Navigating Head and Neck Porocarcinoma: Systematic Review with Special Emphasis on Surgical Safety Margins.

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.

Epidermodysplasia verruciformis-associated eccrine neoplasm: a rare entity with distinctive clinical and histopathologic features.

Most tumors are caused by inherited or acquired genetic changes. However, a subset of tumors is driven by viral infection including Kaposi sarcoma, nasopharyngeal carcinoma, and others. Human papillomavirus (HPV) is an especially common cause of epithelial cancers and hyperplasias. Epidermodysplasia verruciformis (EDV) is a rare type of HPV infection with characteristic histopathologic features and a unique spectrum of HPV subtypes. We report here a distinctive form of EDV-associated eccrine neoplasia. Seven tumors from two patients were analyzed and show highly uniform features including multiple clustered clinical lesions, multifocal epidermal origin, eccrine differentiation with close association with the acrosyringium, an anastomosing growth pattern, and a bland monotonous poroid-to-basaloid cytomorphology. Clinical follow-up for one patient has been benign to date. These tumors show strong similarity to two previously reported cases, suggesting that this type of EDV-associated eccrine neoplasia may represent a rare but reproducible form of skin adnexal tumor with distinctive clinicopathologic features.

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.

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.

A Case of Eccrine Syringofibroadenoma Related to Senile Gluteal Dermatosis.

Eccrine syringofibroadenoma (ESFA) is a tumor of eccrine ductal differentiation. ESFA is a rare disease, with only approximately 80 cases reported worldwide. ESFA can be classified into five subtypes. Senile gluteal dermatosis (SGD) was first reported in Japan in 1979. It is a relatively common geriatric dermatosis in East Asia, and characterized by hyperkeratotic lichenified skin lesions in the gluteal region. An 86-year-old woman presented with a solitary recurrent dark brown plaque in the sacral area. There was a hyperkeratotic lichenified brownish patch around the plaque, which was clinically considered SGD. Histopathological examination of biopsy specimen revealed thin anastomosing reticulated strands of basaloid cuboidal cells. The tumor extends from the basal layer of the epidermis to the dermis. These findings are consistent with those of ESFA. The patient was treated with total excision of the skin lesion. Reactive ESFA is related to tissue regeneration and remodeling after damage, such as trauma and burns. There is no literature reporting ESFA related to SGD so far, but there have been few reports of cases occurring in soles or buttocks, which are constantly under pressure. This is the first report on reactive ESFA related to SGD, and further research is needed to reveal the pathogenic mechanism.

Eccrine Poroma with Concurrent Basal Cell Carcinoma: A Rare Combination.

Eccrine poroma (EP) is a benign skin appendicular tumor that differentiates into the terminal sweat duct and is often differentiated from basal cell carcinoma (BCC) and seborrheic keratosis. This report describes a 58-year-old woman who presented with left occipital plaque. Histopathological analysis showed that the tumor cells were located in the lower part of the epidermis. The tumor cells were cuboidal or circular basal-like cells of the same size. The surrounding cells were not arranged in a palisade shape. Scattered tumor clusters composed of basal-like cells were also seen in the dermis, staining basophilic, and the surrounding cells were arranged in a palisade pattern. Immunohistochemistry showed that BerEP4, epithelial membrane antigen EMA, carcinoembryonic antigen CEA, Bcl-2, CD10, CK7 were positive, AR, PAS were negative. According to the pathological examination and immunohistochemical results, a case of eccrine poroma with concurrent basal cell carcinoma was diagnosed.

Porocarcinoma Concurrent with Psoriasis Vulgaris: The First Report.

Psoriasis is a common chronical inflammatory skin disease with a prevalence of 2%-4% worldwide. In contrast, porocarcinoma is a relatively rare cutaneous neoplasm and an associated localization of both lesions is rare. Here, we describe the first case of porocarcinoma in a patient with psoriasis. A 71-year-old Japanese man was referred to our clinic for evaluation of nodule within a keratotic plaque of 20-years history on his leg. Histopathological examination showed that the plaque revealed acanthosis with regular elongation of rete ridges, agranulosis and the presence of Munro microabscesses. In contrast, massive proliferation of atypical poroid cells and a few cuticular cells in the dermis were seen in the nodule. We speculated that it is likely the porocarcinoma was caused by the elevated risk of skin cancer due to chronic inflammatory process of psoriasis itself in our patient.

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.

Combined tumour of aberrant cytokeratin expressing acral lentiginous melanoma and poroma: Diagnostic challenge.

