Introduction
Primary lymphoma (LP) of the thyroid is a very rare disease. It is less than 2 to 5% of malignant neoplasms of the thyroid and 2 to 2.5% of all lymphomas (Aozasa et al., 1986). It is found mainly in older women. Characterized by a clinical polymorphism, the diagnosis of thyroid LP is often difficult which retards its therapeutic management. The prognosis depends on the histology and disease progression (Brownlie et al., 1991). The objective of this study was to report the clinical, paraclinical and evolutionary characteristics of thyroid LP observed in our practice.

Population and Methodology
This is a retrospective study which records all patients with thyroid PL followed between 1982 and 2014 in our endocrinology.

An information sheet has been prepared to study all epidemiological characteristics (age, sex, family and personal history including autoimmune thyroiditis), clinical (reason for consultation, time to diagnosis, presence of signs of compression and or secondary location), paraclinical (echocardiographic, scintigraphic, hormonal results, staging), histological and immunohistochemical characteristics, therapeutic and evolution of patients.

Results
10 cases were recorded in 33 years. All patients were female. The average of age was 56.5 years (38-72). The warning signs were in all cases represented by a neck mass rapidly changing and local obstructive symptoms made of dyspnea and dysphonia.

In half of the cases, the goiter was with a unique nodular appearance and in the other half bi or multinodular (Table 1).

Table 1  Aspect of goite

The consistence was stony and we noted tenderness to palpation in all patients. There were signs of inflamma-tion in 20% of cases associated with local obstructive symptoms in 90% of cases, and pilgrim edema in 20% of cases. Cervical lymph node metasta¬ses were found in more than 2/3 of the cases. No remote secondary location was observed (Table 2).

Table 2  Clinical characteristics of patients

80% of patients were in biological eutyhroidie. 20% had hypothyroidism with Hashimoto thyroiditis known and treated. In the latter, the appearance of nodules and rapid scalability had raised the diagnosis.

At the paraclinical exploration, all thyroid nodules were hypofixants for the technetium scintigraphy and were hypoechoic heterogeneous to the ultrasound.

The diagnosis of thyroid LP was established preoperatively in 80% cases (excisional biopsy of the lymph nodes and cytological study of thyroid nodules). All patients underwent thyroidectomy associated with lymph node dissection in cases of histological envahissement. The immunohistochemical study found primary non-Hodgkin lymphoma in all cases (Table 3).

Table 3  Histological results of patients

Regarding complementary treatment, three patients were treated with chemotherapy alone and five by combining chemotherapy and radiotherapy treatment. Two women were unfortunately died before any treat-ment. The evolution was marked by the deaths of two patients two months after chemotherapy. No tumor recurrence was observed in the other patients (n = 6) after a mean follow-up of four years.

Discussion
The primary malignant lymphoma of the thyroid is a rare tumor (ten cases collected in 33 years in our service). It can occur at any age, with a peak incidence in the 7th decade.

The clinical symptomatology is dominated by the ap-pearance of a nodule or a rapidly progressive thyroid mass with signs of compression of adjacent organs (Brownlie et al., 1991). Signs of thyroid disease are rare. The chronic thyroiditis is considered as pre-lymphomatous state and the risk of occurrence of primary malignant lymphoma of the thyroid is multiplied by 67 in patients with autoimmune thyroiditis (Compagno and Oertel, 1980; Gaulard, 2000). This association was observed in 20% of our patients.

Indeed, these lymphomas develop after the acquisition of lymphoid tissue MALT type that could be secondary to antigenic stimulation. In gastric localizations, the most frequent, Helicobacter pylori are implicated: the history of Helicobacter gastritis are very common in these patients, and in vitro, experiments have shown that this bacterium was necessary for tumor growth. In addition, the eradication of Helicobacter pylori with antibiotics is often followed by regression or remission (Hussell et al., 1993; Latheef et al., 2013). (Figure 1)


Figure 1 MALT lymphoma of B phenotype

Involvement of the thyroid gland may occur in the context of a systemic disease or rarely be primitive as the case of our patients. Histological subtype the most common is a diffuse large cell lymphoma (Paccalin et al., 2001). 

By their rarity and clinical polymorphism, lymphomas of the thyroid still pose diagnostic difficulties. It should be suspected in any thyroid nodule scalable and compressive especially if it evolves in a context of thyroid disease (Wozniak et al., 1999).

NHL consists of small cells with cytological appearance which may vary (centrocyte-like, lymphocytic, lymphoplasmacytic, monocytic). They infiltrate the epithelial structures performing lymphoepithelial lesions whose recognition requires the using of immunohistochemistry.

In therapeutic terms, the treatment of primary malignant lymphoma of the thyroid is not clearly established. The surgery is useful in the presence of compression and/or if difficult histopathologic diagnosis. In case of extracapsular extension, a combination of chemotherapy and radiotherapy is recommended (Leedman et al., 1990).

Monitoring, beyond of hormone replacement therapy, is that of all lymphomas. Their prognosis depends as all lymphoma in histology and the stage of disease. In localized tumors, it is usually favorable with a survival rate at 5 years from 70% to 80% (Brownlie et al., 1991).

The diagnosis of malt lymphoma type B of the thyroid gland should be considered in a rapid increase in the size of a nodule or a goiter. Treatment with total thyroidectomy in combination with chemotherapy and radiotherapy seems to provide good results in the long term, although some authors advocate surgical abstention.

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