Non-gynaecological Cytology
Thyroid cytology
Anatomy and physiology of the thyroid
Thyroid nodules
Classification of thyroid neoplasms
Fine needle aspiration (FNA)
Adequacy of the specimen
Evaluation of the specimen
Terminology for reporting results
Benign conditions
The follicular lesions
Malignant tumours
Parathyroid tumours

Lymphoma

Primary thyroid non-Hodgkin lymphoma (PTNHL) is a rare neoplasm, which typically occurs in older-aged women in the setting of Hashimoto`s thyroiditis. The risk for a patient with thyroditis is much greater than in the general population, but occurrence of a lymphoma is very rare. Most patients present with an enlarging neck mass and cervical lymph nodes can be involved.

The three common types of PTNHL are: marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type (MZL); diffuse large B-cell lymphoma (DLBL); mixed MZL-DLBL type.

Cytologic diagnostic features

  • high cellularity
  • isolated lymphoid cells

MZL type is predominantly composed of small lymphoid cells (centrocytes, plasma cells, monocytoid B cells) with interspersed large lymphoid cells. The characteristic lymphoepithelial lesions are difficult to see on smears. DLBL type is composed of large lymphoid cells (centroblasts, immunoblasts, Burkitt-like cells).

Differential diagnosis

  • Hashimoto`s thyroiditis

The main differential diagnosis is Hashimoto`s thyroiditis. When large, highly atypical lymphoid cells are present, the differential diagnosis is not difficult. The small cell lymphomas are hard or impossible to distinguish from Hashimoto`s thyroiditis and immunophenotyping, carried out by flow cytometry or immunocytochemistry, is useful when lymphoma is suspected.

A pure lymphoid population devoid of epithelial cells. A homogeneous population made of large atypical lymphocytes (Pap). The dominant population is made of large, atypical lymphocytes (MGG).

 

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