Combined tumours are uncommon and therefore these tumours may pose a diagnostic challenge. In the current case report, it is aimed to present the clinicopathological features of a combined tumour including melanoma with aberrant cytokeratin expression and poroma.

Wide Local Excision for Eccrine Porocarcinoma of the Forearm.

Eccrine porocarcinoma is a rare and aggressive cutaneous malignancy that develops in the seventh and eight decades of life. We present a 76-year-old male with eccrine porocarcinoma developing from a long standing previously benign lesion who underwent successful treatment with wide local excision. It can also develop de novo, presenting most commonly as a mass or nodule. Tissue biopsy with histopathology is required to confirm the diagnosis. Wide local excision is recommended for local disease. Radiation and chemotherapy can be used as adjuncts in advanced and metastatic disease. Given its rarity, there are no guidelines to direct therapy for locally advance or metastatic disease and for follow-up. Further studies are needed to better understand and guide management of this entity.

The role of line-field confocal optical coherence tomography (LC-OCT) in the diagnosis of eccrine poroma: A case report.

Poroma is skin cancer that arises from the sweat gland cells. Its diagnosis could be difficult. Line-field optical coherence tomography (LC-OCT) is a novel imaging technique that has shown promise in the diagnosis and monitoring of various skin conditions. We report a case of poroma diagnosed by LC-OCT.

18F Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Findings in a Case of Metastatic Eccrine Porocarcinoma - An Extremely Rare Malignant Adnexal Tumor.

Porocarcinoma is a rare malignant neoplasm of eccrine sweat glands representing 0.005 to 0.1% of all cutaneous tumors. As eccrine porocarcinoma carries a high risk of recurrence and metastases, early diagnosis and management are crucial to lower mortality rate. We present the case of porocarcinoma in a 69-years-old woman who underwent 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for staging the disease. PET/CT showed metabolically active multiple cutaneous lesions and also picked up lymph nodal and distant metastases to lungs and breast accurately. PET/CT is useful for accurate staging of the disease and for treatment planning.

Recurrent PAK2 rearrangements in poroma with folliculo-sebaceous differentiation.

AIMS: Poroma is a benign adnexal neoplasm with differentiation towards the upper portion of the sweat gland apparatus. In 2019, Sekine et al. demonstrated recurrent YAP1::MAML2 and YAP1::NUTM1 fusion in poroma and porocarcinoma. Follicular, sebaceous and/or apocrine differentiation has been reported in rare cases of poroma and whether these tumours constitute a variant of poroma or represent a distinctive tumour is a matter to debate. Herein we describe the clinical, immunophenotypic, and molecular features of 13 cases of poroma with folliculo-sebaceous differentiation. METHODS AND RESULTS: Most of the tumours were located on the head and neck region (n = 7), and on the thigh (n = 3). All presented were adults with a slight male predilection. The median tumour size was 10 mm (range: 4-25). Microscopically, lesions displayed features of poroma with nodules of monotonous basophilic cells associated with a second population of larger eosinophilic cells. In all cases, ducts and scattered sebocytes were identified. Infundibular cysts were present in 10 cases. In two cases high mitotic activity was noted, and in three cases cytologic atypia and areas of necrosis were identified. Whole transcriptome RNA sequencing demonstrated in-frame fusion transcripts involving RNF13::PAK2 (n = 4), EPHB3::PAK2 (n = 2), DLG1::PAK2 (n = 2), LRIG1::PAK2 (n = 1), ATP1B3::PAK2 (n = 1), TM9SF4::PAK2 (n = 1), and CTNNA1::PAK2 (n = 1). Moreover, fluorescence in situ hybridisation (FISH) analysis revealed PAK2 rearrangement in an additional case. No YAP1::MAML2 or YAP1::NUTM1 fusion was detected. CONCLUSION: Recurrent fusions involving the PAK2 gene in all analysed poroma with folliculo-sebaceous differentiation in this study confirms that this neoplasm represents a separate tumour entity distinct from YAP1::MAML2 or YAP1::NUTM1 rearranged poromas.

Clinicopathological Spectrum of Benign Skin Adnexal Tumors in the Pakistani Population: A Single-Center Study.

