A 64 year old woman with hypertension, dyslipidemia, grade III obesity and history of pT1cN1R0 breast cancer treated with tumorectomy, chemo, radio and hormonal therapy, presented to a hypertension appointment with her family doctor in October 2023 with a tumefaction in her left scapular region with about 3 months of evolution. A soft tissue ultrasonography revealed “In deep intramuscular topography, a heterogeneous apparently cystic voluminous mass with thick content, measuring 143 x 66 x 31 mm was observed. Correlation with urgent CT scan is advised”.

As such, the patient was referred to her oncologist and then to the Portuguese Institute of Oncology of Porto (IPO Porto). The patient repeated the CT scan which showed, as seen in the image, that “In the left scapular region, in the rhomboid muscle, it is identified an ovoid, solid, well delimited mass with no apparent invasion of the adjacent muscles or bone structures. It has 7, 6 and 5 cm of longitudinal, transverse and anteroposterior diameter, respectively.” The patient underwent a biopsy which revealed a “mesenchymal neoplastic lesion made up of fusiform cells with oval to fusiform nuclei and pinpoint nucleolus. Conclusion: mesenchymal neoplasm with morphological and immunohistochemical features suggestive of fibromatosis”.

The patient was, therefore, diagnosed with aggressive chest wall fibromatosis and it was decided to adopt a watchful waiting posture, in the oncology appointment of April 4th, 2024. The patient has a reassessment appointment in 4 months. The most likely diagnostic hypothesis given the tumefaction features to the physical exam were a lipoma or muscular injury. If such diagnoses were assumed and the patient symptoms undervalued, complementary exams might not have been prescribed and the correct diagnosis might not have been made. This case highlights the importance of valuing patient symptoms and not dismissing rare diagnostic hypothesis.