, pathogenesis, epidemiology, diagnosis, management and prognosis of this rare sweat gland neoplasm. It differentiates towards the intraepidermal spiral ducts in the eccrine gland, is more common in those over 60 years and often affects the head, neck and lower extremities. PC presents as a dome shaped papule, plaque or nodule growing over weeks to months. The exact incidence is unknown but appears to be rising. Diagnosis is difficult because of variable presentations and similar clinical and histological features to cutaneous squamous cell carcinoma. Management involves removal of the tumour, usually using wide local excision or Mohs micrographic surgery. Prognosis is poor with PC recurring after surgery in 35%. Given the lack of standardised protocols and risk profiles, further studies would help better the understanding of PC.

Molecular pathology of skin adnexal tumours

AIMS

Tumours of the cutaneous adnexa arise from, or differentiate towards, structures in normal skin such as hair follicles, sweat ducts/glands, sebaceous glands or a combination of these elements. This class of neoplasms includes benign tumours and highly aggressive carcinomas. Adnexal tumours often present as solitary sporadic lesions, but can herald the presence of an inherited tumour syndrome such as Muir-Torre syndrome, Cowden syndrome or CYLD cutaneous syndrome. In contrast to squamous cell carcinoma and basal cell carcinoma, molecular changes in adnexal neoplasia have been poorly characterised and there are few published reviews on the current state of knowledge.

METHODS AND RESULTS

We reviewed findings in peer-reviewed literature on molecular investigations of cutaneous adnexal tumours published to June 2021.

CONCLUSIONS

Recent discoveries have revealed diverse oncogenic drivers and tumour suppressor alterations in this class of tumours, implicating pathways including Ras/MAPK, PI3K, YAP/TAZ, beta-catenin and nuclear factor kappa B (NF-κB). These observations have identified novel markers, such as NUT for poroma and porocarcinoma and PLAG1 for mixed tumours. Here, we provide a comprehensive overview and update of the molecular findings associated with adnexal tumours of the skin.

NUTM1-Rearranged Neoplasms-A Heterogeneous Group of Primitive Tumors with Expanding Spectrum of Histology and Molecular Alterations-An Updated Review

Nuclear protein of testis (NUT), a protein product of the NUTM1 gene (located on the long arm of chromosome 15) with highly restricted physiologic expression in post-meiotic spermatids, is the oncogenic driver of a group of emerging neoplasms when fused with genes involved in transcription regulation. Although initially identified in a group of lethal midline carcinomas in which NUT forms fusion proteins with bromodomain proteins, NUTM1-rearrangement has since been identified in tumors at non-midline locations, with non-bromodomain partners and with varied morphology. The histologic features of these tumors have also expanded to include sarcoma, skin adnexal tumors, and hematologic malignancies that harbor various fusion partners and are associated with markedly different clinical courses varying from benign to malignant. Most of these tumors have nondescript primitive morphology and therefore should be routinely considered in any undifferentiated neoplasm. The diagnosis is facilitated by the immunohistochemical use of the monoclonal C52 antibody, fluorescence in situ hybridization (FISH), and, recently, RNA-sequencing. The pathogenesis is believed to be altered expression of oncogenes or tumor suppressor genes by NUT-mediated genome-wide histone modification. NUTM1-rearranged neoplasms respond poorly to classical chemotherapy and radiation therapy. Targeted therapies such as bromodomain and extraterminal domain inhibitor (BETi) therapy are being developed. This current review provides an update on NUTM1-rearranged neoplasms, focusing on the correlation between basic sciences and clinical aspects.

Skin adnexal carcinoma with BRD3-NUTM2B fusion

NUT carcinomas are genetically defined epithelial neoplasms. Most tumors harbor fusions of NUTM1 with BRD4 or BRD3. Their histopathologic features have been predominantly reported as undifferentiated or poorly differentiated squamous cell carcinoma, and clinically they tend to be aggressive cancers. However, recent studies have revealed a broader spectrum of NUTM1-rearranged neoplasms with several new fusion partners and associated variable histopathologic phenotypes and clinical behaviors, including benign and malignant cutaneous poroid tumors. We report herein a primary invasive carcinoma of skin adnexal origin with a previously undescribed fusion between BRD3 and NUTM2B. The tumor occurred on the shoulder of a 7-year-old girl and was excised with negative margins. A sentinel lymph node was positive. After follow-up of 23 months, and without systemic treatment, the child remains free of tumor. This case expands the spectrum of NUT carcinomas by including a skin adnexal variant with follicular infundibular differentiation, a novel genomic aberration, and preliminary evidence of a less aggressive clinical course.