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PA19.1-6 | Hodgkin Lymphoma — Gross & Microscopic Identification — Part 1

CLINICAL SCENARIO

You are handed a glass slide labelled 'cervical lymph node biopsy, 22-year-old male, painless neck swelling x 3 months.' On low power you see broad pale bands of collagen dividing the node into nodules, and within each nodule a mixed infiltrate. Your job: find the diagnostic cell, characterise the background, assign the subtype, and confirm with immunohistochemistry. This is the PA19.6 practical.

WHY THIS MATTERS

Hodgkin lymphoma accounts for roughly 30% of all lymphomas and is one of the most curable cancers when diagnosed early. The diagnosis rests entirely on morphology — no other malignancy is diagnosed by identifying a specific named cell the way HL is by the Reed-Sternberg cell. Getting this right in the practical directly translates to correct diagnosis in clinical practice, and misidentifying a reactive node as HL (or missing HL in a reactive-looking node) has immediate consequences for a young patient.

RECALL

Before starting the microscopy, anchor your prior knowledge:

Hodgkin lymphoma arises from germinal-centre B cells (confirmed by clonal Ig rearrangement despite loss of B-cell markers).
The two broad categories are Classic Hodgkin Lymphoma (cHL) — 4 subtypes — and Nodular Lymphocyte-Predominant HL (NLPHL).
cHL subtypes in decreasing frequency: Nodular Sclerosis > Mixed Cellularity > Lymphocyte-Rich > Lymphocyte-Depleted.
EBV is implicated in 30–50% of mixed cellularity and lymphocyte-depleted cHL (less so in nodular sclerosis).
Classic immunophenotype of the neoplastic cell: CD15+, CD30+, CD45−, PAX5+ (dim).

Gross Specimen: What to Look For

Four-panel pathology diagram showing gross features of Hodgkin lymphoma lymph nodes, including matted enlarged nodes, fish-flesh cut surface, nodular sclerosis, extracapsular spread, and splenic white nodules. — **Panel A:** Matted enlarged lymph nodes, rubbery grey-tan external surface, fibrous adhesions, normal lymph node size comparison. **Panel B:** Fish-flesh cut surface, homogeneous pale grey-white tissue, faint yellow-tan areas, loss of normal lymph node architecture. **Panel C:** Nodular sclerosis type, pale nodules, broad grey-white collagen bands, inset of collagen septa. **Panel D:** Extracapsular extension through capsule into pericapsular fat, splenic cut surface with miliary white nodules, cobblestone/cannonball pattern.

In the practical tray or projected image, examine the lymph node systematically:

1. Size and consistency
HL lymph nodes are typically enlarged, matted, and rubbery. Matting (adhesion of nodes into a confluent mass) occurs because of periadenitis and fibrosis. In nodular sclerosis, the node feels firm-to-hard due to collagen deposition.

2. Cut surface
The classic descriptor is fish-flesh appearance — a homogeneous, pale greyish-white or faintly yellow-tan surface resembling the cut surface of raw fish. This reflects replacement of normal lymphoid architecture by neoplastic and fibrotic tissue. In nodular sclerosis, you may see pale nodular areas separated by grey-white bands corresponding to the broad collagen septa.

3. Capsule and pericapsular tissue
In early disease the capsule is intact. In advanced or relapsed disease, extracapsular extension into pericapsular fat may be visible as irregular infiltration of surrounding adipose.

4. Spleen (if present)
Splenic involvement shows miliary white nodules on cut surface — the so-called cobblestone or 'cannonball' pattern of white pulp expansion, distinct from the diffuse red-pulp involvement seen in some NHL.

Three-panel illustration showing the gross pathological features of Hodgkin lymphoma including fish-flesh cut surface, matted lymph nodes, and nodular pattern with collagen bands. — **Panel A:** Fish-flesh cut surface showing characteristic pale grey-white homogeneous appearance. **Panel B:** Matted lymph nodes demonstrating firm, adherent lymph node mass typical of Hodgkin lymphoma. **Panel C:** Nodular areas with visible white collagen bands creating the nodular sclerosis pattern.

Quick check: Describe the gross cut surface of a nodular sclerosis HL lymph node in one sentence before continuing.

SELF-CHECK

A 19-year-old presents with a rubbery, matted cervical lymph node mass. On gross examination the cut surface is homogeneous, pale grey-white, and firm with visible white bands. Which gross descriptor best fits this appearance?

A. Fish-flesh cut surface with collagen bands — nodular sclerosis HL

B. Haemorrhagic, necrotic cut surface — diffuse large B-cell lymphoma

C. Caseating granulomas with central necrosis — tuberculous lymphadenitis

D. Greasy yellow-tan lobulated cut surface — lipoma

Reveal Answer

Answer: A. Fish-flesh cut surface with collagen bands — nodular sclerosis HL

The pale, homogeneous 'fish-flesh' cut surface with firm white bands is the classic gross description of nodular sclerosis HL. Caseating granulomas suggest TB; haemorrhagic necrosis suggests high-grade NHL; greasy lobulation suggests fatty tumour — none match.

Systematic Approach to Reading the Slide

A four-part educational diagram shows the systematic low-, medium-, and high-power approach to reading a lymph node slide for Hodgkin lymphoma, emphasizing nodular sclerosis architecture, mixed inflammatory background, and Reed-Sternberg cell detection. — **Panel A:** Low-power H&E lymph node architecture showing broad collagen bands, cellular nodules, effaced nodal architecture, and nodular sclerosis pattern.. **Panel B:** Medium-power cellular nodule showing mixed inflammatory infiltrate with small mature lymphocytes, eosinophils, plasma cells, histiocytes, neutrophils, and fibrosis.. **Panel C:** High-power diagnostic field showing raster scan path and a classic Reed-Sternberg cell with binucleation and prominent eosinophilic nucleoli among reactive cells.. **Top workflow:** Three-step microscope scan: Step 1 low power for architecture, Step 2 medium power for background composition, Step 3 high power for diagnostic cell..

Use the same three-step scan every time you sit at the microscope for a lymph node section:

Step 1 — Low power (4× or 10×): Architecture
Is the nodal architecture preserved or effaced? Look for:
• Broad collagen bands dividing the node into nodules → nodular sclerosis
• Diffuse effacement with mixed cellularity → mixed cellularity
• Nodular pattern with residual germinal-centre morphology → NLPHL

Step 2 — Medium power (10×–20×): Background composition
Characterise the reactive inflammatory infiltrate:
• Lymphocytes (small, mature), eosinophils, plasma cells, histiocytes, neutrophils, fibrosis
• The ratio and predominance determine the subtype

Step 3 — High power (40×): The diagnostic cell
Search the nodules for the neoplastic cell. Classic RS cells are rare but unmistakable. Systematic scanning in a raster pattern prevents missing them.

Two-panel histological diagram showing nodular sclerosis Hodgkin lymphoma with collagen bands dividing lymph node into cellular nodules. — **Panel A:** Low-power H&E view showing broad collagen bands, cellular nodules, overall nodular architecture, lymphoid tissue compartments. **Panel B:** Higher magnification of cellular nodule showing mixed inflammatory infiltrate and tissue composition within nodular compartments.

Why architecture first? Subtype recognition happens at low power — once you see the nodular pattern and bands, you know you are in nodular sclerosis territory before you ever find an RS cell.

The Diagnostic Cell: Reed-Sternberg Cell

Three-panel pathology diagram showing nodular sclerosing Hodgkin lymphoma at low power, a classic Reed-Sternberg cell at high power, and a checklist of its diagnostic owl-eye morphology. — **Panel A:** Low-power nodular sclerosing Hodgkin lymphoma showing collagen bands, nodular pattern, mixed inflammatory infiltrate, and effaced lymph node architecture.. **Panel B:** Classic Reed-Sternberg cell showing large size, binucleate mirror-image nuclei, eosinophilic owl-eye nucleoli, clear halos, abundant pale cytoplasm, and surrounding reactive inflammatory cells.. **Panel C:** Simplified Reed-Sternberg morphology checklist with large size, bilobed or binucleate nucleus, owl-eye nucleoli with clear halo, abundant pale cytoplasm or lacunar space, and comparison with a small lymphocyte..

The Reed-Sternberg (RS) cell is the pathognomonic neoplastic cell of classic Hodgkin lymphoma.

Key morphological features (memorise all four):
1. Large size — much larger than surrounding lymphocytes (diameter 15–45 µm); stands out even on scan.
2. Binucleate or bilobed nucleus — the two nuclei are mirror images of each other, giving the classic 'owl-eye' appearance.
3. Large, inclusion-like eosinophilic nucleoli — prominent central nucleolus in each lobe, surrounded by a clear halo, resembling a viral inclusion body.
4. Abundant pale cytoplasm — the cell sits in a lacuna (artefactual retraction space in nodular sclerosis variants).

The 'owl-eye' descriptor is the single most tested morphological feature in practicals. The two nucleoli represent the 'eyes'; the surrounding cleared halo the 'face'.

Two-panel histopathological illustration showing nodular sclerosing Hodgkin lymphoma at medium and high power with labeled Reed-Sternberg cells and architectural features. — **Panel A:** Nodular sclerosing pattern with collagen bands, mixed cellular infiltrate, lymph node architecture at 20x magnification. **Panel B:** Classic Reed-Sternberg cell with binucleate mirror-image nuclei, owl-eye nucleoli, pale cytoplasm, surrounding reactive inflammatory cells at 40x magnification.

SELF-CHECK

At 40× magnification you identify a very large cell with two mirror-image nuclei, each containing a prominent eosinophilic nucleolus surrounded by a clear halo. The cell is surrounded by small lymphocytes. What is this cell?

A. Classic Reed-Sternberg cell — diagnostic of Hodgkin lymphoma

B. Multinucleated giant cell (Langhans type) — tuberculous granuloma

C. Plasma cell with Russell body — reactive plasmacytosis

D. Starry-sky macrophage — Burkitt lymphoma

Reveal Answer

Answer: A. Classic Reed-Sternberg cell — diagnostic of Hodgkin lymphoma

The binucleate mirror-image cell with large eosinophilic 'owl-eye' nucleoli is the hallmark RS cell of classic HL. Langhans giant cells have nuclei arranged in a horseshoe at the periphery. Plasma cells with Russell bodies are smaller and mononuclear. Starry-sky macrophages are tingible-body macrophages, not binucleate.