Background Skin adnexal tumors (SATs) are categorized per the site of origin, for example, hair follicles, sebaceous glands, and sweat glands. In our population, there is limited information related to the clinicopathological characteristics of these tumors. Management and prognosis depend largely upon the morphological type of the tumor. In this study, we assessed the disease spectrum and most prevalent subtypes of benign SATs. Methodology An analysis of 565 cases was conducted in this cross-sectional study between January 2018 and December 2022, using a non-probability consecutive sampling approach. Patient age, gender, site of involvement, and diagnosis were documented according to the fourth edition of the WHO Classification of Skin Tumors published in 2018. Data were entered and analyzed using SPSS Version 26.0 (IBM Corp., Armonk, NY). Results Our study had 565 patients, out of which 271 (47.9%) were males and 294 (52.1%) were females. The mean age was 40.97±19.3 years (range, 2-100 years). Anatomical site variations were as follows, head and neck (n=336, 59.4%), extremities (n=124, 22%), trunk (n=84, 14.9%), and genital areas (n=21, 3.7%). The most common histological subtypes of benign SATs were sweat gland origin (n=350, 62.0%), followed by hair follicle origin (n=161, 28.5 %), and sebaceous gland origin (n=54, 9.5%). Conclusion Sweat gland tumors were the most prevalent class of benign SATs in our study, in which hidradenoma and poroma were the most frequent subtypes. Hair follicle origin was the second most prevalent class of tumors with pilomatricoma being the most frequent. Sebaceous tumors were overall uncommon; nevus sebaceous of Jadasshon was the most common tumor in this class.

Cryotherapy for Eccrine Poroma: A Case Report.

Eccrine poroma (EP) is a benign adnexal tumor that is derived from acrosyringium, the intraepidermal eccrine duct of sweat glands. The standard treatment for eccrine poroma is complete excision. However, this case report highlights cryotherapy as one of the modalities in treating eccrine poroma. We present a case of a 33-year-old male patient who was a known case of generalized vitiligo since he was nine years old. During our skin checkup before starting him on phototherapy, we found a mass over the palmar aspect of the middle finger of the right hand that started to appear five years ago. The mass gradually increased in size, was painless, has no discharge, and was not associated with a history of trauma or infection. The review of systems was unremarkable. Skin examination revealed an asymptomatic, 2.0 × 1.5 cm-sized, solitary, collarette-encircled, dome-shaped, flesh-colored, non-pigmented, deep-red nodule protrusion from the palmar aspect of the middle finger of the right hand. Poroma was considered as the diagnosis, and a punch skin biopsy was performed to confirm the diagnosis and to roll out pyogenic granuloma, amelanotic melanoma, and porocarcinoma as differential diagnoses. A 3 mm punch skin biopsy was performed under local anesthesia and was found to be histologically consistent with eccrine poroma. Hence, cryosurgery was chosen based on histological favorable features. We used cryospray in a single session of 15 seconds in three applications, with five-second intervals in between (skin frosting recovery). Furthermore, the lesion was completely curative with a single session of cryotherapy. The patient followed up for one year without evidence of recurrence.

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.

Poroma. Estudio retrospectivo de 80 pacientes en un hospital terciario / Poroma: A Retrospective Series of 80 Patients at a Tertiary Care Hospital

Introducción El poroma es un tumor anexial benigno exclusivo de la piel que tiene una predilección por la piel palmoplantar.Objetivo Analizar las características clínicas del poroma en nuestra población.Material y métodosEstudio retrospectivo de los pacientes con poroma diagnosticados entre 2002 y 2021. Se revisaron las historias clínicas para obtener los siguientes datos: edad, sexo, localización, número de lesiones, diámetro, tiempo de evolución, características clínicas de los tumores, diagnóstico clínico de sospecha, estado de los márgenes de resección, desarrollo de recidiva y tiempo de seguimiento. Las variables categóricas se compararon mediante la prueba exacta de Fisher. Las variables continuas se compararon mediante la prueba t de Student cuando se confirmó la normalidad de la distribución de datos. De lo contrario, se realizó la prueba U de Mann-Whitney. ResultadosSe incluyeron 80 pacientes con poroma (31 mujeres y 49 varones, con una edad mediana de 65,5 años y rango intercuartílico [RIC] 29 años). La mediana del tiempo medio de evolución fue de 12 meses, RIC 21 meses y la mediana del diámetro 8mm, RIC 7. Ningún paciente presentó lesiones múltiples. Las lesiones se localizaron en la cabeza y el cuello en 13 casos, en el tronco en 13, en las extremidades superiores en 11 y en las extremidades inferiores en 43. Veintitrés lesiones (28,8%) se localizaron en piel acral (palmas 5, plantas 18). La localización en el cuero cabelludo fue más frecuente en el sexo femenino (p=0,041). Las lesiones acrales fueron con mayor frecuencia eritematosas (p=0,014). Cinco pacientes presentaron recidiva local. Conclusiones Aunque los poromas son especialmente frecuentes en la piel acral, sobre todo de los pies, en la mayoría de pacientes se localizan en otras regiones anatómicas (71,3%). El aspecto clínico clásico de lesión exofítica eritematosa se observa con una mayor frecuencia en las lesiones acrales. (AU)

