ALK-Positive Anaplastic Large Cell Lymphoma resembling Nodular Sclerosing Hodgkin Lymphoma

Definition

About 3% of cases of anaplastic large cell lymphoma show a close resemblance to Hodgkin lymphoma^1,2. The understanding is that this is not a true biological overlap but morphological mimicry. Diagnosis requires positivity for ALK1.

Epidemiology

Although occurring across a wide age range, this variant of anaplastic large cell lymphoma is most common in children.

Histopathology

There is marked capsular fibrosis, with thick fibrous bands separating cellular nodules. Most of the neoplastic cells are mononuclear but with variable numbers of binucleate Reed-Sternberg like cells. Mummified and rare lacunar-like cells may be seen. The neoplastic cells may form cohesive sheets. In some cases they show a strong perivascular distribution, as seen in the small cell variant of ALCL. They may be seen within lymphatic sinuses. In cases with residual germinal centres, neoplastic cells show a perifollicular distribution. The background cells are lymphocytes and plasma cells, with most cases lacking substantial numbers of eosinophils or neutrophils. Some histiocytes may be present but granulomata are lacking.

Immunohistochemistry

The neoplastic cells may be of T or null immunophenotype.

	CD2	3/71
	CD3	4/101
	CD4	4/71
	CD5	4/71
	CD7	2/71
	CD8	0/71
	CD15	0/101
	CD20	0/101
	CD30	10/10 (staining emphasized the perivascular distribution of neoplastic cells)1
	CD43 (MT1)	6/91
	ALK1	10/10 (large neoplastic cells show cytoplasmic, nuclear and nucleolar staining: there may be a population of smaller cells with limited nuclear staining, as seen in the small cell variant of ALCL. Staining emphasized the perivascular distribution of neoplastic cells.)1
	EMA	9/91
	Perforin	8/8 (all cases tested showed strong staining)1
	EBV/LMP1	0/81
	Pax5/BSAP	0/6 (the malignant cells were negative but residual B-cells were positive)1
	BNH9	4/61

EBER by in situ hybridisation: 0/6.

Differential diagnosis

• Hodgkin lymphoma, particularly nodular sclerosing type II: the possibility of ALCL resembling Hodgkin lymphoma should be considered in cases with neoplastic cells strongly positive for EMA or positive for T-cell markers (Hodgkin lymphoma may show cytoplasmic dot-like positivity for CD3)

• Atypical T-cell lymphoma, e.g. nodal cytotoxic T-cell lymphoma.

References

¹ Vassallo J, Lamant L, Brugieres L, et al. ALK-positive anaplastic large cell lymphoma mimicking nodular sclerosis Hodgkin's lymphoma: report of 10 cases. Am J Surg Pathol 2006; 30:223-9

² Falini B, Bigerna B, Fizzotti M, et al. ALK expression defines a distinct group of T/null lymphomas ("ALK lymphomas") with a wide morphological spectrum. Am J Pathol 1998; 153:875-86

This page last revised 9.4.2006.

©SMUHT/PW Bishop