A 40-year-old Caucasian man presented with a 2-year history of slow-growing white-blue dome-shaped asymptomatic nodule localized on the one-third lower part of his right arm (Fig. 1). The main histological component of the tumor consisted of the mixture of short spindle cells producing collagen fibers, lymphocytes, plasma cells and histiocytoid cells (Figs. 2-3). The histiocytoid cells had oval, folded nuclei with fine chromatin, inconspicuous nucleoli and thin nuclear membrane. Some of them presented longitudinal nuclear grooves (Fig. 4). The additional component of the histological texture was a well circumscribed area of mononucleated epithelioid cells characterized by coffee bean- or kidney-shaped nuclei and moderate amount of clear or eosinophilic cytoplasm (Fig. 5). The border between two components of neoplasm was sharp (Fig. 6).

Katarzyna Woszczyna1, Artur Kowalik2, Agnieszka Harazin-Lechowska1, Janusz Ryś1

1Department of Tumour Pathology, Maria Sklodowska-Curie Memorial Cancer Centre and Insitute of Oncology, Krakow Branch, Krakow, Poland
2Department of Molecular Diagnosis, Holycross Cancer Center, Kielce, Poland

Answers should be sent to the Editorial Office by 31.12.2016. The correct answer will be announced in the next issue of the Polish Journal of Pathology. All participants with the highest number of correct answers to the quizzes published in vol. 67 (4 issues) will be entered into the prize draw for a book.