Background Poroma is a benign, exclusively cutaneous, adnexal tumor with a predilection for palmoplantar skin. Objective To analyze the clinical characteristics of poroma in our population.Material and methodsRetrospective study of patients diagnosed with poroma between 2002 and 2021. We conducted a chart review to record age; sex; number, location, and diameter of lesions; time since onset; clinical characteristics; suspected clinical diagnosis; resection margin status; recurrences; and follow-up duration. Categorical variables were compared using the Fisher exact test. Continuous variables were compared using the t test or the Mann-Whitney U test depending on whether they were normally or nonnormally distributed. Results We studied 80 patients (31 women and 49 men) with a median (interquartile range [IQR]) age of 65.5 (29) years. Median time since onset of poroma was 12 (21) months. Median lesion diameter was 8(7)mm, and none of the patients had multiple lesions. The lesions were located on the head and neck in 13 cases, the trunk in 13, the upper extremities in 11, and the lower extremities in 43. Twenty-three lesions (28.8%) were located at acral sites (5 on the palms and 18 on the soles). Women were more likely to have scalp lesions (P=.041). Acral lesions were more likely to be erythematous (P=.014). Five patients experienced local recurrence. Conclusions Although poromas are particularly common in acral locations (especially the feet), most of the lesions in our series (71.3%) were located elsewhere. Acral lesions were more likely to show the classic clinical features of erythema and exophytic growth. (AU)

[Translated article] Poroma: A Retrospective Series of 80 Patients at a Tertiary Care Hospital / Poroma. Estudio retrospectivo de 80 pacientes en un hospital terciario

Background Poroma is a benign, exclusively cutaneous, adnexal tumor with a predilection for palmoplantar skin. Objective To analyze the clinical characteristics of poroma in our population.Material and methods Retrospective study of patients diagnosed with poroma between 2002 and 2021. We conducted a chart review to record age; sex; number, location, and diameter of lesions; time since onset; clinical characteristics; suspected clinical diagnosis; resection margin status; recurrences; and follow-up duration. Categorical variables were compared using the Fisher exact test. Continuous variables were compared using the t test or the Mann–Whitney U test depending on whether they were normally or nonnormally distributed. Results We studied 80 patients (31 women and 49 men) with a median (interquartile range [IQR]) age of 65.5 (29) years. Median time since onset of poroma was 12 (21) months. Median lesion diameter was 8 (7)mm, and none of the patients had multiple lesions. The lesions were located on the head and neck in 13 cases, the trunk in 13, the upper extremities in 11, and the lower extremities in 43. Twenty-three lesions (28.8%) were located at acral sites (5 on the palms and 18 on the soles). Women were more likely to have scalp lesions (P=.041). Acral lesions were more likely to be erythematous (P=.014). Five patients experienced local recurrence. Conclusions Although poromas are particularly common in acral locations (especially the feet), most of the lesions in our series (71.3%) were located elsewhere. Acral lesions were more likely to show the classic clinical features of erythema and exophytic growth. (AU)

