**Core Concept**
The question is testing the ability to diagnose a specific type of lymphoma based on histopathological findings. The characteristic cell type mentioned likely refers to Reed-Sternberg cells, which are a hallmark of Hodgkin lymphoma.

**Why the Correct Answer is Right**
The presence of Reed-Sternberg cells in a lymph node with total effacement of nodal architecture is highly suggestive of Hodgkin lymphoma. To confirm the diagnosis, a specific immunohistochemical study can be performed to identify the presence of CD30 and CD15 antigens on the Reed-Sternberg cells, which are characteristic of classical Hodgkin lymphoma.

**Why Each Wrong Option is Incorrect**
**Option A:** Flow cytometry is useful for identifying specific cell populations in lymph nodes, but it is not the best choice for confirming Hodgkin lymphoma in this case. Flow cytometry would be more useful for identifying non-Hodgkin lymphoma subtypes.

**Option B:** Molecular studies, such as FISH or PCR, can be used to identify specific genetic abnormalities in lymphoma, but they are not the best choice for confirming Hodgkin lymphoma based on the presence of Reed-Sternberg cells.

**Option C:** A bone marrow biopsy may be useful in staging Hodgkin lymphoma, but it is not necessary for confirming the diagnosis based on lymph node histology.

**Option D:** A CT scan of the chest, abdomen, and pelvis may be useful in staging Hodgkin lymphoma, but it is not necessary for confirming the diagnosis based on lymph node histology.

**Clinical Pearl / High-Yield Fact**
When diagnosing lymphoma, it's essential to examine the lymph node architecture and look for characteristic cell types, such as Reed-Sternberg cells in Hodgkin lymphoma. Immunohistochemical studies can help confirm the diagnosis by identifying specific antigens on the tumor cells.

**Correct Answer:** . **Immunohistochemical study for CD30 and CD15 antigens.**