ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Methods: A 54-year-old male with no significant medical history presented with a cutaneous mass on the medial aspect of the left lower limb. Excisional biopsy specimen revealed a 3,6x3,5x1,2 cm grossly friable papillomatous lesion. Results: Histological sections showed a poorly circumscribed adnexal tumour with irregular borders. The morphological appearance was variable throughout the tumour. Epidermis showed papillomatosis and acanthosis, composed of neoplastic cells having large, clear eosinophilic cytoplasm and small nucleoli. The infiltrating component, extending from dermis into the subcutaneous adipose tissue, was not clearly demarcated from the epidermis. However, a distinct connection to the epidermal proliferation was also not observed. The infiltrative foci showed nests of relatively fusiform cells with eosinophilic cytoplasm and conspicuous nucleoli in a markedly hyalinized stroma. Mitotic activity was found to be prominent (2 mitoses per 10 high-power fields). No necrosis, no vascular or perineural invasion were observed. Conclusion: In conclusion, the tumour was evaluated to be consistent with atypical hidradenoma. To the best of our knowledge, there exists a limited number of cases of this neoplasm in the literature. This case report would contribute to our knowledge about this particular entity. The risk of recurrence and malignant potential of atypical hidradenomas are reported to be increased; therefore, recognising atypical features in an otherwise benign hidradenoma is crucial. E-PS-05-022 Secondary localized cutaneous amyloidosis in mycosis fungoides E. Aydemir*, I.E. Zemheri *Health Sciences University Umraniye Education and Training Hospital, Pathology Department, Turkey Background & objectives: Secondary localized cutaneous amyloido- sis is a histopathological finding that occurs in various in-flammatory skin diseases and epithelial skin tumours. It is often not clinically apparent. Cases of secondary cutaneous amyloidosis associated with mycosis fungoides are extremely rare. Methods: We presented a 25-year-old female, presented with flat patches and plaques on the trunk and extremities which appeared 10 years ago, and showed a persistent course. She had not received any medical treatment for her eruptions. Results: In the punch biopsy taken from the left leg of the patient, lymphocytes with hyperchromatic nuclei, lined up at the base of the epidermis, showing focal epidermotropism, containing peripheral halos, were observed. These lymphocytes were positive for CD3, CD4, CD8. The population of CD8+ cells predominated over that of CD4+ cells. In addition, homogeneous amorphous eosinophilic depositions were observed in the papillary dermis in focal areas. We performed Congo red staining, and the deposits were nega- tive for this staining, however positive staining was observed for HMWCK. Conclusion: Literature findings support the theory that amyloid materials are produced by epidermal damage. CD8+ cells are cyto- toxic in nature; therefore, in our case the infiltration of many CD8+ cells can be attributed to the formation of amyloid material from attacks on epidermal keratinocytes. E-PS-05-024 Subcutaneous fat necrosis of the newborn – case report of a rare entity T.M. Costa*, R. Sampaio *Centro Hospitalar Lisboa Ocidental, Portugal Background & objectives: Subcutaneous fat necrosis of the newborn (SCFN) is an uncommon panniculitis of full-term neonates. Its precise incidence is unknown and the pathogenesis remains unclear. SCFN often develops in neonates who have experienced hypoxia or other perinatal stress (obstetric trauma, hypothermia). Methods: We report a full-term girl born by vacuum-assisted vaginal delivery due to shoulder dystocia, that presented with consequent right clavicle fracture. Born to a 27-year-old mother with active COVID-19 infection and group B streptococcal (GBS) colonization, which was adequately treated at delivery. On the 4th day of life presented with multiple, tender erythematous nodules on the shoulder, axilla and back. Results: Initial laboratory tests for electrolytes were normal. The new- born was treated with prophylatic broad-spectrum antibiotics. On the 14th day of life an incisional biopsy of one of the lesions was per- formed. The histologic examination revealed normal epidermis and dermis, underlying lobular panniculitis with focal fat necrosis and mod- erate inflammatory infiltrate, composed by lymphocytes, histiocytes, multinucleated giant cells, eosinophils and neutrophils. The adipocytes showed needle-shaped clefts and crystals in a radial-type arrangement. On the 1st- month consultation there was slight improvement of the lesion but a mild hypercalcemia was detected (Ca2+ 5,8 mg/dL (N: 4,5 - 5,3)). The histopathological findings correlated with the clinical course confirmed the diagnosis of SFN. Conclusion: SFN has a generally good outcome with spontaneous resolution of skin lesions. Nevertheless, the diagnosis of this entity is important, once it may evolve with relevant systemic alterations, especially acute renal injury secondary to hypercalcemia, reason why monitoring is required. The main differential diagnosis for SFN is sclerema neonatorum (SN), a rare frequently fatal condition, in previously ill pre-term infants. SN presents as a rapidly spreading, diffuse confluent nodules and plaques, and it typically affects the legs, buttocks and trunk. E-PS-05-025 Onychocytic matricoma: a case report S. Gamba Torrez*, D. Parron Collar, A. Gartzia Rivero, Y. Aberas- turi Plata, S. Fernandez Sole, E. Oliva Dominguez, S. Acero Rodriguez, I. Orbegozo Arrizabalaga, I. Gantxegi Fernandez, I. Allende Markixana, I. Mendez Maestro, A. Fernández de Larrinoa Santamaría *Cruces University Hospital, Spain Background & objectives: Onychocytic matricoma (OCM) is a benign tumour of the nail matrix, first described by Perrin et al. in 2012. It represents an acanthoma of onychocytes that clinically manifests as a monodactilus longitudinal pachymelanonychia or xantholeucopachyonychia. A new case is described. Methods: A 70-year-old man with no medical history presented a yellowish-white thickened longitudinal stripe on the first finger of the right hand, with a more nodular erythematous zone on the lunula. It was asymptomatic but grew progressively and did not respond to topical treatment with calcipotriol/betametasone. A longitudinal biopsy of the nail matrix, nail bed and nail plate were performed. Results: Histologically, an epithelial acanthosis forming endo- phytic projections with blunt edges was observed, consisting of basaloid cells showing pseudosquamous eddies, which were formed by whorls of endokeratinization with an equal distribution of prekeratogenous zones and eosinophilic keratogenous zones. Scattered melanocytes could be seen, but pigmentation of the epi- thelial cells was not relevant. Changes in the dermis were mini- mal, with isolated lymphocytes. The main histological differential diagnosis is seborrheic keratosis, in which the squamous whorls are not cornified by the cells of the nail plate and, therefore, lack S212