1&2 A malignant round cell tumor characterized by nests and sheets of round cells separated by prominent fibrovascular septa. The tumor cells notably line these septa in a "picket-fence" arrangement while detaching in the center, creating a pseudo-alveolar pattern. Tumor cells exhibit hyperchromatic nuclei, scant eosinophilic cytoplasm, and high mitotic activity. Areas of necrosis are noted. In a 30-year-old patient with a perianal lesion, the differential diagnosis includes alveolar rhabdomyosarcoma, small cell neuroendocrine carcinoma, lymphoma, Ewing sarcoma, and amelanotic melanoma. To definitively classify this lesion, an immunohistochemical panel is required: Myogenin, Desmin, Pan-Cytokeratin, Synaptophysin, CD45, CD99, SOX10 and Ki-67.
3- Cytological examination of the smear preparations demonstrates a highly cellular, discohesive pattern comprised of large, epithelioid to plasmacytoid malignant cells with abundant, dense, granular eosinophilic cytoplasm. The nuclei are eccentrically placed, round-to-oval, and exhibit vesicular chromatin with prominent, often central, macronucleoli; notably, binucleated forms and cells with rhabdoid-like features are scattered throughout the background
History of perianal pain sience for one months. U/S: semi well-defined lobulated thick heterogeneous collections localized in the left perianal area.
Three containers were received:
1- Tissue biopsy: soft tissue fragments collectively measured 6x5x1.3 cm, totally embedded.
2- Tissue biopsy: 11x9x1.4 cm, totally embedded.
3- Bloody fluid from which 2 smears were prepared and stained.
Peri-anal lesion, biopsy:
Peri-anal collection, conventional cytology: