Clinical Aspects and Classification of Lymphoma

Major Classifications of Lymphoma

• Lymphoma is divided into two primary types based on histology:

  • Hodgkin's Lymphoma (also known as Hodgkin's disease).

  • Non-Hodgkin's Lymphoma (NHL).

• The distinction between these types is determined strictly by a lymph node biopsy; a clinical diagnosis cannot definitively distinguish between them without histological examination.

• Hodgkin's Lymphoma Characteristics:

  • Defined by the presence of Reed Sternberg cells.

  • Reed Sternberg cells are giant, multinucleated cells.

  • These cells are derived from germinal center B cells.

• Non-Hodgkin's Lymphoma Characteristics:

  • The majority (approximately $85\%$ to $90\%$) of cases are derived from B lymphocytes.

  • T-cell Non-Hodgkin's lymphomas occur in about $10\%$ to $15\%$ of all lymphoma cases.

Clinical Presentations and Case Examples

Lymphoma presents across a wide variety of ages, genders, and system abnormalities. Presentations can range from specific symptoms to incidental findings during routine testing.

• Specific Clinical Scenarios:

  • Abdominal Pain: A $63 \text{ year old}$ woman presenting with intermittent abdominal pain over several years; CT imaging reveals widespread mesenteric and para-aortic lymphadenopathy.

  • Palpable Lumps: A $27 \text{ year old}$ man who discovers a lump in his neck while showering.

  • Respiratory Symptoms: A $54 \text{ year old}$ woman seeking treatment for a cough lasting one month; a chest X-ray reveals a large mediastinal mass.

  • Incidental Medical Examination: A $44 \text{ year old}$ man undergoing an insurance upgrade is found to have an enlarged spleen on examination.

  • Obstetric Findings: A $29 \text{ year old}$ woman undergoing an obstetric ultrasound at $8 \text{ weeks}$ of pregnancy is found to have a pelvic sidewall mass in addition to a live pregnancy.

  • Specific Organ Masses: An $83 \text{ year old}$ man presenting with an enlarged right testicular mass.

  • Systemic Symptoms: A $55 \text{ year old}$ woman presenting with tiredness; blood tests reveal moderate anemia.

• Common Sites of Lymphadenopathy:

  • Clinically Obvious Lumps: Located in the neck, axilla, or inguinal (groin) regions.

  • Internal Lumps (identifiable via imaging): Located in the brain, thorax, abdomen, pelvis, breast, or testis.

• Detection via Testing:

  • Blood Counts: Incidental findings of anemia, thrombocytopenia, or lymphocytosis.

  • Imaging: Incidental abnormalities found via Chest X-ray, CT, or MRI.

Indolent (Low Grade) Lymphoma

• Characteristics:

  • Typically asymptomatic at the time of diagnosis and frequently found incidentally.

  • Often remains stable for long periods of time.

  • Growth rate is generally very slow.

  • Disease is usually widely spread at the time of diagnosis; more than $85\%$ of cases involve the bone marrow.

• Prognosis and Treatment:

  • Rarely curable with standard chemoradiotherapy.

  • Treatment typically results in a pattern of remission followed by disease recurrence (remission and exacerbation cycle).

  • The average lifespan for patients is generally more than $10 \text{ years}$.

• Specific Types - Follicular Lymphoma:

  • Associated with the overexpression of BCL-2, an anti-apoptosis protein.

  • This overexpression is commonly driven by a translocation between chromosomes $14$ and $18$, noted as $t(14;18)$.

Aggressive (High Grade) Lymphoma

• Characteristics:

  • Much more likely to be symptomatic at the time of diagnosis.

  • In a larger number of cases, the disease can be localized at diagnosis.

  • Clinically aggressive growth cycles occurring over weeks to months.

• Histology:

  • Diffuse Large B Cell Lymphoma (DLBCL): The most common histology.

  • Other types include Mantle cell lymphoma, Burkitt's lymphoma, and Peripheral T cell lymphoma.

  • Histological sections of these lymphomas lack the follicular pattern seen in low-grade cases; cells appear large (e.g., DLBCL).

• Prognosis and Treatment:

  • Responds well to treatment.

  • Approximately $50\%$ of patients can be cured using chemo-immunotherapy.

  • If a cure is not achieved, patients typically relapse or fail to respond, with mortality occurring within months to $1$ or $2 \text{ years}$.

• Genetic Markers in DLBCL:

  • Associated with mutations in genes such as C-MYC, BCL-2, and BCL-6.

  • Double or Triple Hit Lymphomas: Defined by mutations in two or three of these genes.

  • Double or Triple Expressers: Defined by the overexpression of the proteins encoded by these genes without accompanying genetic mutations.

Waldenström's Macroglobulinemia

• This is a common type of indolent (low grade) lymphoma, distinct from Follicular lymphoma.

• Pathophysiology: Characterized by progressive infiltration of the bone marrow by lymphoplasmacytoid cells.

• Morphology: Cells have a plasmacytoid morphology, similar to plasma cells but distinct from myeloma. Characteristics include:

  • A "clock face" nucleus.

  • An eccentric nucleus position.

  • A perinuclear clear zone.

• Diagnostic Markers:

  • Presence of an IgM paraprotein.

  • MYD-88 Signaling Pathway: Involves signaling from the cell exterior to the nucleus.

  • Genetic Tool: A specific mutation, $L265P$, in the MYD-88 signaling pathway is used as a diagnostic tool.

• Clinical Presentation: Often associated with anemia and splenomegaly.

• Management: Usually not treated aggressively as many cases progress extremely slowly or not at all over several years.

Burkitt's Lymphoma

• Burkitt's lymphoma is categorized as a particularly aggressive (high grade) lymphoma.

• Genetics:

  • Specific genetic alteration involving a translocation between chromosomes $8$ and $14$, notation $t(8;14)$.

  • This translocation juxtaposes the C-MYC oncogene to the immunoglobulin heavy chain gene.

  • The cells exhibit a very high mutation rate.

• Morphology: Known for a characteristic "starry sky" appearance under histological examination (pale areas in a dense cellular background).

• Clinical Sites: This disease can affect all age groups and has a predilection for involving the terminal ileum and the central nervous system (CNS).

• Viral Link: In some cases, the Epstein-Barr virus (EBV) is detectable within the lymphoma cells.

• Treatment: Requires aggressive multi-agent chemotherapy, which can highy successfully achieve a cure.