**Myelofibrosis Core Concept**
Myelofibrosis is a type of bone marrow disorder characterized by the replacement of normal bone marrow with fibrotic tissue, leading to ineffective hematopoiesis and extramedullary hematopoiesis. This results in anemia, thrombocytopenia, and leukocytosis due to the accumulation of immature cells in the peripheral blood.

**Why the Correct Answer is Right**
Myelofibrosis is a type of myeloproliferative neoplasm (MPN) that often presents with a dry tap on bone marrow biopsy, indicating fibrosis and scarring of the marrow. The disease is often associated with mutations in the JAK2, CALR, or MPL genes, which lead to the activation of the JAK-STAT signaling pathway and subsequent fibrosis. The disease can also lead to the development of circulating blasts, which are immature white blood cells that can indicate transformation to acute leukemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Myelofibrosis is indeed characterized by the replacement of normal bone marrow with fibrotic tissue, making this statement true.
**Option B:** Splenomegaly is a common feature of myelofibrosis, often due to extramedullary hematopoiesis and sequestration of blood cells, making this statement true.
**Option C:** Anemia, thrombocytopenia, and leukocytosis are common hematological features of myelofibrosis, often due to ineffective hematopoiesis and extramedullary hematopoiesis, making this statement true.

**Clinical Pearl / High-Yield Fact**
The World Health Organization (WHO) classification system recognizes primary myelofibrosis as a distinct entity, characterized by the presence of fibrosis and scarring in the bone marrow, as well as the presence of circulating blasts.

**Correct Answer: D**