• This manual is not a substitute for consultation with an appropriate specialist.
• The contents of this manual have been developed through consensus of a Provincial Tumour Group. Please note the various update dates for each section as some of the content of the manual may not be up to date.

Progressive transformation of germinal centres is a histologic diagnosis and is clinically benign. The importance of its recognition is that this entity may antedate, occur simultaneously with, or follow a diagnosis of Hodgkin's lymphoma, particularly the nodular lymphocyte predominant subtype. PTGC has also been associated with other forms of Hodgkin's lymphoma including nodular sclerosis and mixed cellularity subtypes. Importantly, a diagnosis of PTGC should signal a need for close clinical follow-up of these patients and/or a repeat excisional biopsy should other sites of more significant lymphadenopathy be present.​

Angiofollicular lymph node hyperplasia occurs as two histologic subtypes - the hyaline-vascular type and the plasma cell variant. The hyaline-vascular type is usually localized and not associated with systemic symptoms and is best managed with complete surgical excision. The plasma cell variant accounts for approximately 10% of cases and is often accompanied by systemic symptoms. Management of this entity should be discussed with a medical oncology member of the Lymphoma Tumour Group at one of the BCCA Centers. A multicentric form of Castleman's disease exists with histologic features that overlap both hyaline-vascular and plasma cell variants. The malignant potential of this systemic disease is uncertain and management should be individualized.​

The Langerhans' cell histiocytoses (LCH) are a group of related entities which share a common pathology. The Langerhans' cell histiocytoses include eosinophilic granuloma, Hand-Schuller-Christian disease and Letterer-Siwe disease. These entities are all characterized by a proliferation of Langerhans' cells and are best thought of as monostotic, polyostotic or disseminated forms of the same disease. The malignant potential of this group of diseases is uncertain and treatment should be discussed with a medical oncology member of the Lymphoma Tumour Group at one of the BCCA Centers.

True malignant histiocytosis is a rare disease and is best considered a variant form of malignant lymphoma. Hemophagocytosis by cytologically malignant-appearing cells is typically seen in histologic sections and diagnosis requires careful morphologic and phenotypic assessment. The behaviour is usually similar to that of a large cell lymphoma and treatment should be given as for large cell lymphoma taking into account the stage of the disease and the age of the patient.

This benign, self-limited, skin eruption can be confused with malignant lymphoma, particularly anaplastic large cell lymphoma involving the skin. It is usually confined to one or a few chronically recurring papulo-ulcerative lesions in an otherwise healthy individual. Its major importance is to recognize that it is a self-limited neoplasm and will regress spontaneously. Recent evidence indicates that some cases can be shown to be clonal T-cell lymphoproliferative lesions. However, separation of lymphomatoid papulosis from anaplastic large cell lymphoma involving skin is difficult. Nonetheless, the majority of patients with clinically and pathologically typical lymphomatoid papulosis have a unique disease course which resolves spontaneously, but may relapse and remit for years. It is essential that review of the biopsy material be done by an experienced hematopathologist and dermatopathologist who have been informed of the clinical history.​

The terms angiocentric immunoproliferative lesion and angiocentric lymphoma have become obsolete, at least in part because as many as 1/3 of the lymphomas that belong in this category are not angiocentric. The lesions previously included in these and closely related categories are shown in the table below along with the current correct name for each condition. The correspondence between the old and new names is not exact because progress in lymphoma classification has also led to the recognition that some lesions previously assigned to this category actually represent variants of other recognized lymphoma subtypes. Treatment recommendations for each of these diseases are described in their own specific sections, which should be consulted.