ECP 2023 Abstracts

S190 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-05-041 Epidermolytic acanthoma: a case series of two cases and review of distinctive histological features M. Slevin*, R. Williams *Dorevitch Pathology, Australia Background & objectives: Epidermolytic acanthoma is an uncom- mon and likely underdiagnosed benign acanthotic skin lesion. Two cases diagnosed at our institution are presented with photomicrographs demonstrating key features. Clinical presentation is non-specific, and diagnosis relies on familiarity with the histological features. Methods: We present two cases of epidermolytic acanthoma. Clini- cally, Case A was a 3mm solitary lesion excised from the calf of a 28-year-old woman. Case B was a solitary cyst excised from the back of a 60-year-old woman. Sections from both excised specimens were formalin fixed and rou- tinely processed and stained with haematoxylin and eosin for histo- pathological examination. Results: Microscopically, Case A consisted of a dilated cup-shaped acanthotic infundibular lesion. Case B was an invaginating corrugated epidermal hyperkeratotic epidermal lesion. Both cases demonstrated characteristic epidermal changes of hyper- keratosis, hypergranulosis and epidermal degeneration with coarse keratohyaline granules and reticular eosinophilic material consistent with epidermolytic hyperkeratosis. Both cases had characteristic histopathological features of epidermo- lytic acanthoma. Epidermolytic hyperkeratosis is a focal feature of numerous entities and changes must occupy more than 50% of the lesion surface for a diagno- sis of EA. Predominantly solitary lesions, they occur across anatomical sites with a similar distribution in both sexes, although multiple genital lesions appear to be more common in males. Conclusion: Non-specific clinical presentation as a small asymptomatic keratotic papule means that recognising these classic histological features is few to diagnosis. Distinguishing epidermolysis from koilocytic change is crucial, especially in genital locations where multiple EAs are most common and misdiagnosis may cause harm. Epidermolytic ichthyosis, an inherited dermatosis due to mutations in keratins 1, 2, or 10 demon- strates identical lytic epidermal changes and altered keratin expression is postulated to have a role in pathogenesis of epidermolytic acanthoma. E-PS-05-042 A rare glimpse of monkeypox histology- insights from an unusual case F.M. Soares Nogueira*, A.E. Teles, A. Magarreiro Silva, J. Nogueira, J. Pina Alves, D. Gomes Pinto *Hospital Garcia de Orta, EPE, Portugal Background & objectives: Monkeypox is a zoonotic infection caused by the Monkeypox virus. Since early 2022, cases of Monkeypox have been reported in countries where the disease is not endemic. The aim of this poster is to present this rare and challenging pathology. Methods: The methods employed in this case report encompassed patient assessment, histological analysis of biopsy specimens, digitiza- tion of histological slides, molecular testing and clinical data analysis. Results: A 30-years-old male patient presented with multiple ulcera- tions with a necrotic base, along with vesicles and pustules in the geni- tal, perianal and perioral regions, accompanied by pruritus. An incisional skin biopsy was taken from two lesions, revealing dys- keratosis, spongiosis, and ballooning of the epidermis. In the dermis, we observed a moderate superficial and deep inflammatory infiltrate, perivascular and perianexal, consisting of lymphocytes, neutrophils and eosinophils. In one of the biopsies, there was also a focal full epidermal necrosis accompanied by rare nuclear cytopathic effect. Further testing was performed, and the diagnosis was confirmed using DNA Polymerase Chain Reaction molecular testing. Conclusion: Monkeypox is an emerging disease that poses signifi- cant diagnostic challenges due to its clinical and histological similar- ities with other diseases, including other virus families such as Her- pesviridae, which encompasses herpes simplex virus and varicella, as well as other members of the Poxviridae family, such as smallpox. By providing a unique insight into Monkeypox histology, this case report underscores the significance of employing molecular techniques as the optimal approach for prompt and precise diagnosis. E-PS-05-043 A case of acquired reactive perforating collagenosis: a challenging diagnosis A. Solombrino*, V. Dell’Anna *Ospedale “Vito Fazzi”, Lecce, Italy Background & objectives: Reactive perforating collagenosis is a rare disease belonging to the group of perforating dermatosis. Two types are described: inherited having a childhood onset and acquired manifesting in adulthood. This report describes a case of acquired reactive perforat- ing collagenosis (ARPC). Methods: A 66-year old woman with a history of hypothyroidism and hypertension consulted for multiple umbilicated papules and nodules with a central keratin plug growing on her hands, arms, legs and face. The lesions developed over a period of several months, were not related to minor trauma and showed no regression after steroid treatment. Exci- sional biopsies were performed. Results: Microscopic examination revealed a dense inflammatory infil- trate of lymphocytes, plasma cells and histiocytes aggregating around degenerated collagen bundles in both superficial and deep dermis, in a crater-fashion. Sparse collagen fibres were vertically oriented toward the surface and showed transepidermal penetration and elimination, mixed with neutrophils and tissue debris. In literature ARPC is typically asso- ciated to a systemic disease, especially diabetes and its complications, so the patient underwent multiple tests to exclude increased blood glucose level and kidney failure as well as infections, autoimmune and haemato- logical disorders. In this case systemic examination was unremarkable. Conclusion: ARPC is un uncommon dermatosis of unknown aetiol- ogy characterised by transepidermal elimination of degenerated der- mal collagen. It occurs in adults in association with diabetes and renal insufficiency, but it can be linked to many other diseases, for example thyroid disorders like the case presented, and even to some malignan- cies. Therefore patients need clinical, biochemical, haematological and immunological workup. Currently, there is not standard therapy, but treatment options can be both topic and systemic. Management of coexisting diseases is also beneficial. E-PS-05-044 Merkel cell carcinoma with divergent squamous differentiation: a rare case and short literature review E. Souka*, G. Galanopoulos, G.M. Stanc, L. Karelis, K. Ntatsis, O. Tzaida *Pathology Department Metaxa Cancer Hospital, Greece Background & objectives: Merkel cell carcinoma (MCC), also known as primary cutaneous neuroendocrine carcinoma, is a rare aggressive cancer, affecting mainly sun-exposed skin areas of elderly and immu- nosuppressed patients. Methods: A 75-year-old male with a medical history of chronic lym- phocytic leukaemia (CLL) presented to the dermatology clinic with an ulcerated back skin lesion measuring 18mm which was incompletely removed and diagnosed as metatypical basal cell carcinoma. After 6