Pathology of Primary Cutaneous Anaplastic Large Cell Lymphoma
- CD30 positive Cutaneous Large T cell Lymphoma.
The World Health Organization recognizes 3 entities: primary cutaneous ALCL , anaplastic lymphoma kinase (ALK)-positive ALCL, and, provisionally, ALK-negative ALCL.
CD30+ Cutaneous Large T-cell Lymphoma is a spectrum of rare cutaneous large cell pleomorphic lymphomas.
These lesions were originally termed "atypical regressing histiocytosis" and later classified 'anaplastic large cell lymphoma' by the Kiel and REAL classifications.
Primary cutaneous anaplastic large cell lymphoma is part of the group of CD30+ lymphoproliferative diseases of the skin including lymphomatoid papulosis.
In borderline cases and in lesions with overlapping features, histopathological distinction between ALCL and lymphomatoid papulosis is sometimes difficult.
Clinical history and course of the disease play an important in diagnosis and treatment these cases.
These lesions express CD30+ in a large number of the tumour cells and are associated with an excellent prognosis, approaching 90% survival at 5 years in the EORTC group.
Clinically, 'anaplastic large cell lymphoma' may present as localized (primary) cutaneous disease or widespread systemic disease.
These two forms of 'anaplastic large cell lymphoma' are distinct entities with different clinical and biologic features.
Both types share similar histology with cohesive sheets of large lymphoid cells expressing the Ki-1 (CD30) molecule.
Primary cutaneous anaplastic large cell lymphoma is always anaplastic lymphoma kinase protein (ALK) negative and does not have t(2;5)(p23;q35) translocation.
Primary Cutaneous ALCL:
The lesion usually presents as a solitary, asymptomatic, cutaneous or subcutaneous reddish-violet tumor, which can be superficially ulcerated.
In some cases the disease is characterized by multiple tumour nodules aggregated in a circumscribed area or as multicentric tumors at multiple sites.
Primary cutaneous ALCL has a more favorable prognosis than systemic ALCL (which may secondarily involve the skin).
Histologically, the tumour is composed of non-epidermotropic, diffusely distributed, pleomorphic mononuclear cells.
The large lymphoid cells show chromatin-poor horseshoe-shaped nuclei containing multiple nucleoli.
Cells with these cytologic features have been called "hallmark cell".
In some cases multinucleated cells with Reed-Sternberg-like appearance may be present.
Rarely, the cells have immunoblastic morphology.
An accompanying infiltrate of small reactive lymphocytes, macrophages and eosinophils is often present.
Epidermal hyperplasia overlying the lesion may be prominent.
Differential Diagnosis: CD30 positive large cells are seen in a wide range of conditions like - viral infection, drug reaction and arthropod bite reaction.
Approximately 25% of patients with primary cutaneous ALCL show partial or complete spontaneous regression, accounting for the previous designation of regressing atypical histiocytosis.
Treatment of localized lesions usually includes excision with or without radiation and is associated with long-term survival.
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