A 22 year old male with fatigue, recurrent fever, and enlarged cervical lymph nodes has numerous atypical lymphocytes in his peripheral blood smear. A biopsy from the patient’s enlarged node shows expansion of lymphoid follicles with preservation of the underlying architecture. Numerous atypical lymphocytes are present in the paracoical areas. This patient most likely has ?

## **Core Concept**
The patient's presentation with fatigue, recurrent fever, enlarged cervical lymph nodes, and numerous atypical lymphocytes in the peripheral blood smear suggests a lymphoproliferative disorder. The biopsy findings of expanded lymphoid follicles with preserved underlying architecture and atypical lymphocytes in the paracortical areas are characteristic of a specific type of lymphoma.

## **Why the Correct Answer is Right**
The clinical presentation and biopsy findings are consistent with **Infectious Mononucleosis (IMN)**, also known as glandular fever, which is caused by **Epstein-Barr Virus (EBV)**. The hallmark histopathological features include:
- Preservation of the lymph node architecture
- Expansion of lymphoid follicles
- Atypical lymphocytes, particularly in the paracortical areas

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although it might represent a type of lymphoma, the specific details provided do not match the classic presentation of the disease it represents.
- **Option B:** This option is incorrect as it does not align with the clinical and histopathological findings described.
- **Option C:** This option is incorrect because it represents a different pathological entity that does not match the provided clinical scenario.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **Infectious Mononucleosis** often presents with **atypical lymphocytosis** and can mimic lymphoma on initial evaluation. The presence of **heterophile antibodies** (Monospot test) and **EBV serology** can help confirm the diagnosis.

## **Correct Answer:** D. Infectious Mononucleosis.

✓ Correct Answer: D. Mononucleosis