Borderline Phyllodes Tumor in a Child.

Phyllodes tumor (PT) is considered a rare fibroepithelial tumor. Very few series have been reported in children and adolescents. Based on histopathological features, it can be classified as benign, borderline, or malignant, with the latter having a more aggressive clinical behavior. We report the case of a 10-year-old female who began with an asymptomatic mobile right breast mass. An initial fine needle biopsy (FNB) concluded fibroadenoma (FA). Months later, the mass kept growing, with the appearance of pain and nipple discharge. Benign PT was demonstrated in a new biopsy. A total mastectomy was performed. The post-surgical histopathological examination was compatible with a borderline PT. The patient is now symptom-free and with no signs of relapse. Not all breast masses in the pediatric or adolescent age bracket are FA. Attention is warranted when the clinical behavior does not follow the usual outline. PT has to be considered as a possible diagnosis and treated accordingly.

Soft-Tissue Anaplastic Lymphoma Kinase-Positive Anaplastic Large Cell Lymphoma in a Child Unmasked by COVID-19.

Anaplastic large cell lymphoma (ALCL) is children's most common mature T-cell neoplasm. The majority is positive for anaplastic lymphoma kinase (ALK). Initial presentation as a soft-tissue pelvic mass without nodal involvement is rare and can be easily misdiagnosed. We report a case of a 12-year-old male presenting with pain and movement restriction in the right extremity. Computed tomography (CT) scan revealed a solitary pelvic mass. Initial biopsy examination concluded rhabdomyosarcoma. After developing pediatric multisystemic inflammatory syndrome due to coronavirus disease 2019 (COVID-19), central and peripheral lymph node enlargement appeared. New cervical adenopathy and pelvic mass biopsies were performed. Immunohistochemistry concluded an ALK-positive ALCL with a small-cell pattern. The patient was treated with brentuximab-based chemotherapy and eventually improved. Differential diagnosis of pelvic masses in children and adolescents must include ALCL. An inflammatory trigger may promote the appearance of a typical nodal disease, previously absent. Attention is warranted during histopathological examination to avoid diagnostic errors.