NBME 18 Pleomorphic neoplastic cells producing new woven bone (NBME Answers)

Retired NBME 18 Answers

nbme18/Block 1/Question#19 (reveal difficulty score)
70 yo woman, increasingly severe pain in ...
Pleomorphic neoplastic cells producing new woven bone 🔍 / 📺 / 🌳 / 📖
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submitted by mahesh(7)

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Osteosarcoma histological appearance. Paget disease is one of risk factor

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spow Looking back, I know it's osteosarcoma but the lung metastases made me think of Ewing's +

makinallkindzofgainz Ewing sarcoma is common in boys <15 years old. This patient is a 70 year old woman. The stem notes elevated periosteum and a sunburst pattern which are characteristic of osteosarcoma. +2

llamastep1 Also "sunburst pattern" is a classic description of Osteosarcoma. +1

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submitted by ∗mamed(25)

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What is the neoplastic chondrocytes filling lacunes?

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mumenrider4ever I think that's a chondrosarcoma (tumor of malignant chondrocytes, found in the pelvis, proximal femur and humerus, FA 2020 pg. 465) +1

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submitted by ∗windy48(0)

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Although rare in the elderly,"sunburst" pattern is the textbook presentation of osteosarcoma.
The answer is almost verbatim from FA: "Pleiomorphic osteoid-producing cells (malignant osteoblasts)."
Paget's disease is a risk factor for osteosarcoma

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submitted by ∗step7777(7)

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Of note, osteosarcoma also is the only bone tumor with a biphasic epidemiological distribution. More common in adolescents, but can also occur in elderly.

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drdoom also known as “bimodal” (since distribution shows two modes: in the second decade of life and the eighth) +

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submitted by saraluciachega(1)

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Also, remember that Paget disease increases risk of osteosarcoma (seen in histology as neoplastic spindle-shaped stromal cells admixed with tumor osteoid and thin trabeculated bone)

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