Introducción El poroma es un tumor anexial benigno exclusivo de la piel que tiene predilección por la piel palmoplantar. Objetivo Analizar las características clínicas del poroma en nuestra población. Material y métodos Estudio retrospectivo de los pacientes con poroma diagnosticados entre 2002 y 2021. Se revisaron las historias clínicas para obtener los siguientes datos: edad, sexo, localización, número de lesiones, diámetro, tiempo de evolución, características clínicas de los tumores, diagnóstico clínico de sospecha, estado de los márgenes de resección, desarrollo de recidiva y tiempo de seguimiento. Las variables categóricas se compararon mediante la prueba exacta de Fisher. Las variables continuas se compararon mediante la prueba t de Student cuando se confirmó la normalidad de la distribución de datos. De lo contrario, se realizó la prueba U de Mann-Whitney. Resultados Se incluyeron 80 pacientes con poroma (31 mujeres y 49 varones, con una edad mediana de 65,5años y rango intercuartílico [RIC] de 29 años). La mediana del tiempo medio de evolución fue de 12meses, RIC 21 meses, y la mediana del diámetro 8mm, RIC 7. Ningún paciente presentó lesiones múltiples. Las lesiones se localizaron en la cabeza y en el cuello en 13 casos, en el tronco en 13, en las extremidades superiores en 11 y en las extremidades inferiores en 43. Veintitrés lesiones (28,8%) se localizaron en piel acral (palmas 5, plantas 18). La localización en el cuero cabelludo fue más frecuente en el sexo femenino (p=0,041). Las lesiones acrales fueron con mayor frecuencia eritematosas (p=0,014). Cinco pacientes presentaron recidiva local. Conclusiones Aunque los poromas son especialmente frecuentes en la piel acral, sobre todo de los pies, en la mayoría de pacientes se localizan en otras regiones anatómicas (71,3%). El aspecto clínico clásico de lesión exofítica eritematosa se observa con una mayor frecuencia en las lesiones acrales. (AU)

Distinct regulations driving YAP1 expression loss in poroma, porocarcinoma and RB1-deficient skin carcinoma.

AIMS: Recently, YAP1 fusion genes have been demonstrated in eccrine poroma and porocarcinoma, and the diagnostic use of YAP1 immunohistochemistry has been highlighted in this setting. In other organs, loss of YAP1 expression can reflect YAP1 rearrangement or transcriptional repression, notably through RB1 inactivation. In this context, our objective was to re-evaluate the performance of YAP1 immunohistochemistry for the diagnosis of poroma and porocarcinoma. METHODS AND RESULTS: The expression of the C-terminal part of the YAP1 protein was evaluated by immunohistochemistry in 543 cutaneous epithelial tumours, including 27 poromas, 14 porocarcinomas and 502 other cutaneous tumours. Tumours that showed a lack of expression of YAP1 were further investigated for Rb by immunohistochemistry and for fusion transcripts by real-time PCR (YAP1::MAML2 and YAP1::NUTM1). The absence of YAP1 expression was observed in 24 cases of poroma (89%), 10 porocarcinoma (72%), 162 Merkel cell carcinoma (98%), 14 squamous cell carcinoma (SCC) (15%), one trichoblastoma and one sebaceoma. Fusions of YAP1 were detected in only 16 cases of poroma (n = 66%), 10 porocarcinoma (71%) all lacking YAP1 expression, and in one sebaceoma. The loss of Rb expression was detected in all cases except one of YAP1-deficient SCC (n = 14), such tumours showing significant morphological overlap with porocarcinoma. In-vitro experiments in HaCat cells showed that RB1 knockdown resulted in repression of YAP1 protein expression. CONCLUSION: In addition to gene fusion, we report that transcriptional repression of YAP1 can be observed in skin tumours with RB1 inactivation, including MCC and a subset of SCC.

Poroma: A Retrospective Series of 80 Patients at a Tertiary Care Hospital. / Poroma. Estudio retrospectivo de 80 pacientes en un hospital terciario.

BACKGROUND: Poroma is a benign, exclusively cutaneous, adnexal tumor with a predilection for palmoplantar skin. OBJECTIVE: To analyze the clinical characteristics of poroma in our population. MATERIAL AND METHODS: Retrospective study of patients diagnosed with poroma between 2002 and 2021. We conducted a chart review to record age; sex; number, location, and diameter of lesions; time since onset; clinical characteristics; suspected clinical diagnosis; resection margin status; recurrences; and follow-up duration. Categorical variables were compared using the Fisher exact test. Continuous variables were compared using the t test or the Mann-Whitney U test depending on whether they were normally or nonnormally distributed. RESULTS: We studied 80 patients (31 women and 49 men) with a median (interquartile range [IQR]) age of 65.5 (29) years. Median time since onset of poroma was 12 (21) months. Median lesion diameter was 8(7)mm, and none of the patients had multiple lesions. The lesions were located on the head and neck in 13 cases, the trunk in 13, the upper extremities in 11, and the lower extremities in 43. Twenty-three lesions (28.8%) were located at acral sites (5 on the palms and 18 on the soles). Women were more likely to have scalp lesions (P=.041). Acral lesions were more likely to be erythematous (P=.014). Five patients experienced local recurrence. CONCLUSIONS: Although poromas are particularly common in acral locations (especially the feet), most of the lesions in our series (71.3%) were located elsewhere. Acral lesions were more likely to show the classic clinical features of erythema and exophytic growth.