Primary osteosarcoma of the breast: pathological and imaging findings

Abstract

Financial support: none suMMary Primary osteosarcoma of the breast (POB) is an extremely rare and aggressive tumor. Differential diagnosis of POB includes osteosarcoma of the chest wall and metaplastic breast carcinoma. Imaging tests that exclude the existence of a direct connection between the tumor and chest wall, as well as histopathological and immunohistochemical studies that rule out the presence of an epithelial component are required for the diagnosis of POB. We report a case of a 69-year old woman with POB. Imaging and pathological findings are presented. Therapeutic approach is discussed in the light of current knowledge, including potential complications.Keywords: breast, breast neoplasms, sarcoma, immunochemistry.A 69-year-old woman presented with a 6-month history of a palpable, painless mass in her left breast. Clinical examination revealed a hard, mobile, well-circumscribed, 10 cm mass, occupying practically the entire left breast. Contralateral breast, axilla or nipples showed no abnormalities. She denied having any history of breast trauma, radiotherapy, or breast cancer.Mammography revealed a relatively well-defined, hyperdense irregular mass without calcifications, unconnected to the underlying sternum and ribs ( Figure 1A). Ultrasound revealed a hypoechoic irregular mass with hyperechoic areas, indistinct margins, and posterior acoustic shadowing ( Figure 1B). Core needle biopsy was performed and microscopy showed a malignant poorly differentiated mesenchymal tumor.Thoracic and abdominal computed tomography showed no distant metastasis. The patient underwent simple mastectomy and sentinel lymph node biopsy. Grossly, the cut surface of the tumor was white, hard, with a stony consistency in the center and well-defined margins. The tumor measured 10x9x7 cm (Figure 2).Microscopy showed a malignant immature mesenchymal bone-forming tumor. There were foci of necrosis and cartilage, containing osteoid matrix, some of which were irregularly calcified, surrounded by atypical spindle cells and osteoclast-like multinucleated giant cells. Tumor mitotic count was 16 mitoses/10 high-power field. There was no skin and lymphovascular invasion. Sentinel lymph node was tumor-free. On immunohistochemistry, tumor cells were positive for vimentin. CD68 (KP1) and alpha-1-antitrypsin were positive in osteoclast-like giant cells. Cytokeratin (AE1/AE3), S-100, epithelial membrane antigen (EMA), p63, epidermal growth factor receptor (EGFR), CD99, estrogen and progesterone receptors, and HER2 were negative. The Ki-67 index was 5%. Extensive tumor sampling failed to identify any tumor that was biphasic or had epithelial component. A highgrade primary osteosarcoma of the breast (POB) was di-

Osteosarcoma primario de mama en una paciente con antecedentes de tratamiento radioterápico loco-regional por carcinoma in situ mamario

“…El OSM es un tumor maligno raro que surge del tejido conectivo 9 . Aunque la histogénesis aún es desconocida 2 , se sabe que puede originarse a partir de células madre totipotenciales del estroma mamario, o derivar de la transformación de células preexistentes de un fibroadenoma o un tumor filodes [2][3] . Muy a menudo, surgen como condiciones de novo sin factores de prevención, especialmente después de la RT 1 .…”

“…Típicamente se desarrolla en mujeres de mediana edad y ancianas (22-82años) con una edad media de 62 años 3 (edad similar a la nuestra paciente, con 63 años al diagnóstico); a diferencia del osteosarcoma de esqueleto, que se desarrolla típicamente en edad juvenil 9 . La apariencia histológica del osteosarcoma primario de la mama se clasifica de acuerdo a la composición celular (fibroblástico, osteoblástico y osteoclástico) [2][3][4][5][6][7][8][9][10][11] , así como al tipo y cantidad de matriz existente (condroide, osteoide y óseo) 11 . En nuestra paciente el diagnóstico específico fue de osteocondrosarcoma de mama, por su abundante tejido condroide, evidente por la positividad a la proteina S-100.…”

“…Se podría contemplar la administración de quimioterapia adyuvante (ante características desfavorables que pudiesen empeorar el pronóstico y valorando el tamaño del tumor, grado y subtipo histológico 6 . Así, pacientes con tumores grandes (mayores de 5cm), de alto grado, con márgenes infiltrativos, necrosis y otras características pronósticas desfavorables podrían beneficiarse de la QT (doxorrubicina, cisplatino, metotrexato e ifosfamida), que pueden mostrar actividad antitumoral en el osteosarcoma [2][3][4][5][6] , no existe una evidencia clara de su eficacia en este tipo de tumor 3 , aunque es el tratamiento principal en el estadío metastásico 3 . En casos de márgenes afectos tras cirugía o una gran masa que no puede extirparse, se puede plantear además la administración RT adyuvante 12 .…”

Primary osteosarcoma of the breast: a case report

“…There can be no calcifications on some case [9]. If the mass is calcified, excisional biopsy would be preferred over core needle biopsy because of the hardness of the mass.…”

Primary Osteosarcoma of the Breast in a Patient Treated Previously for Invasive Ductal Carcinoma: An Unusual Presentation of a Very Rare Primary Breast Malignancy

“…Forty-one per cent of patients with POSB develop metastases which highlight the need for effective adjuvant therapy [6]. The role of chemotherapy in the management of patients with POSB is uncertain with limited reports in the literature with differing regimens and outcomes [22][23][24][25][26]. However, because of the dramatic improvement in survival from chemotherapy administration for patients with primary osteosarcoma of the bone, it is reasonable to consider its use for a patient with POSB until better evidence is available to guide management [22].…”