UNASSIGNED: Maligne Schweißdrüsentumoren sind selten, wobei das ekkrine Porokarzinom (EP) das häufigste ist. Etwa 18 % der benignen ekkrinen Porome (EPO) entwickeln sich zum EP. Wissenschaftliche Studien haben erste Einblicke in die Mutationslandschaft von EPs geliefert. Allerdings wurden in nur wenigen Studien Genexpressionsanalysen durchgeführt. Dies hinterlässt eine Lücke im Verständnis der EP‐Biologie und potenzieller Treiber der malignen Transformation von EPO zu EP.
METHODS: Es wurde eine Transkriptomanalyse von 23 Proben primärer EP und normaler Haut (NH) durchgeführt. Die Ergebnisse aus den EP‐Proben wurden dann an 17 EP‐Proben getestet.
UNASSIGNED: Das Transkriptom‐Profiling zeigte eine Vielfalt in der Genexpression und deutete auf biologisch heterogene Subeinheiten sowie eine weit verbreitete Herunterregulierung von Genen im EP hin. Herunterregulierte Gene umfassten CD74, NDGR1, SRRM2, CDC42, ANXA2, KFL9 und NOP53. Die Expressionsniveaus von CD74, NDGR1, SRRM2, ANXA2 und NOP53 zeigten eine stufenweise Abnahme der Expression von NH über EPO zu EP, was die Hypothese unterstützt, dass das EPO einen Zwischenschritt in der EP‐Entwicklung darstellt.
UNASSIGNED: Die Studie zeigt, dass das EP molekular komplex ist und der evolutionäre Verlauf der Tumorinitiierung und ‐progression entspricht. Die Ergebnisse legen eine Beteiligung der p53‐Achse und des EGFR‐Signalwegs nahe. Eine größere Probenanzahl ist erforderlich, um diese Ergebnisse zu bestätigen.

OBJECTIVE: Malignant sweat gland tumors are rare, with the most common being eccrine porocarcinoma (EP). Approximately 18% of benign eccrine poroma (EPO) transit to EP. Previous research has provided first insights into the mutational landscape of EP. However, only few studies have performed gene expression analyses. This leaves a gap in the understanding of EP biology and potential drivers of malignant transformation from EPO to EP.
METHODS: Transcriptome profiling of 23 samples of primary EP and normal skin (NS). Findings from the EP samples were then tested in 17 samples of EPO.
RESULTS: Transcriptome profiling revealed diversity in gene expression and indicated biologically heterogeneous sub-entities as well as widespread gene downregulation in EP. Downregulated genes included CD74, NDGR1, SRRM2, CDC42, ANXA2, KFL9 and NOP53. Expression levels of CD74, NDGR1, SRRM2, ANXA2, and NOP53 showed a stepwise-reduction in expression from NS via EPO to EP, thus supporting the hypothesis that EPO represents a transitional state in EP development.
CONCLUSIONS: We demonstrated that EP is molecularly complex and that evolutionary trajectories correspond to tumor initiation and progression. Our results provide further evidence implicating the p53 axis and the EGFR pathway. Larger samples are warranted to confirm our findings.

Porocarcinoma (PC) is a rare adnexal tumor, mainly found in the elderly. The tumor arises from the acrosyringium of eccrine sweat glands. The risk of lymph node and distant metastasis is high. Differential diagnosis with squamous cell carcinoma is difficult, although NUT expression and YAP1 fusion products can be very useful for diagnosis. Currently, wide local excision is the main surgical treatment, although Mohs micrographic surgery is promising. To date, there is no consensus regarding the role of sentinel lymph node biopsy and consequential lymph node dissection. No guidelines exist for radiotherapy, which is mostly performed based on tumor characteristics and excision margins. Only a few studies report systemic treatment for advanced PC, although therapy with pembrolizumab and EGFR inhibitors show promise. In this review, we discuss epidemiology, clinical features, histopathological features, immunohistochemistry and fusion products, surgical management and survival outcomes according to stage, surgical management, radiotherapy and systemic therapy.

Eccrine porocarcinoma (EPC) is a rare skin adnexal malignancy with a high potential for metastases. The most common metastatic sites are the lymph nodes and lungs. CCutaneous metastasis is extremely rare, particularly the zosteriform variant, with fewer than 5 cases reported in the literature. Here, we report a unique case of EPC in a 71-year-old male, clinically presenting with multiple clusters of ulcerated nodules distributing as a zosteriform pattern throughout his upper left limb, along with draining lymphatic metastases and lymphedema.

