Alveolar rhabdomyosarcoma, the second most common subtype of rhabdomyosarcoma, is a highly aggressive malignant soft tissue tumour that frequently presents with a high disease burden at diagnosis. 1 Metastatic involvement of the breast, however, is exceedingly rare, particularly in adult females. 2 , 3 We report a case of a 35-year-old female, recently admitted for acute gallstone pancreatitis, who re-presented with a ten-day history of abdominal pain and obstructive jaundice. Initial imaging investigations revealed multiple tumour masses, the largest in the pancreatic head (6.6 cm) and tail (6.7 cm), right breast (6.3 cm), and right lateral abdominal wall (4.6 cm), and smaller lesions in the lungs, bone, and lymph nodes. The initial clinical impression was a metastatic right breast malignancy. Core biopsy of the right breast mass revealed a focally necrotic small blue round cell tumour. Immunohistochemical stains demonstrated positivity for myogenin, desmin, PAX8, and CD56, but negativity for GATA3, mammaglobin, AR, ER, PgR, HER2, TTF1, WT1, NKX2.2, and other epithelial, lymphoid, neuroendocrine, and melanocytic markers. Archer FusionPlex next generation sequencing confirmed the presence of the PAX3–FOXO1 fusion. The final diagnosis was an alveolar rhabdomyosarcoma. This case underscores the importance of integrating morphological, immunohistochemical, molecular, and radiologic findings, for accurate diagnosis and management.
Chong et al. (Sun,) studied this question.