Ocular MALT lymphoma

Epidemiology

Less than 1% of all lymphomas are sited in the ocular adnexa but lymphoma is the most common neoplasm at this site. MALT lymphoma is the most common ocular adnexal lymphoma, accounting for 90% of all lymphomas of the ocular adnexa and for 25% of all non-gastric MALT lymphomas. They occur across a wide age range in adults. Most series show a female predominance, although several Asian series show a male predominance.

Aetiology

The aetiological role of Chlamydia psittaci probably varies between countries, with a reported association in 35% of cases from the coast of the USA5. Other studies of US patients have not demonstrated C pssitaci infection2. An Italian study reported positivity for C. psittaci in 80% of ocular adnexal lymphomas3 and the same authors report regression after directed antibiotic therapy4.

Macroscopic appearances

The lymphoma may involve the orbital soft tissue, lacrimal gland, conjunctival mucosa or eyelid. Some cases also show bone marrow involvement.

Histopathology

The tumour is diffuse or vaguely nodular. The typical morphology consists of small lymphocytes wth dense chromatin ans scatn cytoplasm. There are patches of monocytoid cells and a variable number of plasma cells. A low proportion of immunoblasts or centroblasts may be present but not in clusters of more than 20 such cells. Scattered polykaryocytes resemble follicular dendritic cells. Residual follicles may be present which may be undergoing collonisation. There may be haemosiderin depostion. Lymphoepithelial lesions are rare.

Variants show a predominance of monocytoid cells with an abundance of pale cytoplasm. Sometimes plasma cells predominate.

Immunohistochemistry

	CD5	negative, 1/335
	CD10	0/39, 0/345
	CD20	39/39, 34/345
	CD23	negative
	CD38	8/39
	CD43	12/36, 4/345
	CD79a	39/39
	bcl-2	39/39
	bcl-6	0/39
	cytoplasmic bcl-10	8/39
	nuclear bcl-10	11/37
	bcl-XL - high level expression	6/39
	light chain restriction	32/33, 23/34(17 kappa, 6 lambda)5
	MUM1	4/39, 0/345
	Ki-67 - high level expression	9/39
	CDK1	11/39
	CDK2	0/39
	CDK4	12/39
	CDK6	14/39
	CyclinD1	0/39
	CyclinD3	6/39
	CyclinE	7/39
	CicA	4/39
	p16 - high expression	17/39
	p18 - high expression	22/31
	p21 - high expression	4/39
	p27 - high expression	25/39
	p53	0/39
	Hdm2	12/39
	Bax - high level expression	30/39
	pLkBa	19/39
	Caspase 3	1/38
	Survivin - high level expression	6/38
	TUNEL - high level expression	28/36

	HCV seropositivity	5/10
	t(11;18)	0/36
	t(14;18)	5/37

Several of these alterations related to the regulation of apoptosis: caspase 3 activity is abolished and IkBa activity increased. The presence of a large cell component is associated with increased expression of survivin, cyclin A, cyclin E; KI67 and p16 expression are reduced1.

Cytogenetics

t(14;18)(q32;q21) and t(3;14)(p14;q32) are common translocations. Trisomies 3 and 18 are common2.

Differential diagnosis

Reactive lymphoid hyperplasia, particularly if hyperplastic germinal centres are present.

Management

Good control may be obtained by either radiotherapy or chemotherapy.

Prognosis

Most ocular MALT lymphomas have an indolent course. Recurrence after treatment may be local or contralateral. Some cases disseminate. The presence of large cells does not predict behaviour.