OBJECTIVE: Porocarcinoma is a malignant sweat gland tumour differentiated toward the upper part of the sweat duct and may arise from the transformation of a preexisting benign poroma. In 2019, Sekine et al. demonstrated the presence of YAP1::MAML2 and YAP1::NUTM1 fusions in most poromas and porocarcinomas. Recently, our group identified PAK2-fusions in a subset of benign poromas. Herein we report a series of 12 porocarcinoma cases harbouring PAK1/2/3 fusions.
RESULTS: Five patients were male and the median age was 79 years (ranges: 59-95). Tumours were located on the trunk (n = 7), on the thigh (n = 3), neck (n = 1), or groin area (n = 1). Four patients developed distant metastases. Microscopically, seven cases harboured a benign poroma component and a malignant invasive part. Ductal formations were observed in all, while infundibular/horn cysts and cells with vacuolated cytoplasm were detected in seven and six tumours, respectively. In three cases, the invasive component consisted of a proliferation of elongated cells, some of which formed pseudovascular spaces, whereas the others harboured a predominant solid or trabecular growth pattern. Immunohistochemical staining for CEA and EMA confirmed the presence of ducts. Focal androgen receptor expression was detected in three specimens. Whole RNA sequencing evidenced LAMTOR1::PAK1 (n = 2), ZDHHC5::PAK1 (n = 2), DLG1::PAK2, CTDSP1::PAK1, CTNND1::PAK1, SSR1::PAK3, CTNNA1::PAK2, RNF13::PAK2, ROBO1::PAK2, and CD47::PAK2. Activating mutation of HRAS (G13V, n = 3, G13R, n = 1, Q61L, n = 2) was present in six cases.
CONCLUSIONS: Our study suggests that PAK1/2/3 fusions is the oncogenic driver of a subset of porocarcinomas lacking YAP1 rearrangement.

Eccrine porocarcinoma, sharing many features with other skin tumours, is diagnostically challenging. A conventional biopsy might be misleading and surgical excision becomes a primary diagnostic tool and a treatment method. However, the data on surgical safety margins are not consistent. We present a systematic review analysing the surgical margins of porocarcinoma in the head and neck area, which was conducted across the PubMed, Cochrane, and Web of Science databases including studies published from inception to November of 2023. In this systematic review, the PRISMA-ScR checklist was used, and a Cohen\'s Kappa coefficient of 0.92 was applied, indicating very good agreement between reviewers. Out of 529 identified articles, 18 studies yielding 20 cases in total were selected for a thorough analysis. Nine (45%) cases were observed in the facial regions, eight (40%) on the scalp, and three (5%) on the neck. The primary treatment of choice was wide local excision with safety margins ranging from 3 to 22 mm (mean: 10.1). It demonstrated that surgical margins do not differ by age or anatomic regions, with the main point of reference being the tumour size. As observed, the bigger the tumour, the wider the safety margins were. However, the limited disclosure of surgical safety margins in analysed case reports impeded our ability to define the minimum safety margins. Further investigation and a consensus on recommended safety margins are required.

BACKGROUND: Eccrine porocarcinoma (EPC) is a rare skin tumor that mainly affects the elderly population. Tumors often present with slow growth and a good prognosis. EPCs are usually distinguished from other skin tumors using histopathology and immunohistochemistry. However, surgical management alone may be inadequate if the tumor has metastasized. However, currently, surgical resection is the most commonly used treatment modality.
METHODS: A seventy-four-year-old woman presented with a slow-growing nodule in her left temporal area, with no obvious itching or pain, for more than four months. Histopathological examination showed small columnar and short spindle-shaped cells; thus, basal cell carcinoma was suspected. However, immunohistochemical analysis revealed the expression of cytokeratin 5/6, p63 protein, p16 protein, and Ki-67 antigen (40%), and EPC was taken into consideration. The skin biopsy was repeated, and hematoxylin and eosin staining revealed ductal differentiation in some cells. Finally, the patient was diagnosed with EPC, and Mohs micrographic surgery was performed. We adapted follow-up visits in a year and not found any recurrence of nodules.
CONCLUSIONS: This case report emphasizes the diagnosis and differentiation of EPC.

UNASSIGNED: Rare cancers, in aggregate, represent a significant burden of disease in oncology and remain therapeutically challenging to manage due to a lack of clinical trials. Eccrine porocarcinoma is a rare cutaneous sweat-gland malignancy for which there remains no standard approach to metastatic disease.
UNASSIGNED: We describe a patient diagnosed with metastatic disease, confirmed on bone biopsy; pathological analysis further revealed this was oestrogen receptor positive. She was commenced on the aromatase inhibitor letrozole, and denosumab, and showed a significant clinical and radiological response on bone scan within 7 months. At the time of report, over 2 years since commencing letrozole, she remains well with no evidence of progression.
UNASSIGNED: Our experience adds to the literature suggesting anti-oestrogen therapy can have significant benefit in patients with ER-positive non-breast cancer and is in keeping with increasing interest in therapies agnostic to site of origin but guided by expression/mutation of oncogenic drivers.

BACKGROUND: Porocarcinoma is a rare type of skin cancer that originates from sweat gland tumors. It is an aggressive malignant skin cancer that is difficult to diagnose clinically owing to its rarity and similarity to squamous cell carcinoma (SCC).
METHODS: This case involved a 92-year-old woman, a farmer by profession, presented with an exophytic and verrucous mass on her left palm that had formed 2 years prior and caused chronic pain and frequent bleeding. Initially, the patient was diagnosed with SCC using a punch biopsy; however, a repeat biopsy with additional immunohistochemical tests was performed for porocarcinoma. Ultimately, the patient was diagnosed with porocarcinoma and reconstruction was planned using a full-thickness skin graft. After treatment, the range of motion of the palm was preserved, and the aesthetic outcome was favorable. At 6 mo of follow-up, the patient was satisfied with the outcome.
CONCLUSIONS: Porocarcinoma is commonly misdiagnosed as SCC; therefore, clinicians should consider porocarcinomas when evaluating mass-like lesions on the hands.

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